Lordosis distribution index in an asymptomatic elderly population: the role of lower and upper lumbar lordosis according to individual pelvic incidence and Roussouly type

Lordosis distribution index in an asymptomatic elderly population: the role of lower and upper lumbar lordosis according to individual pelvic incidence and Roussouly type | 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 Article Lordosis distribution index in an asymptomatic elderly population: the role of lower and upper lumbar lordosis according to individual pelvic incidence and Roussouly type Seung-Jae Hyun, Sanghyun Han, Youngbae B. Kim This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6166524/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract OBJECTIVE The roles of upper and lower lumbar lordosis (ULL and LLL) in relation to individual pelvic incidence (PI) and Roussouly type have yet to be established. This study aimed to determine the optimal ULL and LLL based on individual pelvic and spinal morphology within a normal asymptomatic elderly population. METHODS Whole spine standing radiographs were obtained from asymptomatic elderly volunteers who had not undergone previous spinal surgery. The following parameters were measured: lumbar lordosis (LL) from the T12 lower endplate (LEP) to the S1 upper endplate (UEP), ULL from the T12 LEP to the L4 UEP, and LLL from the L4 UEP to the S1 UEP. PI and the lordosis distribution index for the upper and lower lumbar spine (ULDI and LDI, respectively) were calculated. Pearson correlation and linear regression analyses were performed, and the mean value for each parameter was obtained according to PI subgroup (PI < 40°, 40° ≤ PI < 50°, 50° ≤ PI < 60°, and 60° ≤ PI) and “theoretical” Roussouly type. RESULTS Overall, 150 male volunteers were enrolled in the study, with an average age of 64.1 ± 6.4 years. The mean height was 167.0 ± 5.5 cm, weight was 67.3 ± 9.8 kg, and body mass index was 24.1 ± 3.1 kg/m 2 . The average LL was −57.5° ± 9.0°, LLL was −39.7° ± 6.8°, and PI was 48.6° ± 8.6°. PT tended to increase with ULL, PI-LL, PI-ULL, PI-LLL, and ULDI and decrease with LLL and LDI. However, PT was not significantly related to LL. The mean ULDI and LDI were 30.4% ± 11.7% and 69.7% ± 11.7%, respectively. The differences between PI and LL (PI-LL) and between PI and LLL (PI-LLL) were −8.9° ± 8.0° and 9.0° ± 9.3°, respectively. As PI increased from low (<40°) to high (≥60°), ULDI increased significantly from 25.9% to 38.9%, while LDI decreased from 74.1% to 61.1%. Additionally, LDI varied by Roussouly type, ranging from 62.6% to 81.0%. The LDIs of Roussouly types 1 and 4 were significantly higher and lower, respectively, than those of types 2 and 3 (p < 0.001). CONCLUSIONS As PI and Roussouly type increase, the contribution of ULL to overall LL rises, reaching up to 38.9%. Conversely, LLL substantially impacts LL in patients with a low PI and those classified as Roussouly type 1. PT is significantly related to LLL instead of LL according to PI. When planning surgical correction, the optimal ULL and LLL should be tailored to the patient’s PI and Roussouly type. Health sciences/Diseases Health sciences/Medical research lumbar distribution index upper lumbar lordosis lower lumbar lordosis pelvic incidence pelvic tilt elderly population Figures Figure 1 Figure 2 Figure 3 Introduction Roussouly et al. reported a spinal morphological classification based on sacral slope (SS), as well as the location of the apex and inflection point in the thoracic and lumbar spine. 1 They posited that SS is more closely related to lumbar lordosis (LL) than other parameters, and accordingly, they classified morphological LL into subgroups based on the magnitude of SS. Their research broadened our understanding of LL and has become widely utilized in spinal realignment surgery. According to Legaye and Duval-Beaupere, 2 LL is more closely proportional to SS than to pelvic incidence (PI). However, SS varies with the relationship between PI and pelvic tilt (PT), and PT also changes based on posture, such as standing, sitting, or leaning. Consequently, SS is not a suitable representation of individual spinopelvic morphology. In contrast, consensus supports the characterization of PI as a constant value for an individual in most situations, 3-5 and it is a critical determinant of sagittal balance regulation. 6 Thus, to better understand and classify sagittal alignment, LL should be described in relation to PI rather than SS. In this context, previous investigators have proposed a theoretical Roussouly classification based on PI values and a so-called current Roussouly classification based on SS. Many studies have discussed the close relationship between LL and PI. 2,6-11 From another perspective, LL can be categorized into two segments based on location: upper LL (ULL) and lower LL (LLL). The ratio of LLL to total LL is known as the lordosis distribution index (LDI). 12,13 Research indicates that LDI is key to determining surgical outcomes. Yilgor et al. introduced the global alignment and proportion (GAP) score, highlighting the importance of LDI and thus LLL. 12 However, limited research has been conducted on these parameters in relation to PI and Roussouly type within the normative population. We examined the ideal LL and LLL in an asymptomatic elderly population. 14 Utilizing previously collected data, we aimed to explore the associations between PI/Roussouly type, ULL/LLL, and LDI in asymptomatic adult volunteers. Methods Data Source and Inclusion/Exclusion Criteria Institutional review board approval was obtained prior to the investigation of this study (BOHUN IRB 2024-09-020-001). All methods were performed in accordance with the BOHUN IRB guidelines and regulations. We recruited asymptomatic Korean adults between March 2007 and September 2010. The study was limited to male volunteers, as the participants were drawn from those visiting the Veterans Health Service Medical Center. Regarding inclusion criteria, participants had to be over 50 years old, have no spinal pathology, and have no history of spinal trauma, surgery, or disorders affecting the area below the hip. Additionally, individuals with a history of neck, back, or lower limb pain were excluded. A total of 183 patients were initially recruited. However, 33 were subsequently excluded for various reasons: seven due to scoliosis greater than 10° in the coronal plane, one due to pelvic obliquity from leg length discrepancy, eight due to the presence of wedging vertebrae, nine due to lumbar disc space narrowing, four because of bilateral isthmic defects in the lumbosacral region, and four due to the presence of metallic foreign bodies (from traditional acupuncture) in the back muscles. Ultimately, 150 patients were included in the study. Informed consent was obtained from all subjects. Radiographic Measurements Standing plain lateral radiographs of the entire spine, including the pelvis, were analyzed in asymptomatic adult male volunteers. The protocol for acquiring these standing plain radiographs followed the methodology described by Horton et al. 15 The radiographs were stored in a picture archiving and communication system (PACS; Maroview; Marotech, Seoul, Korea) in the Digital Imaging and Communications in Medicine format. Radiographic measurements were performed using the ruler and protractor functions in the Maroview PACS. The sagittal vertical axis (SVA) was measured using a plumb line from the center of the C7 vertebra (C7PL) to the posterosuperior corner of the S1 upper endplate (UEP). Thoracic kyphosis (TK) was measured between the UEP of T5 and the lower endplate (LEP) of T12, while LL was measured between the T12 LEP and the S1 UEP. LL was also divided into two components: ULL, between the T12 LEP and the L4 UEP; and LLL, between the L4 UEP and the S1 UEP. SS was defined as the angle between the horizontal line and the line along the sacral endplate, while PI represented the angle formed by a line connecting the center of the sacral endplate to the femoral head axis. PT was measured as the angle between the line from the center of the sacral endplate to the bicoxofemoral axis and the C7PL. These sagittal distance and angular parameters were measured by an orthopedic spine surgeon and a spinal neurosurgeon. The ULL distribution index (ULDI) was calculated as the ratio of ULL to total LL multiplied by 100, while the LLL distribution index, or LDI, was computed as the ratio of LLL to LL multiplied by 100. These indices quantify the proportion of lordosis in the upper and lower arcs, respectively, relative to the entire lumbar curve. The theoretical Roussouly type was determined using methodology previously described by Pizones. Based on their PI values, participants were classified into four theoretical Roussouly types: type 1, PI less than 45° with the apex of the LL below the L4 vertebral body; type 2, PI less than 45° with the apex of the LL above the L4-L5 disc space; type 3, 45° ≤ PI < 60°; and type 4, PI ≥ 60°. Statistical Analysis Intraclass correlation coefficients (ICCs) were calculated to assess the reliability of the measurements, with the following benchmarks: perfect reliability at 1.0, excellent reliability between 0.8 and 0.99, substantial reliability between 0.6 and 0.79, and poor reliability at less than 0.59. The correlations among various sagittal parameters were examined using Pearson correlation coefficients. Pearson correlation and simple linear regression analyses were employed to explore the relationships between these parameters. The mean value for each parameter was calculated according to the PI subgroup (PI < 40°, 40° ≤ PI < 50°, 50° ≤ PI < 60°, and 60° ≤ PI) and the theoretical Roussouly type. A p-value of less than 0.05 was considered to indicate statistical significance. Statistical analyses were performed using SPSS version 22.0 (IBM Corp., Armonk, NY, USA). Results Demographic Data and Measurement Reliability The final cohort for analysis comprised 150 adult male volunteers, with an average age of 64.1 ± 6.4 years. The participants had a mean height of 167.0 ± 5.5 cm, a weight of 67.3 ± 9.8 kg, and a body mass index of 24.1 ± 3.1 kg/m 2 (Table 1 ). These baseline characteristics did not differ significantly among the subgroups categorized by PI and Roussouly type. All ICCs exceeded 0.8 according to the method of Shrout and Fleiss, demonstrating excellent reliability between measurements. Table 1 Parameters of the Elderly Population. Parameters The Elderly Population (N = 150) Mean Standard Deviation Number Age (years) 64.1 6.4 Height (cm) 167. 