Translation, Cross-Cultural Adaptation and Validation of the 10-Item Spine Functional Index (SFI-10) for Greek Patients with Musculoskeletal Spine Disorders

Translation, Cross-Cultural Adaptation and Validation of the 10-Item Spine Functional Index (SFI-10) for Greek Patients with Musculoskeletal Spine Disorders | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Translation, Cross-Cultural Adaptation and Validation of the 10-Item Spine Functional Index (SFI-10) for Greek Patients with Musculoskeletal Spine Disorders Konstantinos Fokas, Anastasios Fotiou, Christos Phil. Komissopoulos, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8821715/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Background Musculoskeletal spine disorders are a leading cause of disability worldwide. The Spine Functional Index (SFI) is a whole-spine patient-reported outcome measure, and its short form (SFI-10) has demonstrated satisfactory psychometric properties across multiple languages. However, no validated Greek version has been available. Methods This cross-sectional study included 110 adults with chronic, non-specific spinal pain. Participants completed the Greek version of the SFI-10, alongside established measures of pain and health-related quality of life. Internal consistency, test-retest reliability, measurement error, structural validity and convergent validity were calculated. Results The Greek SFI-10 demonstrated acceptable internal consistency (Cronbach’s α = 0.794) and excellent test-retest reliability (ICC 2,1 = 0.955). Measurement error was low (SEM = 0.403; MDC 90 = 0.935), and responsiveness indices indicated adequate sensitivity to change. Factor analyses supported a one-factor structure (EFA eigenvalue = 4.96), with good model fit in CFA (CFI = 1.000; RMSEA = 0.000). Convergent validity was confirmed through significant correlations with NPRS (r = 0.634; p < 0.001), SF-BPI pain interference (r = 0.819; p < 0.001), SF-BPI pain severity (r = 0.628; p < 0.001) and EQ-5D-5L (r = − 0.722; p < 0.001). Conclusion The Greek version of the SFI-10 is a valid and reliable patient-reported outcome measure for assessing whole-spine function in individuals with musculoskeletal spine disorders. Its brevity and ease of use support its application in both clinical practice and research, involving Greek-speaking populations. Spine Functional Index SFI-10 cross-cultural adaptation musculoskeletal spine disorders Greek version physiotherapy Figures Figure 1 Figure 2 1. Introduction Musculoskeletal disorders of the spine represent one of the leading causes of disability worldwide, contributing significantly to the global burden of disease and healthcare costs [ 1 , 2 ]. According to the Global Burden of Disease Study, low back pain ranks as the top cause of years lived with disability globally, while neck pain also contributes substantially [ 3 ]. Epidemiological studies indicate that spinal pain, particularly in the lumbar and cervical regions, affects the majority of adults at some stage of life, often becoming chronic and resulting in functional impairment and reduced quality of life [ 1 , 4 ]. To evaluate these conditions, patient-reported outcome measures (PROMs) are widely used in both clinical practice and research, providing direct information on the impact of symptoms on function and quality of life [ 5 , 6 ]. Among the most common instruments, the Roland–Morris Disability Questionnaire (RMDQ) [ 5 , 7 ] and the Oswestry Disability Index (ODI) focus on regional spinal dysfunction [ 8 ]. However, they do not assess spinal functionality as a single kinetic chain and thus have limited applicability in patients with multi-regional symptoms [ 9 , 10 ]. The Spine Functional Index (SFI) was developed to overcome these limitations, providing a whole-spine assessment of functional capacity rather than restricting evaluation to regional segments. The SFI conceptualizes the spine as a single kinetic chain, integrating cervical, thoracic, and lumbar regions to capture multi-segmental dysfunction and compensatory patterns relevant to everyday activities [ 11 ]. Subsequent cross-cultural adaptations into Spanish [ 12 ], Persian [ 13 ], Korean [ 14 ], Turkish [ 15 ], Chinese [ 16 ], and Polish [ 17 ], have demonstrated satisfactory psychometric properties. More recently, a shortened version, the SFI-10, was introduced, retaining strong validity and reliability while reducing respondent burden [ 18 ]. In clinical settings, it offers a brief, reliable, and valid measure that can be used to monitor patients with diverse spinal pathologies, particularly in individuals with symptoms spanning multiple spinal regions, for whom regional PROMs such as the ODI or RMDQ may be insufficient [ 9 ]. In research, it provides an outcome measure aligned with international standards [ 19 , 20 ], enabling cross-cultural comparisons and participation in multicentre studies. In Greece, epidemiological studies confirm similar patterns, with spinal pain affecting a large proportion of adults and leading to chronic pain syndromes that reduce quality of life and increase healthcare utilisation. The prevalence of chronic low back pain in the Greek population has been estimated at approximately 30%, consistent with global findings [ 21 ]. These data underscore the need for reliable and valid assessment tools to evaluate the functional impact of spinal disorders in the Greek population, both for clinical management and research applications. Although the SFI and its shortened version, the SFI-10, have been successfully validated in multiple languages [ 12 , 13 , 14 , 15 , 16 , 17 , 22 ], no validated version has been available for Greek-speaking populations. This represents a significant gap, given the high prevalence of musculoskeletal spinal disorders in Greece [ 21 ] and the absence of culturally adapted tools that assess spinal functionality as a whole. Therefore, the purpose of this study was to translate, cross-culturally adapt, and validate the SFI-10 for Greek-speaking patients with musculoskeletal spinal disorders, in accordance with established international guidelines for the cross-cultural adaptation and validation of patient-reported outcome measures [ 19 , 20 ]. 2. Methods 2.1 Study Design and ethics This study followed established methodological standards for the cross-cultural adaptation and validation of patient-reported outcome measures, including the COSMIN guidelines for evaluating measurement properties [ 19 , 20 ]. A quantitative, cross-sectional design was used, incorporating translation, cross-cultural adaptation, and psychometric evaluation of the Spine Functional Index short form (SFI-10), including test–retest assessment over a 7-day interval. The study was conducted in Athens, Greece, and complied with the Declaration of Helsinki [ 23 ]. Ethical approval was obtained from the relevant institutional research ethics committee. Permission to translate and adapt the SFI-10 was obtained from the original developers. All participants provided written informed consent prior to participation. 2.2 Setting, participants and eligibility All participants were adult Greek-speaking individuals diagnosed with musculoskeletal spine disorders (e.g. low back pain, neck pain), presenting with chronic spinal pain (≥ 3 months) and a pain intensity ≥ 3 on the Numeric Pain Rating Scale (NPRS) [ 24 ]. Patients who had undergone recent spinal surgery (< 6 months), had neurological or systemic inflammatory disorders, lacked a medical diagnosis, or presented with cognitive impairment were excluded. Participants were all volunteers, recruited through contact with orthopaedic clinics, physiotherapy centers, and rehabilitation units within the region of Attica. A minimum sample size of 100 participants was required, in line with the recommended criteria for factor analysis and validation studies [ 25 ]. Of the 116 individuals initially recruited, six were excluded due to incomplete questionnaires. For test-retest reliability, all remaining participants (n = 110) completed the SFI-10 again after a 7-day interval, without having received any treatment in the meantime. To standardise the procedure and ensure the highest possible level of comparability of the collected data, standardised instructions were used to safeguard measurement accuracy. Likewise, data collection was conducted anonymously to protect participants’ privacy [ 26 ]. The statistical analyses were conducted using the Jamovi statistical software [ 27 ] to verify reliability, factor structure, and measurement error. The integration of established PROMs ensures the relevance of the SFI-10 in both clinical and research settings for Greek-speaking populations, with the ultimate goal of cross-cultural adaptation and validation of the short version of the Spine Functional Index (SFI-10) for Greek patients with musculoskeletal spinal disorders. 2.3 Index measures The Spine Functional Index (SFI) evaluates whole-spine function across daily activities; items are rated on a 3-point scale and aggregated to a total score (higher scores indicate better function; range 0–100). The short form SFI-10 preserves content coverage with reduced respondent burden; scoring mirrors the full form and is reported as total [ 18 ]. 2.4 Comparator measures Convergent validity was examined using the NPRS for pain intensity (0–10) [ 24 ], the EQ-5D-5L for health-related quality of life (index and VAS) [ 28 ], and the SF-BPI for pain impact and severity [ 29 ]. Higher scores indicate worse pain sensation, interference, impact and worse pain impact on quality of life; all instruments were used according to their manuals (Table 2.1 ). For the EQ-5D-5L, it has to be noted that it uses value sets, which assign weights to each health profile. These values, usually derived from population preference studies, enable the conversion of data into quality-adjusted life years (QALYs) and their use in economic evaluations. Consequently, results of the EQ-5D-5L may vary depending on the country and cultural differences. The above characteristics make EQ-5D-5L suitable for evaluating the effectiveness of therapeutic interventions and for application across a wide range of conditions, including physiotherapy and rehabilitation [ 28 ]. Although an official Greek translation of the EQ-5D-5L is provided by its developers through their website ( https://euroqol.org/ ), no value set is currently available for the Greek population. Thus, the Italian value set was applied, consistent with previous research using culturally comparable populations [ 30 , 31 ]. Table 2.1 Data collection tools Variable/Measure Question/Scale Categories/N items Source Spinal Functionality Short version of the Spinal Functionality Index (SFI-10) 10 items, score between 0–1 (in 0.5 increments), with lower scores indicating higher functionality Gabel et al., 2024 Pain Intensity Numeric Pain Rating Scale (NPRS) 1 item, score between 0–10 (in 1-point increments), with higher scores indicating greater pain intensity Jensen, 2015 General Pain Assessment and Impact Brief Pain Inventory - Short Form (SF-BPI) 10 items, score between 0–10 (in 1-point increments), with higher scores indicating greater pain impact on the individual Jumbo et al., 2020 Overall Health Assessment Health Questionnaire (EQ-5D-5L) 5 items, score between 1–5 (in 1-point increments), with higher scores indicating greater problems Devlin, Pickard & Busschbach, 2022 2.5 Translation and cross-cultural adaptation The translation and cross-cultural adaptation of the SFI-10 followed a standardized multistep process [ 26 ]: (1) two independent forward translations by native Greek speakers; (2) reconciliation; (3) two independent back-translations blinded to the original version; (4) expert committee review (methodologists, clinicians, translators) to ensure semantic, idiomatic, experiential, and conceptual equivalence; and (5) pre-final cognitive testing in 20 individuals using think-aloud and probing. Minor wording refinements were made and the final Greek version was established after achieving satisfactory item comprehension. This process is aligned with the best practices proposed by the International Society for Quality of Life Research (ISPOR) for ensuring cultural equivalence [ 32 ]. 