Background and Objectives: This study aimed to identify radiographic predictors and optimal cut-off values for determining the need for additional pedicle subtraction osteotomy (PSO) in patients with iatrogenic flatback syndrome following short-segment (≤3 levels) fusion surgery. Materials and Methods: From 2011 to 2022, a total of 49 patients who underwent deformity correction for iatrogenic flatback following short-segment fusion at a single institution were included. We divided all patients into group A (n = 33, only anterior column realignment, ACR) and group B (n = 16, ACR combined with PSO). Among group A patients, we further divided them into two subgroups: The Excessive group, who developed excessive anterior disc height distraction (EADH) during surgery, and the Non-excessive group, who did not. The Receiver Operating Characteristic (ROC) curve was used to determine the cut-off values for spinopelvic parameters associated with the decision to perform additional PSO. Results: Group A had a significantly lower number of previously fused segments compared to Group B (p < 0.001). Preoperative C7 sagittal vertical axis (C7SVA, p = 0.026) and its correction (p = 0.003) in group B were greater than those in group A. Group B showed a significantly more kyphotic preoperative fused segment angle (FSA) compared to Group A (p = 0.001). Postoperatively, EADH occurred in 7 patients (21.2%) in Group A, while no cases were observed in Group B. Subgroup analysis revealed that the dynamic segment angle (DA) was significantly lower in the Excessive group compared to the Non-excessive group (p < 0.001). The optimal cut-off values of preoperative radiographic parameters for selecting PSO were: C7-SVA > 242.8 mm, FSA > −3.2°, and DA < 4.3°. Conclusions: ACR alone and ACR combined with PSO showed satisfactory outcomes in patients with iatrogenic flat back. For selected patients with preoperative C7SVA > 242.8 mm, FSA > −3.2°, or DA < 4.3°, additional PSO may be reasonable to help optimize sagittal alignment.

Background: Thoracolumbar fractures in patients with ankylosing spondylitis (AS) pose unique challenges due to altered spinal biomechanics and sagittal imbalance. Optimal surgical strategies remain controversial, and objective criteria for selecting between deformity-corrective and fusion-only procedures are lacking. Methods: We retrospectively reviewed 41 AS patients with thoracolumbar fractures who underwent surgical treatment. Patients were categorized as vertebral body (VB) type or intervertebral space (IS) type fractures. The primary outcome was surgical strategy selection, defined as pedicle subtraction osteotomy (PSO) versus non-PSO procedures. Propensity score matching (PSM) was performed using preoperative clinical and radiographic parameters to minimize selection bias in comparing outcomes between fracture types. Radiographic outcomes, pain improvement, and complication rates were compared. Predictive modeling using logistic regression and decision tree analysis was conducted to identify determinants of surgical strategy. Results: A total of 41 patients (24 VB-type, 17 IS-type) were included. The VB group exhibited significantly greater preoperative sagittal imbalance and underwent PSO more frequently, while IS-type fractures were treated with posterior spinal fusion (PSF). PSM analysis ( n = 17 per group) confirmed greater radiographic correction in the VB group without differences in pain outcomes. The decision tree model achieved an accuracy of 82.9% and AUC = 0.88 (95% CI: 0.85–0.99), with C7SVA > 222.6 mm as the primary decision criterion. Multivariable logistic regression identified C7SVA as the only statistically significant predictor (OR = 1.013; 95% CI: 1.001–1.026; p = 0.039). These findings suggest promising but preliminary discriminative ability, and external validation is warranted. Conclusions: In AS patients with VB-type thoracolumbar fractures, preoperative C7SVA > 222.6 mm represents a data-supported threshold for PSO, while C7SVA > 186.8 mm combined with BMD ≤ − 2.25 identifies a secondary risk group warranting PSO consideration. PSF alone appears sufficient for IS-type injuries with relatively preserved sagittal alignment. Preoperative sagittal profiling and bone mineral density assessment enable individualized, data-driven surgical planning in this high-risk population.