5.5 Weight (kg) 67.3 9.8 SVA (cm) -0.2 2.8 SVA ≤ 4cm 133 (88.7%) 4cm < SVA ≤ 9cm 17 (11.3%) PI (°) 48.6 8.6 SS (°) 37.4 6.8 PT (°) 11.3 6.4 PT ≤ 20° 139 (92.7%) 20° < PT ≤ 30° 11 (7.3%) TK (°) 30.0 8.8 LL (°) 57.5 9.0 ULL (°) 17.9 8.0 LLL (°) 39.7 6.8 ULDI (%) 30.4 11.7 LDI (%) 69.7 11.7 PI-LL (°) -8.9 8.0 PI-LL ≤ 10° 148 (98.7%) 10° < PI-LL ≤ 20° 2 (1.3%) PI-ULL (°) 30.4 8.9 PI-LLL(°) 9.03 9.3 Numbers in parentheses represent percentages unless otherwise indicated. SVA, sagittal vertical axis; PI, pelvic incidence; SS, Sacral slope; PT, pelvic tilt; TK, thoracic kyphosis; LL, Lumbar lordosis; ULL, upper lumbar lordosis; LLL, lower lumbar lordosis; ULDI, upper lumbar distribution index, LDI, lower lumbar distribution index. Sagittal Parameters and Correlations The sagittal parameters in this study were as follows. The mean C7 SVA was − 0.2 ± 2.8, with 133 instances of C7 SVA ≤ 4 cm and 17 instances where 4 cm < SVA ≤ 9 cm. Pelvic parameters included PI of 48.6° ± 8.6°, SS of 37.3° ± 6.8°, and PT of 11.3° ± 6.4°. The sample included 139 participants with PT < 20° and 11 participants with 20° < PT ≤ 30°. TK was 30.0° ± 8.8°, and LL was 57.5° ± 9.0°. Within LL, ULL and LLL were 17.9° ± 8.0° and 39.7° ± 6.8°, respectively. The ULDI and LDI were 30.4% ± 11.7% and 69.7% ± 11.7%, respectively. The differences between PI and LL (PI-LL), PI and LLL (PI-LLL), and PI and ULL (PI-ULL) were − 8.9° ± 8.0°, 9.0° ± 9.3°, and 30.4° ± 8.9°, respectively. We observed 148 instances of PI-LL ≤ 10° and two instances in which 10° < PI-LL ≤ 20°. The results of the correlation analysis are presented in Table 2 . PI was positively correlated with PT, LL, ULL, LLL, PI-LL, PI-ULL, PI-LLL, and ULDI and negatively correlated with LDI. PT was not significantly related to LL. Furthermore, PT tended to increase with ULL, PI-LL, PI-ULL, PI-LLL, and ULDI and decrease with LLL and LDI. The results of simple linear regression analyses between PT and several parameters are shown in Table 3 . All variables except LL were linearly correlated with PT. Among the variables, PI-LL had the highest regression coefficient ( β ). However, the coefficient of determination ( R 2 ) for PI-LLL was as high as 0.554, indicating the accuracy of this method for predicting PT. Table 2 Pearson’s correlation data PI PT LL ULL LLL PI-LL PI-ULL PI-LLL ULDI LDI PI 1 .626 ** .590 ** .427 ** .288 ** .415 ** .593 ** .718 ** .277 ** − .277 ** PT .626 ** 1 − .025 .167 * − .225 ** .704 ** .460 ** .744 ** .206 * − .204 * * P < 0.05 † P < 0.01 PI, pelvic incidence; PT, pelvic tilt; LL, Lumbar lordosis; ULL, upper lumbar lordosis; LLL, lower lumbar lordosis; ULDI, upper lumbar distribution index, LDI, lower lumbar distribution index Table 3 Simple Linear Regression Analysis about Pelvic Tilt Variable R 2 β (95% CI) P -value LL 0.001 -0.017 (-0.130 to 0.095) 0.763 ULL 0.028 0.132 (0.006 to 0.259) 0.041 LLL 0.051 -0.208 (-0.354 to -0.062) 0.006 PI-LL 0.496 0.550 (0.460 to 0.641) < 0.001 PI-ULL 0.212 0.324 (0.223 to 0.426) < 0.001 PI-LLL 0.554 * 0.499 (0.426 to 0.572) < 0.001 * The highest value among the methods. β , regression coefficient LL, Lumbar lordosis; ULL, upper lumbar lordosis; LLL, lower lumbar lordosis; PI, pelvic incidence; CI, confidence interval. ULDI and LDI by PI and Roussouly Type As indicated in Table 4 , participants were divided into four subgroups based on PI: PI < 40°, 40° ≤ PI < 50°, 50° ≤ PI < 60°, and 60° ≤ PI. We observed changes in various parameters as PI increased. Specifically, as PI rose from low (PI < 40°) to high (60° ≤ PI), the values of PT, LL, ULL, PI-LL, PI-ULL, and PI-LLL increased. Additionally, with an increase in PI, ULDI significantly increased from 25.9% ± 12.7–38.9% ±7.1%, while LDI decreased from 74.1% ± 12.7–61.1% ± 7.1% (Fig. 1 ). However, LLL did not increase beyond 41.7° ± 6.9°, regardless of PI. Table 4 Radiographic Data by Analysis of Pelvic Incidence Subgroup PT(°) LL(°) ULL(°) LLL(°) PI-LL(°) PI-ULL(°) PI-LLL(°) ULDI (%) LDI (%) PI < 40° (N = 25) 7.1 ± 6.0 49.6 ± 6.8 13.2 ± 6.7 36.4 ± 6.0 -13.5 ± 7.0 22.9 ± 6.0 -0.36 ± 7.5 25.9 ± 12.7 74.1 ± 12.7 40°≤ PI < 50° (N = 68) 9.1 ± 4.6 56.3 ± 8.7 17.2 ± 8.2 39.2 ± 6.5 -10.3 ± 7.9 28.8 ± 7.9 6.9 ± 6.2 29.7 ± 12.2 70.4 ± 12.1 50°≤PI < 60° (N = 45) 14.3 ± 5.0 61.2 ± 6.5 19.5 ± 6.6 41.7 ± 6.9 -6.4 ± 6.5 35.3 ± 7.2 13.0 ± 6.7 31.7 ± 10.3 68.4 ± 10.4 60°≤PI (N = 12) 21 ± 5.3 67.6 ± 7.2 26.3 ± 5.8 41.3 ± 6.5 -1.1 ± 7.3 40.2 ± 7.0 25.3 ± 6.8 38.9 ± 7.1 61.1 ± 7.1 PI, pelvic incidence; PT, pelvic tilt; LL, Lumbar lordosis; ULL, upper lumbar lordosis; LLL, lower lumbar lordosis; ULDI, upper lumbar distribution index; LDI, lower lumbar distribution index. Similarly, as the Roussouly type progressed from type 1 (PI < 45°) to type 4 (PI ≥ 60°), increases were observed in PI, PT, LL, ULL, PI-LLL, and ULDI. The LDIs corresponding to Roussouly type were 81.0% ± 10.7%, 65.3% ± 11.0%, 68.0% ± 10.6%, and 62.6% ± 8.2%, respectively (Fig. 2 ). Additionally, as Roussouly type increased, ULDI rose significantly from 19.0% ± 10.5–37.4% ± 7.7%, while LDI decreased from 81.0% ± 10.7–62.6% ± 8.2% (Table 5 ). The LDIs of Roussouly types 1 and 4 were significantly higher and lower, respectively, than those of types 2 and 3 (p < 0.001). However, regardless of Roussouly type, LLL did not exceed 41.9° ± 6.6°. Table 5 Radiographic Data by Analysis of “Theoretical” Roussouly type Roussouly PI(°) PT(°) LL(°) ULL(°) LLL(°) PI-LL(°) PI-ULL(°) PI-LLL(°) ULDI (%) LDI (%) Type 1 (N = 30) 39.6 ± 6.8 8.1 ± 5.5 48.0 ± 6.4 9.4 ± 4.2 38.6 ± 6.1 -8.4 ± 6.1 30.2 ± 6.3 1.0 ± 6.9 19.0 ± 10.5 81.0 ± 10.7 Type 2 (N = 23) 40.4 ± 6.5 8.3 ± 4.7 53.7 ± 7.6 18.7 ± 7.2 35.0 ± 6.5 -13.3 ± 7.3 21.7 ± 7.1 5.4 ± 6.3 34.7 ± 12.0 65.3 ± 11.0 Type 3 (N = 82) 51.2 ± 6.6 11.6 ± 5.1 60.4 ± 6.5 19.5 ± 6.6 40.9 ± 6.9 -9.2 ± 6.9 31.7 ± 7.5 10.3 ± 6.4 32.0 ± 9.4 68.0 ± 10.6 Type 4 (N = 15) 65.2 ± 7.0 20.3 ± 5.4 66.9 ± 7.3 25.1 ± 6.1 41.9 ± 6.6 -1.7 ± 7.2 40.1 ± 7.1 23.3 ± 6.7 37.4 ± 7.7 62.6 ± 8.2 PI, pelvic incidence; PT, pelvic tilt; LL, Lumbar lordosis; ULL, upper lumbar lordosis; LLL, lower lumbar lordosis; ULDI, upper lumbar distribution index; LDI, lower lumbar distribution index. Discussion LL and LLL Several studies have identified LL as a key factor in spinal sagittal balance. Initially, research focused on the relationship between LL and PI or SS. Subsequently, studies have explored morphological classification models of LL. 1 , 2 , 6 , 9 , 15 – 18 Despite this, detailed research on the components of LL—specifically ULL and LLL—remains scarce, although Yilgor and colleagues have discussed LLL and used relative LL and LDI to predict postoperative construct failure. 12 , 13 In this research, we further investigated parameters potentially associated with ULL or LLL, the constituents of LL. Relationship Between LLL and PT PT is a measure of the extent to which the pelvis tilts backward. Essentially, as LL decreases, PT increases to prevent inclination of the trunk. 20 Furthermore, retroversion of the pelvis leads to hip extension as a compensatory action to balance the body’s center of gravity. When this compensatory capacity is maximized, knee flexion serves as an additional compensatory mechanism. 21 , 22 Consequently, if pelvic retroversion occurs, the energy expenditure during gait increases, while the gait distance is shortened. Few studies have attempted to clarify the relationship between PT and other parameters. While some research suggests that PT is directly related to PI and that health-related quality of life decreases as PT increases in pathological situations, 2 , 6 , 7 , 11 , 22 , 23 – 29 other studies present different findings. For instance, a previous report demonstrated that changes in PT were associated with changes in LL, indicating that alterations in LL following spine surgery contribute to determining the value of PT. 16 However, the present study found no such relationship between LL and PT. Nevertheless, the relationship between PI-LLL and PT displayed the highest coefficient of determination in a simple linear regression analysis, suggesting that PT is significantly related to LLL according to PI (Table 3 ). The existence of this relationship in normal asymptomatic populations suggests that greater emphasis should be placed on the correction of LLL when performing lower lumbar fusion under pathological conditions. Role of ULL and LLL In the present study, we established normative values for ULL, LLL, ULDI, and LDI based on PI and Roussouly type. We observed that as PI increased, the mean ULDI rose from 25.9% ± 12.7–38.9% ± 7.1%, while the mean LDI decreased from 74.1% ± 12.7–61.1% ± 7.1%. In spinal realignment surgery, surgeons must consider restoring the optimal LDI for each patient according to their PI and Roussouly type. Nonetheless, our findings indicate that LLL did not exceed 41°, regardless of these individual characteristics. Therefore, an appropriate degree of ULL should be added for patients with a high PI or those classified as Roussouly type 2, 3, or 4. Additionally, we found that LDI represents a minimum of 61.1% of the total LL value. When performing spinal fusion, it is thus important to ensure that LDI continues to account for above 61% of LL. Based on notable previous research regarding GAP score, the range for LDI corresponding to alignment is between 50% and 80%. 