2.6 Procedures At baseline, participants completed demographic data, the SFI-10, and comparator measures in a standardized order. All participants repeated the SFI-10 after 7 days, without intervening treatment, to evaluate reproducibility. 2.7 Statistical analysis Descriptive statistics were calculated using means and standard deviations (SD), for normally distributed variables, and medians and interquartile ranges (IQR), for non-normally distributed data [ 33 ]. Test-retest reliability was assessed (participants completed the scale twice, with a 7-day interval) by calculating the Intraclass Correlation Coefficient (ICC 2,1 , two-way random-effects model, single measures) with desirable reliability levels set at ICC 2,1 ≥ 0.75 [ 34 , 35 ]. From ICC 2,1 , the Standard Error of Measurement (SEM) and the Minimal Detectable Change at 90% confidence (MDC 90 ) were derived [ 36 , 37 ]. Internal consistency was evaluated using Cronbach’s alpha (α), with acceptable levels defined as α ≥ 0.70 [ 38 ]. Convergent validity was examined using Pearson’s correlation coefficient (r), between SFI-10 scores and comparator measures. Correlation values of 0.10–0.29 were considered weak, 0.30–0.49 moderate, and ≥ 0.50 strong [ 39 , 40 ]. Responsiveness was explored using Cohen’s d and the Standardised Response Mean (SRM) [ 41 ]. Finally, Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) were performed to evaluate the structural validity of the Greek version of the SFI-10. CFA was conducted using the Diagonally Weighted Least Squares (DWLS) method, appropriate for ordinal data [ 42 ]. Fit indices included the Comparative Fit Index (CFI), Root Mean Square Error of Approximation (RMSEA), and Standardised Root Mean Square Residual (SRMR). Floor and ceiling effects were also assessed, ensuring that 0.90 and RMSEA < 0.08 were considered indicative of acceptable model fit [ 36 , 43 ]. EFA was conducted using the Kaiser-Meyer-Olkin (KMO) test of sampling adequacy and Bartlett’s test of sphericity, with factor extraction based on eigenvalues > 1. Factor loadings ≥ 0.40 were considered acceptable [ 44 ]. All analyses were performed using the Jamovi software (v2.3.28) [ 27 ], except for the EQ-5D-5L scoring, which was conducted in IBM SPSS Statistics (v17.0) [ 45 ]. Using the Italian value set algorithm, provided by the EuroQol Group [ 46 ]. Statistical significance was set at α = 0.05. 3. Results 3.1 Sample characteristics The final sample consisted of 110 adults (54 men, 56 women) with musculoskeletal spine disorders, with a mean age of 47.9 ± 17.7 years (range 18–84). Low back pain and lumbar disc herniation were the most frequently reported conditions [ 1 , 4 ]. Detailed demographic and clinical characteristics are presented in Table 3.1 , Table 3.1 Characteristics of participants (n = 110) Sex, % (n) Female 50.9% (56) Male 49.1% (54) Age (M, SD) 47.9 (17.7) Type/Origin of Spinal Disorder Low back pain 25.5% (28) Lumbar disc herniation 20.9% (23) Road traffic accident 10.0% (11) Neck pain 9.1% (10) Osteoporosis 8.2% (9) Fall 7.3% (8) Sports injury 6.4% (7) Pain from standing 3.6% (4) Pain related to large breasts 3.6% (4) Scoliosis 2.7% (3) Cervical syndrome 1.8% (2) Spondylolisthesis 0.9% (1) Notes: SD = Standard Deviation; M = Mean; n = number of participants. 3.2 Reliability and measurement error Internal consistency of the Greek SFI-10 was acceptable, with a Cronbach’s alpha of 0.794. Test–retest reliability over a 7-day interval was excellent (ICC 2,1 = 0.955) (Table 3.2 ). Measurement error was low, with a standard error of measurement (SEM) of 0.403 (with SD = 1.90) and a minimal detectable change at the 90% confidence level (MDC 90 ) of 0.935. Table 3.2 Results of Intraclass Correlation Coefficient (ICC 2,1 ) analysis Model One-way random Reference Agreement Coefficient Type ICC 95% Confidence Intervals Lower Upper Two-way random Agreement ICC1 0.954 0.938 0.967 Two-way fixed Consistency ICC2 0.955 0.937 0.967 One-way random Average Agreement ICC3 0.957 0.941 0.968 Two-way random Average Agreement ICC1k 0.977 0.968 0.983 Two-way fixed Average Consistency ICC2k 0.977 0.967 0.983 Model Reference Type 0.978 0.970 0.984 3.3 Convergent Validity Convergent validity was supported by statistically significant correlations between the SFI-10 and comparator measures. Although the distribution of the SFI-10 scores was not perfectly normal, Pearson’s correlation was deemed appropriate given the adequate sample size (n = 110) and the robustness of the coefficient against minor deviations from normality [ 39 , 40 ]. The results were as follows: SF-BPI Pain Interference (r = 0.819), SF-BPI Pain Severity (r = 0.628), NPRS (r = 0.634), and EQ-5D-5L (r = − 0.722). In all measurements the degrees of freedom were df = 108 and p-value < 0.001. All correlations were statistically significant (p < 0.001). 3.4 Responsiveness To evaluate the responsiveness of the SFI-10, a statistical comparison was performed between the SFI_Total_1 and SFI_Total_2 measurements by calculating Cohen’s d and the Standardised Response Mean (SRM) [ 37 , 41 ]. The results were: Cohen’s d = -0.239 and SRM = 0.239 (Table 3.3 ). As no therapeutic intervention occurred between measurements, the observed responsiveness reflects measurement stability over time rather than clinical change. Table 3.3 Responsiveness of the Greek version of the SFI-10 to change Statistical Analysis Value Cohen’s d -0.239 Standardised Response Mean (SRM) 0.239 Variable Mean SD Median Minimum Maximum SFI_Total_1 3.16 1.90 2.50 0.50 9.00 SFI_Total_2 3.02 1.82 2.00 0.00 8.50 Difference (Mean) 0.136 0.570 – -1.50 1.00 3.5 Exploratory Factor Analysis (EFA) The EFA was conducted using the “Factor” module in Jamovi, employing Principal Axis Factoring as the extraction method and oblimin rotation, due to the presumed correlation between potential factors [ 47 ]. Prior to running the EFA, data suitability was assessed. The Kaiser–Meyer–Olkin (KMO) index (Table 3.4 ) was 0.863, which is categorised as “meritorious” [ 48 ], indicating excellent sampling adequacy for factor analysis. Furthermore, Bartlett’s Test of Sphericity was statistically significant (χ² = 299, df = 45, p < 0.001), confirming that correlations among variables were adequate for EFA. Table 3.4 Kaiser–Meyer–Olkin (KMO) measure Variable MSA Overall 0.770 SFI10_1_Q1 0.860 SFI10_1_Q2 0.589 SFI10_1_Q3 0.825 SFI10_1_Q4 0.726 SFI10_1_Q5 0.775 SFI10_1_Q6 0.716 SFI10_1_Q7 0.822 SFI10_1_Q8 0.708 SFI10_1_Q9 0.674 SFI10_1_Q10 0.885 The analysis revealed one factor with an eigenvalue > 1, specifically 4.96, which explained 49.6% of the total variance (Fig. 3.1 ). The decision to retain a single factor was supported by both Kaiser’s criterion (eigenvalue > 1) and inspection of the scree plot, which showed a clear “elbow” after the first factor. This unidimensional solution is consistent with the theoretical structure of the instrument, which was designed to capture a single construct of spinal functionality. Factor loadings for most items were satisfactory (> 0.40), as shown in Table 3.5 . Items with lower loadings were retained to preserve content validity, as the instrument was designed to assess whole-spine functionality across diverse daily activities. Table 3.5 Factor loadings analysis Item Factor 1 Uniqueness SFI-10 1st assessment Q1 0.738 0.456 SFI-10 1st assessment Q2 – 0.936 SFI-10 1st assessment Q3 0.697 0.514 SFI-10 1st assessment Q4 – 0.926 SFI-10 1st assessment Q5 – 0.893 SFI-10 1st assessment Q6 0.474 0.775 SFI-10 1st assessment Q7 0.583 0.660 SFI-10 1st assessment Q8 0.661 0.563 SFI-10 1st assessment Q9 0.647 0.582 SFI-10 1st assessment Q10 0.614 0.623 Note : Factor loadings below 0.40 are not displayed, as this threshold was applied during the analysis. 3.6 Confirmatory Factor Analysis (CFA) and Fit Indices To confirm the unidimensional structure of the Spine Functionality Index (SFI-10), a Confirmatory Factor Analysis (CFA) was conducted in Jamovi (Structural Equation Modelling module), with the aim of statistically validating the model identified through the exploratory factor analysis. Since the items of the instrument are ordinal (each response can take three values: 0–0.5–1), the Diagonally Weighted Least Squares (DWLS) estimation method was applied [ 42 , 49 ]. The model tested included a single latent factor (“Functionality”) loading on ten observed variables (SFI10_1_Q1 to SFI10_1_Q10). The results were as follows: χ² = 28.3, df = 35, p = 0.782 (Table 3.6 ), RMSEA = 0.000, RMSEA p = 0.957, SRMR = 0.069 (Table 3.7 ), CFI = 1.000, and TLI = 1.022 (Table 3.8 , Fig. 3.2 ). Table 3.6 Models tested Label X² df p User Model 28.3 35 0.782 Baseline Model 433.0 45 < .001 Table 3.7 Fit indices 95% Confidence Intervals SRMR RMSEA Lower Upper RMSEA p 0.069 0.000 0.000 0.048 0.957 Table 3.8 Additional fit indices Model Value Comparative Fit Index (CFI) 1.000 Tucker-Lewis Index (TLI) 1.022 Bentler-Bonett Non-normed Fit Index (NNFI) 1.022 Relative Noncentrality Index (RNI) 1.017 Bentler-Bonett Normed Fit Index (NFI) 0.935 Bollen's Relative Fit Index (RFI) 0.916 Bollen's Incremental Fit Index (IFI) 1.017 4. Discussion 4.1 Main results synthesis This study translated, cross-culturally adapted, and validated the Greek version of the Spine Functional Index short form (SFI-10) in patients with musculoskeletal spine disorders. The findings demonstrated good internal consistency [ 50 ], excellent test–retest reliability [ 35 ], and strong convergent validity [ 51 ] with established measures of pain, pain-related interference, and health-related quality of life. These results indicate that the Greek SFI-10 has robust measurement properties and is suitable for assessing whole-spine function in Greek-speaking populations. Structural validity analyses supported a unidimensional structure, consistent with the theoretical framework of the original instrument. Both exploratory and confirmatory factor analyses [ 42 , 49 ], demonstrated an excellent model fit [ 43 , 52 ], confirming that the SFI-10 captures a single construct of spinal function, reinforcing its conceptual coherence and interpretability in clinical and research contexts. Responsiveness analyses demonstrated small effect sizes over the 7-day retest period, which was expected given the absence of therapeutic intervention. This finding suggests that the SFI-10 is stable over short periods without clinical change and is more appropriate for detecting functional improvement following treatment or over longer follow-up intervals. In physiotherapy practice, this characteristic supports its use for monitoring outcomes across treatment episodes rather than short-term reassessment without intervention [ 37 , 41 ]. 