Distal fusion vertebra selection in neurofibromatosis type 1 scoliosis: integrating CT/MRI-detected atrophic changes reduces long-term mechanical complications

Distal fusion vertebra selection in neurofibromatosis type 1 scoliosis: integrating CT/MRI-detected atrophic changes reduces long-term mechanical complications | 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 Distal fusion vertebra selection in neurofibromatosis type 1 scoliosis: integrating CT/MRI-detected atrophic changes reduces long-term mechanical complications Yu Zhang, Xie-xiang Shao, Jian Chen, Yao-long Deng, Tian-yuan Zhang, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9170678/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract Purpose Distal fusion vertebra (DFV) selection in neurofibromatosis type 1 (NF1) scoliosis is traditionally guided by adolescent idiopathic scoliosis (AIS) criteria, which do not account for NF1-specific atrophic changes. We evaluated whether integrating preoperative CT/MRI-detected atrophic changes into DFV selection reduces long-term mechanical complications. Methods This retrospective cohort study included 156 NF1 scoliosis patients (Lenke 1–3, Cobb ≥ 45°) undergoing posterior spinal fusion (2010–2018) with a minimum 5-year follow-up. Patients were stratified into an optimized group (AIS criteria plus CT/MRI atrophic assessment) and a traditional group (AIS criteria alone). Propensity score matching (1:1) yielded 65 matched pairs. Primary outcomes were internal fixation failure (IFF) and distal adding-on. Multivariate logistic regression and ROC analysis were performed. Results The optimized group demonstrated lower IFF (12.3% vs. 32.3%; OR 0.29, 95% CI 0.12–0.68; p = 0.002) and distal adding-on (15.4% vs. 40.0%; OR 0.27, 95% CI 0.12–0.60; p < 0.001). Absolute risk reductions were 20.0% (IFF) and 24.6% (adding-on), corresponding to numbers needed to treat of 5 and 4, respectively. Correction magnitude and fusion length were comparable between groups. DFV adjacency to vertebral (OR 6.12), disc (OR 5.37), and paraspinal soft-tissue atrophy (OR 4.89) independently predicted complications. Combined CT/MRI assessment demonstrated good discrimination (AUC = 0.87; sensitivity 82.6%, specificity 80.3%). Conclusion Integration of CT/MRI-detected atrophic changes into DFV selection was associated with significantly reduced long-term mechanical complications without compromising deformity correction in NF1 scoliosis. Neurofibromatosis type 1 Scoliosis Distal fusion vertebra Atrophic changes Internal fixation failure Distal adding-on Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Neurofibromatosis type 1 (NF1) scoliosis is a distinct pathological entity from adolescent idiopathic scoliosis (AIS), characterized by rapid curve progression, vertebral dysplasia, paraspinal neurofibroma infiltration, and unique atrophic changes (vertebral bodies, intervertebral discs, and paraspinal soft tissues)[ 1 ]. These features compromise bone quality, impair osseointegration, and disrupt spinal biomechanics, resulting in significantly higher postoperative complication rates—including internal fixation failure (IFF, 15–30%) and distal adding-on (25–40%)—compared to AIS (IFF: 5–8%; adding-on: 15–20%)[ 2 – 4 ]. Distal fusion vertebra (DFV) selection is a pivotal determinant of spinal fusion success, as inappropriate selection directly contributes to adding-on and IFF[ 5 ]. In AIS, DFV is chosen based on Lenke classification, curve flexibility, and vertebral rotation, but these criteria do not account for NF1-specific atrophic changes. Vertebral atrophy impairs pedicle screw anchorage; disc atrophy disrupts spinal load distribution; and paraspinal soft tissue atrophy compromises segmental stability, rendering adjacent segments unsuitable as DFV or DFV-adjacent levels[ 6 – 9 ]. Preoperative CT and MRI offer complementary diagnostic advantages: CT accurately assesses vertebral morphology and bone mineral density (BMD), while MRI visualizes disc integrity, soft-tissue atrophy, and neurofibroma infiltration[ 10 , 11 ]. Prior studies have linked these atrophic changes to postoperative complications[ 6 , 12 ], but no investigation has systematically integrated CT/MRI-detected atrophic changes with AIS criteria to optimize DFV selection in NF1 scoliosis. Early pilot studies have explored CT/MRI for fusion segment selection but lacked a standardized algorithm and long-term clinical validation[ 10 , 11 ]. We hypothesized that DFV selection guided by AIS criteria, combined with preoperative CT/MRI-detected atrophic changes, would reduce long-term complications while preserving deformity correction efficacy. This study aimed to: (1) compare the efficacy of optimized versus traditional DFV selection in preventing IFF and distal adding-on in NF1 scoliosis; (2) identify key preoperative imaging markers for DFV adjustment; and (3) establish a practical, evidence-based DFV selection algorithm for NF1 scoliosis patients undergoing PSF. Materials and Methods Study Design and Patient Population This retrospective cohort study was approved by the Institutional Review Board of Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (Approval No.: XHEC-2024-056). Written informed consent was obtained from all patients or their legal guardians, in adherence to the Declaration of Helsinki. This study was reported in accordance with the STROBE statement. Inclusion Criteria : (1) Confirmed NF1 diagnosis per 1997 NIH criteria[13]; (2) Lenke 1-3 curves with a main curve Cobb angle ≥45°; (3) Primary PSF with pedicle screw-rod fixation (no anterior fusion or growth-friendly surgery); (4) Complete preoperative CT (within 1 month) and MRI (within 3 months) imaging; (5) Minimum 5-year postoperative follow-up; (6) Complete clinical and radiological data available for analysis. Exclusion Criteria : (1) Congenital or non-NF1 syndromic scoliosis; (2) Prior spinal surgery; (3) Metabolic bone disease (e.g., osteopenia, osteoporosis unrelated to NF1); (4) Incomplete preoperative imaging or follow-up data; (5) Perioperative mortality or major surgical complications (e.g., spinal cord injury, infection). Group Stratification Optimized Group : DFV selected by standard AIS criteria plus preoperative CT/MRI assessment of atrophic changes (avoiding DFV adjacent to atrophic segments; cephalad shift of 1-2 segments if DFV+1 had ≥1 atrophic change). Traditional Group : DFV selected by AIS criteria alone:(1) Lenke-defined stable vertebrae; (2) Curve flexibility >70%: DFV = lowest vertebra of the main curve; (3) Flexibility 50–70%: DFV = lowest vertebra of the main curve + 1 stable vertebra; (4) Flexibility <50%: DFV = lowest vertebra of the main curve + 2 stable vertebrae; (5) Vertebral rotation ≤5° (Nash-Moe method)[14] . Preoperative CT/MRI Assessment of Atrophic Changes Imaging data were independently reviewed by two senior musculoskeletal radiologists with ≥10 years of experience in spinal imaging, who were blinded to clinical outcomes. Inter-rater reliability was assessed via kappa statistics (κ = 0.83-0.92), and discrepancies were resolved by consensus (Figure 1). CT Protocol (Siemens Somatom Definition, Erlangen, Germany): 120 kV, 200 mAs, 1 mm slice thickness, 0.5 mm reconstruction interval, 300×300 mm field of view (FOV), 512×512 matrix. Vertebral atrophy was defined as type 2-3 lamina changes or type 2-4 pedicle changes described in the previous report[6]. MRI Protocol (GE Discovery MR750, Chicago, IL, USA): Sagittal T1-weighted (TR=500 ms, TE=10 ms), sagittal T2-weighted (TR=3000 ms, TE=100 ms), axial T2-weighted (TR=2500 ms, TE=80 ms), and fat-saturated T2-weighted sequences. Disc atrophy was defined as disc height loss ≥20% (vs. age-matched norms) or Pfirrmann grade ≥Ⅲ[7]. Paraspinal soft tissue atrophy was defined as muscle volume reduction ≥30% (ImageJ-segmented) or fat infiltration fraction ≥30% [8, 10] . Optimized DFV Selection Algorithm The optimized algorithm, as illustrated in the flowchart above (Figure 2), consists of the following steps: Identify the initial DFV (DFV_initial) using standard AIS criteria[14]; Evaluate DFV_initial and DFV_initial+1 for vertebral, disc, or paraspinal soft tissue atrophy via preoperative CT/MRI; Shift DFV cephalad by 1 segment if DFV_initial+1 has ≥1 atrophic change; shift by an additional segment if the newly selected DFV+1 still demonstrates atrophic changes; Confirm the optimized DFV (DFV_optimized) is a stable vertebra (vertebral rotation ≤5°, no translational deformity)[15]. Surgical Technique All surgeries were performed by senior spine surgeons with ≥10 years of specialized experience in scoliosis. PSF was performed via a posterior midline incision, with pedicle screw insertion (4.5-5.5 mm diameter, 30-45 mm length), titanium alloy rod placement (5.5–6.0 mm diameter), curve correction via compression/distraction/derotation, and spinal fusion with a 1:1 ratio of autologous (iliac crest) + allogeneic bone graft. No intraoperative neuromonitoring abnormalities were noted in any patient. Follow-Up and Outcome Measures Patients underwent standardized follow-up at 3 months, 6 months, 1 year, 3 years, and 5 years postoperatively. Clinical evaluations included the Scoliosis Research Society-22 (SRS-22) questionnaire and visual analog scale (VAS) pain score (0-10). Radiological assessments (posteroanterior/lateral spinal radiographs, CT at 2 years) were performed to measure Cobb angle, coronal balance (C7 plumb line deviation, C7PLD), sagittal vertical axis (SVA), fusion rate (Bridwell grade)[16] , IFF, and distal adding-on. Primary Outcomes : IFF: Screw loosening (peri-screw lucency ≥2 mm), screw/rod breakage, or pseudarthrosis (Bridwell grade 1-2 at 2-year CT); Distal adding-on: ≥5° increase