Published papers

Study Design: Retrospective cohort study. Objective: This study aimed to determine whether the outcomes of posterior correction and fusion surgery (PSF) in patients with residual adolescent idiopathic scoliosis (AIS) during adulthood (Lenke type 5 AdIS) are inferior to those in patients with AIS treated during adolescence. Methods: We retrospectively evaluated 48 patients with type 5 AdIS who underwent PSF after 20 years old. As controls, we selected 67 patients with type 5 AIS who underwent PSF before 18 years old. Both groups were matched based on the preoperative thoracic and thoracolumbar/lumbar Cobb angles, resulting in 33 patients in each group. We compared preoperative and postoperative radiographic parameters and SRS-22 scores between the 2 groups. Results: Preoperatively, the AdIS group had significantly lower flexibility index (59.0% ± 13.0% vs 66.6% ± 16.7%; P = 0.01). The preoperative SRS-22 scores for pain and mental health domain were significantly worse in the AdIS group (pain, 3.9 ± 0.8 vs 4.3 ± 0.7, P < 0.01; mental health, 3.6 ± 0.8 vs 4.2 ± 0.6, P < 0.01). The AdIS group had significantly more fused vertebrae and longer intraoperative time than the AIS group. Postoperatively, lumber Cobb angle (16.1° ± 5.6° vs 8.6° ± 4.0°, P < 0.01) and correction rate were both less favorable in the AdIS group. Both pain and mental health scores remained significantly worse in the AdIS group (pain: AdIS, 4.3 ± 0.6 vs AIS, 4.7 ± 0.3; P < 0.01; mental health: AdIS, 4.1 ± 0.7 vs AIS, 4.5 ± 0.5; P = 0.02). Conclusion: Patients with type 5 AdIS had a similar correction of the major curve as those with AIS; however, the surgery was more invasive, with inferior postoperative clinical outcomes, than those with AIS. These findings suggest that the surgical timing should be carefully considered in patients with type 5 AIS to optimize outcomes.

Purpose: This study aimed to examine the changes in thoracolumbar kyphosis (TLK) following correction surgery in patients with Lenke type 5C adolescent idiopathic scoliosis (AIS) and to evaluate its influence on postoperative spinal alignment and clinical outcomes. Methods: Sixty-six patients with Lenke type 5C AIS were included and followed up for a minimum of 5 years after surgery. First, the patients were divided into two groups according to the preoperative TLK angle (Study 1; Kyphosis and Lordosis group). The patients were further classified into two groups according to the presence or absence of postoperative changes in TLK (Study 2; Changed and Maintained groups). Finally, the outcome variables were compared between these groups and analyzed for spinal alignment and clinical outcomes. Results: In Study 1, patients demonstrated a significant kyphotic change in the Lordosis group and a significant lordotic change in the Kyphosis group postoperatively. No statistically significant differences were found between the two groups when comparing the pre- and postoperative coronal and sagittal alignment. In Study 2, there were no statistically significant differences between the Changed and the Maintained groups in each spinal alignment pre- and postoperatively. Each domain of the Scoliosis Research Society 22-item questionnaire remained unchanged at 5 years postoperation. Conclusion: In many patients with Lenke type 5C AIS, TLK changed significantly and approached 0° after surgery. However, the magnitude of the preoperative TLK and the presence or absence of improvement did not affect postoperative spinal alignment. Furthermore, the patients had satisfactory clinical outcomes irrespective of TLK modification. Level of evidence: III.

