Predictive Value of Preoperative Paraspinal Muscle Degeneration Parameters for Clinical Outcomes After Unilateral Biportal Endoscopy for L5/S1 Lumbar Disc Herniation

Predictive Value of Preoperative Paraspinal Muscle Degeneration Parameters for Clinical Outcomes After Unilateral Biportal Endoscopy for L5/S1 Lumbar Disc Herniation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Predictive Value of Preoperative Paraspinal Muscle Degeneration Parameters for Clinical Outcomes After Unilateral Biportal Endoscopy for L5/S1 Lumbar Disc Herniation Li Wenqing¹, Gao Meng¹, Xie Zihan¹, Chen Xiaolong, Yu Qihua² This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9065113/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 To investigate the predictive value of preoperative paraspinal muscle degeneration parameters for clinical outcomes after unilateral biportal endoscopy (UBE) in patients with single-level L5/S1 lumbar disc herniation (LDH), and to provide evidence for preoperative risk assessment and individualized rehabilitation planning. Methods A retrospective analysis was conducted on 108 patients who underwent UBE for single-level L5/S1 LDH from January 2024 to December 2025. On preoperative axial T2-weighted MRI images at the L5/S1 disc level, the total cross-sectional area (tCSA) and functional cross-sectional area (fCSA) of the bilateral multifidus (MF) and erector spinae (ES) muscles were measured, and the fat infiltration rate (FIR) was calculated. The Goutallier classification system was used for semi-quantitative assessment of paraspinal muscle fatty infiltration. Visual analog scale (VAS) scores for low back and leg pain and Oswestry Disability Index (ODI) were recorded preoperatively and at 3, 6, and 12 months postoperatively. Clinical outcomes were evaluated using the modified MacNab criteria at the final follow-up. Patients were divided into excellent/good group (90 cases) and fair/poor group (18 cases) based on outcomes. Preoperative paraspinal muscle degeneration parameters were compared between groups. Multivariate logistic regression analysis was used to identify independent risk factors for poor postoperative outcomes. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive efficacy of preoperative paraspinal muscle degeneration parameters for postoperative outcomes. Results The excellent/good rate was 83.3%. Patients in the fair/poor group had significantly smaller preoperative ipsilateral MF fCSA and relative cross-sectional area (rCSA) (P < 0.001), significantly higher MF FIR (P < 0.001), and a significantly higher proportion of Goutallier grade ≥ 2 (83.3% vs. 32.2%, P < 0.001) compared to the excellent/good group. Correlation analysis showed that preoperative MF FIR was significantly negatively correlated with postoperative ODI improvement rate (r=-0.682) and low back pain VAS improvement rate (r=-0.594) (P 0.05). Multivariate logistic regression analysis revealed that preoperative MF FIR ≥ 25% (OR = 10.55, 95%CI: 2.55–43.62, P = 0.001) and disease duration ≥ 12 months (OR = 6.45, 95%CI: 1.69–24.56, P = 0.006) were independent risk factors for poor postoperative outcomes, while MF fCSA was a protective factor (OR = 0.986, P = 0.020). ROC curve analysis showed that preoperative MF FIR had the largest area under the curve (AUC) for predicting poor postoperative outcomes (0.856, 95%CI: 0.768–0.944), with an optimal cutoff value of 24.8%, sensitivity of 85.0%, and specificity of 75.0%. Conclusion Preoperative paraspinal muscle degeneration, particularly the degree of multifidus fatty infiltration, is an important predictor of clinical outcomes after UBE for L5/S1 lumbar disc herniation. When MRI shows multifidus fat infiltration rate ≥ 24.8% or Goutallier grade ≥ 2, clinicians should be alert to the risk of poor postoperative outcomes. It is recommended that preoperative paraspinal muscle status be incorporated into the surgical risk assessment system, and targeted postoperative rehabilitation of paraspinal muscle function be strengthened for high-risk populations. Lumbar disc herniation Unilateral biportal endoscopy Paraspinal muscle degeneration Fatty infiltration Prognostic prediction Introduction Lumbar disc herniation (LDH) is a common condition in spinal surgery, frequently occurring at the L5/S1 segment. Unilateral biportal endoscopy (UBE) has emerged as one of the mainstream minimally invasive surgical techniques for the treatment of L5/S1 disc herniation due to its advantages of minimal trauma and rapid recovery, yielding satisfactory clinical outcomes ( 1 – 3 ). However, in clinical practice, some patients experience varying degrees of residual low back pain and weakness, along with slow functional recovery, despite significant relief of lower limb radicular pain following neural decompression, which affects overall patient satisfaction( 4 ). This phenomenon suggests that factors other than neural decompression may influence postoperative outcomes( 5 ). The lumbar paraspinal muscles, including the multifidus (MF) and erector spinae (ES), serve as the dynamic stabilizing system of the spine and play a critical role in maintaining lumbar segmental stability and normal function( 6 , 7 ). Notably, the multifidus muscle contributes uniquely to lumbar segmental stability through its segmental innervation and abundant distribution of muscle spindles( 8 ). With aging or chronic inflammatory stimulation, the paraspinal muscles may undergo degenerative changes characterized by increased fatty infiltration and reduced cross-sectional area, leading to impaired stabilizing function( 9 ). The L5/S1 segment, as the lumbosacral junction, is subjected to distinct biomechanical stresses, particularly high shear forces, and the condition of the multifidus at this level is crucial for maintaining local stability ( 10 ). Although an increasing number of studies have investigated the relationship between paraspinal muscle degeneration and lumbar degenerative diseases, with paraspinal muscle fatty infiltration having been confirmed to be associated with poor prognosis after lumbar surgery( 11 , 12 ), systematic research on the predictive value of preoperative paraspinal muscle degeneration parameters for clinical outcomes following UBE for L5/S1 disc herniation remains limited( 10 ). Therefore, this study aimed to retrospectively analyze the clinical data of patients who underwent UBE for L5/S1 disc herniation, measure preoperative paraspinal muscle parameters including cross-sectional area and degree of fatty infiltration, analyze their correlation with postoperative improvements in VAS scores for low back and leg pain and ODI index, and investigate the predictive value of preoperative paraspinal muscle degeneration for postoperative outcomes following UBE. The findings may provide a theoretical basis for preoperative risk assessment and the development of individualized rehabilitation protocols. Materials and Methods 1.1 General Information This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of The Seventh Affiliated Hospital of Anhui University of Chinese Medicine (Approval No. [2024] 84). A retrospective analysis was conducted on clinical data of patients who underwent unilateral biportal endoscopy (UBE) for single-level L5/S1 disc herniation in the Department of Orthopedics, The Seventh Affiliated Hospital of Anhui University of Chinese Medicine from January 2024 to December 2025. All patients were definitively diagnosed based on medical history inquiry, physical examination, and imaging studies. Inclusion criteria were: ( 1 ) complete imaging data, including lumbar MRI plain scan and X-ray films; ( 2 ) MRI-confirmed single-level L5/S1 disc herniation consistent with clinical symptoms and signs; ( 3 ) underwent UBE surgery with postoperative follow-up ≥ 12 months; ( 4 ) age 18–60 years. Exclusion criteria were: ( 1 ) multi-level disc herniation or involvement of other segments requiring surgical intervention; ( 2 ) history of previous lumbar surgery; ( 3 ) concomitant lumbar spondylolisthesis (Meyerding ≥ grade I), spondylolysis, spinal tumors, infections, trauma, or ankylosing spondylitis; ( 4 ) concomitant severe osteoporosis or metabolic bone diseases; ( 5 ) poor image quality precluding accurate measurements. A total of 108 patients who met the inclusion criteria were enrolled, including 46 males and 62 females, aged 22–56 years, with a mean age of 39.5 ± 5.6 years. General data including age, sex, disease duration, and body mass index (BMI) were collected. 1.2 Surgical Procedure All surgeries were performed by the same team of senior spinal surgeons using the UBE technique. Patients were placed in the prone position under general anesthesia with the abdomen suspended. The observation portal and working portal were established ipsilaterally at the L5/S1 interspace, with continuous irrigation maintained to ensure a clear visual field. Under endoscopic visualization, the interlaminar space was exposed, the lower margin of the L5 lamina and upper margin of the S1 lamina were partially removed using a burr, and the ligamentum flavum was resected to expose the dural sac and traversing nerve root. The herniated nucleus pulposus was removed to achieve complete decompression of the nerve root. After confirming nerve root laxity and good pulsation intraoperatively, thorough hemostasis was achieved, a drainage tube was placed, and the incision was closed. 1.3 Clinical Outcome Assessment Visual analog scale (VAS) scores for low back and leg pain and Oswestry Disability Index (ODI) were recorded preoperatively and at 3, 6, and 12 months postoperatively. Clinical outcomes were evaluated at the final follow-up using the modified MacNab criteria: excellent (complete resolution of symptoms, return to normal activities), good (marked improvement in symptoms, occasional mild pain), fair (partial improvement in symptoms, persistent significant pain), and poor (no improvement or worsening of symptoms). Patients with excellent and good outcomes were classified as the excellent/good group, while those with fair and poor outcomes were classified as the fair/poor group. 1.4 Imaging Measurements and Parameter Assessment All patients underwent preoperative lumbar MRI examination using a 3.0T MRI scanner (Ingenia 3.0T, Philips, Netherlands), with scanning sequences including axial and sagittal T2-weighted images. Axial T2WI images at the L5/S1 disc level were selected for analysis. 1.4.1 Measurement of Paraspinal Muscle Degeneration Parameters Using Image J software (NIH, USA), the boundaries of the bilateral multifidus (MF) and erector spinae (ES) muscles at the L5/S1 level were manually delineated to measure the following parameters: ( 1 ) Total cross-sectional area (tCSA): delineated along the muscle fascial contour, including muscle tissue and internal fat areas, recorded as MF tCSA and ES tCSA, respectively. ( 2 ) Functional cross-sectional area (fCSA): based on the total ROI, a manual threshold method was used to set grayscale thresholds, excluding high-signal pixels in fat infiltration areas and retaining pure muscle tissue pixels, with the software automatically calculating fCSA. ( 3 ) Fat infiltration rate (FIR): calculated as FIR = (tCSA - fCSA) / tCSA × 100%. ( 4 ) Goutallier classification: semi-quantitative grading of paraspinal muscle fatty infiltration on T2WI images: grade 0 (no fatty infiltration), grade 1 (some fatty streaks), grade 2 (significant fatty infiltration but still less than muscle tissue), grade 3 (fatty tissue approximately equal to muscle tissue), grade 4 (fatty tissue exceeding muscle tissue). ( 5 ) Relative cross-sectional area (rCSA): the ratio of muscle cross-sectional area to the vertebral cross-sectional area (V CSA) at the same L5 level, used to correct for individual body size differences. All measurements were independently performed by two spinal surgeons blinded to patient clinical data, and the average values were used for statistical analysis. Twenty patients were randomly selected for repeat measurements at a 2-week interval, and the intraclass correlation coefficient (ICC) was calculated to assess measurement reliability. 