Background and Objectives: This study aimed to identify radiographic predictors and opti-mal cut-off values for determining the need for additional pedicle subtraction osteotomy (PSO) in patients with iatrogenic flatback syndrome following short-segment (≤3 levels) fusion surgery. Materials and Methods: From 2011 to 2022, a total of 49 patients who un-derwent deformity correction for iatrogenic flatback following short-segment fusion at a single institution were included. We divided all patients into group A (n= 33, only ACR) and group B (n= 16, ACR combined with PSO). Among group A patients, we further di-vided them into two subgroups: The Excessive group, who developed excessive anterior disc height distraction (EADH) during surgery, and the Non-excessive group, who did not. The Receiver Operating Characteristic (ROC) curve was used to determine the cut-off val-ues for spinopelvic parameters associated with the decision to perform additional PSO. Results: Group A had a significantly lower number of previously fused segments com-pared to Group B (p < 0.001). Preoperative C7 sagittal vertical axis (C7SVA, p=0.026) and its correction (p=0.003) in group B were greater than those in group A. Group B showed a significantly more kyphotic preoperative fused segment angle (FSA) compared to Group A (p = 0.001). Postoperatively, EADH occurred in 7 patients (21.2%) in Group A, while no cases were observed in Group B. Subgroup analysis revealed that the dynamic segment angle (DA) was significantly lower in the Excessive group compared to the Non-excessive group (p 242.8mm, FSA > -3.2°, and DA < 4.3°. Conclusions: ACR alone and ACR combined with PSO showed satisfactory outcomes in patients with iatro-genic flat back. In particular, we highly recommend ACR combined with the PSO in pa-tients with preoperative C7SVA > 242.8 mm, FSA > -3.2°, or DA < 4.3°.

Background and Objectives: Long spinal fusion terminating at L5 remains controversial because of the risk of postoperative junctional failure. Although degeneration of the residual L5–S1 disc has been suggested as a contributing factor, the relative impact of disc degeneration versus sagittal spinopelvic alignment on different junctional failure patterns has not been fully clarified. Materials and Methods: This retrospective cohort study included 47 patients aged ≥60 years who underwent ≥5-level thoracolumbar fusion ending at L5 with a minimum follow-up of 2 years. Junctional failures were classified as proximal junctional failure (PJF) or distal junctional failure (DJF). Preoperative L5–S1 disc degeneration was assessed using modified Weiner and Pfirrmann classifications. Spinopelvic parameters were measured preoperatively, postoperatively, and at final follow-up. Junctional failure–free survival was analyzed using the Kaplan–Meier method, and risk factors were explored using Cox proportional hazards models. Results: Junctional failures occurred in 28 patients (59.6%), including 16 PJFs (34.0%) and 10 DJFs (21.3%). Lower grades of L5–S1 disc degeneration (Weiner grades 0–1) were more frequently associated with PJFs, whereas higher grades (≥2) were predominantly associated with DJFs (p = 0.024). Multivariate analysis showed that preoperative thoracolumbar kyphosis (hazard ratio [HR] = 1.164), preoperative T1 pelvic angle (HR = 1.269), and postoperative pelvic incidence–lumbar lordosis mismatch (HR = 0.877) as significant risk factors for PJF. Postoperative proximal junctional angle (HR = 0.899) and lumbar lordosis (HR = 0.920) were independently associated with DJF. Conclusions: Sagittal spinopelvic alignment parameters appear to have a greater influence on junctional failure patterns than residual L5–S1 disc degeneration in long fusions terminating at L5. Adequate sagittal correction should be prioritized to reduce the risk of both proximal and distal junctional failures.

Background and Objectives: The selection of the optimal distal level of fusion in long-level fusion surgery remains controversial. Fusion ending at L5 preserves motion but increases the risk of L5–S1 disc degeneration. The L5 laminar hook has been introduced to enhance distal fixation, but its indications and clinical effects remain unclear. This study aimed to investigate the indication of the L5 laminar hook and its effect on adjacent segment degeneration when performing long-level fusion terminating at L5 in patients with degenerative sagittal imbalance (DSI). Materials and Methods: 112 patients with DSI who had undergone corrective surgery and ended at L5 were analyzed retrospectively. Finally, 64 were treated with an L5 laminar hook (Group I), while 48 were not (Group II). We compared radiographic spinopelvic parameters between the two groups and followed up disc degeneration at the L5–S1 level. Additional analysis was conducted within Group I to determine the indications for L5 laminar hook. Results: Preoperative C7 sagittal vertical axis (C7SVA), lumbar lordosis (LL), and pelvic incidence (PI)-LL mismatch were significantly greater in Group I than in Group II (p < 0.05). At 2 years of follow-up, advanced L5–S1 disc degeneration had developed in 14 patients (21.9%) in Group I and 36 patients (75%) in Group II. Patients in Group B (exacerbated L5–S1) had a significantly higher body mass index (BMI), larger preoperative C7SVA, and PI-LL mismatch than patients in Group A (preserved L5–S1). The C7SVA and PI-LL mismatch cut-off values for Group A were 15.8 cm and 40.8°, respectively. Conclusions: L5 laminar hook helps to reduce disc degeneration at the L5–S1 level and can be used to maintain the deformity correction ending at L5 in patients with DSI. We propose a series of indicators for the use of L5 laminar hooks in patients with DSI: a low BMI, a PI-LL mismatch < 40.8°, and a C7SVA < 15.8 cm.