in the DFV+1 Cobb angle vs. immediate postoperative values, or inclusion of DFV+1 into the main scoliotic curve. Secondary Outcomes : DFV level, fusion segment length, main curve correction rate, coronal/sagittal spinal balance, fusion rate (Bridwell grade 3-4), SRS-22 total/subscores, VAS pain score, and reoperation rate (for IFF, adding-on, or pseudarthrosis). Statistical Analysis Statistical analysis was performed using SPSS 26.0 (IBM Corp., Armonk, NY, USA). Continuous variables were expressed as mean±standard deviation (SD) or median (interquartile range, IQR); categorical variables as counts (percentages). PSM (1:1, caliper=0.2) was used to balance baseline characteristics between groups. Group comparisons were conducted using the independent samples t-test (continuous variables), chi-square test, or Fisher’s exact test (categorical variables). Multivariate logistic regression was used to identify independent predictors of postoperative complications. ROC curves were generated to assess the predictive value of combined CT/MRI atrophic change assessment, with AUC, sensitivity, and specificity calculated. Kaplan-Meier curves were used to compare complication-free survival, with the log-rank test for significance. A two-tailed P<0.05 was considered statistically significant. Results Baseline Characteristics A total of 156 patients were included (Optimized Group n=78, Traditional Group n=78). After PSM, 65 matched pairs (130 patients) were analyzed, with no significant baseline differences between groups (Table 1). In the Optimized Group, 41 patients (63.1%) underwent a cephalad DFV shift to avoid atrophic segments (32 patients: 1 segment, 9 patients: 2 segments). Preoperative atrophic change prevalence was comparable between groups after PSM (P>0.05 for all). Table 1. Baseline Characteristics Before and After Propensity Score Matching (PSM) Optimized Group (n=78) Traditional Group (n=78) Optimized Group (n=65) Traditional Group (n=65) Age (years), mean±SD 13.7±3.8 13.9±3.7 13.8±3.7 13.9±3.6 Female, n (%) 45 (57.7) 47 (60.3) 36 (55.4) 37 (56.9) Risser sign 0–1, n (%) 43 (55.1) 41 (52.6) 35 (53.8) 34 (52.3) Main curve Cobb angle (°), mean±SD 58.9±13.4 59.3±14.1 59.1±13.2 59.2±14.0 Lenke type 1/2/3, n 38/23/17 36/25/17 31/19/15 30/20/15 Paraspinal neurofibroma, n (%) 41 (52.6) 39 (50.0) 33 (50.8) 32 (49.2) Preoperative atrophic changes, n (%) – Vertebral atrophy 39 (60.0) 37 (56.9) 32 (49.2) 30 (46.2) – Disc atrophy 35 (53.8) 33 (50.8) 29 (44.6) 27 (41.5) – Paraspinal soft tissue atrophy 32 (49.2) 30 (46.2) 27 (41.5) 25 (38.5) Note : All P>0.05 for between-group comparisons after PSM. Primary Outcomes At 5-year follow-up, the Optimized Group had a significantly lower IFF rate (12.3% [8/65] vs. 32.3% [21/65], P=0.002) and distal adding-on incidence (15.4% [10/65] vs. 40.0% [26/65], P<0.001) than the Traditional Group (Table 2). Kaplan-Meier analysis demonstrated significantly longer IFF-free and distal adding-on-free survival in the Optimized Group (log-rank P<0.001 for both; Figure 3). Secondary Outcomes Radiological Outcomes : The Optimized Group had a more cephalad median DFV level (T11 vs. T12, P<0.001), but fusion segment lengths were comparable between groups (7.2±1.1 vs. 7.0±1.0 vertebrae, P=0.213; Table 2). Main curve correction rates were similar (80.1%±8.7% vs. 78.5%±9.2%, P=0.286), but the Optimized Group had superior coronal balance (1.2±0.7 vs. 1.7±0.9 cm, P=0.003) and sagittal balance (SVA: 1.6±1.0 vs. 2.2±1.2 cm, P=0.004). Fusion rates were high and comparable between groups (96.9% vs. 93.8%, P=0.421). Clinical Outcomes : The Optimized Group had significantly higher SRS-22 total scores (4.1±0.4 vs. 3.6±0.5, P<0.001), lower VAS pain scores (1.6±0.8 vs. 2.9±1.1, P<0.001), and a lower reoperation rate (9.2% [6/65] vs. 30.8% [20/65], P=0.001) than the Traditional Group (Table 2). Reoperations in the Traditional Group were primarily for IFF (n=12) and distal adding-on (n=8); reoperations in the Optimized Group were for pseudarthrosis (n=4) and minor rod malposition (n=2). Table 2. Clinical and Radiological Outcomes at 5-Year Follow-Up (65 Matched Pairs) IFF rate, n (%) 8 (12.3) 21 (32.3) 0.002 Distal adding-on incidence, n (%) 10 (15.4) 26 (40.0) <0.001 DFV level (median, range) T12 (T10–L2) L1 (T11–L3) <0.001 Fusion segment length (vertebrae), mean±SD 7.2±1.1 7.0±1.0 0.213 Main curve correction rate (%), mean±SD 80.1±8.7 78.5±9.2 0.286 Coronal balance (C7PLD, cm), mean±SD 1.2±0.7 1.7±0.9 0.003 SVA (cm), mean±SD 1.6±1.0 2.2±1.2 0.004 Fusion rate (Bridwell 3–4), n (%) 63 (96.9) 61 (93.8) 0.421 SRS-22 total score, mean±SD 4.1±0.4 3.6±0.5 <0.001 VAS pain score (0–10), mean±SD 1.6±0.8 2.9±1.1 <0.001 Reoperation rate, n (%) 6 (9.2) 20 (30.8) 0.001 Note : IFF=internal fixation failure; DFV=distal fusion vertebra; C7PLD=C7 plumb line deviation; SVA=sagittal vertical axis; SRS-22=Scoliosis Research Society-22; VAS=visual analog scale. Predictive Value of Atrophic Changes Multivariate Logistic Regression : DFV adjacency to atrophic segments was the strongest independent predictor of postoperative complications (Table 3). For IFF, the top predictors were vertebral atrophy (OR=6.12, 95% CI: 2.15-17.43, P<0.001) and disc atrophy (OR=5.37, 95% CI: 1.89-15.21, P=0.001). For distal adding-on, the top predictors were disc atrophy (OR=5.78, 95% CI: 2.03-16.45, P0.05). ROC Curve Analysis : Combined preoperative CT/MRI assessment of atrophic changes predicted IFF with an AUC of 0.85 (95% CI: 0.77-0.93, P<0.001; sensitivity=80.2%, specificity=78.9%) and distal adding-on with an AUC of 0.87 (95% CI: 0.80-0.94, P<0.001; sensitivity=82.6%, specificity=80.3%) (Figure 4). Table 3. Multivariate Logistic Regression for Independent Predictors of Postoperative Complications DFV adjacent to vertebral atrophy 6.12 (2.15–17.43) <0.001 4.23 (1.51–11.82) 0.006 DFV adjacent to disc atrophy 5.37 (1.89–15.21) 0.001 5.78 (2.03–16.45) <0.001 DFV adjacent to paraspinal soft tissue atrophy 4.51 (1.58–12.87) 0.005 4.89 (1.72–13.92) 0.002 Lenke type 3 2.18 (0.76–6.29) 0.148 2.35 (0.82–6.73) 0.112 Note : OR=odds ratio; CI=confidence interval; IFF=internal fixation failure; DFV=distal fusion vertebra. Typical Case A 10-year-old female with NF1, Lenke 1 curve (preoperative Cobb angle 47°), Risser sign 0, and paraspinal neurofibromatosis (T9-T11) underwent PSF with optimized DFV selection. Preoperative CT identified no vertebral atrophy in DFV_initial (L1); MRI demonstrated L1-2 disc atrophy (Pfirrmann grade Ⅲ, height loss 22%) and paraspinal soft tissue atrophy (fat infiltration=36%). DFV_initial (L1) was shifted cephalad to T12 following the optimized algorithm. The immediate postoperative Cobb angle was 12° (correction rate=74.5%). At 5-year follow-up, there was no IFF or distal adding-on, and the SRS-22 total score was 4.3 (Figure 5). Solid fusion (Bridwell grade 4) was confirmed on 5-year CT. Discussion This study shows that an optimized DFV selection strategy integrating AIS fusion criteria with preoperative CT/MRI-detected atrophic changes significantly reduces long-term internal fixation failure (IFF) and distal adding-on in NF1 scoliosis, while maintaining deformity correction and improving spinal balance and patient-reported outcomes. The key principle of this strategy is to avoid selecting a DFV adjacent to NF1-specific atrophic segments, which appear to be imaging markers of segmental instability. Traditional AIS-based DFV selection does not account for the distinctive pathological features of NF1 scoliosis, including vertebral dysplasia, reduced bone mineral density, and paraspinal soft-tissue abnormalities[ 1 , 6 ]. This limitation was reflected in our Traditional Group, which showed high rates of IFF and distal adding-on, consistent with previous reports in NF1 scoliosis[ 15 , 17 ]. In contrast, the Optimized Group achieved a 62% reduction in both complications, suggesting that fusion to or adjacent to atrophied segments is a major contributor to mechanical failure. Our multivariate analysis further supports this interpretation, identifying vertebral atrophy as the strongest predictor of IFF (OR = 6.12). Notably, Shao et al. recently reported that DFV selection in NF1 non-dystrophic scoliosis requires a tailored approach distinct from AIS, but their study did not integrate CT/MRI-detected atrophic changes or focus on long-term complications[ 15 ]. Our study builds on this work by establishing a standardized algorithm that addresses both dystrophic and non-dystrophic subsets, with a 5-year follow-up to capture late complications common in NF1 scoliosis. Our findings also highlight the complementary value of CT and MRI in preoperative assessment. CT is particularly useful for evaluating vertebral morphology, trabecular integrity, and bone quality relevant to screw anchorage, whereas MRI provides information on disc status, paraspinal soft tissue atrophy, neurofibroma infiltration, and intraspinal abnormalities[ 8 , 10 ]. In our cohort, a combined CT/MRI assessment accurately predicted IFF and distal adding-on, supporting the use of both modalities for DFV planning in NF1 scoliosis. Compared with prior studies that relied on single-modality imaging or did not directly incorporate imaging findings into segment selection[ 12 , 18 ], our study provides a practical imaging-guided framework with 5-year validation. An important concern when modifying the DFV is whether fusion may become too short or unnecessarily extended[ 19 ]. Tauchi et al. reported that early definitive fusion in NF1 scoliosis preserves spinal alignment but may compromise mobility if fusion segments are excessive—emphasizing the need for targeted DFV selection[ 20 ]. Our approach avoids both pitfalls: in patients with no atrophic changes (36.9% of the Optimized Group), DFV remained consistent with AIS criteria, avoiding unnecessary cephalad shift and potential under-fusion. In patients with multiple atrophic changes, a 2-segment cephalad shift ensured fusion to a stable vertebra, avoiding over-fusion by only shifting the minimum number of segments needed to bypass atrophied levels. This personalized strategy explains why the Optimized Group achieved superior spinal balance (coronal and sagittal) compared to the Traditional Group—stable DFV anchor points reduce junctional instability and improve long-term alignment maintenance. Recent studies in NF1 scoliosis have mainly focused on surgical technique, implant strategy, or biological enhancement, whereas segment selection has received less attention. Jia et al. reported that combined anterior-posterior fusion improves fusion rates in dystrophic NF1 scoliosis but does not reduce IFF or distal adding-on, highlighting that technical enhancement alone cannot overcome the risks of poor segment selection[ 21 ]. Neifert et al. demonstrated that customized pedicle screws improve anchorage in NF1 scoliosis but failed to address the underlying instability of atrophied segments, which remains a major driver of complications[ 22 ]. Our study fills this critical gap by demonstrating that imaging-guided DFV selection is a cost-effective, accessible strategy to reduce complications without requiring specialized implants or biologics—an important consideration for clinical practice, particularly in resource-limited settings. Notably, the 5-year IFF rate of 12.3% in our Optimized Group is the lowest reported in contemporary NF1 scoliosis literature. Prior studies have reported IFF rates of 24–36% with traditional DFV selection and adding-on rates of 25–40%[ 22 ] —both significantly higher than in our Optimized Group. This improvement is clinically meaningful, as NF1 patients require lifelong spinal follow-up, and late complications (e.g., screw breakage, pseudarthrosis) can significantly impact quality of life and require revision surgery. Our SRS-22 results (4.1 ± 0.4 vs. 3.6 ± 0.5, P < 0.001) confirm that reducing complications translates to better patient-reported outcomes, including improved pain, physical function, and self-image—key measures of success in spinal deformity surgery. 5. Study Limitations This study has several limitations. First, it was a retrospective single-center study, although propensity score matching was used to reduce baseline imbalance. Second, the spinal range of motion was not assessed. Third, external validation is still needed, particularly across different surgical techniques and broader NF1 scoliosis populations. Conclusions Optimized distal fusion vertebra selection for NF1 scoliosis, integrating AIS fusion criteria with preoperative CT/MRI-detected atrophic changes, reduces long-term internal fixation failure and distal adding-on without compromising deformity correction. The key clinical principle is to avoid selecting a DFV adjacent to vertebral, disc, or paraspinal soft tissue atrophy, as these findings may indicate segmental instability. This strategy preserves fusion length, improves spinal balance, and enhances patient-reported outcomes, providing a practical imaging-guided framework for surgical planning in NF1 scoliosis. External multicenter validation is warranted before broader implementation. Declarations Author Contribution Y.Z., X.Z., and WY.S. conceived and designed the study. XX.S., J.C., YL.D. and TY.Z. acquired the data. XX.S., J.C. and TY.Z. performed the statistical analyses. Y.Z., XX.S. and WY.S. wrote the main manuscript text, and Y.Z. and WY.S. prepared all the Figures. JF.Y. and JL.Y. critically revised the manuscript. YL.D. and JL.Y. supervised the study. Notably, Y.Z. and X.Z. contributed equally to this work. All authors reviewed and approved the manuscript. References Kaspiris A, Savvidou OD, Vasiliadis ES, et al (2022) Current Aspects on the Pathophysiology of Bone Metabolic Defects during Progression of Scoliosis in Neurofibromatosis Type 1. J Clin Med 11:444. https://doi.org/10.3390/jcm11020444 Yao Z, Li H, Zhang X, et al (2018) Incidence and Risk Factors for Instrumentation-related Complications After Scoliosis Surgery in Pediatric Patients With NF-1. SPINE 43:1719–1724. https://doi.org/10.1097/brs.0000000000002720 Bouthors C, Dukan R, Glorion C, Miladi L (2020) Outcomes of growing rods in a series of early-onset scoliosis patients with neurofibromatosis type 1. J Neurosurg: Spine 33:373–380. https://doi.org/10.3171/2020.2.spine191308 Paul JC, Lonner BS, Vira S, et al (2018) Does Reoperation Risk Vary for Different Types of Pediatric Scoliosis? J Pediatr Orthop 38:459–464. https://doi.org/10.1097/bpo.0000000000000850 Park B-J, Hyun S-J, Wui S-H, et al (2020) Surgical Outcomes and Complications Following All Posterior Approach for Spinal Deformity Associated with Neurofibromatosis Type-1. J Korean Neurosurg Soc 63:738–746. https://doi.org/10.3340/jkns.2019.0218 Pushpa BT, Rajasekaran S, Anand KSSV, et al (2022) Anatomical changes in vertebra in dystrophic scoliosis due to neurofibromatosis and its implications on surgical safety. Spine Deform 10:159–167. https://doi.org/10.1007/s43390-021-00392-6 Li S, Mao S, Du C, et al (2021) Assessing the unique characteristics associated with surgical treatment of dystrophic lumbar scoliosis secondary to neurofibromatosis type 1: a single-center experience of more than 10 years. J Neurosurg: Spine 34:413–423. https://doi.org/10.3171/2020.6.spine20898 Haider S, Le LQ, Cho G, et al (2022) Scoliosis in Neurofibromatosis Type 1 on Whole-Body Magnetic Resonance Imaging: Frequency and Association With Intraspinal and Paraspinal Tumors. J Comput Assist Tomogr 46:231–235. https://doi.org/10.1097/rct.0000000000001263 Heyde C-E, Völker A, Höh NH von der, et al (2021) Wirbelsäulendeformitäten bei Neurofibromatose Typ 1. Orthop 50:650–656. https://doi.org/10.1007/s00132-021-04130-8 Thakur U, Ramachandran S, Mazal AT, et al (2025) Multiparametric whole-body MRI of patients with neurofibromatosis type I: spectrum of imaging findings. Skelet Radiol 54:407–422. https://doi.org/10.1007/s00256-024-04765-6 Well L, Careddu A, Stark M, et al (2021) Phenotyping spinal abnormalities in patients with Neurofibromatosis type 1 using whole-body MRI. Sci Rep 11:16889. https://doi.org/10.1038/s41598-021-96310-x Shi B-L, Li Y, Zhu Z-Z, et al (2021) Curve evolution during bracing in children with scoliosis secondary to early-onset neurofibromatosis type 1: indicators of rapid curve progression. Chin Méd J 134:1983–1987. https://doi.org/10.1097/cm9.0000000000001606 Ferner RE, Huson SM, Thomas N, et al (2007) Guidelines for the diagnosis and management of individuals with neurofibromatosis 1. J Méd Genet 44:81. https://doi.org/10.1136/jmg.2006.045906 King HA, Moe JH, Bradford DS, Winter RB (1983) The selection of fusion levels in thoracic idiopathic scoliosis. J Bone Jt Surg 65:1302–1313. https://doi.org/10.2106/00004623-198365090-00012 Shao X, Zhang T, Yang J, et al (2023) How to select the lowest instrumented vertebra in NF-1 non-dystrophic scoliosis. Eur Spine J 32:1153–1160. https://doi.org/10.1007/s00586-023-07600-z Yu A, Tiao J, Cai CW, et al (2025) Radiographic Assessment of Successful Lumbar Spinal Fusion: A Systematic Review of Fusion Criteria in Randomized Trials. Glob Spine J 21925682251384662. https://doi.org/10.1177/21925682251384662 Zhao X, Li J, Shi L, et al (2016) Surgical Treatment of Dystrophic Spinal Curves Caused by Neurofibromatosis Type 1. Medicine 95:e3292. https://doi.org/10.1097/md.0000000000003292 Marrache M, Suresh KV, Miller DJ, et al (2021) Early-Onset Spinal Deformity in Neurofibromatosis Type 1: Natural History, Treatment, and Imaging Surveillance. JBJS Rev 9:e20.00285. https://doi.org/10.2106/jbjs.rvw.20.00285 Jain A, Sponseller PD, Flynn JM, et al (2016) Avoidance of “Final” Surgical Fusion After Growing-Rod Treatment for Early-Onset Scoliosis. J Bone Jt Surg 98:1073–1078. https://doi.org/10.2106/jbjs.15.01241 Tauchi R, Kawakami N, Castro MA, et al (2020) Long-term Surgical Outcomes After Early Definitive Spinal Fusion for Early-onset Scoliosis With Neurofibromatosis Type 1 at Mean Follow-up of 14 Years. J Pediatr Orthop 40:42-47. https://doi.org/10.1097/bpo.0000000000001090 Jia F, Wang G, Sun J, Liu X (2021) Combined Anterior-Posterior Versus Posterior-only Spinal Fusion in Treating Dystrophic Neurofibromatosis Scoliosis With Modern Instrumentation: A Systematic Review and Meta-analysis. Clin Spine Surg 34:132–142. https://doi.org/10.1097/bsd.0000000000001069 Neifert SN, Khan HA, Kurland DB, et al (2022) Management and surgical outcomes of dystrophic scoliosis in neurofibromatosis type 1: a systematic review. Neurosurg Focus 52:E7. https://doi.org/10.3171/2022.2.focus21790 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 08 Apr, 2026 Reviews received at journal 08 Apr, 2026 Reviews received at journal 03 Apr, 2026 Reviewers agreed at journal 31 Mar, 2026 Reviews received at journal 30 Mar, 2026 Reviewers agreed at journal 30 Mar, 2026 Reviewers agreed at journal 30 Mar, 2026 Reviewers invited by journal 29 Mar, 2026 Editor assigned by journal 23 Mar, 2026 Submission checks completed at journal 23 Mar, 2026 First submitted to journal 19 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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-9170678","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":614854728,"identity":"f8ddfd81-cac1-40ef-8e08-393ab40beb4a","order_by":0,"name":"Yu Zhang","email":"","orcid":"","institution":"Second Affiliated Hospital of Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Yu","middleName":"","lastName":"Zhang","suffix":""},{"id":614854729,"identity":"742d3e37-3a1e-40af-84b6-24b00ccb1013","order_by":1,"name":"Xie-xiang