4.2 Context within the current literature The psychometric performance of the Greek SFI-10 is consistent with the results of previous cross-cultural adaptations of the instrument. Internal consistency in our study (Cronbach’s α = 0.794) was slightly lower but still acceptable compared with the Spanish (α = 0.85; [ 12 ]), Turkish (α = 0.85; [ 15 ]), Persian (α = 0.81; [ 13 ]), Korean (α = 0.91; [ 14 ]), Chinese (α = 0.91; [ 16 ]), Polish (α = 0.91; [ 17 ]), and Brazilian (α = 0.864; [ 22 ]) versions. This indicates a satisfactory level of homogeneity among the items in all language versions, confirming the stability of the questionnaire’s structure across diverse populations. Test–retest reliability in the present study (ICC 2,1 = 0.955) was particularly strong, comparable with the original SFI validation (ICC 2,1 = 0.97) [ 11 ] and aligned with, or exceeded, values reported in earlier validations, indicating strong measurement stability: Spanish (ICC 2,1 = 0.96) [ 12 ], Turkish (ICC 2,1 = 0.95) [ 15 ], Persian (ICC 2,1 = 0.96) [ 13 ], Chinese (ICC 2,1 = 0.96) [ 16 ], and Polish (ICC 2,1 = 0.97) [ 17 ]. Convergent validity findings were also comparable with those reported in other adaptations, where the SFI demonstrated strong associations with region-specific disability measures and pain-related outcomes. The observed correlations with pain intensity, pain interference, and health-related quality of life confirm that the Greek SFI-10 captures functional impairment relevant to patients with musculoskeletal spine disorders. The unidimensional structure identified in the present study is consistent with the original validation and several subsequent adaptations, further supporting the construct validity of the short-form SFI as a measure of whole-spine function. 4.3 Strengths and clinical applicability This study provides the first validated Greek version of a whole-spine patient reported outcome measure, suitable for use in physiotherapy practice. The brevity of the SFI-10 reduces respondent burden while maintaining strong measurement properties, making it feasible for routine clinical use [ 18 ]. Its whole-spine approach is particularly valuable in patients presenting with multi-regional spinal symptoms, a common presentation in physiotherapy, where region-specific instruments may not fully capture functional limitations. The availability of a validated Greek SFI-10 also facilitates participation in multicentre and cross-cultural research and supports the use of standardised outcome measures in both clinical and research settings. 4.4 Limitations and prospects for future research Several limitations should be acknowledged. Participants were recruited from a single geographic region, which may limit generalisability to the broader Greek population. Future studies should include more diverse samples to confirm the stability of the instrument across settings. Although cognitive testing was performed during the adaptation process, a fully structured cognitive debriefing procedure was not implemented [ 32 , 53 ]. Future research incorporating in-depth patient interviews could further strengthen evidence for content and face validity [ 54 ]. Responsiveness was assessed over a short retest interval without intervention, resulting in small effect sizes - an expected outcome given the limited time for clinical change [ 37 , 41 ]. Longitudinal studies evaluating responsiveness following physiotherapy interventions are needed, as well as studies aimed at establishing minimal clinically important differences (MCID). Finally, the use of a non-Greek EQ-5D-5L value set [ 30 , 31 ] may have influenced some validity estimates, although this approach was necessary due to the absence of a Greek-specific value set. 5. Conclusion This study provides the first validated Greek version of the 10-item Spine Functional Index (SFI-10) for Greek-speaking patients with musculoskeletal spine disorders. The findings support the Greek SFI-10 as a valid and reliable patient-reported outcome measure for assessing whole-spine function [ 11 , 18 ]. Its concise format and whole-spine approach make the SFI-10 particularly suitable for physiotherapy practice, especially in patients with multi-regional spinal symptoms where region-specific instruments may be insufficient. The availability of a culturally adapted Greek version enables its use in routine clinical assessment and supports the inclusion of Greek-speaking populations in cross-cultural and multicentre research. Future studies should investigate responsiveness following physiotherapy interventions, establish minimal clinically important differences, and confirm the instrument’s applicability in broader and more diverse Greek populations Declarations Supplementary Information Supplementary material associated with this article includes the final Greek version of the 10-item Spine Functional Index (SFI-10) (Supplementary Material 1). Ethical Approval Ethical approval for this study was obtained from the relevant institutional research ethics committee with the relevant reference number. All participants provided written informed consent prior to participation. Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Conflict of interest The authors declare no competing interests. References Hartvigsen J, Hancock MJ, Kongsted A, Louw Q, Ferreira ML, Genevay S, et al. What low back pain is and why we need to pay attention. Vol. 391, The Lancet. Lancet Publishing Group; 2018. p. 2356–67. World Health Organization. Musculoskeletal health . 2022 Jul 14 cited 2026. Available from: https://www.who.int/news-room/fact-sheets/detail/musculoskeletal-conditions Wu A, March L, Zheng X, Huang J, Wang X, Zhao J, et al. Global low back pain prevalence and years lived with disability from 1990 to 2017: estimates from the Global Burden of Disease Study 2017. 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WMA DECLARATION OF HELSINKI-ETHICAL PRINCIPLES FOR MEDICAL RESEARCH INVOLVING HUMAN PARTICIPANTS GENERAL PRINCIPLES. Jensen MP. Hypnosis for Chronic Pain Management: Therapist Guide. Hypnosis for Chronic Pain Management: Therapist Guide. Oxford University Press; 2015. Terwee CB, Mokkink LB, Knol DL, Ostelo RWJG, Bouter LM, De Vet HCW. Rating the methodological quality in systematic reviews of studies on measurement properties: A scoring system for the COSMIN checklist. Vol. 21, Quality of Life Research. 2012. p. 651–7. Galanis P. Translation and cross-cultural adaptation methodology. Arch Hellenic Med . 2019;36(1):124–135. The jamovi project. jamovi. Version 2.3; 2022. Devlin N, Pickard S, Busschbach J. The development of the EQ-5D-5L and its value sets. In: Value Sets for EQ-5D-5L: A Compendium, Comparative Review & User Guide. Springer International Publishing; 2022. p. 1–12. Jumbo SU, MacDermid JC, Kalu ME, Packham TL, Athwal GS, Faber KJ. Measurement properties of the brief pain inventory- short form (BPI-SF) and the revised short mcgill pain questionnaire-version-2 (SF-MPQ-2) in pain-related musculoskeletal conditions: A systematic review protocol. Vol. 8, Archives of Bone and Joint Surgery. Mashhad University of Medical Sciences; 2020. p. 131–41. Roudijk B, Janssen B, Olsen JA. How do EQ-5D-5L value sets differ? In: Value Sets for EQ-5D-5L: A Compendium, Comparative Review & User Guide. Springer International Publishing; 2022. p. 235–58. Scalone L, Cortesi PA, Ciampichini R, Belisari A, D’Angiolella LS, Cesana G, et al. Italian population-based values of EQ-5D health states. Value in Health. 2013 Jul;16(5):814–22. Wild D, Grove A, Martin M, Eremenco S, McElroy S, Verjee-Lorenz A, et al. Volume 8 • Number 2 • 2005 V A L U E I N H E A L T H Principles of Good Practice for the Translation and Cultural Adaptation Process for Patient-Reported Outcomes (PRO) Measures: Report of the ISPOR Task Force for Translation and Cultural Adaptation Background and Rationale [Internet]. 2005. Available from: http://www.ispor.org Field A. Discovering Statistics Using IBM SPSS Statistics. 2018. McGraw KO, Wong SP. Forming Inferences about Some Intraclass Correlation Coefficients. Psychol Methods. 1996;1(1):30–46. Koo TK, Li MY. A Guideline of Selecting and Reporting Intraclass Correlation Coefficients for Reliability Research. J Chiropr Med. 2016 Jun 1;15(2):155–63. Schermelleh-Engel K, Moosbrugger H, Müller H. Evaluating the Fit of Structural Equation Models: Tests of Significance and Descriptive Goodness-of-Fit Measures. Vol. 8, Methods of Psychological Research Online. 2003. Haley SM, Fragala-Pinkham MA. Interpreting Change Scores of Tests and Measures Used in Physical Therapy [Internet]. Vol. 86, Physical Therapy. 2006. Available from: https://academic.oup.com/ptj/article/86/5/735/2857473 Tavakol M, Dennick R. Making sense of Cronbach’s alpha. Vol. 2, International journal of medical education. 2011. p. 53–5. Havlicek LL, Peterson NL. Effect of the Violation of Assumptions Upon Significance Levels of the Pearson r. Vol. 84, Psychological Bulletin. 1977. Norman G. Likert scales, levels of measurement and the “laws” of statistics. Advances in Health Sciences Education. 2010 Dec;15(5):625–32. Liang MH, Fossel AH, Larson MG. Comparisons of Five Health Status Instruments for Orthopedic Evaluation. Vol. 28, Care. 1990. Li CH. Confirmatory factor analysis with ordinal data: Comparing robust maximum likelihood and diagonally weighted least squares. Behav Res Methods. 2016 Sep 1;48(3):936–49. Hu LT, Bentler PM. Cutoff criteria for fit indexes in covariance structure analysis: Conventional criteria versus new alternatives. Structural Equation Modeling. 1999;6(1):1–55. Hair J. F. BW, C, BBJ, ARE. hair et al 2010 - Multivariate Data Analysis. 2010. IBM Corp. IBM SPSS Statistics for Windows . Version 17.0. Armonk, NY; 2008. EuroQol Foundation. EuroQol Group. 2025. Available from: https://euroqol.org Fabrigar LR, Wegener DT, Maccallum RC, Strahan EJ. Evaluating the Use of Exploratory Factor Analysis in Psychological Research. Vol. 4, Psychological Methods. 1999. Kaiser HF. AN INDEX OF FACTORIAL SIMPLICITY*. 1974. Brown TA. Confirmatory Factor Analysis for Applied Research Methodology in the Social Sciences [Internet]. 2015. Available from: www.guilford.com/MSS DeVellis RF. Scale Development Fourth Edition 2. 2017. Fayers PM, Machin D. Front Matter. In: Quality of Life. Wiley; 2007. Kline RB. Principles and Practice of Structural Equation Modeling. 2016. Beaton DE, Bombardier C, Guillemin F, Ferraz MB. Guidelines for the Process of Cross-Cultural Adaptation of Self-Report Measures. Vol. 25, SPINE. 2000. Gjersing L, Rm Caplehorn J, Clausen T. Cross-cultural adaptation of research instruments: language, setting, time and statistical considerations [Internet]. 2010. Available from: http://www.biomedcentral.com/1471-2288/10/13 Additional Declarations No competing interests reported. Supplementary Files SupplementaryMaterialGreekSFI10.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers invited by journal 11 Feb, 2026 Editor assigned by journal 10 Feb, 2026 Submission checks completed at journal 10 Feb, 2026 First submitted to journal 08 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8821715","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":589977810,"identity":"b085e28c-68e4-4571-8af8-0ddabaf6ec17","order_by":0,"name":"Konstantinos Fokas","email":"data:image/png;base64,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","orcid":"","institution":"Metropolitan College","correspondingAuthor":true,"prefix":"","firstName":"Konstantinos","middleName":"","lastName":"Fokas","suffix":""},{"id":589977812,"identity":"575d1008-6ee0-4ec8-944a-8648cd39c2c0","order_by":1,"name":"Anastasios Fotiou","email":"","orcid":"","institution":"Metropolitan College","correspondingAuthor":false,"prefix":"","firstName":"Anastasios","middleName":"","lastName":"Fotiou","suffix":""},{"id":589977813,"identity":"91ebc7a1-c825-4230-92bd-0bb0e55a4547","order_by":2,"name":"Christos Phil. Komissopoulos","email":"","orcid":"","institution":"Metropolitan College","correspondingAuthor":false,"prefix":"","firstName":"Christos","middleName":"Phil.","lastName":"Komissopoulos","suffix":""},{"id":589977814,"identity":"c6c35282-71ba-42d9-875b-e867ba4077e4","order_by":3,"name":"Konstantinos N. Papakonstantinou","email":"","orcid":"","institution":"Metropolitan College","correspondingAuthor":false,"prefix":"","firstName":"Konstantinos","middleName":"N.","lastName":"Papakonstantinou","suffix":""}],"badges":[],"createdAt":"2026-02-08 13:08:41","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8821715/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8821715/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102862363,"identity":"c38c8acf-48ac-4401-ab5e-3fccbe9b10a1","added_by":"auto","created_at":"2026-02-17 16:16:51","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":19515,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eFigure 3.1.