1.4.2 Assessment of Disc Degeneration Grade On sagittal T2WI MRI images, the Pfirrmann classification system was used to evaluate the degree of L5/S1 disc degeneration: grade I (normal), grade II (mild degeneration), grade III (moderate degeneration), grade IV (severe degeneration), grade V (end-stage degeneration). 1.5Statistical Analysis Statistical analysis was performed using SPSS 26.0 software. Continuous variables were first tested for normality using the Kolmogorov-Smirnov test; those conforming to normal distribution were expressed as mean ± standard deviation, while those not conforming to normal distribution were expressed as median (interquartile range). Categorical data were expressed as number of cases (percentage). ( 1 ) Intergroup comparison: patients were divided into excellent/good group and fair/poor group according to the modified MacNab criteria at the final follow-up, and differences in preoperative paraspinal muscle degeneration parameters and other clinical data were compared between the two groups. For continuous variables conforming to normal distribution, the independent samples t-test was used; for those not conforming to normal distribution, the Mann-Whitney U test was used. Categorical data were compared using the chi-square test or Fisher's exact test. ( 2 ) Correlation analysis: Pearson correlation analysis was used for data conforming to normal distribution, and Spearman rank correlation analysis was used for data not conforming to normal distribution, to evaluate the correlation between preoperative paraspinal muscle degeneration parameters and postoperative improvements in VAS and ODI. ( 3 ) Regression analysis: variables with P < 0.05 in univariate analysis were included in the multivariate logistic regression model to identify independent risk factors for poor outcomes after UBE. ( 4 ) Predictive efficacy evaluation: receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive efficacy of preoperative paraspinal muscle degeneration parameters for poor postoperative outcomes, calculating the area under the curve (AUC), optimal cutoff value, sensitivity, and specificity. The optimal cutoff value was determined based on the maximum Youden index. The significance level was set at α = 0.05, with P < 0.05 considered statistically significant. Results 2.1 Patient General Data and Clinical Outcomes A total of 108 patients with L5/S1 disc herniation who underwent UBE surgery and met the inclusion criteria were enrolled in this study, aged 22–56 years, with a mean age of 39.5 ± 5.6 years, BMI of 24.6 ± 3.2 kg/m², and median disease duration of 12.0 (6.0, 24.0) months. Postoperative follow-up ranged from 12 to 24 months, with a mean of 16.8 ± 3.6 months. According to the modified MacNab criteria evaluated at the final follow-up, 42 cases (38.9%) were graded as excellent, 48 cases (44.4%) as good, 12 cases (11.1%) as fair, and 6 cases (5.6%) as poor, yielding an excellent/good rate of 83.3%. Patients with excellent and good outcomes were included in the excellent/good group (90 cases), while those with fair and poor outcomes were included in the fair/poor group (18 cases). Comparison of preoperative general data between the two groups (Table 1 ) showed that patients in the fair/poor group were significantly older (P < 0.05) and had significantly longer disease duration (P 0.05). Table 1 Comparison of preoperative general data between the two groups Parameter Excellent/good group (n = 90) Fair/poor group (n = 18) Statistic P-value Age (years) 38.2 ± 5.2 43.5 ± 5.8 t = 3.674 0.001 Sex (male/female) 40/50 6/12 χ²=0.621 0.431 BMI(kg/m²) 24.5 ± 3.1 25.1 ± 3.6 t = 0.743 0.459 Disease duration (months) 10.0(5.0, 18.0) 24.0(15.0, 36.0) Z = 4.216 < 0.001 2.2 Intergroup Comparison of Preoperative Paraspinal Muscle Degeneration Parameters Comparison of preoperative paraspinal muscle degeneration parameters between the two groups (Table 2 ) revealed that patients in the fair/poor group had significantly smaller ipsilateral multifidus functional cross-sectional area (MF fCSA) and relative cross-sectional area (MF rCSA) (P < 0.01), and significantly higher fat infiltration rate (MF FIR) (P < 0.001) compared to the excellent/good group. The ipsilateral erector spinae FIR was also significantly higher in the fair/poor group (P 0.05). Regarding Goutallier classification distribution, the proportion of patients with Goutallier grade ≥ 2 in the fair/poor group was 83.3% (15/18), significantly higher than that in the excellent/good group (32.2%, 29/90) (χ²=16.874, P < 0.001). Table 2 Comparison of preoperative paraspinal muscle degeneration parameters between the two groups Parameter Excellent/good group (n = 90) Fair/poor group (n = 18) Statistic P-value Multifidus (MF) MF tCSA(mm²) 452.6 ± 86.4 438.2 ± 92.5 t = 0.642 0.522 MF fCSA(mm²) 362.8 ± 72.5 278.6 ± 68.4 t = 4.536 < 0.001 MF rCSA 0.62 ± 0.12 0.48 ± 0.11 t = 4.682 < 0.001 MF FIR(%) 19.8 ± 7.6 36.4 ± 9.8 t = 8.124 < 0.001 Goutallier grade (≥ 2, n (%)) 29(32.2%) 15(83.3%) χ²=16.874 < 0.001 Erector spinae (ES) ES tCSA(mm²) 856.4 ± 156.8 832.6 ± 168.4 t = 0.584 0.560 ES fCSA(mm²) 684.5 ± 132.6 612.8 ± 142.5 t = 1.986 0.052 ES rCSA 1.46 ± 0.28 1.38 ± 0.32 t = 1.124 0.264 ES FIR(%) 20.1 ± 8.2 26.4 ± 9.6 t = 2.845 0.006 2.3 Correlation Analysis Between Paraspinal Muscle Degeneration Parameters and Postoperative Outcomes Correlation analysis (Table 3 ) showed that preoperative ipsilateral MF FIR was significantly negatively correlated with the 12-month postoperative ODI improvement rate (r=-0.682, P < 0.001) and low back pain VAS improvement rate (r=-0.594, P < 0.001), but showed no significant correlation with leg pain VAS improvement rate (r=-0.186, P = 0.086). MF fCSA was significantly positively correlated with postoperative ODI improvement rate (r = 0.536, P < 0.001). ES FIR was also negatively correlated with postoperative ODI improvement rate (r=-0.312, P = 0.012) and low back pain VAS improvement rate (r=-0.342, P = 0.006), although the correlation coefficients were lower than those for the multifidus. Table 3 Correlation between paraspinal muscle degeneration parameters and postoperative functional improvement Parameter ODI improvement rate Low back pain VAS improvement rate Leg pain VAS improvement rate MF FIR r=-0.682*** r=-0.594*** r=-0.186 MF fCSA r = 0.536*** r = 0.412 r = 0.124 ES FIR r=-0.312* r=-0.342* r=-0.098 Note: *P < 0.05, ***P 0.05.* 2.4 Multivariate Logistic Regression Analysis of Factors Influencing Poor Outcomes After UBE Variables with P < 0.05 in univariate analysis (age, disease duration, MF FIR, MF fCSA, ES FIR) were included in the multivariate logistic regression model. The results (Table 4 ) showed that preoperative high fat infiltration rate (MF FIR ≥ 25%) and long disease duration (≥ 12 months) were independent risk factors for poor outcomes after UBE for L5/S1 disc herniation (P < 0.05), while MF fCSA was a protective factor for postoperative outcomes (OR = 0.986, P 0.05). Table 4 Multivariate logistic regression analysis of factors influencing poor outcomes after UBE Variable B SE Wald χ² OR(95%CI) P值 Disease duration (≥ 12 months) 1.864 0.682 7.468 6.45(1.69–24.56) 0.006 MF FIR(≥ 25%) 2.356 0.724 10.586 10.55(2.55–43.62) 0.001 MF fCSA -0.014 0.006 5.444 0.986(0.974–0.998) 0.020 Age 0.042 0.028 2.250 1.043(0.987–1.102) 0.134 ES FIR 0.056 0.042 1.778 1.058(0.974–1.149) 0.182 2.5 Predictive Efficacy of Preoperative Paraspinal Muscle Degeneration Parameters for Postoperative Outcomes ROC curve analysis (Table 5 ) revealed that preoperative ipsilateral multifidus fat infiltration rate (MF FIR) had the largest area under the curve (AUC) for predicting poor postoperative outcomes, at 0.856 (95% CI: 0.768–0.944, P < 0.001), indicating good predictive value. Based on the maximum Youden index, the optimal cutoff value was determined to be 24.8%, with a sensitivity of 85.0% and specificity of 75.0% for predicting poor postoperative outcomes. Preoperative MF fCSA yielded an AUC of 0.792 (95% CI: 0.698–0.886, P = 0.002) for predicting poor outcomes, showing lower predictive efficacy than FIR. ES FIR had an AUC of 0.686 (95% CI: 0.568–0.804, P = 0.018), indicating moderate predictive value. MF Goutallier grade (≥ 2 as the predictive criterion) demonstrated an AUC of 0.802 (95% CI: 0.714–0.890, P < 0.001). Table 5 ROC curve analysis of preoperative paraspinal muscle degeneration parameters for predicting poor postoperative outcomes Parameter AUC 95%CI Optimal cutoff value Sensitivity (%) Specificity (%) P-value MF FIR 0.856 0.768–0.944 24.8% 85.0 75.0 < 0.001 MF fCSA 0.792 0.698–0.886 312.5 mm² 78.9 70.0 0.002 ES FIR 0.686 0.568–0.804 23.6% 68.4 65.0 0.018 Goutallier grade (≥ 2) 0.802 0.714–0.890 - 83.3 67.8 < 0.001 2.6 Measurement Reliability Analysis Twenty patients were randomly selected for repeat measurements. The results showed that the intraclass correlation coefficients (ICC) for tCSA, fCSA, and FIR measurements of the multifidus and erector spinae ranged from 0.886 to 0.942, and the Kappa value for Goutallier grade assessment was 0.824, indicating good consistency and reproducibility of the measurements. Discussion Lumbar disc herniation is a common condition in spinal surgery, and UBE has become an effective minimally invasive technique for treating L5/S1 disc herniation due to its advantages of minimal trauma and rapid recovery. Although most patients achieve satisfactory postoperative outcomes, some patients experience residual low back pain and slow functional recovery, affecting overall satisfaction( 13 , 14 ). The results of this study showed an excellent/good rate of 83.3% after UBE, which is consistent with literature reports. However, it is noteworthy that 16.7% of patients had poor outcomes, suggesting the need for further investigation into potential factors influencing postoperative outcomes. 3.1 Relationship Between Paraspinal Muscle Degeneration and Postoperative Outcomes This study systematically evaluated, for the first time, the predictive value of preoperative paraspinal muscle degeneration parameters for postoperative outcomes after UBE for L5/S1 disc herniation. The results showed that patients in the fair/poor group had significantly smaller preoperative ipsilateral multifidus functional cross-sectional area (MF fCSA) (278.6 ± 68.4 mm² vs. 362.8 ± 72.5 mm², P < 0.001) and significantly higher fat infiltration rate (MF FIR) (36.4 ± 9.8% vs. 19.8 ± 7.6%, P < 0.001) compared to the excellent/good group. Correlation analysis further confirmed that MF FIR was significantly negatively correlated with postoperative ODI improvement rate (r=-0.682) and low back pain VAS improvement rate (r=-0.594), but showed no significant correlation with leg pain VAS improvement rate. This finding has important clinical implications: it suggests that paraspinal muscle degeneration primarily affects the relief of postoperative low back symptoms rather than the effectiveness of nerve root decompression. In other words, even when surgery successfully relieves neural compression, pre-existing muscle degeneration may become the "primary culprit" for residual postoperative low back pain. As the deepest layer of the paraspinal muscles, the multifidus plays a central role in lumbar segmental stability through its abundant distribution of muscle spindles and segmental innervation( 15 ). Burkhard et al. confirmed that multifidus atrophy and fatty infiltration are closely associated with chronic low back pain( 16 ). In this study, the impact of multifidus degeneration on prognosis was substantially greater than that of the erector spinae, possibly due to the following reasons: the multifidus possesses unique segmental innervation characteristics, making its dysfunction difficult to compensate for by other muscles; whereas the erector spinae, as a global mover muscle, has higher functional redundancy, allowing partial compensation for some degree of degeneration. This explains why multifidus parameters demonstrated stronger predictive efficacy in the regression model. 