12,13 The authors also suggested that an LDI exceeding 80% represents a risk factor for mechanical failure following spinal realignment surgery. However, our data revealed that the mean LDI was 81.0% ± 10.7% in asymptomatic individuals classified as Roussouly type 1. Moreover, we have frequently observed excellent clinical- and radiographic outcomes without any mechanical failure in Roussouly type 1 patients having exceeding 80% LDI after surgery (Fig. 3 ). Consequently, we propose that the optimal LDI and ULL should be customized based on the individual’s PI and Roussouly type. This study had several limitations. First, the study sample was restricted to men due to the demographics of the public veterans’ hospital where the research was conducted. Second, the participants lacked age diversity, with most being of old age. While this reflects the typical patient demographic for spinal disease and is thus relevant for surgical applications and research in elderly patients, we recommend investigating the distributions of ULL, LLL, and LDI values across a broader age range. Conclusions As PI and Roussouly type increase, the contribution of ULL to LL also increases, up to 38.9%. Conversely, LLL substantially impacts LL in patients with a low PI and those classified as Roussouly type 1. PT is significantly related to LLL instead of LL according to PI. Therefore, in spinal corrective surgery, the optimal ULL and LLL should be tailored to the patient’s individual PI and Roussouly type. Declarations Author Contribution YBK conceptualized the project. All authors collected data. SJH and SHK analyzed data. SJH and SHK wrote the main manuscript text and SJH and SHK prepared figures 1-3. All authors reviewed the manuscript. Data Availability The authors confirm that the datasets used and/or analysed during the current study available from the corresponding author on reasonable request. References Roussouly P, Labelle H, Rouissi J, et al. Pre-and post-operative sagittal balance in idiopathic scoliosis: a comparison over the ages of two cohorts of 132 adolescents and 52 adults. European Spine Journal 2013;22:203-15. Legaye J, Duval-Beaupere G. Sagittal plane alignment of the spine and gravity: a radiological and clinical evaluation. Acta Orthop Belg 2005;71:213-20. Schwab F, Ungar B, Blondel B, et al. Scoliosis Research Society-Schwab adult spinal deformity classification: a validation study. Spine (Phila Pa 1976) 2012;37:1077-82. Schwab F, Lafage V, Patel A, et al. Sagittal plane considerations and the pelvis in the adult patient. Spine (Phila Pa 1976) 2009;34:1828. Marty C, Boisaubert B, Descamps H, et al. The sagittal anatomy of the sacrum among young adults, infants, and spondylolisthesis patients. European Spine Journal 2002;11:119-25. Legaye J, Duval-Beaupere G, Hecquet J, et al. Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves. Eur Spine J 1998;7:99-103. Le Huec JC, Hasegawa K. Normative values for the spine shape parameters using 3D standing analysis from a database of 268 asymptomatic Caucasian and Japanese subjects. European Spine Journal 2016;25:3630-7. Le Huec J, Aunoble S, Philippe L, et al. Pelvic parameters: origin and significance. European Spine Journal 2011;20:564. Lafage V, Schwab F, Patel A, et al. Pelvic tilt and truncal inclination: two key radiographic parameters in the setting of adults with spinal deformity. Spine (Phila Pa 1976) 2009;34:E599-606. Duval-Beaupere G, Schmidt C, Cosson P. A Barycentremetric study of the sagittal shape of spine and pelvis: the conditions required for an economic standing position. Ann Biomed Eng 1992;20:451-62. Boulay C, Tardieu C, Hecquet J, et al. Sagittal alignment of spine and pelvis regulated by pelvic incidence: standard values and prediction of lordosis. Eur Spine J 2006;15:415-22. Yilgor C, Sogunmez N, Boissiere L, et al. Global Alignment and Proportion (GAP) Score: Development and Validation of a New Method of Analyzing Spinopelvic Alignment to Predict Mechanical Complications After Adult Spinal Deformity Surgery. The Journal of bone and joint surgery. American volume 2017;99:1661-72. Yilgor C, Sogunmez N, Yavuz Y, et al. Relative lumbar lordosis and lordosis distribution index: individualized pelvic incidence–based proportional parameters that quantify lumbar lordosis more precisely than the concept of pelvic incidence minus lumbar lordosis. Neurosurgical focus 2017;43:E5. Hyun SJ, Han S, Kim YB, et al. Predictive formula of ideal lumbar lordosis and lower lumbar lordosis determined by individual pelvic incidence in asymptomatic elderly population. Eur Spine J . 2019 Sep;28(9):1906-1913. Horton WC, Brown CW, Bridwell KH, et al. Is there an optimal patient stance for obtaining a lateral 36” radiograph?: a critical comparison of three techniques. Spine 2005;30:427-33. Liu H, Li S, Wang J, et al. An analysis of spinopelvic sagittal alignment after lumbar lordosis reconstruction for degenerative spinal diseases: how much balance can be obtained? Spine (Phila Pa 1976) 2014;39:B52-9. Lafage V, Schwab F, Vira S, et al. Spino-pelvic parameters after surgery can be predicted: a preliminary formula and validation of standing alignment. Spine (Phila Pa 1976) 2011;36:1037-45. Cho W, Mason JR, Smith JS, et al. Failure of lumbopelvic fixation after long construct fusions in patients with adult spinal deformity: clinical and radiographic risk factors. Journal of neurosurgery. Spine 2013. Schwab F, Patel A, Ungar B, et al. Adult spinal deformity—postoperative standing imbalance: how much can you tolerate? An overview of key parameters in assessing alignment and planning corrective surgery. Spine 2010;35:2224-31. Moal B. Adultes avec déformation rachidienne: traitement chirurgical et évaluation musculaire: Ecole nationale supérieure d'arts et métiers-ENSAM, 2014. Cheng X, Zhang F, Wu J, et al. Spontaneous improvement of compensatory knee flexion after surgical correction of mismatch between pelvic incidence and lumbar lordosis. Spine 2016;41:1303-9. Barrey C, Roussouly P, Le Huec J-C, et al. Compensatory mechanisms contributing to keep the sagittal balance of the spine. European spine journal 2013;22:834-41. Kang KB, Ahn YJ, Kim YJ, et al. Changes in Sagittal Spinopelvic Parameters according to Pelvic Incidence in Asymptomatic Old Korean Men. J Korean Soc Spine Surg 2011;18:223-9. Lee JK, Hyun SJ, Kim KJ. Optimizing Surgical Strategy for Cervical Spinal Deformity: Global Alignment and Surgical Targets. Neurospine . 2023 Dec;20(4):1246-1255. Shin HK, Park JH, Jeon SR, et al. Sacropelvic Fixation for Adult Deformity Surgery Comparing Iliac Screw and Sacral 2 Alar-Iliac Screw Fixation: Systematic Review and Updated Meta-Analysis. Neurospine . 2023 Dec;20(4):1469-1476. Seo SH, Hyun SJ, Lee JK, et al. Unintended readmissions and reoperations within 30 and 90 days following adult spinal deformity surgery. J Neurosurg Spine . 2024 Oct 18:1-10. Lee CH, Jo DJ, Oh JK, et al. Development and Validation of an Online Calculator to Predict Proximal Junctional Kyphosis After Adult Spinal Deformity Surgery Using Machine Learning. Neurospine . 2023 Dec;20(4):1272-1280. Mun J, Hyun SJ, Lee JK, et al. Surgical and Clinical Outcomes Associated With the Use of Barbed Sutures and Self-Adhering Mesh System and Polymeric Glue for Wound Closure in Multilevel or Revision Spinal Surgery: A Matched Cohort Comparative Study With Conventional Wound Closure Procedure. Neurospine . 2023 Sep;20(3):981-988. Do SH, Bae S, Jo DJ, et al. Distal Junctional Failure After Fusion Stopping at L5 in Patients With Adult Spinal Deformity: Incidence, Risk Factors, and Radiographic Criteria. Neurospine . 2024 Sep;21(3):856-864. Additional Declarations No competing interests reported. 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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-6166524","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":436341854,"identity":"fe02b4c2-a043-4ebc-b9f6-02cd2f505391","order_by":0,"name":"Seung-Jae Hyun","email":"","orcid":"","institution":"Seoul National University Bundang Hospital","correspondingAuthor":false,"prefix":"","firstName":"Seung-Jae","middleName":"","lastName":"Hyun","suffix":""},{"id":436341855,"identity":"1224f7cc-c3e2-4e7c-9f92-c8261b79fcc4","order_by":1,"name":"Sanghyun Han","email":"","orcid":"","institution":"Asan Chungmu Hospital","correspondingAuthor":false,"prefix":"","firstName":"Sanghyun","middleName":"","lastName":"Han","suffix":""},{"id":436341856,"identity":"cf84ccca-3417-4e68-86a9-844ed73c17f4","order_by":2,"name":"Youngbae B. Kim","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzElEQVRIiWNgGAWjYBACAxjJD6ITCkjRItkA0mJAtBYQ4wAKFw8wZ+89/Lmg4I6c8fnViR8eGDDI84sdwK/FsudcmvQMg2fGZjfebpYAOsxw5uwEAg67kWPGzGNwOHHbjbMbQFoSDG4T0nL/jfFnoJb6zTPObv5BnJYbPAbSQC0JBvy924izxbInxwzol8OGM27wbrNIMJAg7Bdz9jPGnwv+HJbn7z+7+eaPCht5fmkCWkCAGUxKgFVKEFaO0MJ/gDjVo2AUjIJRMPIAAEIIQ9a8/G4sAAAAAElFTkSuQmCC","orcid":"","institution":"Veterans Health Service Medical Center","correspondingAuthor":true,"prefix":"","firstName":"Youngbae","middleName":"B.","lastName":"Kim","suffix":""}],"badges":[],"createdAt":"2025-03-06 03:08:20","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6166524/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6166524/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79831483,"identity":"887f354a-5bf9-4b2b-9b43-1c05bf1dab44","added_by":"auto","created_at":"2025-04-03 10:36:45","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":233736,"visible":true,"origin":"","legend":"\u003cp\u003eBar graph of mean ULDI and LDI by pelvic incidence subgroup. ULDI, upper lumbar lordosis distribution index; LDI, lower lumbar lordosis distribution index; PI, pelvic incidence.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6166524/v1/227373bc370ed43c931492a6.png"},{"id":79829794,"identity":"532f8be1-7f62-4f03-8814-ffa236b216e6","added_by":"auto","created_at":"2025-04-03 10:20:45","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":52173,"visible":true,"origin":"","legend":"\u003cp\u003eMean value bar graph of the lordosis distribution index (LDI) according to Roussouly type. The LDI for Roussouly type 1 significantly exceeded the LDIs for the other types.