\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e Eigenvalues\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.1.png","url":"https://assets-eu.researchsquare.com/files/rs-8821715/v1/a90b02b343ef7695a428c99a.png"},{"id":102862362,"identity":"0f4cb997-66d2-49df-9a14-55495337bf0c","added_by":"auto","created_at":"2026-02-17 16:16:51","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":33361,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eFigure 3.2. \u003c/strong\u003e\u003c/em\u003e\u003cem\u003eSchematic representation of factor loadings\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.2.png","url":"https://assets-eu.researchsquare.com/files/rs-8821715/v1/0b4e5dab772a2aa4147ba956.png"},{"id":102963524,"identity":"becea6e8-efa4-4db2-9d18-75f67788ff9a","added_by":"auto","created_at":"2026-02-19 04:18:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1379258,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8821715/v1/a075048f-cc85-4e75-b37a-4343719289cc.pdf"},{"id":102862361,"identity":"88438648-f7fc-4fdd-8af8-f62257cccbd6","added_by":"auto","created_at":"2026-02-17 16:16:51","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":95088,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterialGreekSFI10.docx","url":"https://assets-eu.researchsquare.com/files/rs-8821715/v1/1eb831e6495be0865a6c6b0a.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Translation, Cross-Cultural Adaptation and Validation of the 10-Item Spine Functional Index (SFI-10) for Greek Patients with Musculoskeletal Spine Disorders","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eMusculoskeletal disorders of the spine represent one of the leading causes of disability worldwide, contributing significantly to the global burden of disease and healthcare costs [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. According to the Global Burden of Disease Study, low back pain ranks as the top cause of years lived with disability globally, while neck pain also contributes substantially [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Epidemiological studies indicate that spinal pain, particularly in the lumbar and cervical regions, affects the majority of adults at some stage of life, often becoming chronic and resulting in functional impairment and reduced quality of life [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo evaluate these conditions, patient-reported outcome measures (PROMs) are widely used in both clinical practice and research, providing direct information on the impact of symptoms on function and quality of life [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Among the most common instruments, the Roland\u0026ndash;Morris Disability Questionnaire (RMDQ) [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] and the Oswestry Disability Index (ODI) focus on regional spinal dysfunction [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. However, they do not assess spinal functionality as a single kinetic chain and thus have limited applicability in patients with multi-regional symptoms [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe Spine Functional Index (SFI) was developed to overcome these limitations, providing a whole-spine assessment of functional capacity rather than restricting evaluation to regional segments. The SFI conceptualizes the spine as a single kinetic chain, integrating cervical, thoracic, and lumbar regions to capture multi-segmental dysfunction and compensatory patterns relevant to everyday activities [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Subsequent cross-cultural adaptations into Spanish [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], Persian [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], Korean [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], Turkish [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], Chinese [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], and Polish [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], have demonstrated satisfactory psychometric properties. More recently, a shortened version, the SFI-10, was introduced, retaining strong validity and reliability while reducing respondent burden [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In clinical settings, it offers a brief, reliable, and valid measure that can be used to monitor patients with diverse spinal pathologies, particularly in individuals with symptoms spanning multiple spinal regions, for whom regional PROMs such as the ODI or RMDQ may be insufficient [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. In research, it provides an outcome measure aligned with international standards [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], enabling cross-cultural comparisons and participation in multicentre studies.\u003c/p\u003e \u003cp\u003eIn Greece, epidemiological studies confirm similar patterns, with spinal pain affecting a large proportion of adults and leading to chronic pain syndromes that reduce quality of life and increase healthcare utilisation. The prevalence of chronic low back pain in the Greek population has been estimated at approximately 30%, consistent with global findings [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. These data underscore the need for reliable and valid assessment tools to evaluate the functional impact of spinal disorders in the Greek population, both for clinical management and research applications.\u003c/p\u003e \u003cp\u003eAlthough the SFI and its shortened version, the SFI-10, have been successfully validated in multiple languages [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], no validated version has been available for Greek-speaking populations. This represents a significant gap, given the high prevalence of musculoskeletal spinal disorders in Greece [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] and the absence of culturally adapted tools that assess spinal functionality as a whole. Therefore, the purpose of this study was to translate, cross-culturally adapt, and validate the SFI-10 for Greek-speaking patients with musculoskeletal spinal disorders, in accordance with established international guidelines for the cross-cultural adaptation and validation of patient-reported outcome measures [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Study Design and ethics\u003c/h2\u003e \u003cp\u003eThis study followed established methodological standards for the cross-cultural adaptation and validation of patient-reported outcome measures, including the COSMIN guidelines for evaluating measurement properties [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. A quantitative, cross-sectional design was used, incorporating translation, cross-cultural adaptation, and psychometric evaluation of the Spine Functional Index short form (SFI-10), including test\u0026ndash;retest assessment over a 7-day interval. The study was conducted in Athens, Greece, and complied with the Declaration of Helsinki [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Ethical approval was obtained from the relevant institutional research ethics committee. Permission to translate and adapt the SFI-10 was obtained from the original developers. All participants provided written informed consent prior to participation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Setting, participants and eligibility\u003c/h2\u003e \u003cp\u003eAll participants were adult Greek-speaking individuals diagnosed with musculoskeletal spine disorders (e.g. low back pain, neck pain), presenting with chronic spinal pain (\u0026ge;\u0026thinsp;3 months) and a pain intensity\u0026thinsp;\u0026ge;\u0026thinsp;3 on the Numeric Pain Rating Scale (NPRS) [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Patients who had undergone recent spinal surgery (\u0026lt;\u0026thinsp;6 months), had neurological or systemic inflammatory disorders, lacked a medical diagnosis, or presented with cognitive impairment were excluded. Participants were all volunteers, recruited through contact with orthopaedic clinics, physiotherapy centers, and rehabilitation units within the region of Attica.\u003c/p\u003e \u003cp\u003eA minimum sample size of 100 participants was required, in line with the recommended criteria for factor analysis and validation studies [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Of the 116 individuals initially recruited, six were excluded due to incomplete questionnaires. For test-retest reliability, all remaining participants (n\u0026thinsp;=\u0026thinsp;110) completed the SFI-10 again after a 7-day interval, without having received any treatment in the meantime. To standardise the procedure and ensure the highest possible level of comparability of the collected data, standardised instructions were used to safeguard measurement accuracy. Likewise, data collection was conducted anonymously to protect participants\u0026rsquo; privacy [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe statistical analyses were conducted using the Jamovi statistical software [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] to verify reliability, factor structure, and measurement error. The integration of established PROMs ensures the relevance of the SFI-10 in both clinical and research settings for Greek-speaking populations, with the ultimate goal of cross-cultural adaptation and validation of the short version of the Spine Functional Index (SFI-10) for Greek patients with musculoskeletal spinal disorders.