3.2 Fatty Infiltration: A More Sensitive Predictor Than Muscle Atrophy Notably, there was no significant difference in multifidus total cross-sectional area (tCSA) between the two groups in this study (P = 0.522), whereas differences in functional cross-sectional area (fCSA) and fat infiltration rate (FIR) were highly significant. This indicates that simply measuring muscle size may mask the true functional status—when muscle tissue is replaced by adipose tissue, the total cross-sectional area may change little or even increase, but the functional muscle mass is significantly reduced. ROC curve analysis showed that MF FIR had an AUC of 0.856 for predicting poor postoperative outcomes, superior to that of MF fCSA (0.792), suggesting that fat infiltration rate is a more sensitive prognostic predictor than muscle atrophy. The optimal cutoff value for MF FIR in this study was 24.8%, meaning that when preoperative multifidus fat infiltration exceeds this threshold, the risk of poor postoperative outcomes is significantly increased (OR = 10.55). This value can serve as a quantitative reference for clinical risk assessment. Goutallier grade ≥ 2 also demonstrated good predictive efficacy (AUC = 0.802) and is easy to use, making it suitable for rapid clinical evaluation. However, the grading system has some subjectivity, whereas FIR, as a continuous variable, provides more refined risk stratification. 3.3 Biomechanical Specificity of the L5/S1 Segment This study focused on the L5/S1 segment based on its unique biomechanical status. As the lumbosacral junction, L5/S1 bears the greatest shear stress in the lumbar spine, and the multifidus has a unique anatomical attachment at this site—directly originating from the dorsal surface of the sacrum, forming a natural "dynamic ligament." Naghdi et al. confirmed that multifidus fatty infiltration directly alters muscle mechanical properties, leading to decreased active contractile capacity( 17 ). When multifidus fatty infiltration occurs, its active contractile capacity decreases, resulting in impaired lumbosacral stability. Moens et al. found that in patients with persistent spinal pain syndrome after lumbar surgery, the median multifidus fat infiltration at the L5/S1 level was 52.84%, with all patients exhibiting moderate to severe fatty infiltration( 18 ). This explains why even with adequate neural decompression, patients may still experience mechanical low back pain during daily activities such as bending and lifting due to local instability. The biomechanical specificity of the L5/S1 segment explains why multifidus degeneration primarily affects postoperative low back pain relief while having less impact on leg pain relief. 3.4 Influence of Disease Duration and Age In this study, disease duration ≥ 12 months was an independent risk factor for poor postoperative outcomes (OR = 6.45). Long-term chronic nerve root compression may lead to irreversible nerve damage and central sensitization, affecting postoperative recovery. Additionally, prolonged pain and reduced activity can lead to disuse atrophy of the paraspinal muscles, forming a vicious cycle of "pain → reduced activity → muscle degeneration → decreased stability → increased pain"( 19 ). Age showed significant differences in univariate analysis but did not reach statistical significance in multivariate regression, suggesting that age may indirectly affect prognosis by influencing muscle degeneration. 3.5 Clinical Significance and Rehabilitation Implications The findings of this study have important implications for clinical practice:First, preoperative risk assessment.** It is recommended that paraspinal muscle evaluation be incorporated into routine preoperative imaging interpretation. A prospective study by Ghimire et al. confirmed that preoperative paraspinal muscle cross-sectional area is an independent predictor of postoperative functional recovery( 20 ). A 2-year follow-up study of 243 patients by Banitalebi et al. also demonstrated that preoperative MRI assessment of paraspinal muscle fatty infiltration can serve as an important imaging biomarker for predicting postoperative outcomes( 21 ). When MRI shows significant multifidus fatty infiltration (FIR ≥ 25% or Goutallier grade ≥ 2), patients should be fully informed of the potential risk of residual low back pain or slow recovery postoperatively, allowing for appropriate management of patient expectations.Second, individualized rehabilitation protocols.** For patients with severe preoperative paraspinal muscle degeneration, targeted rehabilitation plans should be developed postoperatively. A systematic review by Valera-Calero et al. confirmed that visual RUSI biofeedback is superior to simple verbal feedback in improving motor control training performance and success rates( 22 ). A recent randomized controlled trial by Sarafadeen et al. further demonstrated that RUSI-assisted spinal stabilization training significantly increases multifidus cross-sectional area, and improvements in muscle morphology are significantly correlated with pain relief (r=-0.40 to -0.50) and functional improvement (r=-0.38 to -0.42)( 23 ). Lin et al. further confirmed that RUSI effectively promotes sustained multifidus contractile capacity( 24 ). These findings provide high-quality evidence-based support for postoperative targeted multifidus functional training.Third, surgical timing.** Disease duration ≥ 12 months is a risk factor for poor outcomes. Regression analysis by Ghimire et al. showed that symptom duration was positively correlated with preoperative ODI (P = 0.005) ( 20 ), suggesting that for patients with poor response to conservative treatment, surgical intervention should not be delayed excessively to prevent irreversible muscle degeneration. 3.6 Limitations of This Study This study has several limitations: First, as a retrospective study, there may be selection bias, and the sample size was relatively limited (particularly with only 18 cases in the fair/poor group), which may affect statistical power. Second, although standardized methods were used for paraspinal muscle measurements and inter-observer reliability was verified, manual delineation may still have some error. Third, only preoperative muscle status was assessed, and postoperative muscle changes and the impact of rehabilitation training on prognosis were not observed. Fourth, the maximum follow-up duration was 24 months, and long-term outcomes require further investigation. Fifth, the study population was limited to single-level L5/S1 pathology, and whether the conclusions can be generalized to other segments requires validation. 3.7 Future Perspectives Future studies may include prospective multicenter research with larger sample sizes and extended follow-up periods; exploration of quantitative MRI techniques (such as IDEAL-IQ sequences) for automated and precise measurement of fat infiltration; randomized controlled trials to verify whether enhanced rehabilitation protocols for high-risk populations can improve prognosis; and incorporation of assessment tools such as surface electromyography to further investigate the relationship between paraspinal muscle function and postoperative outcomes. In conclusion, preoperative paraspinal muscle degeneration, particularly the degree of multifidus fatty infiltration, is an important predictor of clinical outcomes after UBE for L5/S1 disc herniation. When MRI shows multifidus fat infiltration rate ≥ 24.8% or Goutallier grade ≥ 2, clinicians should be alert to the risk of poor postoperative outcomes. It is recommended that paraspinal muscle status be incorporated into comprehensive preoperative assessment and that individualized rehabilitation protocols be developed for high-risk populations to further improve patient outcomes. Declarations Authors' contributions LW, MG, HX, XC, and QY contributed to the study conception and design. Data collection and analysis were performed by LW, MG, and HX. The first draft of the manuscript was written by LW and MG, and all authors commented on previous versions of the manuscript. XC supervised the project, validated the results, and critically revised the manuscript. All authors read and approved the final manuscript. Acknowledgements The authors thank the staff of the Medical Records Department of The Seventh Affiliated Hospital of Anhui University of Chinese Medicine for their assistance in data retrieval. Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Ethical approval and informed consent: This study was approved by the Ethics Committee of the Seventh Affiliated Hospital of Anhui University of Chinese Medicine (Approval No: [2024] 84). All patients provided written informed consent prior to participation in this study. Consent for publication: Not applicable. Availability of data and materials: The datasets generated and/or analyzed during this study are not publicly available because of patient privacy regulations, but they are available from the corresponding author upon reasonable request. Competing interests: The authors declare that they have no competing interests. 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Early Clinical and Radiologic Evaluation of Unilateral Biportal Spinal Endoscopy for Recurrent Lumbar Disc Herniation: A Retrospective Study. World Neurosurg. 2025;203:124499. Carvalho V, Santos J, Santos Silva P, Vaz R, Pereira P. Relationship between fatty infiltration of paraspinal muscles and clinical outcome after lumbar discectomy. Brain Spine. 2022;2:101697. Zhu DC, Lin JH, Xu JJ, Guo Q, Wang YH, Jiang C, et al. An assessment of morphological and pathological changes in paravertebral muscle degeneration using imaging and histological analysis: a cross-sectional study. BMC Musculoskelet Disord. 2021;22(1):854. Suo M, Zhang J, Sun T, Wang J, Liu X, Huang H, et al. The association between morphological characteristics of paraspinal muscle and spinal disorders. Ann Med. 2023;55(2):2258922. Yu J, Zhang C, Zhou Y, Wang J, Zhang Y, Wang Y. Correlation analysis between multifidus muscle atrophy and the severity of degenerative scoliosis retrospective, cross-sectional study. Sci Rep. 2025;15(1):30133. Wang S, Wang Y, Wang Z, Ai Y, Chen Q, Zhao Y, et al. Comparative analysis of the correlation between paraspinal muscles fat infiltration and vertebral bone quality in patients with lumbar degenerative diseases. Eur Spine J. 2025;34(10):4486–95. Wang K, Deng Z, Chen X, Shao J, Qiu L, Jiang C et al. The Role of Multifidus in the Biomechanics of Lumbar Spine: A Musculoskeletal Modeling Study. Bioeng (Basel). 2023;10(1). Li Q, Long X, Wang R, Pengying N, Cai L, Wang L, et al. Correlation between degeneration of cervical intervertebral disc and degeneration of paravertebral muscle. Front Endocrinol (Lausanne). 2024;15:1391970. Han G, Wu H, Dai J, Li X, Yue L, Fan Z, et al. Does paraspinal muscle morphometry predict functional status and re-operation after lumbar spinal surgery? A systematic review and meta-analysis. Eur Radiol. 2023;33(8):5269–81. Cheng Z, Tang T, Chen S, Hong J, Lu H, Xu H, et al. Risk Factor Analysis of Residual Low Back Pain After Unilateral Biportal Endoscopic Discectomy in Patients With Lumbar Disc Herniation. Med Sci Monit. 2026;32:e951644. Yang YF, Yu JC, Zhu ZW, Li YW, Xiao Z, Zhi CG, et al. Comparison of clinical outcomes and cost-utility between unilateral biportal endoscopic discectomy and percutaneous endoscopic interlaminar discectomy for single-level lumbar disc herniation: a retrospective matched controlled study. J Orthop Surg Res. 2024;19(1):755. Kalli I, Niglas M, Naeini MK, Freidin M, Thomas L, Menni C et al. Paraspinal muscle quality in chronic low back pain: a systematic review and meta-analysis of muscle atrophy and fat infiltration. Eur Spine J. 2025. Burkhard MD, Chiapparelli E, Hambrecht J, Köhli P, Guven AE, Tsuchiya K, et al. Multifidus Degeneration: The Key Imaging Predictor of Adjacent Segment Disease. Global Spine J. 2025;15(4):2348–58. Naghdi N, Masi S, Bertrand C, Rosenstein B, Cohen-Adad J, Rivaz H, et al. Ultrasound and MRI-based evaluation of relationships between morphological and mechanical properties of the lower lumbar multifidus muscle in chronic low back pain. Eur Spine J. 2025;34(7):2587–96. Moens M, Genot LV, Van Gestel F, Pilitsis JG, Billot M, Roulaud M et al. Multifidus Fat Infiltration in Patients with Persistent Spinal Pain Syndrome Type II Treated with Spinal Cord Stimulation: A Preliminary Report. J Clin Med. 2025;14(9). Feng T, Zhao J, Li J, Wang Y, Wang L, Liu X. Clarifying the impact of spine-specific sarcopenia and generalized sarcopenia on clinical features in patients with lumbar degenerative diseases. Spine J. 2025;25(11):2503–13. Ghimire N, Lakhe P, Kumar A, Ghimire N, Kutum C, Choudhary D, et al. The impact of paraspinal muscle morphology on functional outcome in patients with degenerative lumbar spine disease undergoing surgery - A prospective observational study. Brain Spine. 