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6166524/v1/deb3b007eb499b933cf9b031.png"},{"id":79830828,"identity":"90fbcb49-f170-481a-aa1a-13d607e70ea1","added_by":"auto","created_at":"2025-04-03 10:28:45","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":293924,"visible":true,"origin":"","legend":"\u003cp\u003eA representative case. A patient who had Roussouly type 1 and low PI experienced excellent clinical- and radiographic outcomes without any mechanical failure after spinal realignment surgery although the postoperative LDI exceeded 80%.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6166524/v1/9199dcc66686037dc49f4b27.png"},{"id":80122230,"identity":"5a1f474e-8d29-42d6-9c08-0e1616561826","added_by":"auto","created_at":"2025-04-08 07:47:04","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1379443,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6166524/v1/805fdc1b-ebc8-407a-8aaf-8294efce85e2.pdf"},{"id":79829804,"identity":"7e98317b-abb2-4900-9c98-74ca5edf0f07","added_by":"auto","created_at":"2025-04-03 10:20:45","extension":"xlsx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":50545,"visible":true,"origin":"","legend":"","description":"","filename":"RawDataLDI.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6166524/v1/63bf9648700f016672cd757e.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Lordosis distribution index in an asymptomatic elderly population: the role of lower and upper lumbar lordosis according to individual pelvic incidence and Roussouly type","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRoussouly et al. reported a spinal morphological classification based on sacral slope (SS), as well as the location of the apex and inflection point in the thoracic and lumbar spine.\u003ca href=\"#_ENREF_1\" title=\"Roussouly, 2013 #91\"\u003e\u003csup\u003e1\u003c/sup\u003e\u003c/a\u003e They posited that SS is more closely related to lumbar lordosis (LL) than other parameters, and accordingly, they classified morphological LL into subgroups based on the magnitude of SS. Their research broadened our understanding of LL and has become widely utilized in spinal realignment surgery.\u003c/p\u003e\n\u003cp\u003eAccording to Legaye and Duval-Beaupere,\u003csup\u003e2\u003c/sup\u003e LL is more closely proportional to SS than to pelvic incidence (PI). However, SS varies with the relationship between PI and pelvic tilt (PT), and PT also changes based on posture, such as standing, sitting, or leaning. Consequently, SS is not a suitable representation of individual spinopelvic morphology. In contrast, consensus supports the characterization of PI as a constant value for an individual in most situations,\u003csup\u003e3-5\u003c/sup\u003e and it is a critical determinant of sagittal balance regulation.\u003csup\u003e6\u003c/sup\u003e Thus, to better understand and classify sagittal alignment, LL should be described in relation to PI rather than SS. In this context, previous investigators have proposed a theoretical Roussouly classification based on PI values and a so-called current Roussouly classification based on SS.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Many studies have discussed the close relationship between LL and PI.\u003csup\u003e2,6-11\u003c/sup\u003e From another perspective, LL can be categorized into two segments based on location: upper LL (ULL) and lower LL (LLL). The ratio of LLL to total LL is known as the lordosis distribution index (LDI).\u003csup\u003e12,13\u003c/sup\u003e Research indicates that LDI is key to determining surgical outcomes. Yilgor et al. introduced the global alignment and proportion (GAP) score, highlighting the importance of LDI and thus LLL.\u003csup\u003e12\u003c/sup\u003e However, limited research has been conducted on these parameters in relation to PI and Roussouly type within the normative population. We examined the ideal LL and LLL in an asymptomatic elderly population.\u003csup\u003e14\u003c/sup\u003e Utilizing previously collected data, we aimed to explore the associations between PI/Roussouly type, ULL/LLL, and LDI in asymptomatic adult volunteers.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eData Source and Inclusion/Exclusion Criteria\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInstitutional review board approval was obtained prior to the investigation of this study (BOHUN IRB 2024-09-020-001). All methods were performed in accordance with the BOHUN IRB guidelines and regulations. We recruited asymptomatic Korean adults between March 2007 and September 2010. The study was limited to male volunteers, as the participants were drawn from those visiting the Veterans Health Service Medical Center. Regarding inclusion criteria, participants had to be over 50 years old, have no spinal pathology, and have no history of spinal trauma, surgery, or disorders affecting the area below the hip. Additionally, individuals with a history of neck, back, or lower limb pain were excluded. A total of 183 patients were initially recruited. However, 33 were subsequently excluded for various reasons: seven due to scoliosis greater than 10° in the coronal plane, one due to pelvic obliquity from leg length discrepancy, eight due to the presence of wedging vertebrae, nine due to lumbar disc space narrowing, four because of bilateral isthmic defects in the lumbosacral region, and four due to the presence of metallic foreign bodies (from traditional acupuncture) in the back muscles. Ultimately, 150 patients were included in the study. Informed consent was obtained from all subjects.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRadiographic Measurements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eStanding plain lateral radiographs of the entire spine, including the pelvis, were analyzed in asymptomatic adult male volunteers. The protocol for acquiring these standing plain radiographs followed the methodology described by Horton et al.\u003csup\u003e15\u003c/sup\u003e The radiographs were\u0026nbsp;stored in a picture archiving and communication system (PACS; Maroview; Marotech, Seoul, Korea) in the Digital Imaging and Communications in Medicine format. Radiographic measurements were performed using the ruler and protractor functions in the Maroview PACS. The sagittal vertical axis (SVA) was measured using a plumb line from the center of the C7 vertebra (C7PL) to the posterosuperior corner of the S1 upper endplate (UEP). Thoracic kyphosis (TK) was measured between the UEP of T5 and the lower endplate (LEP) of T12, while LL was measured between the T12 LEP and the S1 UEP. LL was also divided into two components: ULL, between the T12 LEP and the L4 UEP; and LLL, between the L4 UEP and the S1 UEP. SS was defined as the angle between the horizontal line and the line along the sacral endplate, while PI represented the angle formed by a line connecting the center of the sacral endplate to the femoral head axis. PT was measured as the angle between the line from the center of the sacral endplate to the bicoxofemoral axis and the C7PL. These sagittal distance and angular parameters were measured by an orthopedic spine surgeon and a spinal neurosurgeon.\u003c/p\u003e\n\u003cp\u003eThe ULL distribution index (ULDI) was calculated as the ratio of ULL to total LL multiplied by 100, while the LLL distribution index, or LDI, was computed as the ratio of LLL to LL multiplied by 100. These indices quantify the proportion of lordosis in the upper and lower arcs, respectively, relative to the entire lumbar curve. The theoretical Roussouly type was determined using methodology previously described by Pizones. Based on their PI values, participants were classified into four theoretical Roussouly types: type 1, PI less than 45° with the apex of the LL below the L4 vertebral body; type 2, PI less than 45° with the apex of the LL above the L4-L5 disc space; type 3, 45° ≤ PI \u0026lt; 60°; and type 4, PI ≥ 60°.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical Analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIntraclass correlation coefficients (ICCs) were calculated to assess the reliability of the measurements, with the following benchmarks: perfect reliability at 1.0, excellent reliability between 0.8 and 0.99, substantial reliability between 0.6 and 0.79, and poor reliability at less than 0.59. The correlations among various sagittal parameters were examined using Pearson correlation coefficients. Pearson correlation and simple linear regression analyses were employed to explore the relationships between these parameters. The mean value for each parameter was calculated according to the PI subgroup (PI \u0026lt; 40°, 40° ≤ PI \u0026lt; 50°, 50° ≤ PI \u0026lt; 60°, and 60° ≤ PI) and the theoretical Roussouly type. A p-value of less than 0.05 was considered to indicate statistical significance. Statistical analyses were performed using SPSS version 22.0 (IBM Corp., Armonk, NY, USA).\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eDemographic Data and Measurement Reliability\u003c/h2\u003e \u003cp\u003eThe final cohort for analysis comprised 150 adult male volunteers, with an average age of 64.1\u0026thinsp;\u0026plusmn;\u0026thinsp;6.4 years. The participants had a mean height of 167.0\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5 cm, a weight of 67.3\u0026thinsp;\u0026plusmn;\u0026thinsp;9.8 kg, and a body mass index of 24.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1 kg/m\u003csup\u003e2\u003c/sup\u003e (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). These baseline characteristics did not differ significantly among the subgroups categorized by PI and Roussouly type. All ICCs exceeded 0.8 according to the method of Shrout and Fleiss, demonstrating excellent reliability between measurements.\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 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eParameters of the Elderly Population.