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Index measures\u003c/h2\u003e \u003cp\u003eThe Spine Functional Index (SFI) evaluates whole-spine function across daily activities; items are rated on a 3-point scale and aggregated to a total score (higher scores indicate better function; range 0\u0026ndash;100). The short form SFI-10 preserves content coverage with reduced respondent burden; scoring mirrors the full form and is reported as total [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Comparator measures\u003c/h2\u003e \u003cp\u003eConvergent validity was examined using the NPRS for pain intensity (0\u0026ndash;10) [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], the EQ-5D-5L for health-related quality of life (index and VAS) [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], and the SF-BPI for pain impact and severity [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Higher scores indicate worse pain sensation, interference, impact and worse pain impact on quality of life; all instruments were used according to their manuals (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e2.1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFor the EQ-5D-5L, it has to be noted that it uses value sets, which assign weights to each health profile. These values, usually derived from population preference studies, enable the conversion of data into quality-adjusted life years (QALYs) and their use in economic evaluations. Consequently, results of the EQ-5D-5L may vary depending on the country and cultural differences. The above characteristics make EQ-5D-5L suitable for evaluating the effectiveness of therapeutic interventions and for application across a wide range of conditions, including physiotherapy and rehabilitation [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAlthough an official Greek translation of the EQ-5D-5L is provided by its developers through their website (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://euroqol.org/\u003c/span\u003e\u003cspan address=\"https://euroqol.org/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e), no value set is currently available for the Greek population. Thus, the Italian value set was applied, consistent with previous research using culturally comparable populations [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2.1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eData collection tools\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable/Measure\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eQuestion/Scale\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCategories/N items\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSource\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eSpinal Functionality\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eShort version of the Spinal Functionality Index (SFI-10)\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003e10 items, score between 0\u0026ndash;1 (in 0.5 increments), with lower scores indicating higher functionality\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eGabel et al., 2024\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ePain Intensity\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eNumeric Pain Rating Scale (NPRS)\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003e1 item, score between 0\u0026ndash;10 (in 1-point increments), with higher scores indicating greater pain intensity\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eJensen, 2015\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eGeneral Pain Assessment and Impact\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eBrief Pain Inventory - Short Form (SF-BPI)\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003e10 items, score between 0\u0026ndash;10 (in 1-point increments), with higher scores indicating greater pain impact on the individual\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eJumbo et al., 2020\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eOverall Health Assessment\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eHealth Questionnaire (EQ-5D-5L)\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003e5 items, score between 1\u0026ndash;5 (in 1-point increments), with higher scores indicating greater problems\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eDevlin, Pickard \u0026amp; Busschbach, 2022\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Translation and cross-cultural adaptation\u003c/h2\u003e \u003cp\u003eThe translation and cross-cultural adaptation of the SFI-10 followed a standardized multistep process [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]: (1) two independent forward translations by native Greek speakers; (2) reconciliation; (3) two independent back-translations blinded to the original version; (4) expert committee review (methodologists, clinicians, translators) to ensure semantic, idiomatic, experiential, and conceptual equivalence; and (5) pre-final cognitive testing in 20 individuals using think-aloud and probing. Minor wording refinements were made and the final Greek version was established after achieving satisfactory item comprehension. This process is aligned with the best practices proposed by the International Society for Quality of Life Research (ISPOR) for ensuring cultural equivalence [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Procedures\u003c/h2\u003e \u003cp\u003eAt baseline, participants completed demographic data, the SFI-10, and comparator measures in a standardized order. All participants repeated the SFI-10 after 7 days, without intervening treatment, to evaluate reproducibility.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.7 Statistical analysis\u003c/h2\u003e \u003cp\u003eDescriptive statistics were calculated using means and standard deviations (SD), for normally distributed variables, and medians and interquartile ranges (IQR), for non-normally distributed data [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTest-retest reliability was assessed (participants completed the scale twice, with a 7-day interval) by calculating the Intraclass Correlation Coefficient (ICC\u003csub\u003e2,1\u003c/sub\u003e, two-way random-effects model, single measures) with desirable reliability levels set at ICC\u003csub\u003e2,1\u003c/sub\u003e \u0026ge; 0.75 [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. From ICC\u003csub\u003e2,1\u003c/sub\u003e, the Standard Error of Measurement (SEM) and the Minimal Detectable Change at 90% confidence (MDC\u003csub\u003e90\u003c/sub\u003e) were derived [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eInternal consistency was evaluated using Cronbach\u0026rsquo;s alpha (α), with acceptable levels defined as α\u0026thinsp;\u0026ge;\u0026thinsp;0.70 [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eConvergent validity was examined using Pearson\u0026rsquo;s correlation coefficient (r), between SFI-10 scores and comparator measures. Correlation values of 0.10\u0026ndash;0.29 were considered weak, 0.30\u0026ndash;0.49 moderate, and \u0026ge;\u0026thinsp;0.50 strong [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eResponsiveness was explored using Cohen\u0026rsquo;s d and the Standardised Response Mean (SRM) [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFinally, Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) were performed to evaluate the structural validity of the Greek version of the SFI-10. CFA was conducted using the Diagonally Weighted Least Squares (DWLS) method, appropriate for ordinal data [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. Fit indices included the Comparative Fit Index (CFI), Root Mean Square Error of Approximation (RMSEA), and Standardised Root Mean Square Residual (SRMR). Floor and ceiling effects were also assessed, ensuring that \u0026lt;\u0026thinsp;15% of participants achieved extreme scores. CFI values\u0026thinsp;\u0026gt;\u0026thinsp;0.90 and RMSEA\u0026thinsp;\u0026lt;\u0026thinsp;0.08 were considered indicative of acceptable model fit [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eEFA was conducted using the Kaiser-Meyer-Olkin (KMO) test of sampling adequacy and Bartlett\u0026rsquo;s test of sphericity, with factor extraction based on eigenvalues\u0026thinsp;\u0026gt;\u0026thinsp;1. Factor loadings\u0026thinsp;\u0026ge;\u0026thinsp;0.40 were considered acceptable [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAll analyses were performed using the Jamovi software (v2.3.28) [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], except for the EQ-5D-5L scoring, which was conducted in IBM SPSS Statistics (v17.0) [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. Using the Italian value set algorithm, provided by the EuroQol Group [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. Statistical significance was set at α\u0026thinsp;=\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Sample characteristics\u003c/h2\u003e \u003cp\u003eThe final sample consisted of 110 adults (54 men, 56 women) with musculoskeletal spine disorders, with a mean age of 47.9\u0026thinsp;\u0026plusmn;\u0026thinsp;17.7 years (range 18\u0026ndash;84). Low back pain and lumbar disc herniation were the most frequently reported conditions [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Detailed demographic and clinical characteristics are presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e3.1\u003c/span\u003e,\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3.1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacteristics of participants (n\u0026thinsp;=\u0026thinsp;110)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex, % (n)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e50.9% (56)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e49.1% (54)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAge (M, SD)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e47.9 (17.7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eType/Origin of Spinal Disorder\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLow back pain\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e25.5% (28)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLumbar disc herniation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e20.9% (23)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRoad traffic accident\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e10.0% (11)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNeck pain\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9.1% (10)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOsteoporosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.2% (9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFall\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.3% (8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSports injury\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6.4% (7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePain from standing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.6% (4)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePain related to large breasts\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.6% (4)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eScoliosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.7% (3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCervical syndrome\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.8% (2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpondylolisthesis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.9% (1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003eNotes: SD\u0026thinsp;=\u0026thinsp;Standard Deviation; M\u0026thinsp;=\u0026thinsp;Mean; n\u0026thinsp;=\u0026thinsp;number of participants.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Reliability and measurement error\u003c/h2\u003e \u003cp\u003eInternal consistency of the Greek SFI-10 was acceptable, with a Cronbach\u0026rsquo;s alpha of 0.794. Test\u0026ndash;retest reliability over a 7-day interval was excellent (ICC\u003csub\u003e2,1\u003c/sub\u003e = 0.955) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3.2\u003c/span\u003e). Measurement error was low, with a standard error of measurement (SEM) of 0.403 (with SD\u0026thinsp;=\u0026thinsp;1.90) and a minimal detectable change at the 90% confidence level (MDC\u003csub\u003e90\u003c/sub\u003e) of 0.935.