BACKGROUND Iatrogenic pseudomeningocele incidence after lumbar surgery is 0.068%–2%, and most lumbar pseudomeningoceles are smaller than 5 cm; however, in rare cases, “giant” pseudomeningoceles greater than 8 cm in size may develop. Normal pressure hydrocephalus (NPH) is another rare condition in which the ventricles expand despite the presence of normal intracranial pressure. To date, pseudomeningocele associated with NPH has not been reported. OBSERVATIONS An 80-year-old woman underwent L3–5 laminectomy and posterior lumbar interbody fusion, and her symptoms improved after surgery. However, dementia appeared 1 month after surgery. Repeated brain computed tomography showed ventricular enlargement, and lumbar magnetic resonance imaging showed a long pseudomeningocele in the subcutaneous tissues at the L4 level. Here, the authors report a rare case of an iatrogenic giant pseudomeningocele accompanied by NPH after lumbar surgery. The symptoms of NPH in the present case occurred after spinal surgery and recovered after dural repair surgery, indicating that the changes in cerebrospinal fluid circulation and/or pressure due to pseudomeningoceles may cause NPH. LESSONS The prevention of dural tears through precise surgical technique and primary repair of dural tears are the best approaches to prevent pseudomeningocele incidence and subsequent events.

Study Design. A retrospective comparative study. Objective. The purpose of this study is to evaluate the relationship between pelvic incidence (PI) and proximal junctional kyphosis (PJK) in patients with Lenke type 5 adolescent idiopathic scoliosis (AIS). Background. Although PJK is a common complication of sagittal malalignment after posterior correction and fusion surgery (PSF), few studies have assessed its risk factors. The significance of pelvic morphology in relation to PJK has been suggested but remains unclear in Lenke type 5 AIS patients. Materials and Methods. A total of 92 patients with Lenke type 5 AIS who underwent selective thoracolumbar PSF with a minimum follow-up of two years were included. Patients were divided into PJK and non-PJK groups based on postoperative radiographs. The influence of PI on PJK occurrence was evaluated through binary logistic analysis. Subgroup analysis was performed based on the PI value (low PI, <45°; high PI, ≥ 45°) to identify factors affecting PJK occurrence. Results. PJK was observed in 17.4% of the whole cohort. Binary logistic regression analysis identified low PI and large TL/L curve as a risk factor for PJK (PI, odds ratio, 0.933; TL/L curve, odds ratio, 1.080). Subgroup analysis showed that the postoperative increase in the upper instrumented vertebra slope in PJK cases was comparable in both the low and high PI groups. Meanwhile, lordotic changes in the fused area in the PJK cases were observed only in the low PI group. No difference in the Scoliosis Research Society 22 scores was observed between the two groups. Conclusion. From this study a low PI was identified as a risk factor for the occurrence of PJK in Lenke type 5 AIS patients. The occurrence of PJK is influenced by lordotic changes in the fused area and the limited compensatory capacity of the pelvis in patients with a low PI.

Study Design: Prospective multicenter cohort study. Objective: To evaluate the prevalence, clinical characteristics, and surgical outcomes of neuropathic pain in patients with degenerative cervical myelopathy (DCM), using the Neuropathic Pain Symptom Inventory (NPSI). Summary of Background Data: Neuropathic pain is increasingly recognized as a major determinant of quality of life (QOL) in DCM. However, few prospective studies have comprehensively evaluated its distribution, severity, and postoperative trajectory. Methods: A total of 816 DCM patients from 10 institutions were prospectively enrolled. Preoperative and 2-year postoperative assessments included the NPSI, cervical Japanese Orthopaedic Association (JOA) score, visual analog scale (VAS), and 36-Item Short Form Health Survey (SF-36). Correlation and multiple regression analyses were performed to identify associations between NPSI scores and QOL, as well as predictive factors for postoperative improvement. Results: Preoperatively, 88.5% of patients reported symptoms of neuropathic pain, with paresthesia/dysesthesia being the most prominent subtype. At 2 years postoperatively, all NPSI subdomains showed significant improvement (p <.001), though paresthesia/dysesthesia remained most persistent. Higher preoperative NPSI scores were significantly associated with greater postoperative pain reduction (β = -.556, p <.001). Total NPSI scores significantly correlated with all SF-36 subdomains both before and after surgery (all p <.001), indicating a strong relationship between pain and QOL. Conclusion: This study provides the first large-scale prospective evaluation of neuropathic pain in DCM. While neuropathic pain is prevalent and improves with surgery, residual symptoms-especially paresthesia/dysesthesia-remain common and impactful. These findings highlight the importance of individualized postoperative pain management strategies to optimize long-term QOL.