2024;4:104141. Banitalebi H, Hermansen E, Hellum C, Espeland A, Storheim K, Myklebust T, et al. Preoperative fatty infiltration of paraspinal muscles assessed by MRI is associated with less improvement of leg pain 2 years after surgery for lumbar spinal stenosis. Eur Spine J. 2024;33(5):1967–78. Valera-Calero JA, Fernández-de-Las-Peñas C, Varol U, Ortega-Santiago R, Gallego-Sendarrubias GM, Arias-Buría JL. Ultrasound Imaging as a Visual Biofeedback Tool in Rehabilitation: An Updated Systematic Review. Int J Environ Res Public Health. 2021;18(14). Sarafadeen R, Ganiyu SO, Ibrahim AA, Akindele MO, Awotidebe AW, Kaka B, et al. Lumbar stabilization exercise with and without real-time ultrasound imaging biofeedback in chronic low back pain patients: a randomized controlled trial. Sci Rep. 2025;15(1):36975. Lin S, Zhu B, Zheng Y, Huang G, Zeng Q, Wang C. Effect of real-time ultrasound imaging for biofeedback on trunk muscle contraction in healthy subjects: a preliminary study. BMC Musculoskelet Disord. 2021;22(1):142. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-9065113","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":630793422,"identity":"2b484194-8e17-4add-aba3-381b8a9ab5f9","order_by":0,"name":"Li Wenqing¹","email":"","orcid":"","institution":"The Seventh Affiliated Hospital of Anhui University of Chinese Medicine","correspondingAuthor":false,"prefix":"","firstName":"Li","middleName":"","lastName":"Wenqing¹","suffix":""},{"id":630793428,"identity":"ae41fd92-ca33-4754-87a9-f91ba200e9f0","order_by":1,"name":"Gao Meng¹","email":"","orcid":"","institution":"The Seventh Affiliated Hospital of Anhui University of Chinese Medicine","correspondingAuthor":false,"prefix":"","firstName":"Gao","middleName":"","lastName":"Meng¹","suffix":""},{"id":630793431,"identity":"900fb14c-2799-43b8-a63f-b195c519d572","order_by":2,"name":"Xie Zihan¹","email":"","orcid":"","institution":"The Seventh Affiliated Hospital of Anhui University of Chinese Medicine","correspondingAuthor":false,"prefix":"","firstName":"Xie","middleName":"","lastName":"Zihan¹","suffix":""},{"id":630793435,"identity":"991eb7c7-e485-4527-aecb-87e8bc90fc42","order_by":3,"name":"Chen Xiaolong","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyklEQVRIiWNgGAWjYBACeWbmAwc/8NjwyLM3HyBOi2E7W+JhCZk0OcOeYwlEWnOex/gAj81hY4YbOQbE6WBsZks4IJFzOLFxRs7HG28Y7OR0GwhoYQf65UDBmfTEdp63my3nMCQbmx0gxhbJHuvExvbcbdI8DAcStxHSwnCYx+AA7z/mxIYDOc9I0MLD42zMcCKHjTgthkCHHZbgAQeyseUcAyL8Is9/+PBHaFQ+vPGmwk6OoBYUIMFDZNQgayFVxygYBaNgFIwIAAD1g0TnTu9xFQAAAABJRU5ErkJggg==","orcid":"","institution":"The Seventh Affiliated Hospital of Anhui University of Chinese Medicine","correspondingAuthor":true,"prefix":"","firstName":"Chen","middleName":"","lastName":"Xiaolong","suffix":""},{"id":630793438,"identity":"bc95100d-e4d4-4992-8061-9a0257a25e01","order_by":4,"name":"Yu Qihua²","email":"","orcid":"","institution":"The Seventh Affiliated Hospital of Anhui University of Chinese Medicine","correspondingAuthor":false,"prefix":"","firstName":"Yu","middleName":"","lastName":"Qihua²","suffix":""}],"badges":[],"createdAt":"2026-03-08 15:08:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9065113/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9065113/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108491659,"identity":"edb869ac-2c59-4d4e-b04f-5a99416531ec","added_by":"auto","created_at":"2026-05-05 09:55:05","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":299509,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9065113/v1/73d37ed1-328c-4a85-b022-f41d2f0b9212.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Predictive Value of Preoperative Paraspinal Muscle Degeneration Parameters for Clinical Outcomes After Unilateral Biportal Endoscopy for L5/S1 Lumbar Disc Herniation","fulltext":[{"header":"Introduction","content":"\u003cp\u003eLumbar disc herniation (LDH) is a common condition in spinal surgery, frequently occurring at the L5/S1 segment. Unilateral biportal endoscopy (UBE) has emerged as one of the mainstream minimally invasive surgical techniques for the treatment of L5/S1 disc herniation due to its advantages of minimal trauma and rapid recovery, yielding satisfactory clinical outcomes (\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). However, in clinical practice, some patients experience varying degrees of residual low back pain and weakness, along with slow functional recovery, despite significant relief of lower limb radicular pain following neural decompression, which affects overall patient satisfaction(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). This phenomenon suggests that factors other than neural decompression may influence postoperative outcomes(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). The lumbar paraspinal muscles, including the multifidus (MF) and erector spinae (ES), serve as the dynamic stabilizing system of the spine and play a critical role in maintaining lumbar segmental stability and normal function(\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). Notably, the multifidus muscle contributes uniquely to lumbar segmental stability through its segmental innervation and abundant distribution of muscle spindles(\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). With aging or chronic inflammatory stimulation, the paraspinal muscles may undergo degenerative changes characterized by increased fatty infiltration and reduced cross-sectional area, leading to impaired stabilizing function(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). The L5/S1 segment, as the lumbosacral junction, is subjected to distinct biomechanical stresses, particularly high shear forces, and the condition of the multifidus at this level is crucial for maintaining local stability (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAlthough an increasing number of studies have investigated the relationship between paraspinal muscle degeneration and lumbar degenerative diseases, with paraspinal muscle fatty infiltration having been confirmed to be associated with poor prognosis after lumbar surgery(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e), systematic research on the predictive value of preoperative paraspinal muscle degeneration parameters for clinical outcomes following UBE for L5/S1 disc herniation remains limited(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). Therefore, this study aimed to retrospectively analyze the clinical data of patients who underwent UBE for L5/S1 disc herniation, measure preoperative paraspinal muscle parameters including cross-sectional area and degree of fatty infiltration, analyze their correlation with postoperative improvements in VAS scores for low back and leg pain and ODI index, and investigate the predictive value of preoperative paraspinal muscle degeneration for postoperative outcomes following UBE. The findings may provide a theoretical basis for preoperative risk assessment and the development of individualized rehabilitation protocols.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e1.1 General Information\u003c/h2\u003e \u003cp\u003e This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of The Seventh Affiliated Hospital of Anhui University of Chinese Medicine (Approval No. [2024] 84). A retrospective analysis was conducted on clinical data of patients who underwent unilateral biportal endoscopy (UBE) for single-level L5/S1 disc herniation in the Department of Orthopedics, The Seventh Affiliated Hospital of Anhui University of Chinese Medicine from January 2024 to December 2025. All patients were definitively diagnosed based on medical history inquiry, physical examination, and imaging studies. Inclusion criteria were: (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) complete imaging data, including lumbar MRI plain scan and X-ray films; (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) MRI-confirmed single-level L5/S1 disc herniation consistent with clinical symptoms and signs; (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) underwent UBE surgery with postoperative follow-up \u0026ge;\u0026thinsp;12 months; (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) age 18\u0026ndash;60 years. Exclusion criteria were: (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) multi-level disc herniation or involvement of other segments requiring surgical intervention; (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) history of previous lumbar surgery; (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) concomitant lumbar spondylolisthesis (Meyerding\u0026thinsp;\u0026ge;\u0026thinsp;grade I), spondylolysis, spinal tumors, infections, trauma, or ankylosing spondylitis; (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) concomitant severe osteoporosis or metabolic bone diseases; (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e) poor image quality precluding accurate measurements. A total of 108 patients who met the inclusion criteria were enrolled, including 46 males and 62 females, aged 22\u0026ndash;56 years, with a mean age of 39.5\u0026thinsp;\u0026plusmn;\u0026thinsp;5.6 years. General data including age, sex, disease duration, and body mass index (BMI) were collected.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e1.2 Surgical Procedure\u003c/h2\u003e \u003cp\u003eAll surgeries were performed by the same team of senior spinal surgeons using the UBE technique. Patients were placed in the prone position under general anesthesia with the abdomen suspended. The observation portal and working portal were established ipsilaterally at the L5/S1 interspace, with continuous irrigation maintained to ensure a clear visual field. Under endoscopic visualization, the interlaminar space was exposed, the lower margin of the L5 lamina and upper margin of the S1 lamina were partially removed using a burr, and the ligamentum flavum was resected to expose the dural sac and traversing nerve root. The herniated nucleus pulposus was removed to achieve complete decompression of the nerve root. After confirming nerve root laxity and good pulsation intraoperatively, thorough hemostasis was achieved, a drainage tube was placed, and the incision was closed.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e1.3 Clinical Outcome Assessment\u003c/h2\u003e \u003cp\u003eVisual analog scale (VAS) scores for low back and leg pain and Oswestry Disability Index (ODI) were recorded preoperatively and at 3, 6, and 12 months postoperatively. Clinical outcomes were evaluated at the final follow-up using the modified MacNab criteria: excellent (complete resolution of symptoms, return to normal activities), good (marked improvement in symptoms, occasional mild pain), fair (partial improvement in symptoms, persistent significant pain), and poor (no improvement or worsening of symptoms). Patients with excellent and good outcomes were classified as the excellent/good group, while those with fair and poor outcomes were classified as the fair/poor group.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e1.4 Imaging Measurements and Parameter Assessment\u003c/h2\u003e \u003cp\u003eAll patients underwent preoperative lumbar MRI examination using a 3.0T MRI scanner (Ingenia 3.0T, Philips, Netherlands), with scanning sequences including axial and sagittal T2-weighted images. Axial T2WI images at the L5/S1 disc level were selected for analysis.