Shao","email":"","orcid":"","institution":"XinHua Hospital","correspondingAuthor":false,"prefix":"","firstName":"Xie-xiang","middleName":"","lastName":"Shao","suffix":""},{"id":614854730,"identity":"a5306812-20ee-4b0b-b290-75f4c42f5a2d","order_by":2,"name":"Jian Chen","email":"","orcid":"","institution":"XinHua Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jian","middleName":"","lastName":"Chen","suffix":""},{"id":614854731,"identity":"58383ed4-ffc9-4edb-82e6-d8f8b13c5de5","order_by":3,"name":"Yao-long Deng","email":"","orcid":"","institution":"XinHua Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yao-long","middleName":"","lastName":"Deng","suffix":""},{"id":614854732,"identity":"c437e4da-de58-4cee-aa88-f4732fa4ac40","order_by":4,"name":"Tian-yuan Zhang","email":"","orcid":"","institution":"XinHua Hospital","correspondingAuthor":false,"prefix":"","firstName":"Tian-yuan","middleName":"","lastName":"Zhang","suffix":""},{"id":614854733,"identity":"e652f9e1-88fd-4e48-87eb-7ece01b6cfc3","order_by":5,"name":"Jing-fan Yang","email":"","orcid":"","institution":"XinHua Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jing-fan","middleName":"","lastName":"Yang","suffix":""},{"id":614854734,"identity":"24707da3-3b33-44e1-9fbe-bc5f43529a17","order_by":6,"name":"Jun-lin Yang","email":"","orcid":"","institution":"XinHua Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jun-lin","middleName":"","lastName":"Yang","suffix":""},{"id":614854735,"identity":"4ba1479a-17e6-45b7-b92b-cc718e305421","order_by":7,"name":"Xin Zhang","email":"","orcid":"","institution":"XinHua Hospital","correspondingAuthor":false,"prefix":"","firstName":"Xin","middleName":"","lastName":"Zhang","suffix":""},{"id":614854736,"identity":"d271b721-66f7-4dc7-a947-532b46dae229","order_by":8,"name":"Wen-yuan Sui","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwUlEQVRIiWNgGAWjYNACAwYGfmbmgw9I0yLZzpZsQKJF53nMBIhSKT8jx/hzQcEdOePDDGYMDDU20YQNv5FjJj3D4Jmx2WGGtAcMx9JyGwhqkc4xY+YxOJy47TDDcQPGhsOEtcjPBjoMqKV+czNjmwRRWhhu5xhIA7UkGDAzsxGnxeD+szKgXw4bzjjMxmyQQIxf5HsOb/5c8OewPH//+Y8PPtTYEOEwBg4DZjg7gbByEGB/wExQzSgYBaNgFIxsAAA4GzxBOiZPrAAAAABJRU5ErkJggg==","orcid":"","institution":"XinHua Hospital","correspondingAuthor":true,"prefix":"","firstName":"Wen-yuan","middleName":"","lastName":"Sui","suffix":""}],"badges":[],"createdAt":"2026-03-19 14:38:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9170678/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9170678/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106093970,"identity":"8d5f330c-9a1a-4a56-9e56-c12029e03bc5","added_by":"auto","created_at":"2026-04-03 11:40:23","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":406196,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eStandardized CT/MRI Measurement of NF1-Specific Atrophic Changes. \u003c/strong\u003eA) Axial CT image showing vertebral atrophy (laminar changes, type 2); B) Sagittal T2-weighted MRI image showing disc atrophy (Pfirrmann grade Ⅲ, orange arrow); C) Axial T2-weighted MRI image showing paraspinal soft tissue atrophy (fat infiltration=32%, green; muscle cross-sectional area=68%, blue)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9170678/v1/6d51dc427b0ec759361b652f.png"},{"id":106093546,"identity":"8cce3f11-01fd-4f83-b495-5e857de9c6ba","added_by":"auto","created_at":"2026-04-03 11:37:57","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":122862,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOptimized DFV Selection Algorithm for NF1 Scoliosis.\u003c/strong\u003e Flowchart illustrating the four-step, evidence-based process: Step 1 = Identify initial DFV via standard AIS criteria; Step 2 = Evaluate DFV_initial and DFV_initial+1 for vertebral, disc, or paraspinal soft tissue atrophy via preoperative CT/MRI; Step 3 = Shift DFV cephalad by 1–2 segments if atrophic changes are present; Step 4 = Confirm DFV_optimized is a stable vertebra (rotation ≤5°, no translational deformity)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9170678/v1/39601f0131d0b78f7538550e.png"},{"id":106093694,"identity":"1963b353-5a59-4cf2-bfd6-2af8d88755f1","added_by":"auto","created_at":"2026-04-03 11:38:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":242950,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eKaplan-Meier Curves for Complication-Free Survival at 5-Year Follow-Up. \u003c/strong\u003eA) IFF-free survival; B) Distal adding-on-free survival. Blue curve = Optimized Group, red curve = Traditional Group. Log-rank P\u0026lt;0.001 for both comparisons.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9170678/v1/2d010ff7b1ae573575b8a265.png"},{"id":105982245,"identity":"cfde0c6d-9123-42ad-99f8-bf3054c29311","added_by":"auto","created_at":"2026-04-02 06:58:23","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":109038,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eROC Curves for Predicting Postoperative Complications. \u003c/strong\u003eBlue curve = Prediction of IFF (AUC=0.85, 95%CI:0.77–0.93); red curve = Prediction of distal adding-on (AUC=0.87, 95%CI:0.80–0.94). Dashed line = reference (AUC=0.5)\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9170678/v1/03be7e2a0285d43b0f8c6b5f.png"},{"id":105982248,"identity":"34725a87-71e1-4bfc-b186-b018858c587d","added_by":"auto","created_at":"2026-04-02 06:58:23","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":498418,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTypical Case: 10-Year-Old Female with NF1 Scoliosis Treated with Optimized DFV Selection.\u003c/strong\u003eA) Preoperative posteroanterior (PA) and lateral radiograph (Lenke 1 Curve, Cobb angle=47°); B) Preoperative axial CT showing no atrophy in L1 vertebral; C) Preoperative axial T2-weighted MRI showing paraspinal soft tissue atrophy at L1 level (green arrow, fat infiltration=36%); D) Preoperative sagittal T2-weighted MRI showing L1-4 disc atrophy (orange arrow, Pfirrmann grade Ⅲ); E) Immediate postoperative PA and lateral radiograph (DFV=T12, fusion T4–T12, Cobb angle=12°); F) 5-year postoperative PA and lateral radiograph (no distal adding-on, Cobb angle=14°). Optimized DFV selection (cephalad shift to T12) avoids atrophic segments (L1/2), resulting in no IFF or distal adding-on at 5-year follow-up and excellent spinal alignment\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9170678/v1/41afab4834dffb2999979331.png"},{"id":106095690,"identity":"981dd0c4-944f-43b9-8350-21e734df8bfc","added_by":"auto","created_at":"2026-04-03 11:50:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2592453,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9170678/v1/4da5efea-1180-4f1b-b60f-e20761034519.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Distal fusion vertebra selection in neurofibromatosis type 1 scoliosis: integrating CT/MRI-detected atrophic changes reduces long-term mechanical complications","fulltext":[{"header":"Introduction","content":"\u003cp\u003eNeurofibromatosis type 1 (NF1) scoliosis is a distinct pathological entity from adolescent idiopathic scoliosis (AIS), characterized by rapid curve progression, vertebral dysplasia, paraspinal neurofibroma infiltration, and unique atrophic changes (vertebral bodies, intervertebral discs, and paraspinal soft tissues)[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. These features compromise bone quality, impair osseointegration, and disrupt spinal biomechanics, resulting in significantly higher postoperative complication rates\u0026mdash;including internal fixation failure (IFF, 15\u0026ndash;30%) and distal adding-on (25\u0026ndash;40%)\u0026mdash;compared to AIS (IFF: 5\u0026ndash;8%; adding-on: 15\u0026ndash;20%)[\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDistal fusion vertebra (DFV) selection is a pivotal determinant of spinal fusion success, as inappropriate selection directly contributes to adding-on and IFF[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In AIS, DFV is chosen based on Lenke classification, curve flexibility, and vertebral rotation, but these criteria do not account for NF1-specific atrophic changes. Vertebral atrophy impairs pedicle screw anchorage; disc atrophy disrupts spinal load distribution; and paraspinal soft tissue atrophy compromises segmental stability, rendering adjacent segments unsuitable as DFV or DFV-adjacent levels[\u003cspan additionalcitationids=\"CR7 CR8\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePreoperative CT and MRI offer complementary diagnostic advantages: CT accurately assesses vertebral morphology and bone mineral density (BMD), while MRI visualizes disc integrity, soft-tissue atrophy, and neurofibroma infiltration[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Prior studies have linked these atrophic changes to postoperative complications[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], but no investigation has systematically integrated CT/MRI-detected atrophic changes with AIS criteria to optimize DFV selection in NF1 scoliosis. Early pilot studies have explored CT/MRI for fusion segment selection but lacked a standardized algorithm and long-term clinical validation[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWe hypothesized that DFV selection guided by AIS criteria, combined with preoperative CT/MRI-detected atrophic changes, would reduce long-term complications while preserving deformity correction efficacy. This study aimed to: (1) compare the efficacy of optimized versus traditional DFV selection in preventing IFF and distal adding-on in NF1 scoliosis; (2) identify key preoperative imaging markers for DFV adjustment; and (3) establish a practical, evidence-based DFV selection algorithm for NF1 scoliosis patients undergoing PSF.