\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\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eThe Elderly Population (N\u0026thinsp;=\u0026thinsp;150)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eStandard Deviation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNumber\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\u003eAge (years)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e64.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eHeight (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e167.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eWeight (kg)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e67.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSVA (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSVA\u0026thinsp;\u0026le;\u0026thinsp;4cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e133 (88.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4cm\u0026thinsp;\u0026lt;\u0026thinsp;SVA\u0026thinsp;\u0026le;\u0026thinsp;9cm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e17 (11.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePI (\u0026deg;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e48.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSS (\u0026deg;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e37.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePT (\u0026deg;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e11.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePT\u0026thinsp;\u0026le;\u0026thinsp;20\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e139 (92.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e20\u0026deg; \u0026lt; PT\u0026thinsp;\u0026le;\u0026thinsp;30\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e11 (7.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTK (\u0026deg;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLL (\u0026deg;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e57.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eULL (\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e17.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLLL (\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e39.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eULDI (%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLDI (%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e69.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePI-LL (\u0026deg;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-8.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePI-LL\u0026thinsp;\u0026le;\u0026thinsp;10\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e148 (98.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u0026deg; \u0026lt; PI-LL\u0026thinsp;\u0026le;\u0026thinsp;20\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2 (1.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePI-ULL (\u0026deg;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePI-LLL(\u0026deg;)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eNumbers in parentheses represent percentages unless otherwise indicated.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eSVA, sagittal vertical axis; PI, pelvic incidence; SS, Sacral slope; PT, pelvic tilt; TK, thoracic kyphosis; LL, Lumbar lordosis; ULL, upper lumbar lordosis; LLL, lower lumbar lordosis; ULDI, upper lumbar distribution index, LDI, lower lumbar distribution index.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSagittal Parameters and Correlations\u003c/h3\u003e\n\u003cp\u003eThe sagittal parameters in this study were as follows. The mean C7 SVA was \u0026minus;\u0026thinsp;0.2\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8, with 133 instances of C7 SVA\u0026thinsp;\u0026le;\u0026thinsp;4 cm and 17 instances where 4 cm\u0026thinsp;\u0026lt;\u0026thinsp;SVA\u0026thinsp;\u0026le;\u0026thinsp;9 cm. Pelvic parameters included PI of 48.6\u0026deg; \u0026plusmn; 8.6\u0026deg;, SS of 37.3\u0026deg; \u0026plusmn; 6.8\u0026deg;, and PT of 11.3\u0026deg; \u0026plusmn; 6.4\u0026deg;. The sample included 139 participants with PT\u0026thinsp;\u0026lt;\u0026thinsp;20\u0026deg; and 11 participants with 20\u0026deg; \u0026lt; PT\u0026thinsp;\u0026le;\u0026thinsp;30\u0026deg;. TK was 30.0\u0026deg; \u0026plusmn; 8.8\u0026deg;, and LL was 57.5\u0026deg; \u0026plusmn; 9.0\u0026deg;. Within LL, ULL and LLL were 17.9\u0026deg; \u0026plusmn; 8.0\u0026deg; and 39.7\u0026deg; \u0026plusmn; 6.8\u0026deg;, respectively. The ULDI and LDI were 30.4% \u0026plusmn; 11.7% and 69.7% \u0026plusmn; 11.7%, respectively. The differences between PI and LL (PI-LL), PI and LLL (PI-LLL), and PI and ULL (PI-ULL) were \u0026minus;\u0026thinsp;8.9\u0026deg; \u0026plusmn; 8.0\u0026deg;, 9.0\u0026deg; \u0026plusmn; 9.3\u0026deg;, and 30.4\u0026deg; \u0026plusmn; 8.9\u0026deg;, respectively. We observed 148 instances of PI-LL\u0026thinsp;\u0026le;\u0026thinsp;10\u0026deg; and two instances in which 10\u0026deg; \u0026lt; PI-LL\u0026thinsp;\u0026le;\u0026thinsp;20\u0026deg;. The results of the correlation analysis are presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. PI was positively correlated with PT, LL, ULL, LLL, PI-LL, PI-ULL, PI-LLL, and ULDI and negatively correlated with LDI. PT was not significantly related to LL. Furthermore, PT tended to increase with ULL, PI-LL, PI-ULL, PI-LLL, and ULDI and decrease with LLL and LDI. The results of simple linear regression analyses between PT and several parameters are shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. All variables except LL were linearly correlated with PT. Among the variables, PI-LL had the highest regression coefficient (\u003cem\u003eβ\u003c/em\u003e). However, the coefficient of determination (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e) for PI-LLL was as high as 0.554, indicating the accuracy of this method for predicting PT.\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 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePearson\u0026rsquo;s correlation data\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePT\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLL\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eULL\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLLL\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePI-LL\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003ePI-ULL\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003ePI-LLL\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eULDI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eLDI\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e.626\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e.590\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e.427\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e.288\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e.415\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e.593\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e.718\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e.277\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;\u0026thinsp;.277\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e.626\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026minus;\u0026thinsp;.025\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e.167\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026minus;\u0026thinsp;.225\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e.704\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e.460\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e.744\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e.206\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u0026minus;\u0026thinsp;.204\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e* P\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003cp\u003e\u0026dagger; P\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"11\"\u003ePI, pelvic incidence; PT, pelvic tilt; LL, Lumbar lordosis; ULL, upper lumbar lordosis; LLL, lower lumbar lordosis; ULDI, upper lumbar distribution index,\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"11\"\u003eLDI, lower lumbar distribution index\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \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\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSimple Linear Regression Analysis about Pelvic Tilt\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=\"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 \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\u003e\u003cem\u003eR\u003c/em\u003e\u003csup\u003e\u003cem\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eβ\u003c/em\u003e (95% CI)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.017 (-0.130 to 0.095)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.763\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eULL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.028\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.132 (0.006 to 0.259)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.041\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLLL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.051\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.208 (-0.354 to -0.062)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePI-LL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.496\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.550\u003c/b\u003e (0.460 to 0.641)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePI-ULL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.212\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.324 (0.223 to 0.426)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePI-LLL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e0.554\u003c/b\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.499 (0.426 to 0.572)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e* The highest value among the methods. \u003cem\u003eβ\u003c/em\u003e, regression coefficient\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eLL, Lumbar lordosis; ULL, upper lumbar lordosis; LLL, lower lumbar lordosis; PI, pelvic incidence; CI, confidence interval.