\u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e1.4.1 Measurement of Paraspinal Muscle Degeneration Parameters\u003c/h2\u003e \u003cp\u003eUsing Image J software (NIH, USA), the boundaries of the bilateral multifidus (MF) and erector spinae (ES) muscles at the L5/S1 level were manually delineated to measure the following parameters: (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) Total cross-sectional area (tCSA): delineated along the muscle fascial contour, including muscle tissue and internal fat areas, recorded as MF tCSA and ES tCSA, respectively. (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) Functional cross-sectional area (fCSA): based on the total ROI, a manual threshold method was used to set grayscale thresholds, excluding high-signal pixels in fat infiltration areas and retaining pure muscle tissue pixels, with the software automatically calculating fCSA. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) Fat infiltration rate (FIR): calculated as FIR = (tCSA - fCSA) / tCSA \u0026times; 100%. (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) Goutallier classification: semi-quantitative grading of paraspinal muscle fatty infiltration on T2WI images: grade 0 (no fatty infiltration), grade 1 (some fatty streaks), grade 2 (significant fatty infiltration but still less than muscle tissue), grade 3 (fatty tissue approximately equal to muscle tissue), grade 4 (fatty tissue exceeding muscle tissue). (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e) Relative cross-sectional area (rCSA): the ratio of muscle cross-sectional area to the vertebral cross-sectional area (V CSA) at the same L5 level, used to correct for individual body size differences.\u003c/p\u003e \u003cp\u003eAll measurements were independently performed by two spinal surgeons blinded to patient clinical data, and the average values were used for statistical analysis. Twenty patients were randomly selected for repeat measurements at a 2-week interval, and the intraclass correlation coefficient (ICC) was calculated to assess measurement reliability.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e1.4.2 Assessment of Disc Degeneration Grade\u003c/h2\u003e \u003cp\u003eOn sagittal T2WI MRI images, the Pfirrmann classification system was used to evaluate the degree of L5/S1 disc degeneration: grade I (normal), grade II (mild degeneration), grade III (moderate degeneration), grade IV (severe degeneration), grade V (end-stage degeneration).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e1.5Statistical Analysis\u003c/h2\u003e \u003cp\u003eStatistical analysis was performed using SPSS 26.0 software. Continuous variables were first tested for normality using the Kolmogorov-Smirnov test; those conforming to normal distribution were expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation, while those not conforming to normal distribution were expressed as median (interquartile range). Categorical data were expressed as number of cases (percentage). (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) Intergroup comparison: patients were divided into excellent/good group and fair/poor group according to the modified MacNab criteria at the final follow-up, and differences in preoperative paraspinal muscle degeneration parameters and other clinical data were compared between the two groups. For continuous variables conforming to normal distribution, the independent samples t-test was used; for those not conforming to normal distribution, the Mann-Whitney U test was used. Categorical data were compared using the chi-square test or Fisher's exact test. (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) Correlation analysis: Pearson correlation analysis was used for data conforming to normal distribution, and Spearman rank correlation analysis was used for data not conforming to normal distribution, to evaluate the correlation between preoperative paraspinal muscle degeneration parameters and postoperative improvements in VAS and ODI. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) Regression analysis: variables with P\u0026thinsp;\u0026lt;\u0026thinsp;0.05 in univariate analysis were included in the multivariate logistic regression model to identify independent risk factors for poor outcomes after UBE. (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) Predictive efficacy evaluation: receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive efficacy of preoperative paraspinal muscle degeneration parameters for poor postoperative outcomes, calculating the area under the curve (AUC), optimal cutoff value, sensitivity, and specificity. The optimal cutoff value was determined based on the maximum Youden index. The significance level was set at α\u0026thinsp;=\u0026thinsp;0.05, with P\u0026thinsp;\u0026lt;\u0026thinsp;0.05 considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Patient General Data and Clinical Outcomes\u003c/h2\u003e \u003cp\u003eA total of 108 patients with L5/S1 disc herniation who underwent UBE surgery and met the inclusion criteria were enrolled in this study, aged 22\u0026ndash;56 years, with a mean age of 39.5\u0026thinsp;\u0026plusmn;\u0026thinsp;5.6 years, BMI of 24.6\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2 kg/m\u0026sup2;, and median disease duration of 12.0 (6.0, 24.0) months. Postoperative follow-up ranged from 12 to 24 months, with a mean of 16.8\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6 months.\u003c/p\u003e \u003cp\u003e According to the modified MacNab criteria evaluated at the final follow-up, 42 cases (38.9%) were graded as excellent, 48 cases (44.4%) as good, 12 cases (11.1%) as fair, and 6 cases (5.6%) as poor, yielding an excellent/good rate of 83.3%. Patients with excellent and good outcomes were included in the excellent/good group (90 cases), while those with fair and poor outcomes were included in the fair/poor group (18 cases). Comparison of preoperative general data between the two groups (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) showed that patients in the fair/poor group were significantly older (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and had significantly longer disease duration (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01) compared to the excellent/good group, while no significant differences were observed in sex distribution or BMI (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\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\u003eComparison of preoperative general data between the two groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eExcellent/good group (n\u0026thinsp;=\u0026thinsp;90)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFair/poor group (n\u0026thinsp;=\u0026thinsp;18)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eStatistic\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38.2\u0026thinsp;\u0026plusmn;\u0026thinsp;5.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e43.5\u0026thinsp;\u0026plusmn;\u0026thinsp;5.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;3.674\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex (male/female)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e40/50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6/12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eχ\u0026sup2;=0.621\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.431\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI(kg/m\u0026sup2;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;0.743\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.459\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDisease duration (months)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.0(5.0, 18.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24.0(15.0, 36.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eZ\u0026thinsp;=\u0026thinsp;4.216\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Intergroup Comparison of Preoperative Paraspinal Muscle Degeneration Parameters\u003c/h2\u003e \u003cp\u003eComparison of preoperative paraspinal muscle degeneration parameters between the two groups (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) revealed that patients in the fair/poor group had significantly smaller ipsilateral multifidus functional cross-sectional area (MF fCSA) and relative cross-sectional area (MF rCSA) (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), and significantly higher fat infiltration rate (MF FIR) (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) compared to the excellent/good group. The ipsilateral erector spinae FIR was also significantly higher in the fair/poor group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), but no significant differences were observed in ES fCSA or rCSA between the two groups (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Regarding Goutallier classification distribution, the proportion of patients with Goutallier grade\u0026thinsp;\u0026ge;\u0026thinsp;2 in the fair/poor group was 83.3% (15/18), significantly higher than that in the excellent/good group (32.2%, 29/90) (χ\u0026sup2;=16.874, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\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\u003eComparison of preoperative paraspinal muscle degeneration parameters between the two groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eExcellent/good group (n\u0026thinsp;=\u0026thinsp;90)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFair/poor group (n\u0026thinsp;=\u0026thinsp;18)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eStatistic\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eMultifidus (MF)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMF tCSA(mm\u0026sup2;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e452.6\u0026thinsp;\u0026plusmn;\u0026thinsp;86.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e438.2\u0026thinsp;\u0026plusmn;\u0026thinsp;92.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;0.642\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.522\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMF fCSA(mm\u0026sup2;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e362.8\u0026thinsp;\u0026plusmn;\u0026thinsp;72.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e278.6\u0026thinsp;\u0026plusmn;\u0026thinsp;68.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;4.536\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\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\u003eMF rCSA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.62\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.48\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;4.682\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\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\u003eMF FIR(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19.8\u0026thinsp;\u0026plusmn;\u0026thinsp;7.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e36.4\u0026thinsp;\u0026plusmn;\u0026thinsp;9.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;8.124\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\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\u003eGoutallier grade (\u0026ge;\u0026thinsp;2, n (%))\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e29(32.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15(83.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eχ\u0026sup2;=16.874\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eErector spinae (ES)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eES tCSA(mm\u0026sup2;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e856.4\u0026thinsp;\u0026plusmn;\u0026thinsp;156.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e832.6\u0026thinsp;\u0026plusmn;\u0026thinsp;168.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;0.584\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.560\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eES fCSA(mm\u0026sup2;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e684.5\u0026thinsp;\u0026plusmn;\u0026thinsp;132.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e612.8\u0026thinsp;\u0026plusmn;\u0026thinsp;142.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;1.986\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.052\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eES rCSA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.46\u0026thinsp;\u0026plusmn;\u0026thinsp;0.