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3.2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eResults of Intraclass Correlation Coefficient (ICC\u003csub\u003e2,1\u003c/sub\u003e) analysis\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eModel\u003c/p\u003e \u003cp\u003eOne-way random\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003cp\u003eAgreement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCoefficient Type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eICC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e95% Confidence Intervals\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLower\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eUpper\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTwo-way random\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAgreement\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eICC1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.954\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.938\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.967\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTwo-way fixed\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eConsistency\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eICC2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.955\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.937\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.967\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOne-way random\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAverage Agreement\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eICC3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.957\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.941\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.968\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTwo-way random\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAverage Agreement\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eICC1k\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.977\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.968\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.983\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTwo-way fixed\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAverage Consistency\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eICC2k\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.977\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.967\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.983\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eModel\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eReference\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eType\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.978\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.970\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.984\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Convergent Validity\u003c/h2\u003e \u003cp\u003eConvergent validity was supported by statistically significant correlations between the SFI-10 and comparator measures. Although the distribution of the SFI-10 scores was not perfectly normal, Pearson\u0026rsquo;s correlation was deemed appropriate given the adequate sample size (n\u0026thinsp;=\u0026thinsp;110) and the robustness of the coefficient against minor deviations from normality [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. The results were as follows: SF-BPI Pain Interference (r\u0026thinsp;=\u0026thinsp;0.819), SF-BPI Pain Severity (r\u0026thinsp;=\u0026thinsp;0.628), NPRS (r\u0026thinsp;=\u0026thinsp;0.634), and EQ-5D-5L (r = \u0026minus;\u0026thinsp;0.722). In all measurements the degrees of freedom were df\u0026thinsp;=\u0026thinsp;108 and p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.001. All correlations were statistically significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Responsiveness\u003c/h2\u003e \u003cp\u003eTo evaluate the responsiveness of the SFI-10, a statistical comparison was performed between the SFI_Total_1 and SFI_Total_2 measurements by calculating Cohen\u0026rsquo;s d and the Standardised Response Mean (SRM) [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. The results were: Cohen\u0026rsquo;s d = -0.239 and SRM\u0026thinsp;=\u0026thinsp;0.239 (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e3.3\u003c/span\u003e). As no therapeutic intervention occurred between measurements, the observed responsiveness reflects measurement stability over time rather than clinical change.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3.3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eResponsiveness of the Greek version of the SFI-10 to change\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eStatistical Analysis\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eCohen\u0026rsquo;s d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e \u003cp\u003e-0.239\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eStandardised Response Mean (SRM)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e \u003cp\u003e0.239\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eVariable\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eMean\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eSD\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eMedian\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eMinimum\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eMaximum\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSFI_Total_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSFI_Total_2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDifference (Mean)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.136\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.570\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-1.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Exploratory Factor Analysis (EFA)\u003c/h2\u003e \u003cp\u003eThe EFA was conducted using the \u0026ldquo;Factor\u0026rdquo; module in Jamovi, employing Principal Axis Factoring as the extraction method and oblimin rotation, due to the presumed correlation between potential factors [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. Prior to running the EFA, data suitability was assessed. The Kaiser\u0026ndash;Meyer\u0026ndash;Olkin (KMO) index (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e3.4\u003c/span\u003e) was 0.863, which is categorised as \u0026ldquo;meritorious\u0026rdquo; [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e], indicating excellent sampling adequacy for factor analysis. Furthermore, Bartlett\u0026rsquo;s Test of Sphericity was statistically significant (χ\u0026sup2; = 299, df\u0026thinsp;=\u0026thinsp;45, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), confirming that correlations among variables were adequate for EFA.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3.4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eKaiser\u0026ndash;Meyer\u0026ndash;Olkin (KMO) measure\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMSA\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOverall\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.770\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI10_1_Q1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.860\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI10_1_Q2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.589\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI10_1_Q3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.825\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI10_1_Q4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.726\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI10_1_Q5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.775\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI10_1_Q6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.716\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI10_1_Q7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.822\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI10_1_Q8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.708\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI10_1_Q9\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.674\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI10_1_Q10\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.885\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe analysis revealed one factor with an eigenvalue\u0026thinsp;\u0026gt;\u0026thinsp;1, specifically 4.96, which explained 49.6% of the total variance (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e3.1\u003c/span\u003e). The decision to retain a single factor was supported by both Kaiser\u0026rsquo;s criterion (eigenvalue\u0026thinsp;\u0026gt;\u0026thinsp;1) and inspection of the scree plot, which showed a clear \u0026ldquo;elbow\u0026rdquo; after the first factor. This unidimensional solution is consistent with the theoretical structure of the instrument, which was designed to capture a single construct of spinal functionality.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFactor loadings for most items were satisfactory (\u0026gt;\u0026thinsp;0.40), as shown in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e3.5\u003c/span\u003e. Items with lower loadings were retained to preserve content validity, as the instrument was designed to assess whole-spine functionality across diverse daily activities.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3.5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eFactor loadings analysis\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eItem\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFactor\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eUniqueness\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI-10 1st assessment Q1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.738\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.456\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI-10 1st assessment Q2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.936\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI-10 1st assessment Q3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.697\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.514\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI-10 1st assessment Q4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.926\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI-10 1st assessment Q5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026ndash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.893\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI-10 1st assessment Q6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.474\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.775\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI-10 1st assessment Q7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.583\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.660\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI-10 1st assessment Q8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.661\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.563\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI-10 1st assessment Q9\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.647\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.582\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSFI-10 1st assessment Q10\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.614\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.623\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"3\"\u003e\u003cb\u003eNote\u003c/b\u003e: Factor loadings below 0.40 are not displayed, as this threshold was applied during the analysis.