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eULDI and LDI by PI and Roussouly Type\u003c/h3\u003e\n\u003cp\u003eAs indicated in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, participants were divided into four subgroups based on PI: PI\u0026thinsp;\u0026lt;\u0026thinsp;40\u0026deg;, 40\u0026deg; \u0026le; PI\u0026thinsp;\u0026lt;\u0026thinsp;50\u0026deg;, 50\u0026deg; \u0026le; PI\u0026thinsp;\u0026lt;\u0026thinsp;60\u0026deg;, and 60\u0026deg; \u0026le; PI. We observed changes in various parameters as PI increased. Specifically, as PI rose from low (PI\u0026thinsp;\u0026lt;\u0026thinsp;40\u0026deg;) to high (60\u0026deg; \u0026le; PI), the values of PT, LL, ULL, PI-LL, PI-ULL, and PI-LLL increased. Additionally, with an increase in PI, ULDI significantly increased from 25.9% \u0026plusmn; 12.7\u0026ndash;38.9% \u0026plusmn;7.1%, while LDI decreased from 74.1% \u0026plusmn; 12.7\u0026ndash;61.1% \u0026plusmn; 7.1% (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). However, LLL did not increase beyond 41.7\u0026deg; \u0026plusmn; 6.9\u0026deg;, regardless of PI.\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 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eRadiographic Data by Analysis of Pelvic Incidence Subgroup\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePT(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eULL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLLL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePI-LL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePI-ULL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003ePI-LLL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eULDI (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eLDI (%)\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\u003ePI\u0026thinsp;\u0026lt;\u0026thinsp;40\u0026deg;\u003c/b\u003e\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;25)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e7.1\u0026thinsp;\u0026plusmn;\u0026thinsp;6.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e49.6\u0026thinsp;\u0026plusmn;\u0026thinsp;6.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e13.2\u0026thinsp;\u0026plusmn;\u0026thinsp;6.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e36.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e-13.5\u0026thinsp;\u0026plusmn;\u0026thinsp;7.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e22.9\u0026thinsp;\u0026plusmn;\u0026thinsp;6.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e-0.36\u0026thinsp;\u0026plusmn;\u0026thinsp;7.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e25.9\u0026thinsp;\u0026plusmn;\u0026thinsp;12.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e74.1\u0026thinsp;\u0026plusmn;\u0026thinsp;12.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e40\u0026deg;\u0026le; PI\u0026thinsp;\u0026lt;\u0026thinsp;50\u0026deg;\u003c/b\u003e\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;68)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e9.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e56.3\u0026thinsp;\u0026plusmn;\u0026thinsp;8.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e17.2\u0026thinsp;\u0026plusmn;\u0026thinsp;8.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e39.2\u0026thinsp;\u0026plusmn;\u0026thinsp;6.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e-10.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e28.8\u0026thinsp;\u0026plusmn;\u0026thinsp;7.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e6.9\u0026thinsp;\u0026plusmn;\u0026thinsp;6.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e29.7\u0026thinsp;\u0026plusmn;\u0026thinsp;12.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e70.4\u0026thinsp;\u0026plusmn;\u0026thinsp;12.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e50\u0026deg;\u0026le;PI\u0026thinsp;\u0026lt;\u0026thinsp;60\u0026deg;\u003c/b\u003e\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;45)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e14.3\u0026thinsp;\u0026plusmn;\u0026thinsp;5.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e61.2\u0026thinsp;\u0026plusmn;\u0026thinsp;6.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e19.5\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e41.7\u0026thinsp;\u0026plusmn;\u0026thinsp;6.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e-6.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e35.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e13.0\u0026thinsp;\u0026plusmn;\u0026thinsp;6.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e31.7\u0026thinsp;\u0026plusmn;\u0026thinsp;10.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e68.4\u0026thinsp;\u0026plusmn;\u0026thinsp;10.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e60\u0026deg;\u0026le;PI\u003c/b\u003e\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e21\u0026thinsp;\u0026plusmn;\u0026thinsp;5.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e67.6\u0026thinsp;\u0026plusmn;\u0026thinsp;7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e26.3\u0026thinsp;\u0026plusmn;\u0026thinsp;5.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e41.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e-1.1\u0026thinsp;\u0026plusmn;\u0026thinsp;7.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e40.2\u0026thinsp;\u0026plusmn;\u0026thinsp;7.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e25.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e38.9\u0026thinsp;\u0026plusmn;\u0026thinsp;7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e61.1\u0026thinsp;\u0026plusmn;\u0026thinsp;7.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"10\"\u003ePI, pelvic incidence; PT, pelvic tilt; LL, Lumbar lordosis; ULL, upper lumbar lordosis; LLL, lower lumbar lordosis;\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"10\"\u003eULDI, upper lumbar distribution index; LDI, lower lumbar distribution index.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSimilarly, as the Roussouly type progressed from type 1 (PI\u0026thinsp;\u0026lt;\u0026thinsp;45\u0026deg;) to type 4 (PI\u0026thinsp;\u0026ge;\u0026thinsp;60\u0026deg;), increases were observed in PI, PT, LL, ULL, PI-LLL, and ULDI. The LDIs corresponding to Roussouly type were 81.0% \u0026plusmn; 10.7%, 65.3% \u0026plusmn; 11.0%, 68.0% \u0026plusmn; 10.6%, and 62.6% \u0026plusmn; 8.2%, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Additionally, as Roussouly type increased, ULDI rose significantly from 19.0% \u0026plusmn; 10.5\u0026ndash;37.4% \u0026plusmn; 7.7%, while LDI decreased from 81.0% \u0026plusmn; 10.7\u0026ndash;62.6% \u0026plusmn; 8.2% (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The LDIs of Roussouly types 1 and 4 were significantly higher and lower, respectively, than those of types 2 and 3 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). However, regardless of Roussouly type, LLL did not exceed 41.9\u0026deg; \u0026plusmn; 6.6\u0026deg;.\u003c/p\u003e \u003cp\u003e \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 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eRadiographic Data by Analysis of \u0026ldquo;Theoretical\u0026rdquo; Roussouly type\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRoussouly\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePI(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePT(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eULL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLLL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePI-LL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003ePI-ULL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003ePI-LLL(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eULDI (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eLDI (%)\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\u003eType 1\u003c/b\u003e\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e39.6\u0026thinsp;\u0026plusmn;\u0026thinsp;6.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e8.1\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e48.0\u0026thinsp;\u0026plusmn;\u0026thinsp;6.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e9.4\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e38.6\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e-8.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e30.2\u0026thinsp;\u0026plusmn;\u0026thinsp;6.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e1.0\u0026thinsp;\u0026plusmn;\u0026thinsp;6.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e19.0\u0026thinsp;\u0026plusmn;\u0026thinsp;10.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c11\"\u003e \u003cp\u003e81.0\u0026thinsp;\u0026plusmn;\u0026thinsp;10.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eType 2\u003c/b\u003e\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;23)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e40.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e8.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e53.7\u0026thinsp;\u0026plusmn;\u0026thinsp;7.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e18.7\u0026thinsp;\u0026plusmn;\u0026thinsp;7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e35.0\u0026thinsp;\u0026plusmn;\u0026thinsp;6.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e-13.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e21.7\u0026thinsp;\u0026plusmn;\u0026thinsp;7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e5.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e34.7\u0026thinsp;\u0026plusmn;\u0026thinsp;12.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c11\"\u003e \u003cp\u003e65.3\u0026thinsp;\u0026plusmn;\u0026thinsp;11.