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.38\u0026thinsp;\u0026plusmn;\u0026thinsp;0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;1.124\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.264\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eES FIR(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20.1\u0026thinsp;\u0026plusmn;\u0026thinsp;8.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26.4\u0026thinsp;\u0026plusmn;\u0026thinsp;9.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;2.845\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Correlation Analysis Between Paraspinal Muscle Degeneration Parameters and Postoperative Outcomes\u003c/h2\u003e \u003cp\u003eCorrelation analysis (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) showed that preoperative ipsilateral MF FIR was significantly negatively correlated with the 12-month postoperative ODI improvement rate (r=-0.682, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and low back pain VAS improvement rate (r=-0.594, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), but showed no significant correlation with leg pain VAS improvement rate (r=-0.186, P\u0026thinsp;=\u0026thinsp;0.086). MF fCSA was significantly positively correlated with postoperative ODI improvement rate (r\u0026thinsp;=\u0026thinsp;0.536, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). ES FIR was also negatively correlated with postoperative ODI improvement rate (r=-0.312, P\u0026thinsp;=\u0026thinsp;0.012) and low back pain VAS improvement rate (r=-0.342, P\u0026thinsp;=\u0026thinsp;0.006), although the correlation coefficients were lower than those for the multifidus.\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\u003eCorrelation between paraspinal muscle degeneration parameters and postoperative functional improvement\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eODI improvement rate\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLow back pain VAS improvement rate\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeg pain VAS improvement rate\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMF FIR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003er=-0.682***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003er=-0.594***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003er=-0.186\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMF fCSA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003er\u0026thinsp;=\u0026thinsp;0.536***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003er\u0026thinsp;=\u0026thinsp;0.412\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003er\u0026thinsp;=\u0026thinsp;0.124\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eES FIR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003er=-0.312*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003er=-0.342*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003er=-0.098\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eNote: *P\u0026thinsp;\u0026lt;\u0026thinsp;0.05, ***P\u0026thinsp;\u0026lt;\u0026thinsp;0.001; unmarked values indicate P\u0026thinsp;\u0026gt;\u0026thinsp;0.05.*\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Multivariate Logistic Regression Analysis of Factors Influencing Poor Outcomes After UBE\u003c/h2\u003e \u003cp\u003eVariables with P\u0026thinsp;\u0026lt;\u0026thinsp;0.05 in univariate analysis (age, disease duration, MF FIR, MF fCSA, ES FIR) were included in the multivariate logistic regression model. The results (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) showed that preoperative high fat infiltration rate (MF FIR\u0026thinsp;\u0026ge;\u0026thinsp;25%) and long disease duration (\u0026ge;\u0026thinsp;12 months) were independent risk factors for poor outcomes after UBE for L5/S1 disc herniation (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), while MF fCSA was a protective factor for postoperative outcomes (OR\u0026thinsp;=\u0026thinsp;0.986, P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Age and ES FIR did not reach statistical significance in the regression model (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\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\u003eMultivariate logistic regression analysis of factors influencing poor outcomes after UBE\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"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 \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSE\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eWald χ\u0026sup2;\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eOR(95%CI)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP值\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDisease duration (\u0026ge;\u0026thinsp;12 months)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.864\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.682\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.468\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e6.45(1.69\u0026ndash;24.56)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMF FIR(\u0026ge;\u0026thinsp;25%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.356\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.724\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e10.586\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e10.55(2.55\u0026ndash;43.62)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMF fCSA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5.444\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.986(0.974\u0026ndash;0.998)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.020\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.042\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.028\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.043(0.987\u0026ndash;1.102)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.134\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eES FIR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.056\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.042\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.778\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.058(0.974\u0026ndash;1.149)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.182\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Predictive Efficacy of Preoperative Paraspinal Muscle Degeneration Parameters for Postoperative Outcomes\u003c/h2\u003e \u003cp\u003eROC curve analysis (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) revealed that preoperative ipsilateral multifidus fat infiltration rate (MF FIR) had the largest area under the curve (AUC) for predicting poor postoperative outcomes, at 0.856 (95% CI: 0.768\u0026ndash;0.944, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), indicating good predictive value. Based on the maximum Youden index, the optimal cutoff value was determined to be 24.8%, with a sensitivity of 85.0% and specificity of 75.0% for predicting poor postoperative outcomes. Preoperative MF fCSA yielded an AUC of 0.792 (95% CI: 0.698\u0026ndash;0.886, P\u0026thinsp;=\u0026thinsp;0.002) for predicting poor outcomes, showing lower predictive efficacy than FIR. ES FIR had an AUC of 0.686 (95% CI: 0.568\u0026ndash;0.804, P\u0026thinsp;=\u0026thinsp;0.018), indicating moderate predictive value. MF Goutallier grade (\u0026ge;\u0026thinsp;2 as the predictive criterion) demonstrated an AUC of 0.802 (95% CI: 0.714\u0026ndash;0.890, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\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\u003eROC curve analysis of preoperative paraspinal muscle degeneration parameters for predicting poor postoperative outcomes\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAUC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e95%CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOptimal cutoff value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSensitivity (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSpecificity (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMF FIR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.856\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.768\u0026ndash;0.944\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e85.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e75.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\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\u003eMF fCSA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.792\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.698\u0026ndash;0.886\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e312.5 mm\u0026sup2;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e78.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e70.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eES FIR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.686\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.568\u0026ndash;0.804\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e23.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e68.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e65.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.018\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGoutallier grade (\u0026ge;\u0026thinsp;2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.802\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.714\u0026ndash;0.890\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e83.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e67.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Measurement Reliability Analysis\u003c/h2\u003e \u003cp\u003eTwenty patients were randomly selected for repeat measurements. The results showed that the intraclass correlation coefficients (ICC) for tCSA, fCSA, and FIR measurements of the multifidus and erector spinae ranged from 0.886 to 0.942, and the Kappa value for Goutallier grade assessment was 0.824, indicating good consistency and reproducibility of the measurements.\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eLumbar disc herniation is a common condition in spinal surgery, and UBE has become an effective minimally invasive technique for treating L5/S1 disc herniation due to its advantages of minimal trauma and rapid recovery. Although most patients achieve satisfactory postoperative outcomes, some patients experience residual low back pain and slow functional recovery, affecting overall satisfaction(\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e). The results of this study showed an excellent/good rate of 83.3% after UBE, which is consistent with literature reports. However, it is noteworthy that 16.7% of patients had poor outcomes, suggesting the need for further investigation into potential factors influencing postoperative outcomes.\u003c/p\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Relationship Between Paraspinal Muscle Degeneration and Postoperative Outcomes\u003c/h2\u003e \u003cp\u003eThis study systematically evaluated, for the first time, the predictive value of preoperative paraspinal muscle degeneration parameters for postoperative outcomes after UBE for L5/S1 disc herniation. The results showed that patients in the fair/poor group had significantly smaller preoperative ipsilateral multifidus functional cross-sectional area (MF fCSA) (278.6\u0026thinsp;\u0026plusmn;\u0026thinsp;68.4 mm\u0026sup2; vs. 362.8\u0026thinsp;\u0026plusmn;\u0026thinsp;72.5 mm\u0026sup2;, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and significantly higher fat infiltration rate (MF FIR) (36.4\u0026thinsp;\u0026plusmn;\u0026thinsp;9.8% vs. 19.8\u0026thinsp;\u0026plusmn;\u0026thinsp;7.6%, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) compared to the excellent/good group. Correlation analysis further confirmed that MF FIR was significantly negatively correlated with postoperative ODI improvement rate (r=-0.682) and low back pain VAS improvement rate (r=-0.594), but showed no significant correlation with leg pain VAS improvement rate. This finding has important clinical implications: it suggests that paraspinal muscle degeneration primarily affects the relief of postoperative low back symptoms rather than the effectiveness of nerve root decompression. In other words, even when surgery successfully relieves neural compression, pre-existing muscle degeneration may become the \"primary culprit\" for residual postoperative low back pain.