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003ch3\u003eStudy Design and Patient Population\u003c/h3\u003e\n\u003cp\u003eThis retrospective cohort study was approved by the Institutional Review Board of Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (Approval No.: XHEC-2024-056). Written informed consent was obtained from all patients or their legal guardians, in adherence to the Declaration of Helsinki. This study was reported in accordance with the STROBE statement.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInclusion Criteria\u003c/strong\u003e: (1) Confirmed NF1 diagnosis per 1997 NIH criteria[13]; (2) Lenke 1-3 curves with a main curve Cobb angle \u0026ge;45\u0026deg;; (3) Primary PSF with pedicle screw-rod fixation (no anterior fusion or growth-friendly surgery); (4) Complete preoperative CT (within 1 month) and MRI (within 3 months) imaging; (5) Minimum 5-year postoperative follow-up; (6) Complete clinical and radiological data available for analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eExclusion Criteria\u003c/strong\u003e: (1) Congenital or non-NF1 syndromic scoliosis; (2) Prior spinal surgery; (3) Metabolic bone disease (e.g., osteopenia, osteoporosis unrelated to NF1); (4) Incomplete preoperative imaging or follow-up data; (5) Perioperative mortality or major surgical complications (e.g., spinal cord injury, infection).\u003c/p\u003e\n\u003ch3\u003eGroup Stratification\u003c/h3\u003e\n\u003cp\u003e\u003cstrong\u003eOptimized Group\u003c/strong\u003e: DFV selected by standard AIS criteria plus preoperative CT/MRI assessment of atrophic changes (avoiding DFV adjacent to atrophic segments; cephalad shift of 1-2 segments if DFV+1 had \u0026ge;1 atrophic change).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTraditional Group\u003c/strong\u003e: DFV selected by AIS criteria alone:(1) Lenke-defined stable vertebrae; (2) Curve flexibility \u0026gt;70%: DFV = lowest vertebra of the main curve; (3) Flexibility 50\u0026ndash;70%: DFV = lowest vertebra of the main curve + 1 stable vertebra; (4) Flexibility \u0026lt;50%: DFV = lowest vertebra of the main curve + 2 stable vertebrae; (5) Vertebral rotation \u0026le;5\u0026deg; (Nash-Moe method)[14]\u0026nbsp;.\u003c/p\u003e\n\u003ch3\u003ePreoperative CT/MRI Assessment of Atrophic Changes\u003c/h3\u003e\n\u003cp\u003eImaging data were independently reviewed by two senior musculoskeletal radiologists with \u0026ge;10 years of experience in spinal imaging, who were blinded to clinical outcomes. Inter-rater reliability was assessed via kappa statistics (\u0026kappa; = 0.83-0.92), and discrepancies were resolved by consensus (Figure 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCT Protocol\u003c/strong\u003e (Siemens Somatom Definition, Erlangen, Germany): 120 kV, 200 mAs, 1 mm slice thickness, 0.5 mm reconstruction interval, 300\u0026times;300 mm field of view (FOV), 512\u0026times;512 matrix. Vertebral atrophy was defined as type 2-3 lamina changes or type 2-4 pedicle changes described in the previous report[6].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMRI Protocol\u003c/strong\u003e (GE Discovery MR750, Chicago, IL, USA): Sagittal T1-weighted (TR=500 ms, TE=10 ms), sagittal T2-weighted (TR=3000 ms, TE=100 ms), axial T2-weighted (TR=2500 ms, TE=80 ms), and fat-saturated T2-weighted sequences. Disc atrophy was defined as disc height loss \u0026ge;20% (vs. age-matched norms) or Pfirrmann grade \u0026ge;Ⅲ[7]. Paraspinal soft tissue atrophy was defined as muscle volume reduction \u0026ge;30% (ImageJ-segmented) or fat infiltration fraction \u0026ge;30%\u003cw:sdt docpart=\"1639389FCE464FFFB38914B06DF3EEE3\" title=\"SmartCite Citation\" sdttag=\"dd3af151-20fe-44b1-88a2-b84a12b0f53a:ba835b2e-6209-4949-b973-8ff93f587b1f,dd3af151-20fe-44b1-88a2-b84a12b0f53a:83427055-a040-4c76-b951-9ba5033003f8+\" id=\"-650751332\"\u003e[8, 10]\u003c/w:sdt\u003e.\u003c/p\u003e\n\u003ch3\u003eOptimized DFV Selection Algorithm\u003c/h3\u003e\n\u003cp\u003eThe optimized algorithm, as illustrated in the flowchart above (Figure 2), consists of the following steps:\u003c/p\u003e\n\u003cp\u003eIdentify the initial DFV (DFV_initial) using standard AIS criteria[14];\u003c/p\u003e\n\u003cp\u003eEvaluate DFV_initial and DFV_initial+1 for vertebral, disc, or paraspinal soft tissue atrophy via preoperative CT/MRI;\u003c/p\u003e\n\u003cp\u003eShift DFV cephalad by 1 segment if DFV_initial+1 has \u0026ge;1 atrophic change; shift by an additional segment if the newly selected DFV+1 still demonstrates atrophic changes;\u003c/p\u003e\n\u003cp\u003eConfirm the optimized DFV (DFV_optimized) is a stable vertebra (vertebral rotation \u0026le;5\u0026deg;, no translational deformity)[15].\u003c/p\u003e\n\u003ch3\u003eSurgical Technique\u003c/h3\u003e\n\u003cp\u003eAll surgeries were performed by senior spine surgeons with \u0026ge;10 years of specialized experience in scoliosis. PSF was performed via a posterior midline incision, with pedicle screw insertion (4.5-5.5 mm diameter, 30-45 mm length), titanium alloy rod placement (5.5\u0026ndash;6.0 mm diameter), curve correction via compression/distraction/derotation, and spinal fusion with a 1:1 ratio of autologous (iliac crest) + allogeneic bone graft. No intraoperative neuromonitoring abnormalities were noted in any patient.\u003c/p\u003e\n\u003ch3\u003eFollow-Up and Outcome Measures\u003c/h3\u003e\n\u003cp\u003ePatients underwent standardized follow-up at 3 months, 6 months, 1 year, 3 years, and 5 years postoperatively. Clinical evaluations included the Scoliosis Research Society-22 (SRS-22) questionnaire and visual analog scale (VAS) pain score (0-10). Radiological assessments (posteroanterior/lateral spinal radiographs, CT at 2 years) were performed to measure Cobb angle, coronal balance (C7 plumb line deviation, C7PLD), sagittal vertical axis (SVA), fusion rate (Bridwell grade)[16]\u0026nbsp;, IFF, and distal adding-on.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePrimary Outcomes\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003eIFF: Screw loosening (peri-screw lucency \u0026ge;2 mm), screw/rod breakage, or pseudarthrosis (Bridwell grade 1-2 at 2-year CT);\u003c/p\u003e\n\u003cp\u003eDistal adding-on: \u0026ge;5\u0026deg; increase in the DFV+1 Cobb angle vs. immediate postoperative values, or inclusion of DFV+1 into the main scoliotic curve.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSecondary Outcomes\u003c/strong\u003e: DFV level, fusion segment length, main curve correction rate, coronal/sagittal spinal balance, fusion rate (Bridwell grade 3-4), SRS-22 total/subscores, VAS pain score, and reoperation rate (for IFF, adding-on, or pseudarthrosis).\u003c/p\u003e\n\u003ch3\u003eStatistical Analysis\u003c/h3\u003e\n\u003cp\u003eStatistical analysis was performed using SPSS 26.0 (IBM Corp., Armonk, NY, USA). Continuous variables were expressed as mean\u0026plusmn;standard deviation (SD) or median (interquartile range, IQR); categorical variables as counts (percentages). PSM (1:1, caliper=0.2) was used to balance baseline characteristics between groups. Group comparisons were conducted using the independent samples t-test (continuous variables), chi-square test, or Fisher\u0026rsquo;s exact test (categorical variables). Multivariate logistic regression was used to identify independent predictors of postoperative complications. ROC curves were generated to assess the predictive value of combined CT/MRI atrophic change assessment, with AUC, sensitivity, and specificity calculated. Kaplan-Meier curves were used to compare complication-free survival, with the log-rank test for significance. A two-tailed P\u0026lt;0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"Results","content":"\u003ch3\u003eBaseline Characteristics\u003c/h3\u003e\n\u003cp\u003eA total of 156 patients were included (Optimized Group n=78, Traditional Group n=78). After PSM, 65 matched pairs (130 patients) were analyzed, with no significant baseline differences between groups (Table 1). In the Optimized Group, 41 patients (63.1%) underwent a cephalad DFV shift to avoid atrophic segments (32 patients: 1 segment, 9 patients: 2 segments). Preoperative atrophic change prevalence was comparable between groups after PSM (P\u0026gt;0.05 for all).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1. Baseline Characteristics Before and After Propensity Score Matching (PSM)\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 186px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003eOptimized Group (n=78)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 98px;\"\u003e\n \u003cp\u003eTraditional Group (n=78)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003eOptimized Group (n=65)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 98px;\"\u003e\n \u003cp\u003eTraditional Group (n=65)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAge (years), mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e13.7\u0026plusmn;3.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e13.9\u0026plusmn;3.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e13.8\u0026plusmn;3.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e13.9\u0026plusmn;3.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eFemale, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e45 (57.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e47 (60.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e36 (55.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e37 (56.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eRisser sign 0\u0026ndash;1, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e43 (55.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e41 (52.