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eType 3\u003c/b\u003e\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;82)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e51.2\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e11.6\u0026thinsp;\u0026plusmn;\u0026thinsp;5.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e60.4\u0026thinsp;\u0026plusmn;\u0026thinsp;6.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e19.5\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e40.9\u0026thinsp;\u0026plusmn;\u0026thinsp;6.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e-9.2\u0026thinsp;\u0026plusmn;\u0026thinsp;6.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e31.7\u0026thinsp;\u0026plusmn;\u0026thinsp;7.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e10.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e32.0\u0026thinsp;\u0026plusmn;\u0026thinsp;9.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c11\"\u003e \u003cp\u003e68.0\u0026thinsp;\u0026plusmn;\u0026thinsp;10.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eType 4\u003c/b\u003e\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;15)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e65.2\u0026thinsp;\u0026plusmn;\u0026thinsp;7.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e20.3\u0026thinsp;\u0026plusmn;\u0026thinsp;5.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e66.9\u0026thinsp;\u0026plusmn;\u0026thinsp;7.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e25.1\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e41.9\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e-1.7\u0026thinsp;\u0026plusmn;\u0026thinsp;7.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e40.1\u0026thinsp;\u0026plusmn;\u0026thinsp;7.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c9\"\u003e \u003cp\u003e23.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c10\"\u003e \u003cp\u003e37.4\u0026thinsp;\u0026plusmn;\u0026thinsp;7.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c11\"\u003e \u003cp\u003e62.6\u0026thinsp;\u0026plusmn;\u0026thinsp;8.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"11\"\u003ePI, pelvic incidence; PT, pelvic tilt; LL, Lumbar lordosis; ULL, upper lumbar lordosis; LLL, lower lumbar lordosis;\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"11\"\u003eULDI, upper lumbar distribution index; LDI, lower lumbar distribution index.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eLL and LLL\u003c/h2\u003e \u003cp\u003eSeveral studies have identified LL as a key factor in spinal sagittal balance. Initially, research focused on the relationship between LL and PI or SS. Subsequently, studies have explored morphological classification models of LL.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan additionalcitationids=\"CR16 CR17\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e Despite this, detailed research on the components of LL\u0026mdash;specifically ULL and LLL\u0026mdash;remains scarce, although Yilgor and colleagues have discussed LLL and used relative LL and LDI to predict postoperative construct failure.\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e In this research, we further investigated parameters potentially associated with ULL or LLL, the constituents of LL.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eRelationship Between LLL and PT\u003c/h3\u003e\n\u003cp\u003ePT is a measure of the extent to which the pelvis tilts backward. Essentially, as LL decreases, PT increases to prevent inclination of the trunk.\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e Furthermore, retroversion of the pelvis leads to hip extension as a compensatory action to balance the body\u0026rsquo;s center of gravity. When this compensatory capacity is maximized, knee flexion serves as an additional compensatory mechanism.\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e Consequently, if pelvic retroversion occurs, the energy expenditure during gait increases, while the gait distance is shortened.\u003c/p\u003e \u003cp\u003eFew studies have attempted to clarify the relationship between PT and other parameters. While some research suggests that PT is directly related to PI and that health-related quality of life decreases as PT increases in pathological situations,\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan additionalcitationids=\"CR24 CR25 CR26 CR27 CR28\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e other studies present different findings. For instance, a previous report demonstrated that changes in PT were associated with changes in LL, indicating that alterations in LL following spine surgery contribute to determining the value of PT.\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e However, the present study found no such relationship between LL and PT. Nevertheless, the relationship between PI-LLL and PT displayed the highest coefficient of determination in a simple linear regression analysis, suggesting that PT is significantly related to LLL according to PI (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The existence of this relationship in normal asymptomatic populations suggests that greater emphasis should be placed on the correction of LLL when performing lower lumbar fusion under pathological conditions.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eRole of ULL and LLL\u003c/h2\u003e \u003cp\u003eIn the present study, we established normative values for ULL, LLL, ULDI, and LDI based on PI and Roussouly type. We observed that as PI increased, the mean ULDI rose from 25.9% \u0026plusmn; 12.7\u0026ndash;38.9% \u0026plusmn; 7.1%, while the mean LDI decreased from 74.1% \u0026plusmn; 12.7\u0026ndash;61.1% \u0026plusmn; 7.1%. In spinal realignment surgery, surgeons must consider restoring the optimal LDI for each patient according to their PI and Roussouly type. Nonetheless, our findings indicate that LLL did not exceed 41\u0026deg;, regardless of these individual characteristics. Therefore, an appropriate degree of ULL should be added for patients with a high PI or those classified as Roussouly type 2, 3, or 4. Additionally, we found that LDI represents a minimum of 61.1% of the total LL value. When performing spinal fusion, it is thus important to ensure that LDI continues to account for above 61% of LL. Based on notable previous research regarding GAP score, the range for LDI corresponding to alignment is between 50% and 80%.\u003csup\u003e12,13\u003c/sup\u003e The authors also suggested that an LDI exceeding 80% represents a risk factor for mechanical failure following spinal realignment surgery. However, our data revealed that the mean LDI was 81.0% \u0026plusmn; 10.7% in asymptomatic individuals classified as Roussouly type 1. Moreover, we have frequently observed excellent clinical- and radiographic outcomes without any mechanical failure in Roussouly type 1 patients having exceeding 80% LDI after surgery (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Consequently, we propose that the optimal LDI and ULL should be customized based on the individual\u0026rsquo;s PI and Roussouly type.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThis study had several limitations. First, the study sample was restricted to men due to the demographics of the public veterans\u0026rsquo; hospital where the research was conducted. Second, the participants lacked age diversity, with most being of old age. While this reflects the typical patient demographic for spinal disease and is thus relevant for surgical applications and research in elderly patients, we recommend investigating the distributions of ULL, LLL, and LDI values across a broader age range.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eAs PI and Roussouly type increase, the contribution of ULL to LL also increases, up to 38.9%. Conversely, LLL substantially impacts LL in patients with a low PI and those classified as Roussouly type 1. PT is significantly related to LLL instead of LL according to PI. Therefore, in spinal corrective surgery, the optimal ULL and LLL should be tailored to the patient\u0026rsquo;s individual PI and Roussouly type.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eYBK conceptualized the project. All authors collected data. SJH and SHK analyzed data. SJH and SHK wrote the main manuscript text and SJH and SHK prepared figures 1-3. All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe authors confirm that the datasets used and/or analysed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eRoussouly P, Labelle H, Rouissi J, et al. Pre-and post-operative sagittal balance in idiopathic scoliosis: a comparison over the ages of two cohorts of 132 adolescents and 52 adults. \u003cem\u003eEuropean Spine Journal\u003c/em\u003e 2013;22:203-15.\u003c/li\u003e\n \u003cli\u003eLegaye J, Duval-Beaupere G. Sagittal plane alignment of the spine and gravity: a radiological and clinical evaluation. \u003cem\u003eActa Orthop Belg\u003c/em\u003e 2005;71:213-20.\u003c/li\u003e\n \u003cli\u003eSchwab F, Ungar B, Blondel B, et al. Scoliosis Research Society-Schwab adult spinal deformity classification: a validation study. \u003cem\u003eSpine (Phila Pa 1976)\u003c/em\u003e 2012;37:1077-82.\u003c/li\u003e\n \u003cli\u003eSchwab F, Lafage V, Patel A, et al. Sagittal plane considerations and the pelvis in the adult patient. \u003cem\u003eSpine (Phila Pa 1976)\u003c/em\u003e 2009;34:1828.\u003c/li\u003e\n \u003cli\u003eMarty C, Boisaubert B, Descamps H, et al. The sagittal anatomy of the sacrum among young adults, infants, and spondylolisthesis patients. \u003cem\u003eEuropean Spine Journal\u003c/em\u003e 2002;11:119-25.\u003c/li\u003e\n \u003cli\u003eLegaye J, Duval-Beaupere G, Hecquet J, et al. Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves. \u003cem\u003eEur Spine J\u003c/em\u003e 1998;7:99-103.\u003c/li\u003e\n \u003cli\u003eLe Huec JC, Hasegawa K. Normative values for the spine shape parameters using 3D standing analysis from a database of 268 asymptomatic Caucasian and Japanese subjects. \u003cem\u003eEuropean Spine Journal\u003c/em\u003e 2016;25:3630-7.