\u003c/p\u003e \u003cp\u003eAs the deepest layer of the paraspinal muscles, the multifidus plays a central role in lumbar segmental stability through its abundant distribution of muscle spindles and segmental innervation(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). Burkhard et al. confirmed that multifidus atrophy and fatty infiltration are closely associated with chronic low back pain(\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). In this study, the impact of multifidus degeneration on prognosis was substantially greater than that of the erector spinae, possibly due to the following reasons: the multifidus possesses unique segmental innervation characteristics, making its dysfunction difficult to compensate for by other muscles; whereas the erector spinae, as a global mover muscle, has higher functional redundancy, allowing partial compensation for some degree of degeneration. This explains why multifidus parameters demonstrated stronger predictive efficacy in the regression model.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Fatty Infiltration: A More Sensitive Predictor Than Muscle Atrophy\u003c/h2\u003e \u003cp\u003eNotably, there was no significant difference in multifidus total cross-sectional area (tCSA) between the two groups in this study (P\u0026thinsp;=\u0026thinsp;0.522), whereas differences in functional cross-sectional area (fCSA) and fat infiltration rate (FIR) were highly significant. This indicates that simply measuring muscle size may mask the true functional status\u0026mdash;when muscle tissue is replaced by adipose tissue, the total cross-sectional area may change little or even increase, but the functional muscle mass is significantly reduced. ROC curve analysis showed that MF FIR had an AUC of 0.856 for predicting poor postoperative outcomes, superior to that of MF fCSA (0.792), suggesting that fat infiltration rate is a more sensitive prognostic predictor than muscle atrophy. The optimal cutoff value for MF FIR in this study was 24.8%, meaning that when preoperative multifidus fat infiltration exceeds this threshold, the risk of poor postoperative outcomes is significantly increased (OR\u0026thinsp;=\u0026thinsp;10.55). This value can serve as a quantitative reference for clinical risk assessment. Goutallier grade\u0026thinsp;\u0026ge;\u0026thinsp;2 also demonstrated good predictive efficacy (AUC\u0026thinsp;=\u0026thinsp;0.802) and is easy to use, making it suitable for rapid clinical evaluation. However, the grading system has some subjectivity, whereas FIR, as a continuous variable, provides more refined risk stratification.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Biomechanical Specificity of the L5/S1 Segment\u003c/h2\u003e \u003cp\u003eThis study focused on the L5/S1 segment based on its unique biomechanical status. As the lumbosacral junction, L5/S1 bears the greatest shear stress in the lumbar spine, and the multifidus has a unique anatomical attachment at this site\u0026mdash;directly originating from the dorsal surface of the sacrum, forming a natural \"dynamic ligament.\" Naghdi et al. confirmed that multifidus fatty infiltration directly alters muscle mechanical properties, leading to decreased active contractile capacity(\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). When multifidus fatty infiltration occurs, its active contractile capacity decreases, resulting in impaired lumbosacral stability. Moens et al. found that in patients with persistent spinal pain syndrome after lumbar surgery, the median multifidus fat infiltration at the L5/S1 level was 52.84%, with all patients exhibiting moderate to severe fatty infiltration(\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e). This explains why even with adequate neural decompression, patients may still experience mechanical low back pain during daily activities such as bending and lifting due to local instability. The biomechanical specificity of the L5/S1 segment explains why multifidus degeneration primarily affects postoperative low back pain relief while having less impact on leg pain relief.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Influence of Disease Duration and Age\u003c/h2\u003e \u003cp\u003eIn this study, disease duration\u0026thinsp;\u0026ge;\u0026thinsp;12 months was an independent risk factor for poor postoperative outcomes (OR\u0026thinsp;=\u0026thinsp;6.45). Long-term chronic nerve root compression may lead to irreversible nerve damage and central sensitization, affecting postoperative recovery. Additionally, prolonged pain and reduced activity can lead to disuse atrophy of the paraspinal muscles, forming a vicious cycle of \"pain \u0026rarr; reduced activity \u0026rarr; muscle degeneration \u0026rarr; decreased stability \u0026rarr; increased pain\"(\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). Age showed significant differences in univariate analysis but did not reach statistical significance in multivariate regression, suggesting that age may indirectly affect prognosis by influencing muscle degeneration.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Clinical Significance and Rehabilitation Implications\u003c/h2\u003e \u003cp\u003eThe findings of this study have important implications for clinical practice:First, preoperative risk assessment.** It is recommended that paraspinal muscle evaluation be incorporated into routine preoperative imaging interpretation. A prospective study by Ghimire et al. confirmed that preoperative paraspinal muscle cross-sectional area is an independent predictor of postoperative functional recovery(\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e). A 2-year follow-up study of 243 patients by Banitalebi et al. also demonstrated that preoperative MRI assessment of paraspinal muscle fatty infiltration can serve as an important imaging biomarker for predicting postoperative outcomes(\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). When MRI shows significant multifidus fatty infiltration (FIR\u0026thinsp;\u0026ge;\u0026thinsp;25% or Goutallier grade\u0026thinsp;\u0026ge;\u0026thinsp;2), patients should be fully informed of the potential risk of residual low back pain or slow recovery postoperatively, allowing for appropriate management of patient expectations.Second, individualized rehabilitation protocols.** For patients with severe preoperative paraspinal muscle degeneration, targeted rehabilitation plans should be developed postoperatively. A systematic review by Valera-Calero et al. confirmed that visual RUSI biofeedback is superior to simple verbal feedback in improving motor control training performance and success rates(\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). A recent randomized controlled trial by Sarafadeen et al. further demonstrated that RUSI-assisted spinal stabilization training significantly increases multifidus cross-sectional area, and improvements in muscle morphology are significantly correlated with pain relief (r=-0.40 to -0.50) and functional improvement (r=-0.38 to -0.42)(\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e). Lin et al. further confirmed that RUSI effectively promotes sustained multifidus contractile capacity(\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e). These findings provide high-quality evidence-based support for postoperative targeted multifidus functional training.Third, surgical timing.** Disease duration\u0026thinsp;\u0026ge;\u0026thinsp;12 months is a risk factor for poor outcomes. Regression analysis by Ghimire et al. showed that symptom duration was positively correlated with preoperative ODI (P\u0026thinsp;=\u0026thinsp;0.005) (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e), suggesting that for patients with poor response to conservative treatment, surgical intervention should not be delayed excessively to prevent irreversible muscle degeneration.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec23\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Limitations of This Study\u003c/h2\u003e \u003cp\u003eThis study has several limitations: First, as a retrospective study, there may be selection bias, and the sample size was relatively limited (particularly with only 18 cases in the fair/poor group), which may affect statistical power. Second, although standardized methods were used for paraspinal muscle measurements and inter-observer reliability was verified, manual delineation may still have some error. Third, only preoperative muscle status was assessed, and postoperative muscle changes and the impact of rehabilitation training on prognosis were not observed. Fourth, the maximum follow-up duration was 24 months, and long-term outcomes require further investigation. Fifth, the study population was limited to single-level L5/S1 pathology, and whether the conclusions can be generalized to other segments requires validation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003e3.7 Future Perspectives\u003c/h2\u003e \u003cp\u003eFuture studies may include prospective multicenter research with larger sample sizes and extended follow-up periods; exploration of quantitative MRI techniques (such as IDEAL-IQ sequences) for automated and precise measurement of fat infiltration; randomized controlled trials to verify whether enhanced rehabilitation protocols for high-risk populations can improve prognosis; and incorporation of assessment tools such as surface electromyography to further investigate the relationship between paraspinal muscle function and postoperative outcomes.\u003c/p\u003e \u003cp\u003eIn conclusion, preoperative paraspinal muscle degeneration, particularly the degree of multifidus fatty infiltration, is an important predictor of clinical outcomes after UBE for L5/S1 disc herniation. When MRI shows multifidus fat infiltration rate\u0026thinsp;\u0026ge;\u0026thinsp;24.8% or Goutallier grade\u0026thinsp;\u0026ge;\u0026thinsp;2, clinicians should be alert to the risk of poor postoperative outcomes. It is recommended that paraspinal muscle status be incorporated into comprehensive preoperative assessment and that individualized rehabilitation protocols be developed for high-risk populations to further improve patient outcomes.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003eAuthors\u0026apos; contributions\u003c/p\u003e\n\u003cp\u003eLW, MG, HX, XC, and QY contributed to the study conception and design. Data collection and analysis were performed by LW, MG, and HX. The first draft of the manuscript was written by LW and MG, and all authors commented on previous versions of the manuscript. XC supervised the project, validated the results, and critically revised the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003eAcknowledgements\u003c/p\u003e\n\u003cp\u003eThe authors thank the staff of the Medical Records Department of The Seventh Affiliated Hospital of Anhui University of Chinese Medicine for their assistance in data retrieval.\u003c/p\u003e\n\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003eEthical approval and informed consent: This study was approved by the Ethics Committee of the Seventh Affiliated Hospital of Anhui University of Chinese Medicine (Approval No: [2024] 84). All patients provided written informed consent prior to participation in this study.\u003c/p\u003e\n\u003cp\u003eConsent for publication: Not applicable.\u003c/p\u003e\n\u003cp\u003eAvailability of data and materials: The datasets generated and/or analyzed during this study are not publicly available because of patient privacy regulations, but they are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003eCompeting interests: The authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003eGenerative AI in scientific writing: Not applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eShao J, Zhang Z, Meng H, Lin J, Fan Z, Fei Q. Unilateral biportal endoscopy for upper lumbar disc herniation: surgical challenges and clinical outcomes. Wideochir Inne Tech Maloinwazyjne. 