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e35 (53.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e34 (52.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMain curve Cobb angle (\u0026deg;), mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e58.9\u0026plusmn;13.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e59.3\u0026plusmn;14.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e59.1\u0026plusmn;13.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e59.2\u0026plusmn;14.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eLenke type 1/2/3, n\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e38/23/17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e36/25/17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e31/19/15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e30/20/15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eParaspinal neurofibroma, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e41 (52.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e39 (50.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e33 (50.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e32 (49.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePreoperative atrophic changes, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026ndash; Vertebral atrophy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e39 (60.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e37 (56.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e32 (49.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e30 (46.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026ndash; Disc atrophy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e35 (53.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e33 (50.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e29 (44.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e27 (41.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026ndash; Paraspinal soft tissue atrophy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e32 (49.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e30 (46.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e27 (41.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e25 (38.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eNote\u003c/em\u003e: All P\u0026gt;0.05 for between-group comparisons after PSM.\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch3\u003ePrimary Outcomes\u003c/h3\u003e\n\u003cp\u003eAt 5-year follow-up, the Optimized Group had a significantly lower IFF rate (12.3% [8/65] vs. 32.3% [21/65], P=0.002) and distal adding-on incidence (15.4% [10/65] vs. 40.0% [26/65], P\u0026lt;0.001) than the Traditional Group (Table 2). Kaplan-Meier analysis demonstrated significantly longer IFF-free and distal adding-on-free survival in the Optimized Group (log-rank P\u0026lt;0.001 for both; Figure 3).\u003c/p\u003e\n\u003ch3\u003eSecondary Outcomes\u003c/h3\u003e\n\u003cp\u003e\u003cstrong\u003eRadiological Outcomes\u003c/strong\u003e: The Optimized Group had a more cephalad median DFV level (T11 vs. T12, P\u0026lt;0.001), but fusion segment lengths were comparable between groups (7.2\u0026plusmn;1.1 vs. 7.0\u0026plusmn;1.0 vertebrae, P=0.213; Table 2). Main curve correction rates were similar (80.1%\u0026plusmn;8.7% vs. 78.5%\u0026plusmn;9.2%, P=0.286), but the Optimized Group had superior coronal balance (1.2\u0026plusmn;0.7 vs. 1.7\u0026plusmn;0.9 cm, P=0.003) and sagittal balance (SVA: 1.6\u0026plusmn;1.0 vs. 2.2\u0026plusmn;1.2 cm, P=0.004). Fusion rates were high and comparable between groups (96.9% vs. 93.8%, P=0.421).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Outcomes\u003c/strong\u003e: The Optimized Group had significantly higher SRS-22 total scores (4.1\u0026plusmn;0.4 vs. 3.6\u0026plusmn;0.5, P\u0026lt;0.001), lower VAS pain scores (1.6\u0026plusmn;0.8 vs. 2.9\u0026plusmn;1.1, P\u0026lt;0.001), and a lower reoperation rate (9.2% [6/65] vs. 30.8% [20/65], P=0.001) than the Traditional Group (Table 2). Reoperations in the Traditional Group were primarily for IFF (n=12) and distal adding-on (n=8); reoperations in the Optimized Group were for pseudarthrosis (n=4) and minor rod malposition (n=2).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2. Clinical and Radiological Outcomes at 5-Year Follow-Up (65 Matched Pairs)\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 391px;\"\u003e\n \u003cp\u003eIFF rate, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 69px;\"\u003e\n \u003cp\u003e8 (12.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e21 (32.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 48px;\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eDistal adding-on incidence, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e10 (15.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e26 (40.0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eDFV level (median, range)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eT12 (T10\u0026ndash;L2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eL1 (T11\u0026ndash;L3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eFusion segment length (vertebrae), mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e7.2\u0026plusmn;1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e7.0\u0026plusmn;1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.213\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMain curve correction rate (%), mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e80.1\u0026plusmn;8.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e78.5\u0026plusmn;9.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.286\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eCoronal balance (C7PLD, cm), mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1.2\u0026plusmn;0.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1.7\u0026plusmn;0.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSVA (cm), mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1.6\u0026plusmn;1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.2\u0026plusmn;1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.004\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eFusion rate (Bridwell 3\u0026ndash;4), n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e63 (96.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e61 (93.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.421\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSRS-22 total score, mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e4.1\u0026plusmn;0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.6\u0026plusmn;0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eVAS pain score (0\u0026ndash;10), mean\u0026plusmn;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1.6\u0026plusmn;0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.9\u0026plusmn;1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eReoperation rate, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e6 (9.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e20 (30.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eNote\u003c/em\u003e: IFF=internal fixation failure; DFV=distal fusion vertebra; C7PLD=C7 plumb line deviation; SVA=sagittal vertical axis; SRS-22=Scoliosis Research Society-22; VAS=visual analog scale.\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch3\u003ePredictive Value of Atrophic Changes\u003c/h3\u003e\n\u003cp\u003e\u003cstrong\u003eMultivariate Logistic Regression\u003c/strong\u003e: DFV adjacency to atrophic segments was the strongest independent predictor of postoperative complications (Table 3). For IFF, the top predictors were vertebral atrophy (OR=6.12, 95% CI: 2.15-17.43, P\u0026lt;0.001) and disc atrophy (OR=5.37, 95% CI: 1.89-15.21, P=0.001). For distal adding-on, the top predictors were disc atrophy (OR=5.78, 95% CI: 2.03-16.45, P\u0026lt;0.001) and paraspinal soft-tissue atrophy (OR=4.89, 95% CI: 1.72-13.92, P=0.002). Lenke type 3 was not a significant predictor of either complication (P\u0026gt;0.05).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eROC Curve Analysis\u003c/strong\u003e: Combined preoperative CT/MRI assessment of atrophic changes predicted IFF with an AUC of 0.85 (95% CI: 0.77-0.93, P\u0026lt;0.001; sensitivity=80.2%, specificity=78.9%) and distal adding-on with an AUC of 0.87 (95% CI: 0.80-0.94, P\u0026lt;0.001; sensitivity=82.6%, specificity=80.3%) (Figure 4).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3. Multivariate Logistic Regression for Independent Predictors of Postoperative Complications\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 153px;\"\u003e\n \u003cp\u003eDFV adjacent to vertebral atrophy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 153px;\"\u003e\n \u003cp\u003e6.12 (2.15\u0026ndash;17.43)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 153px;\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 153px;\"\u003e\n \u003cp\u003e4.23 (1.51\u0026ndash;11.82)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 153px;\"\u003e\n \u003cp\u003e0.006\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eDFV adjacent to disc atrophy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e5.37 (1.89\u0026ndash;15.21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e5.78 (2.03\u0026ndash;16.45)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eDFV adjacent to paraspinal soft tissue atrophy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e4.51 (1.58\u0026ndash;12.87)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.005\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e4.89 (1.72\u0026ndash;13.92)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eLenke type 3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.18 (0.76\u0026ndash;6.29)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.148\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.35 (0.82\u0026ndash;6.73)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.112\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eNote\u003c/em\u003e: OR=odds ratio; CI=confidence interval; IFF=internal fixation failure; DFV=distal fusion vertebra.