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Confirmatory Factor Analysis (CFA) and Fit Indices\u003c/h2\u003e \u003cp\u003eTo confirm the unidimensional structure of the Spine Functionality Index (SFI-10), a Confirmatory Factor Analysis (CFA) was conducted in Jamovi (Structural Equation Modelling module), with the aim of statistically validating the model identified through the exploratory factor analysis. Since the items of the instrument are ordinal (each response can take three values: 0\u0026ndash;0.5\u0026ndash;1), the Diagonally Weighted Least Squares (DWLS) estimation method was applied [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe model tested included a single latent factor (\u0026ldquo;Functionality\u0026rdquo;) loading on ten observed variables (SFI10_1_Q1 to SFI10_1_Q10). The results were as follows: χ\u0026sup2; = 28.3, df\u0026thinsp;=\u0026thinsp;35, p\u0026thinsp;=\u0026thinsp;0.782 (Table\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e3.6\u003c/span\u003e), RMSEA\u0026thinsp;=\u0026thinsp;0.000, RMSEA p\u0026thinsp;=\u0026thinsp;0.957, SRMR\u0026thinsp;=\u0026thinsp;0.069 (Table\u0026nbsp;\u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e3.7\u003c/span\u003e), CFI\u0026thinsp;=\u0026thinsp;1.000, and TLI\u0026thinsp;=\u0026thinsp;1.022 (Table\u0026nbsp;\u003cspan refid=\"Tab9\" class=\"InternalRef\"\u003e3.8\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3.2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab7\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3.6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eModels tested\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLabel\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eX\u0026sup2;\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003edf\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUser Model\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e28.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.782\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBaseline Model\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e433.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab8\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3.7\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eFit indices\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e95% Confidence Intervals\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSRMR\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eRMSEA\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eLower\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eUpper\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eRMSEA p\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.069\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.048\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.957\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab9\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3.8\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAdditional fit indices\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eModel\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eComparative Fit Index (CFI)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTucker-Lewis Index (TLI)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.022\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBentler-Bonett Non-normed Fit Index (NNFI)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.022\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRelative Noncentrality Index (RNI)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.017\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBentler-Bonett Normed Fit Index (NFI)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.935\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBollen's Relative Fit Index (RFI)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.916\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBollen's Incremental Fit Index (IFI)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.017\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Main results synthesis\u003c/h2\u003e \u003cp\u003eThis study translated, cross-culturally adapted, and validated the Greek version of the Spine Functional Index short form (SFI-10) in patients with musculoskeletal spine disorders. The findings demonstrated good internal consistency [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e], excellent test\u0026ndash;retest reliability [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e], and strong convergent validity [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e] with established measures of pain, pain-related interference, and health-related quality of life. These results indicate that the Greek SFI-10 has robust measurement properties and is suitable for assessing whole-spine function in Greek-speaking populations.\u003c/p\u003e \u003cp\u003eStructural validity analyses supported a unidimensional structure, consistent with the theoretical framework of the original instrument. Both exploratory and confirmatory factor analyses [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e], demonstrated an excellent model fit [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e], confirming that the SFI-10 captures a single construct of spinal function, reinforcing its conceptual coherence and interpretability in clinical and research contexts.\u003c/p\u003e \u003cp\u003eResponsiveness analyses demonstrated small effect sizes over the 7-day retest period, which was expected given the absence of therapeutic intervention. This finding suggests that the SFI-10 is stable over short periods without clinical change and is more appropriate for detecting functional improvement following treatment or over longer follow-up intervals. In physiotherapy practice, this characteristic supports its use for monitoring outcomes across treatment episodes rather than short-term reassessment without intervention [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Context within the current literature\u003c/h2\u003e \u003cp\u003eThe psychometric performance of the Greek SFI-10 is consistent with the results of previous cross-cultural adaptations of the instrument. Internal consistency in our study (Cronbach\u0026rsquo;s α\u0026thinsp;=\u0026thinsp;0.794) was slightly lower but still acceptable compared with the Spanish (α\u0026thinsp;=\u0026thinsp;0.85; [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]), Turkish (α\u0026thinsp;=\u0026thinsp;0.85; [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]), Persian (α\u0026thinsp;=\u0026thinsp;0.81; [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]), Korean (α\u0026thinsp;=\u0026thinsp;0.91; [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]), Chinese (α\u0026thinsp;=\u0026thinsp;0.91; [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]), Polish (α\u0026thinsp;=\u0026thinsp;0.91; [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]), and Brazilian (α\u0026thinsp;=\u0026thinsp;0.864; [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]) versions. This indicates a satisfactory level of homogeneity among the items in all language versions, confirming the stability of the questionnaire\u0026rsquo;s structure across diverse populations.\u003c/p\u003e \u003cp\u003eTest\u0026ndash;retest reliability in the present study (ICC\u003csub\u003e2,1\u003c/sub\u003e = 0.955) was particularly strong, comparable with the original SFI validation (ICC\u003csub\u003e2,1\u003c/sub\u003e = 0.97) [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] and aligned with, or exceeded, values reported in earlier validations, indicating strong measurement stability: Spanish (ICC\u003csub\u003e2,1\u003c/sub\u003e = 0.96) [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], Turkish (ICC\u003csub\u003e2,1\u003c/sub\u003e = 0.95) [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], Persian (ICC\u003csub\u003e2,1\u003c/sub\u003e = 0.96) [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], Chinese (ICC\u003csub\u003e2,1\u003c/sub\u003e = 0.96) [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], and Polish (ICC\u003csub\u003e2,1\u003c/sub\u003e = 0.97) [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eConvergent validity findings were also comparable with those reported in other adaptations, where the SFI demonstrated strong associations with region-specific disability measures and pain-related outcomes. The observed correlations with pain intensity, pain interference, and health-related quality of life confirm that the Greek SFI-10 captures functional impairment relevant to patients with musculoskeletal spine disorders.\u003c/p\u003e \u003cp\u003eThe unidimensional structure identified in the present study is consistent with the original validation and several subsequent adaptations, further supporting the construct validity of the short-form SFI as a measure of whole-spine function.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Strengths and clinical applicability\u003c/h2\u003e \u003cp\u003eThis study provides the first validated Greek version of a whole-spine patient reported outcome measure, suitable for use in physiotherapy practice. The brevity of the SFI-10 reduces respondent burden while maintaining strong measurement properties, making it feasible for routine clinical use [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Its whole-spine approach is particularly valuable in patients presenting with multi-regional spinal symptoms, a common presentation in physiotherapy, where region-specific instruments may not fully capture functional limitations.\u003c/p\u003e \u003cp\u003eThe availability of a validated Greek SFI-10 also facilitates participation in multicentre and cross-cultural research and supports the use of standardised outcome measures in both clinical and research settings.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Limitations and prospects for future research\u003c/h2\u003e \u003cp\u003eSeveral limitations should be acknowledged. Participants were recruited from a single geographic region, which may limit generalisability to the broader Greek population. Future studies should include more diverse samples to confirm the stability of the instrument across settings. Although cognitive testing was performed during the adaptation process, a fully structured cognitive debriefing procedure was not implemented [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e]. Future research incorporating in-depth patient interviews could further strengthen evidence for content and face validity [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eResponsiveness was assessed over a short retest interval without intervention, resulting in small effect sizes - an expected outcome given the limited time for clinical change [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Longitudinal studies evaluating responsiveness following physiotherapy interventions are needed, as well as studies aimed at establishing minimal clinically important differences (MCID).\u003c/p\u003e \u003cp\u003eFinally, the use of a non-Greek EQ-5D-5L value set [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] may have influenced some validity estimates, although this approach was necessary due to the absence of a Greek-specific value set.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThis study provides the first validated Greek version of the 10-item Spine Functional Index (SFI-10) for Greek-speaking patients with musculoskeletal spine disorders. The findings support the Greek SFI-10 as a valid and reliable patient-reported outcome measure for assessing whole-spine function [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIts concise format and whole-spine approach make the SFI-10 particularly suitable for physiotherapy practice, especially in patients with multi-regional spinal symptoms where region-specific instruments may be insufficient. The availability of a culturally adapted Greek version enables its use in routine clinical assessment and supports the inclusion of Greek-speaking populations in cross-cultural and multicentre research.