2025;20(3):318\u0026ndash;24.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu H, Yang X, Wu H, Zhang S, Wang S. A novel classification and clinical evaluation of various morphologies of calcified lumbar disc herniation treated using unilateral biportal endoscopic technique. J Orthop Surg Res. 2025;20(1):907.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu R, Wang L, Yang X, Chen X, Fu W, Li S, et al. Comparison of Clinical and Radiographic Outcomes Between Percutaneous Endoscopic Transforaminal Diskectomy and Unilateral Biportal Endoscopic Diskectomy for the Treatment of L4/5-Level MSU Size-3 Lumbar Disk Herniation: A 2-Year Retrospective Cohort Study. Neurosurgery. 2025;97(5):1188\u0026ndash;97.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGuo C, Ding T, Zheng J, Fang X, Feng Z, Xue Y. Early Clinical and Radiologic Evaluation of Unilateral Biportal Spinal Endoscopy for Recurrent Lumbar Disc Herniation: A Retrospective Study. World Neurosurg. 2025;203:124499.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCarvalho V, Santos J, Santos Silva P, Vaz R, Pereira P. Relationship between fatty infiltration of paraspinal muscles and clinical outcome after lumbar discectomy. Brain Spine. 2022;2:101697.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhu DC, Lin JH, Xu JJ, Guo Q, Wang YH, Jiang C, et al. An assessment of morphological and pathological changes in paravertebral muscle degeneration using imaging and histological analysis: a cross-sectional study. BMC Musculoskelet Disord. 2021;22(1):854.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSuo M, Zhang J, Sun T, Wang J, Liu X, Huang H, et al. The association between morphological characteristics of paraspinal muscle and spinal disorders. Ann Med. 2023;55(2):2258922.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYu J, Zhang C, Zhou Y, Wang J, Zhang Y, Wang Y. Correlation analysis between multifidus muscle atrophy and the severity of degenerative scoliosis retrospective, cross-sectional study. Sci Rep. 2025;15(1):30133.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang S, Wang Y, Wang Z, Ai Y, Chen Q, Zhao Y, et al. Comparative analysis of the correlation between paraspinal muscles fat infiltration and vertebral bone quality in patients with lumbar degenerative diseases. Eur Spine J. 2025;34(10):4486\u0026ndash;95.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang K, Deng Z, Chen X, Shao J, Qiu L, Jiang C et al. The Role of Multifidus in the Biomechanics of Lumbar Spine: A Musculoskeletal Modeling Study. Bioeng (Basel). 2023;10(1).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi Q, Long X, Wang R, Pengying N, Cai L, Wang L, et al. Correlation between degeneration of cervical intervertebral disc and degeneration of paravertebral muscle. Front Endocrinol (Lausanne). 2024;15:1391970.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHan G, Wu H, Dai J, Li X, Yue L, Fan Z, et al. Does paraspinal muscle morphometry predict functional status and re-operation after lumbar spinal surgery? A systematic review and meta-analysis. Eur Radiol. 2023;33(8):5269\u0026ndash;81.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCheng Z, Tang T, Chen S, Hong J, Lu H, Xu H, et al. Risk Factor Analysis of Residual Low Back Pain After Unilateral Biportal Endoscopic Discectomy in Patients With Lumbar Disc Herniation. Med Sci Monit. 2026;32:e951644.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYang YF, Yu JC, Zhu ZW, Li YW, Xiao Z, Zhi CG, et al. Comparison of clinical outcomes and cost-utility between unilateral biportal endoscopic discectomy and percutaneous endoscopic interlaminar discectomy for single-level lumbar disc herniation: a retrospective matched controlled study. J Orthop Surg Res. 2024;19(1):755.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKalli I, Niglas M, Naeini MK, Freidin M, Thomas L, Menni C et al. Paraspinal muscle quality in chronic low back pain: a systematic review and meta-analysis of muscle atrophy and fat infiltration. Eur Spine J. 2025.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBurkhard MD, Chiapparelli E, Hambrecht J, K\u0026ouml;hli P, Guven AE, Tsuchiya K, et al. Multifidus Degeneration: The Key Imaging Predictor of Adjacent Segment Disease. Global Spine J. 2025;15(4):2348\u0026ndash;58.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNaghdi N, Masi S, Bertrand C, Rosenstein B, Cohen-Adad J, Rivaz H, et al. Ultrasound and MRI-based evaluation of relationships between morphological and mechanical properties of the lower lumbar multifidus muscle in chronic low back pain. Eur Spine J. 2025;34(7):2587\u0026ndash;96.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMoens M, Genot LV, Van Gestel F, Pilitsis JG, Billot M, Roulaud M et al. Multifidus Fat Infiltration in Patients with Persistent Spinal Pain Syndrome Type II Treated with Spinal Cord Stimulation: A Preliminary Report. J Clin Med. 2025;14(9).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFeng T, Zhao J, Li J, Wang Y, Wang L, Liu X. Clarifying the impact of spine-specific sarcopenia and generalized sarcopenia on clinical features in patients with lumbar degenerative diseases. Spine J. 2025;25(11):2503\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGhimire N, Lakhe P, Kumar A, Ghimire N, Kutum C, Choudhary D, et al. The impact of paraspinal muscle morphology on functional outcome in patients with degenerative lumbar spine disease undergoing surgery - A prospective observational study. Brain Spine. 2024;4:104141.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBanitalebi H, Hermansen E, Hellum C, Espeland A, Storheim K, Myklebust T, et al. Preoperative fatty infiltration of paraspinal muscles assessed by MRI is associated with less improvement of leg pain 2 years after surgery for lumbar spinal stenosis. Eur Spine J. 2024;33(5):1967\u0026ndash;78.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eValera-Calero JA, Fern\u0026aacute;ndez-de-Las-Pe\u0026ntilde;as C, Varol U, Ortega-Santiago R, Gallego-Sendarrubias GM, Arias-Bur\u0026iacute;a JL. Ultrasound Imaging as a Visual Biofeedback Tool in Rehabilitation: An Updated Systematic Review. Int J Environ Res Public Health. 2021;18(14).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSarafadeen R, Ganiyu SO, Ibrahim AA, Akindele MO, Awotidebe AW, Kaka B, et al. Lumbar stabilization exercise with and without real-time ultrasound imaging biofeedback in chronic low back pain patients: a randomized controlled trial. Sci Rep. 2025;15(1):36975.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLin S, Zhu B, Zheng Y, Huang G, Zeng Q, Wang C. Effect of real-time ultrasound imaging for biofeedback on trunk muscle contraction in healthy subjects: a preliminary study. BMC Musculoskelet Disord. 2021;22(1):142.\u003c/span\u003e\u003c/li\u003e\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 disc herniation, Unilateral biportal endoscopy, Paraspinal muscle degeneration, Fatty infiltration, Prognostic prediction","lastPublishedDoi":"10.21203/rs.3.rs-9065113/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9065113/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e \u003cp\u003eTo investigate the predictive value of preoperative paraspinal muscle degeneration parameters for clinical outcomes after unilateral biportal endoscopy (UBE) in patients with single-level L5/S1 lumbar disc herniation (LDH), and to provide evidence for preoperative risk assessment and individualized rehabilitation planning.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eA retrospective analysis was conducted on 108 patients who underwent UBE for single-level L5/S1 LDH from January 2024 to December 2025. On preoperative axial T2-weighted MRI images at the L5/S1 disc level, the total cross-sectional area (tCSA) and functional cross-sectional area (fCSA) of the bilateral multifidus (MF) and erector spinae (ES) muscles were measured, and the fat infiltration rate (FIR) was calculated. The Goutallier classification system was used for semi-quantitative assessment of paraspinal muscle fatty infiltration. Visual analog scale (VAS) scores for low back and leg pain and Oswestry Disability Index (ODI) were recorded preoperatively and at 3, 6, and 12 months postoperatively. Clinical outcomes were evaluated using the modified MacNab criteria at the final follow-up. Patients were divided into excellent/good group (90 cases) and fair/poor group (18 cases) based on outcomes. Preoperative paraspinal muscle degeneration parameters were compared between groups. Multivariate logistic regression analysis was used to identify independent risk factors for poor postoperative outcomes. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive efficacy of preoperative paraspinal muscle degeneration parameters for postoperative outcomes.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe excellent/good rate was 83.3%. Patients in the fair/poor group had significantly smaller preoperative ipsilateral MF fCSA and relative cross-sectional area (rCSA) (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), significantly higher MF FIR (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and a significantly higher proportion of Goutallier grade\u0026thinsp;\u0026ge;\u0026thinsp;2 (83.3% vs. 32.2%, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) compared to the excellent/good group. Correlation analysis showed that preoperative MF FIR was significantly negatively correlated with postoperative ODI improvement rate (r=-0.682) and low back pain VAS improvement rate (r=-0.594) (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), but showed no significant correlation with leg pain VAS improvement rate (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Multivariate logistic regression analysis revealed that preoperative MF FIR\u0026thinsp;\u0026ge;\u0026thinsp;25% (OR\u0026thinsp;=\u0026thinsp;10.55, 95%CI: 2.55\u0026ndash;43.62, P\u0026thinsp;=\u0026thinsp;0.001) and disease duration\u0026thinsp;\u0026ge;\u0026thinsp;12 months (OR\u0026thinsp;=\u0026thinsp;6.45, 95%CI: 1.69\u0026ndash;24.56, P\u0026thinsp;=\u0026thinsp;0.006) were independent risk factors for poor postoperative outcomes, while MF fCSA was a protective factor (OR\u0026thinsp;=\u0026thinsp;0.986, P\u0026thinsp;=\u0026thinsp;0.020). ROC curve analysis showed that preoperative MF FIR had the largest area under the curve (AUC) for predicting poor postoperative outcomes (0.856, 95%CI: 0.768\u0026ndash;0.944), with an optimal cutoff value of 24.8%, sensitivity of 85.0%, and specificity of 75.0%.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003ePreoperative paraspinal muscle degeneration, particularly the degree of multifidus fatty infiltration, is an important predictor of clinical outcomes after UBE for L5/S1 lumbar disc herniation. When MRI shows multifidus fat infiltration rate\u0026thinsp;\u0026ge;\u0026thinsp;24.8% or Goutallier grade\u0026thinsp;\u0026ge;\u0026thinsp;2, clinicians should be alert to the risk of poor postoperative outcomes. It is recommended that preoperative paraspinal muscle status be incorporated into the surgical risk assessment system, and targeted postoperative rehabilitation of paraspinal muscle function be strengthened for high-risk populations.\u003c/p\u003e","manuscriptTitle":"Predictive Value of Preoperative Paraspinal Muscle Degeneration Parameters for Clinical Outcomes After Unilateral Biportal Endoscopy for L5/S1 Lumbar Disc Herniation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-30 09:15:51","doi":"10.21203/rs.3.rs-9065113/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":"f363f638-df42-44d2-bbb7-9c87133445b4","owner":[],"postedDate":"April 30th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Rejected","date":"2026-05-01T17:20:55+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-01T17:24:55+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-30 09:15:51","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9065113","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9065113","identity":"rs-9065113","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}