\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch3\u003eTypical Case\u003c/h3\u003e\n\u003cp\u003eA 10-year-old female with NF1, Lenke 1 curve (preoperative Cobb angle 47\u0026deg;), Risser sign 0, and paraspinal neurofibromatosis (T9-T11) underwent PSF with optimized DFV selection. Preoperative CT identified no vertebral atrophy in DFV_initial (L1); MRI demonstrated L1-2 disc atrophy (Pfirrmann grade Ⅲ, height loss 22%) and paraspinal soft tissue atrophy (fat infiltration=36%). DFV_initial (L1) was shifted cephalad to T12 following the optimized algorithm. The immediate postoperative Cobb angle was 12\u0026deg; (correction rate=74.5%). At 5-year follow-up, there was no IFF or distal adding-on, and the SRS-22 total score was 4.3 (Figure 5). Solid fusion (Bridwell grade 4) was confirmed on 5-year CT.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study shows that an optimized DFV selection strategy integrating AIS fusion criteria with preoperative CT/MRI-detected atrophic changes significantly reduces long-term internal fixation failure (IFF) and distal adding-on in NF1 scoliosis, while maintaining deformity correction and improving spinal balance and patient-reported outcomes. The key principle of this strategy is to avoid selecting a DFV adjacent to NF1-specific atrophic segments, which appear to be imaging markers of segmental instability.\u003c/p\u003e \u003cp\u003eTraditional AIS-based DFV selection does not account for the distinctive pathological features of NF1 scoliosis, including vertebral dysplasia, reduced bone mineral density, and paraspinal soft-tissue abnormalities[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. This limitation was reflected in our Traditional Group, which showed high rates of IFF and distal adding-on, consistent with previous reports in NF1 scoliosis[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. In contrast, the Optimized Group achieved a 62% reduction in both complications, suggesting that fusion to or adjacent to atrophied segments is a major contributor to mechanical failure. Our multivariate analysis further supports this interpretation, identifying vertebral atrophy as the strongest predictor of IFF (OR\u0026thinsp;=\u0026thinsp;6.12). Notably, Shao et al. recently reported that DFV selection in NF1 non-dystrophic scoliosis requires a tailored approach distinct from AIS, but their study did not integrate CT/MRI-detected atrophic changes or focus on long-term complications[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Our study builds on this work by establishing a standardized algorithm that addresses both dystrophic and non-dystrophic subsets, with a 5-year follow-up to capture late complications common in NF1 scoliosis.\u003c/p\u003e \u003cp\u003eOur findings also highlight the complementary value of CT and MRI in preoperative assessment. CT is particularly useful for evaluating vertebral morphology, trabecular integrity, and bone quality relevant to screw anchorage, whereas MRI provides information on disc status, paraspinal soft tissue atrophy, neurofibroma infiltration, and intraspinal abnormalities[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In our cohort, a combined CT/MRI assessment accurately predicted IFF and distal adding-on, supporting the use of both modalities for DFV planning in NF1 scoliosis. Compared with prior studies that relied on single-modality imaging or did not directly incorporate imaging findings into segment selection[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], our study provides a practical imaging-guided framework with 5-year validation.\u003c/p\u003e \u003cp\u003eAn important concern when modifying the DFV is whether fusion may become too short or unnecessarily extended[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Tauchi et al. reported that early definitive fusion in NF1 scoliosis preserves spinal alignment but may compromise mobility if fusion segments are excessive\u0026mdash;emphasizing the need for targeted DFV selection[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Our approach avoids both pitfalls: in patients with no atrophic changes (36.9% of the Optimized Group), DFV remained consistent with AIS criteria, avoiding unnecessary cephalad shift and potential under-fusion. In patients with multiple atrophic changes, a 2-segment cephalad shift ensured fusion to a stable vertebra, avoiding over-fusion by only shifting the minimum number of segments needed to bypass atrophied levels. This personalized strategy explains why the Optimized Group achieved superior spinal balance (coronal and sagittal) compared to the Traditional Group\u0026mdash;stable DFV anchor points reduce junctional instability and improve long-term alignment maintenance.\u003c/p\u003e \u003cp\u003eRecent studies in NF1 scoliosis have mainly focused on surgical technique, implant strategy, or biological enhancement, whereas segment selection has received less attention. Jia et al. reported that combined anterior-posterior fusion improves fusion rates in dystrophic NF1 scoliosis but does not reduce IFF or distal adding-on, highlighting that technical enhancement alone cannot overcome the risks of poor segment selection[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Neifert et al. demonstrated that customized pedicle screws improve anchorage in NF1 scoliosis but failed to address the underlying instability of atrophied segments, which remains a major driver of complications[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOur study fills this critical gap by demonstrating that imaging-guided DFV selection is a cost-effective, accessible strategy to reduce complications without requiring specialized implants or biologics\u0026mdash;an important consideration for clinical practice, particularly in resource-limited settings. Notably, the 5-year IFF rate of 12.3% in our Optimized Group is the lowest reported in contemporary NF1 scoliosis literature. Prior studies have reported IFF rates of 24\u0026ndash;36% with traditional DFV selection and adding-on rates of 25\u0026ndash;40%[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] \u0026mdash;both significantly higher than in our Optimized Group. This improvement is clinically meaningful, as NF1 patients require lifelong spinal follow-up, and late complications (e.g., screw breakage, pseudarthrosis) can significantly impact quality of life and require revision surgery. Our SRS-22 results (4.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4 vs. 3.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) confirm that reducing complications translates to better patient-reported outcomes, including improved pain, physical function, and self-image\u0026mdash;key measures of success in spinal deformity surgery.\u003c/p\u003e \u003cp\u003e \u003cb\u003e5. Study Limitations\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThis study has several limitations. First, it was a retrospective single-center study, although propensity score matching was used to reduce baseline imbalance. Second, the spinal range of motion was not assessed. Third, external validation is still needed, particularly across different surgical techniques and broader NF1 scoliosis populations.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eOptimized distal fusion vertebra selection for NF1 scoliosis, integrating AIS fusion criteria with preoperative CT/MRI-detected atrophic changes, reduces long-term internal fixation failure and distal adding-on without compromising deformity correction. The key clinical principle is to avoid selecting a DFV adjacent to vertebral, disc, or paraspinal soft tissue atrophy, as these findings may indicate segmental instability. This strategy preserves fusion length, improves spinal balance, and enhances patient-reported outcomes, providing a practical imaging-guided framework for surgical planning in NF1 scoliosis. External multicenter validation is warranted before broader implementation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eY.Z., X.Z., and WY.S. conceived and designed the study. XX.S., J.C., YL.D. and TY.Z. acquired the data. XX.S., J.C. and TY.Z. performed the statistical analyses. Y.Z., XX.S. and WY.S. wrote the main manuscript text, and Y.Z. and WY.S. prepared all the Figures. JF.Y. and JL.Y. critically revised the manuscript. YL.D. and JL.Y. supervised the study. Notably, Y.Z. and X.Z. contributed equally to this work. All authors reviewed and approved the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eKaspiris A, Savvidou OD, Vasiliadis ES, et al (2022) Current Aspects on the Pathophysiology of Bone Metabolic Defects during Progression of Scoliosis in Neurofibromatosis Type 1. J Clin Med 11:444. https://doi.org/10.3390/jcm11020444\u003c/li\u003e\n\u003cli\u003eYao Z, Li H, Zhang X, et al (2018) Incidence and Risk Factors for Instrumentation-related Complications After Scoliosis Surgery in Pediatric Patients With NF-1. SPINE 43:1719\u0026ndash;1724. https://doi.org/10.1097/brs.0000000000002720\u003c/li\u003e\n\u003cli\u003eBouthors C, Dukan R, Glorion C, Miladi L (2020) Outcomes of growing rods in a series of early-onset scoliosis patients with neurofibromatosis type 1. J Neurosurg: Spine 33:373\u0026ndash;380. https://doi.org/10.3171/2020.2.spine191308\u003c/li\u003e\n\u003cli\u003ePaul JC, Lonner BS, Vira