\u003c/li\u003e\n \u003cli\u003eLe Huec J, Aunoble S, Philippe L, et al. Pelvic parameters: origin and significance. \u003cem\u003eEuropean Spine Journal\u003c/em\u003e 2011;20:564.\u003c/li\u003e\n \u003cli\u003eLafage V, Schwab F, Patel A, et al. Pelvic tilt and truncal inclination: two key radiographic parameters in the setting of adults with spinal deformity. \u003cem\u003eSpine (Phila Pa 1976)\u003c/em\u003e 2009;34:E599-606.\u003c/li\u003e\n \u003cli\u003eDuval-Beaupere G, Schmidt C, Cosson P. A Barycentremetric study of the sagittal shape of spine and pelvis: the conditions required for an economic standing position. \u003cem\u003eAnn Biomed Eng\u003c/em\u003e 1992;20:451-62.\u003c/li\u003e\n \u003cli\u003eBoulay C, Tardieu C, Hecquet J, et al. Sagittal alignment of spine and pelvis regulated by pelvic incidence: standard values and prediction of lordosis. \u003cem\u003eEur Spine J\u003c/em\u003e 2006;15:415-22.\u003c/li\u003e\n \u003cli\u003eYilgor C, Sogunmez N, Boissiere L, et al. Global Alignment and Proportion (GAP) Score: Development and Validation of a New Method of Analyzing Spinopelvic Alignment to Predict Mechanical Complications After Adult Spinal Deformity Surgery. \u003cem\u003eThe Journal of bone and joint surgery. American volume\u003c/em\u003e 2017;99:1661-72.\u003c/li\u003e\n \u003cli\u003eYilgor C, Sogunmez N, Yavuz Y, et al. Relative lumbar lordosis and lordosis distribution index: individualized pelvic incidence\u0026ndash;based proportional parameters that quantify lumbar lordosis more precisely than the concept of pelvic incidence minus lumbar lordosis. \u003cem\u003eNeurosurgical focus\u003c/em\u003e 2017;43:E5.\u003c/li\u003e\n \u003cli\u003eHyun SJ, Han S, Kim YB, et al. Predictive formula of ideal lumbar lordosis and lower lumbar lordosis determined by individual pelvic incidence in asymptomatic elderly population.\u0026nbsp;\u003cem\u003eEur Spine J\u003c/em\u003e. 2019 Sep;28(9):1906-1913.\u003c/li\u003e\n \u003cli\u003eHorton WC, Brown CW, Bridwell KH, et al. Is there an optimal patient stance for obtaining a lateral 36\u0026rdquo; radiograph?: a critical comparison of three techniques. \u003cem\u003eSpine\u003c/em\u003e 2005;30:427-33.\u003c/li\u003e\n \u003cli\u003eLiu H, Li S, Wang J, et al. An analysis of spinopelvic sagittal alignment after lumbar lordosis reconstruction for degenerative spinal diseases: how much balance can be obtained? \u003cem\u003eSpine (Phila Pa 1976)\u003c/em\u003e 2014;39:B52-9.\u003c/li\u003e\n \u003cli\u003eLafage V, Schwab F, Vira S, et al. Spino-pelvic parameters after surgery can be predicted: a preliminary formula and validation of standing alignment. \u003cem\u003eSpine (Phila Pa 1976)\u003c/em\u003e 2011;36:1037-45.\u003c/li\u003e\n \u003cli\u003eCho W, Mason JR, Smith JS, et al. Failure of lumbopelvic fixation after long construct fusions in patients with adult spinal deformity: clinical and radiographic risk factors. \u003cem\u003eJournal of neurosurgery. Spine\u003c/em\u003e 2013.\u003c/li\u003e\n \u003cli\u003eSchwab F, Patel A, Ungar B, et al. Adult spinal deformity\u0026mdash;postoperative standing imbalance: how much can you tolerate? An overview of key parameters in assessing alignment and planning corrective surgery. \u003cem\u003eSpine\u003c/em\u003e 2010;35:2224-31.\u003c/li\u003e\n \u003cli\u003eMoal B. Adultes avec d\u0026eacute;formation rachidienne: traitement chirurgical et \u0026eacute;valuation musculaire: Ecole nationale sup\u0026eacute;rieure d\u0026apos;arts et m\u0026eacute;tiers-ENSAM, 2014.\u003c/li\u003e\n \u003cli\u003eCheng X, Zhang F, Wu J, et al. Spontaneous improvement of compensatory knee flexion after surgical correction of mismatch between pelvic incidence and lumbar lordosis. \u003cem\u003eSpine\u003c/em\u003e 2016;41:1303-9.\u003c/li\u003e\n \u003cli\u003eBarrey C, Roussouly P, Le Huec J-C, et al. Compensatory mechanisms contributing to keep the sagittal balance of the spine. \u003cem\u003eEuropean spine journal\u003c/em\u003e 2013;22:834-41.\u003c/li\u003e\n \u003cli\u003eKang KB, Ahn YJ, Kim YJ, et al. Changes in Sagittal Spinopelvic Parameters according to Pelvic Incidence in Asymptomatic Old Korean Men. \u003cem\u003eJ Korean Soc Spine Surg\u003c/em\u003e 2011;18:223-9.\u003c/li\u003e\n \u003cli\u003eLee JK, Hyun SJ, Kim KJ. Optimizing Surgical Strategy for Cervical Spinal Deformity: Global Alignment and Surgical Targets. \u003cem\u003eNeurospine\u003c/em\u003e. 2023 Dec;20(4):1246-1255.\u003c/li\u003e\n \u003cli\u003eShin HK, Park JH, Jeon SR, et al. Sacropelvic Fixation for Adult Deformity Surgery Comparing Iliac Screw and Sacral 2 Alar-Iliac Screw Fixation: Systematic Review and Updated Meta-Analysis. \u003cem\u003eNeurospine\u003c/em\u003e. 2023 Dec;20(4):1469-1476.\u003c/li\u003e\n \u003cli\u003eSeo SH, Hyun SJ, Lee JK, et al. Unintended readmissions and reoperations within 30 and 90 days following adult spinal deformity surgery. \u003cem\u003eJ Neurosurg Spine\u003c/em\u003e. 2024 Oct 18:1-10.\u003c/li\u003e\n \u003cli\u003eLee CH, Jo DJ, Oh JK, et al. Development and Validation of an Online Calculator to Predict Proximal Junctional Kyphosis After Adult Spinal Deformity Surgery Using Machine Learning. \u003cem\u003eNeurospine\u003c/em\u003e. 2023 Dec;20(4):1272-1280.\u003c/li\u003e\n \u003cli\u003eMun J, Hyun SJ, Lee JK, et al. Surgical and Clinical Outcomes Associated With the Use of Barbed Sutures and Self-Adhering Mesh System and Polymeric Glue for Wound Closure in Multilevel or Revision Spinal Surgery: A Matched Cohort Comparative Study With Conventional Wound Closure Procedure. \u003cem\u003eNeurospine\u003c/em\u003e. 2023 Sep;20(3):981-988.\u003c/li\u003e\n \u003cli\u003eDo SH, Bae S, Jo DJ, et al. Distal Junctional Failure After Fusion Stopping at L5 in Patients With Adult Spinal Deformity: Incidence, Risk Factors, and Radiographic Criteria. \u003cem\u003eNeurospine\u003c/em\u003e. 2024 Sep;21(3):856-864.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"lumbar distribution index, upper lumbar lordosis, lower lumbar lordosis, pelvic incidence, pelvic tilt, elderly population","lastPublishedDoi":"10.21203/rs.3.rs-6166524/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6166524/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eOBJECTIVE\u003c/strong\u003e The roles of upper and lower lumbar lordosis (ULL and LLL) in relation to individual pelvic incidence (PI) and Roussouly type have yet to be established. This study aimed to determine the optimal ULL and LLL based on individual pelvic and spinal morphology within a normal asymptomatic elderly population.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMETHODS\u003c/strong\u003e Whole spine standing radiographs were obtained from asymptomatic elderly volunteers who had not undergone previous spinal surgery. The following parameters were measured: lumbar lordosis (LL) from the T12 lower endplate (LEP) to the S1 upper endplate (UEP), ULL from the T12 LEP to the L4 UEP, and LLL from the L4 UEP to the S1 UEP. PI and the lordosis distribution index for the upper and lower lumbar spine (ULDI and LDI, respectively) were calculated. Pearson correlation and linear regression analyses were performed, and the mean value for each parameter was obtained according to PI subgroup (PI \u0026lt; 40°, 40° ≤ PI \u0026lt; 50°, 50° ≤ PI \u0026lt; 60°, and 60° ≤ PI) and “theoretical” Roussouly type.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRESULTS\u003c/strong\u003e Overall, 150 male volunteers were enrolled in the study, with an average age of 64.1 ± 6.4 years. The mean height was 167.0 ± 5.5 cm, weight was 67.3 ± 9.8 kg, and body mass index was 24.1 ± 3.1 kg/m\u003csup\u003e2\u003c/sup\u003e. The average LL was −57.5° ± 9.0°, LLL was −39.7° ± 6.8°, and PI was 48.6° ± 8.6°. PT tended to increase with ULL, PI-LL, PI-ULL, PI-LLL, and ULDI and decrease with LLL and LDI.\u003cem\u003e \u003c/em\u003eHowever, PT was not significantly related to LL. The mean ULDI and LDI were 30.4% ± 11.7% and 69.7% ± 11.7%, respectively. The differences between PI and LL (PI-LL) and between PI and LLL (PI-LLL) were −8.9° ± 8.0° and 9.0° ± 9.3°, respectively. As PI increased from low (\u0026lt;40°) to high (≥60°), ULDI increased significantly from\u003csub\u003e \u003c/sub\u003e25.9% to 38.9%, while LDI\u003csub\u003e \u003c/sub\u003edecreased from 74.1% to 61.1%. Additionally, LDI varied by Roussouly type, ranging from 62.6% to 81.0%. The LDIs of Roussouly types 1 and 4 were significantly higher and lower, respectively, than those of types 2 and 3 (p \u0026lt; 0.001).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCONCLUSIONS\u003c/strong\u003e As PI and Roussouly type increase, the contribution of ULL to overall LL rises, reaching up to 38.9%. Conversely, LLL substantially impacts LL in patients with a low PI and those classified as Roussouly type 1. PT is significantly related to LLL instead of LL according to PI. When planning surgical correction, the optimal ULL and LLL should be tailored to the patient’s PI and Roussouly type.\u003c/p\u003e","manuscriptTitle":"Lordosis distribution index in an asymptomatic elderly population: the role of lower and upper lumbar lordosis according to individual pelvic incidence and Roussouly type","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-03 10:20:40","doi":"10.21203/rs.3.rs-6166524/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d686f343-8b0e-4172-84f8-f876469b8b5b","owner":[],"postedDate":"April 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":46458277,"name":"Health sciences/Diseases"},{"id":46458278,"name":"Health sciences/Medical research"}],"tags":[],"updatedAt":"2025-04-08T07:38:46+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-03 10:20:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6166524","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6166524","identity":"rs-6166524","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}