\u003c/p\u003e \u003cp\u003eFuture studies should investigate responsiveness following physiotherapy interventions, establish minimal clinically important differences, and confirm the instrument\u0026rsquo;s applicability in broader and more diverse Greek populations\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eSupplementary Information\u003c/p\u003e\n\u003cp\u003eSupplementary material associated with this article includes the final Greek version of the 10-item Spine Functional Index (SFI-10) (Supplementary Material 1).\u003c/p\u003e\n\u003cp\u003eEthical Approval\u003c/p\u003e\n\u003cp\u003eEthical approval for this study was obtained from the relevant institutional research ethics committee with the relevant reference number. All participants provided written informed consent prior to participation.\u003c/p\u003e\n\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003eConflict of interest\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHartvigsen J, Hancock MJ, Kongsted A, Louw Q, Ferreira ML, Genevay S, et al. What low back pain is and why we need to pay attention. Vol. 391, The Lancet. Lancet Publishing Group; 2018. p. 2356\u0026ndash;67.\u003c/li\u003e\n\u003cli\u003eWorld Health Organization. \u003cstrong\u003eMusculoskeletal health\u003c/strong\u003e. 2022 Jul 14 cited 2026. Available from: https://www.who.int/news-room/fact-sheets/detail/musculoskeletal-conditions\u003c/li\u003e\n\u003cli\u003eWu A, March L, Zheng X, Huang J, Wang X, Zhao J, et al. 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Springer Science and Business Media Deutschland GmbH; 2023.\u003c/li\u003e\n\u003cli\u003eRoland and Morris 1983 - Roland, M., \u0026amp; Morris, R. (1983). A study of the natural history of back pain - Part 1 - Development of a reliable and sensitive measure of disability in low-back pain.\u003c/li\u003e\n\u003cli\u003eFairbank JCT, Pynsent PB. The Oswestry Disability Index. Vol. 25, Number. 2000.\u003c/li\u003e\n\u003cli\u003eLeahy E, Davidson M, Benjamin D, Wajswelner H. Patient-Reported Outcome (PRO) questionnaires for people with pain in any spine region. A systematic review. Vol. 22, Manual Therapy. Churchill Livingstone; 2016. p. 22\u0026ndash;30.\u003c/li\u003e\n\u003cli\u003eHartmann C, Liegl G, Rose M, Fischer F. Towards Standardized Assessment of Outcomes in Back Pain\u0026mdash;Validation of Linking Studies Between Disease-Specific and Generic Patient-Reported Outcome Measures. J Clin Med. 2024 Nov 1;13(21).\u003c/li\u003e\n\u003cli\u003eGabel CP, Melloh M, Burkett B, Michener LA. The Spine Functional Index: development and clinimetric validation of a new whole-spine functional outcome measure. Spine Journal. 2019 Feb 1;19(2):e19\u0026ndash;27.\u003c/li\u003e\n\u003cli\u003eCuesta-Vargas AI, Gabel CP. Validation of a Spanish version of the Spine Functional Index. Health Qual Life Outcomes. 2014 Jun 27;12(1).\u003c/li\u003e\n\u003cli\u003eMokhtarinia HR, Hosseini A, Maleki-Ghahfarokhi A, Gabel CP, Zohrabi M. Cross-cultural adaptation, validity, and reliability of the Persian version of the spine functional index. Health Qual Life Outcomes. 2018 May 15;16(1).\u003c/li\u003e\n\u003cli\u003eIn TS. The reliability and validity of the Korean version of the spine functional index. 2017 Jun.\u003c/li\u003e\n\u003cli\u003eTonga E, Gabel CP, Karayazgan S, Cuesta-Vargas AI. 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BMC Musculoskelet Disord. 2024 Dec 1;25(1).\u003c/li\u003e\n\u003cli\u003eMokkink LB, Terwee CB, Patrick DL, Alonso J, Stratford PW, Knol DL, et al. The COSMIN checklist for assessing the methodological quality of studies on measurement properties of health status measurement instruments: An international Delphi study. Quality of Life Research. 2010 May;19(4):539\u0026ndash;49.\u003c/li\u003e\n\u003cli\u003ePrinsen CAC, Mokkink LB, Bouter LM, Alonso J, Patrick DL, de Vet HCW, et al. COSMIN guideline for systematic reviews of patient-reported outcome measures. Quality of Life Research. 2018 May 1;27(5):1147\u0026ndash;57.\u003c/li\u003e\n\u003cli\u003eHellenic Statistical Authority. Health survey 2019. 2019. Available from: https://www.statistics.gr\u003c/li\u003e\n\u003cli\u003edo Nascimento Freitas DW, Dibai-Filho AV, Pontes-Silva A, Araujo GGC, de Oliveira AR, da Cunha Leal P, et al. 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Translation and cross-cultural adaptation methodology. \u003cem\u003eArch Hellenic Med\u003c/em\u003e. 2019;36(1):124\u0026ndash;135.\u003c/li\u003e\n\u003cli\u003eThe jamovi project. jamovi. Version 2.3; 2022.\u003c/li\u003e\n\u003cli\u003eDevlin N, Pickard S, Busschbach J. The development of the EQ-5D-5L and its value sets. In: Value Sets for EQ-5D-5L: A Compendium, Comparative Review \u0026amp; User Guide. Springer International Publishing; 2022. p. 1\u0026ndash;12.\u003c/li\u003e\n\u003cli\u003eJumbo SU, MacDermid JC, Kalu ME, Packham TL, Athwal GS, Faber KJ. Measurement properties of the brief pain inventory- short form (BPI-SF) and the revised short mcgill pain questionnaire-version-2 (SF-MPQ-2) in pain-related musculoskeletal conditions: A systematic review protocol. Vol. 8, Archives of Bone and Joint Surgery. Mashhad University of Medical Sciences; 2020. p. 131\u0026ndash;41.\u003c/li\u003e\n\u003cli\u003eRoudijk B, Janssen B, Olsen JA. How do EQ-5D-5L value sets differ? In: Value Sets for EQ-5D-5L: A Compendium, Comparative Review \u0026amp; User Guide. Springer International Publishing; 2022. p. 235\u0026ndash;58.\u003c/li\u003e\n\u003cli\u003eScalone L, Cortesi PA, Ciampichini R, Belisari A, D\u0026rsquo;Angiolella LS, Cesana G, et al. Italian population-based values of EQ-5D health states. Value in Health. 2013 Jul;16(5):814\u0026ndash;22.\u003c/li\u003e\n\u003cli\u003eWild D, Grove A, Martin M, Eremenco S, McElroy S, Verjee-Lorenz A, et al. Volume 8 \u0026bull; Number 2 \u0026bull; 2005 V A L U E I N H E A L T H Principles of Good Practice for the Translation and Cultural Adaptation Process for Patient-Reported Outcomes (PRO) Measures: Report of the ISPOR Task Force for Translation and Cultural Adaptation Background and Rationale [Internet]. 2005. Available from: http://www.ispor.org\u003c/li\u003e\n\u003cli\u003eField A. Discovering Statistics Using IBM SPSS Statistics. 2018.\u003c/li\u003e\n\u003cli\u003eMcGraw KO, Wong SP. 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Structural Equation Modeling. 1999;6(1):1\u0026ndash;55.\u003c/li\u003e\n\u003cli\u003eHair J. F. BW, C, BBJ, ARE. hair et al 2010 - Multivariate Data Analysis. 2010.\u003c/li\u003e\n\u003cli\u003eIBM Corp. \u003cem\u003eIBM SPSS Statistics for Windows\u003c/em\u003e. Version 17.0. Armonk, NY; 2008.\u003c/li\u003e\n\u003cli\u003eEuroQol Foundation. EuroQol Group. 2025. Available from: https://euroqol.org\u003c/li\u003e\n\u003cli\u003eFabrigar LR, Wegener DT, Maccallum RC, Strahan EJ. Evaluating the Use of Exploratory Factor Analysis in Psychological Research. Vol. 4, Psychological Methods. 1999. \u003c/li\u003e\n\u003cli\u003eKaiser HF. AN INDEX OF FACTORIAL SIMPLICITY*. 1974. \u003c/li\u003e\n\u003cli\u003eBrown TA. Confirmatory Factor Analysis for Applied Research Methodology in the Social Sciences [Internet]. 2015. Available from: www.guilford.com/MSS\u003c/li\u003e\n\u003cli\u003eDeVellis RF. 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Available from: http://www.biomedcentral.com/1471-2288/10/13 \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"european-spine-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"esjo","sideBox":"Learn more about [European Spine Journal](http://link.springer.com/journal/586)","snPcode":"586","submissionUrl":"https://submission.springernature.com/new-submission/586/3","title":"European Spine Journal","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Spine Functional Index, SFI-10, cross-cultural adaptation, musculoskeletal spine disorders, Greek version, physiotherapy","lastPublishedDoi":"10.21203/rs.3.rs-8821715/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8821715/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eMusculoskeletal spine disorders are a leading cause of disability worldwide. The Spine Functional Index (SFI) is a whole-spine patient-reported outcome measure, and its short form (SFI-10) has demonstrated satisfactory psychometric properties across multiple languages. However, no validated Greek version has been available.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis cross-sectional study included 110 adults with chronic, non-specific spinal pain. Participants completed the Greek version of the SFI-10, alongside established measures of pain and health-related quality of life. Internal consistency, test-retest reliability, measurement error, structural validity and convergent validity were calculated.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe Greek SFI-10 demonstrated acceptable internal consistency (Cronbach\u0026rsquo;s α\u0026thinsp;=\u0026thinsp;0.794) and excellent test-retest reliability (ICC\u003csub\u003e2,1\u003c/sub\u003e = 0.955). Measurement error was low (SEM\u0026thinsp;=\u0026thinsp;0.403; MDC\u003csub\u003e90\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.935), and responsiveness indices indicated adequate sensitivity to change. Factor analyses supported a one-factor structure (EFA eigenvalue\u0026thinsp;=\u0026thinsp;4.96), with good model fit in CFA (CFI\u0026thinsp;=\u0026thinsp;1.000; RMSEA\u0026thinsp;=\u0026thinsp;0.000). Convergent validity was confirmed through significant correlations with NPRS (r\u0026thinsp;=\u0026thinsp;0.634; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), SF-BPI pain interference (r\u0026thinsp;=\u0026thinsp;0.819; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), SF-BPI pain severity (r\u0026thinsp;=\u0026thinsp;0.628; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and EQ-5D-5L (r = \u0026minus;\u0026thinsp;0.722; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eThe Greek version of the SFI-10 is a valid and reliable patient-reported outcome measure for assessing whole-spine function in individuals with musculoskeletal spine disorders. Its brevity and ease of use support its application in both clinical practice and research, involving Greek-speaking populations.\u003c/p\u003e","manuscriptTitle":"Translation, Cross-Cultural Adaptation and Validation of the 10-Item Spine Functional Index (SFI-10) for Greek Patients with Musculoskeletal Spine Disorders","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-17 16:16:42","doi":"10.21203/rs.3.rs-8821715/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewersInvited","content":"","date":"2026-02-12T03:40:57+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-10T06:49:58+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-10T06:47:38+00:00","index":"","fulltext":""},{"type":"submitted","content":"European Spine Journal","date":"2026-02-08T12:52:07+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"european-spine-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"esjo","sideBox":"Learn more about [European Spine Journal](http://link.springer.com/journal/586)","snPcode":"586","submissionUrl":"https://submission.springernature.com/new-submission/586/3","title":"European Spine Journal","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"52516ca8-d9f3-4c4b-9aa9-987bcbb53ba6","owner":[],"postedDate":"February 17th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-17T16:16:43+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-17 16:16:42","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8821715","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8821715","identity":"rs-8821715","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}