S, et al (2018) Does Reoperation Risk Vary for Different Types of Pediatric Scoliosis? J Pediatr Orthop 38:459\u0026ndash;464. https://doi.org/10.1097/bpo.0000000000000850\u003c/li\u003e\n\u003cli\u003ePark B-J, Hyun S-J, Wui S-H, et al (2020) Surgical Outcomes and Complications Following All Posterior Approach for Spinal Deformity Associated with Neurofibromatosis Type-1. J Korean Neurosurg Soc 63:738\u0026ndash;746. https://doi.org/10.3340/jkns.2019.0218\u003c/li\u003e\n\u003cli\u003ePushpa BT, Rajasekaran S, Anand KSSV, et al (2022) Anatomical changes in vertebra in dystrophic scoliosis due to neurofibromatosis and its implications on surgical safety. Spine Deform 10:159\u0026ndash;167. https://doi.org/10.1007/s43390-021-00392-6\u003c/li\u003e\n\u003cli\u003eLi S, Mao S, Du C, et al (2021) Assessing the unique characteristics associated with surgical treatment of dystrophic lumbar scoliosis secondary to neurofibromatosis type 1: a single-center experience of more than 10 years. J Neurosurg: Spine 34:413\u0026ndash;423. https://doi.org/10.3171/2020.6.spine20898\u003c/li\u003e\n\u003cli\u003eHaider S, Le LQ, Cho G, et al (2022) Scoliosis in Neurofibromatosis Type 1 on Whole-Body Magnetic Resonance Imaging: Frequency and Association With Intraspinal and Paraspinal Tumors. J Comput Assist Tomogr 46:231\u0026ndash;235. https://doi.org/10.1097/rct.0000000000001263\u003c/li\u003e\n\u003cli\u003eHeyde C-E, V\u0026ouml;lker A, H\u0026ouml;h NH von der, et al (2021) Wirbels\u0026auml;ulendeformit\u0026auml;ten bei Neurofibromatose Typ 1. Orthop 50:650\u0026ndash;656. https://doi.org/10.1007/s00132-021-04130-8\u003c/li\u003e\n\u003cli\u003eThakur U, Ramachandran S, Mazal AT, et al (2025) Multiparametric whole-body MRI of patients with neurofibromatosis type I: spectrum of imaging findings. Skelet Radiol 54:407\u0026ndash;422. https://doi.org/10.1007/s00256-024-04765-6\u003c/li\u003e\n\u003cli\u003eWell L, Careddu A, Stark M, et al (2021) Phenotyping spinal abnormalities in patients with Neurofibromatosis type 1 using whole-body MRI. Sci Rep 11:16889. https://doi.org/10.1038/s41598-021-96310-x\u003c/li\u003e\n\u003cli\u003eShi B-L, Li Y, Zhu Z-Z, et al (2021) Curve evolution during bracing in children with scoliosis secondary to early-onset neurofibromatosis type 1: indicators of rapid curve progression. Chin Méd J 134:1983\u0026ndash;1987. https://doi.org/10.1097/cm9.0000000000001606\u003c/li\u003e\n\u003cli\u003eFerner RE, Huson SM, Thomas N, et al (2007) Guidelines for the diagnosis and management of individuals with neurofibromatosis 1. J Méd Genet 44:81. https://doi.org/10.1136/jmg.2006.045906\u003c/li\u003e\n\u003cli\u003eKing HA, Moe JH, Bradford DS, Winter RB (1983) The selection of fusion levels in thoracic idiopathic scoliosis. J Bone Jt Surg 65:1302\u0026ndash;1313. https://doi.org/10.2106/00004623-198365090-00012\u003c/li\u003e\n\u003cli\u003eShao X, Zhang T, Yang J, et al (2023) How to select the lowest instrumented vertebra in NF-1 non-dystrophic scoliosis. Eur Spine J 32:1153\u0026ndash;1160. https://doi.org/10.1007/s00586-023-07600-z\u003c/li\u003e\n\u003cli\u003eYu A, Tiao J, Cai CW, et al (2025) Radiographic Assessment of Successful Lumbar Spinal Fusion: A Systematic Review of Fusion Criteria in Randomized Trials. Glob Spine J 21925682251384662. https://doi.org/10.1177/21925682251384662\u003c/li\u003e\n\u003cli\u003eZhao X, Li J, Shi L, et al (2016) Surgical Treatment of Dystrophic Spinal Curves Caused by Neurofibromatosis Type 1. Medicine 95:e3292. https://doi.org/10.1097/md.0000000000003292\u003c/li\u003e\n\u003cli\u003eMarrache M, Suresh KV, Miller DJ, et al (2021) Early-Onset Spinal Deformity in Neurofibromatosis Type 1: Natural History, Treatment, and Imaging Surveillance. JBJS Rev 9:e20.00285. https://doi.org/10.2106/jbjs.rvw.20.00285\u003c/li\u003e\n\u003cli\u003eJain A, Sponseller PD, Flynn JM, et al (2016) Avoidance of \u0026ldquo;Final\u0026rdquo; Surgical Fusion After Growing-Rod Treatment for Early-Onset Scoliosis. J Bone Jt Surg 98:1073\u0026ndash;1078. https://doi.org/10.2106/jbjs.15.01241\u003c/li\u003e\n\u003cli\u003eTauchi R, Kawakami N, Castro MA, et al (2020) Long-term Surgical Outcomes After Early Definitive Spinal Fusion for Early-onset Scoliosis With Neurofibromatosis Type 1 at Mean Follow-up of 14 Years. J Pediatr Orthop 40:42-47. https://doi.org/10.1097/bpo.0000000000001090\u003c/li\u003e\n\u003cli\u003eJia F, Wang G, Sun J, Liu X (2021) Combined Anterior-Posterior Versus Posterior-only Spinal Fusion in Treating Dystrophic Neurofibromatosis Scoliosis With Modern Instrumentation: A Systematic Review and Meta-analysis. Clin Spine Surg 34:132\u0026ndash;142. https://doi.org/10.1097/bsd.0000000000001069\u003c/li\u003e\n\u003cli\u003eNeifert SN, Khan HA, Kurland DB, et al (2022) Management and surgical outcomes of dystrophic scoliosis in neurofibromatosis type 1: a systematic review. Neurosurg Focus 52:E7. https://doi.org/10.3171/2022.2.focus21790\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"european-spine-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"esjo","sideBox":"Learn more about [European Spine Journal](http://link.springer.com/journal/586)","snPcode":"586","submissionUrl":"https://submission.springernature.com/new-submission/586/3","title":"European Spine Journal","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Neurofibromatosis type 1, Scoliosis, Distal fusion vertebra, Atrophic changes, Internal fixation failure, Distal adding-on","lastPublishedDoi":"10.21203/rs.3.rs-9170678/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9170678/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePurpose\u003c/h2\u003e \u003cp\u003eDistal fusion vertebra (DFV) selection in neurofibromatosis type 1 (NF1) scoliosis is traditionally guided by adolescent idiopathic scoliosis (AIS) criteria, which do not account for NF1-specific atrophic changes. We evaluated whether integrating preoperative CT/MRI-detected atrophic changes into DFV selection reduces long-term mechanical complications.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis retrospective cohort study included 156 NF1 scoliosis patients (Lenke 1\u0026ndash;3, Cobb\u0026thinsp;\u0026ge;\u0026thinsp;45\u0026deg;) undergoing posterior spinal fusion (2010\u0026ndash;2018) with a minimum 5-year follow-up. Patients were stratified into an optimized group (AIS criteria plus CT/MRI atrophic assessment) and a traditional group (AIS criteria alone). Propensity score matching (1:1) yielded 65 matched pairs. Primary outcomes were internal fixation failure (IFF) and distal adding-on. Multivariate logistic regression and ROC analysis were performed.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe optimized group demonstrated lower IFF (12.3% vs. 32.3%; OR 0.29, 95% CI 0.12\u0026ndash;0.68; p\u0026thinsp;=\u0026thinsp;0.002) and distal adding-on (15.4% vs. 40.0%; OR 0.27, 95% CI 0.12\u0026ndash;0.60; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Absolute risk reductions were 20.0% (IFF) and 24.6% (adding-on), corresponding to numbers needed to treat of 5 and 4, respectively. Correction magnitude and fusion length were comparable between groups. DFV adjacency to vertebral (OR 6.12), disc (OR 5.37), and paraspinal soft-tissue atrophy (OR 4.89) independently predicted complications. Combined CT/MRI assessment demonstrated good discrimination (AUC\u0026thinsp;=\u0026thinsp;0.87; sensitivity 82.6%, specificity 80.3%).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eIntegration of CT/MRI-detected atrophic changes into DFV selection was associated with significantly reduced long-term mechanical complications without compromising deformity correction in NF1 scoliosis.\u003c/p\u003e","manuscriptTitle":"Distal fusion vertebra selection in neurofibromatosis type 1 scoliosis: integrating CT/MRI-detected atrophic changes reduces long-term mechanical complications","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-02 06:58:18","doi":"10.21203/rs.3.rs-9170678/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-08T20:30:28+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-08T12:09:00+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-03T10:38:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"64397248231657772876218974730309289910","date":"2026-04-01T01:16:13+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-30T21:12:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"187851578564035907708655169186839639197","date":"2026-03-30T15:23:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"102336891543729813393709531323928535197","date":"2026-03-30T07:24:50+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-29T17:40:36+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-24T01:36:16+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-24T01:35:27+00:00","index":"","fulltext":""},{"type":"submitted","content":"European Spine Journal","date":"2026-03-19T14:22:43+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"european-spine-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"esjo","sideBox":"Learn more about [European Spine Journal](http://link.springer.com/journal/586)","snPcode":"586","submissionUrl":"https://submission.springernature.com/new-submission/586/3","title":"European Spine Journal","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"69e47704-8d55-45ca-a1ae-52cd594097dc","owner":[],"postedDate":"April 2nd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-11T14:58:13+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-02 06:58:18","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9170678","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9170678","identity":"rs-9170678","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}