Study design. Prospective multicenter cohort study. Objective. To compare clinical outcomes between posterior decompression without fusion (PD) and anterior cervical discectomy and fusion (ACDF) in patients with 1-2-level degenerative cervical myelopathy (DCM). Summary of Background Data. While numerous studies have assessed surgical strategies for multilevel DCM, limited evidence is available for cases involving only one or two levels. Methods. Among 1,482 patients with degenerative cervical spine disorders from 10 Japanese institutions, 353 patients with 1-2-level DCM treated with either PD (n=233) or ACDF (n=120) and followed for two years were included. Clinical outcomes included the Japanese Orthopaedic Association (JOA) score, Visual Analog Scale (VAS), Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ), and Short Form-36 (SF-36). Group comparisons were adjusted for baseline characteristics and preoperative clinical outcomes using a general linear model. Results. Perioperative complication and reoperation rates did not significantly differ between groups. ACDF provided significantly greater improvements in VAS scores for neck pain (-22.6 mm vs.-6.1 mm, P=0.003), upper extremity pain/numbness (-32.7 mm vs.-18.3 mm, P=0.011), and SF-36 bodily pain (22.8 vs. 10.1, P=0.003) and physical component summary (PCS) scores (9.1 vs. 3.5, P=0.007) compared to the PD group. Conversely, PD yielded greater improvement in the SF-36 social functioning domain (13.3 vs. 2.6, P=0.011). No significant differences were observed in JOA scores, the five domains of JOACMEQ, or other SF-36 domains. Conclusions. Both PD and ACDF provided comparable improvements in neurological function as measured by JOA and JOACMEQ scores, indicating similar efficacy in treating DCM. ACDF was more effective for alleviating neck and arm pain and enhancing physical health, while PD resulted in social functioning. Given similar complication rates, surgical strategy should be individualized based on each patient's clinical presentation.

Objective: To examine the factors influencing cervical sagittal alignment (CSA) after posterior correction and fusion surgery (PSF) for patients with Lenke type 2 adolescent idiopathic scoliosis (AIS). Methods: A total of 102 female patients with Lenke 2 AIS and a minimum 2-year follow-up were included. The upper instrumented vertebra was T2 in all patients. Sagittal and coronal parameters were measured before and 2 years after surgery. Patients were categorized into cervical malalignment (CM) and noncervical malalignment (NCM) groups following Passias’ criteria. Radiographic factors influencing CSA were analyzed. Results: Preoperatively, 57 patients (55.9%) were assigned to the CM group and 45 patients (44.1%) to the NCM groups. The cervical lordosis (CL) in CM group was more kyphotic (19.3° vs. 3.3°), smaller proximal thoracic kyphosis (PTK; 9.7° vs. 15.4°), and smaller T1 slope (7.1° vs. 14.0°) than those in the NCM group. Main thoracic kyphosis (MTK) did not show significantly difference between the 2 groups (11.3° vs. 14.4°). Two years after surgery, the CM group demonstrated significant improvements in CSA. PTK increased from 9.7° to 13.5°, T1 slope increased from 7.1° to 10.5°, and cervical kyphosis improved from-19.3° to-8.8°, while MTK remained unchanged (11.3° vs. 11.6°). Conclusion: PSF significantly improved CSA in patients with preoperative CM. Increased PTK, correlated with improved CL, suggests that PSF-induced PTK enhancement, rather than MTK, drives T1 slope and subsequent CSA improvement.

Study Design: A retrospective comparative study Objectives: This study aimed to evaluate the radiographical changes in cervical sagittal alignment (CSA) and clinical outcomes after tumor resection using a posterior unilateral approach without spinal fixation for patients with cervical dumbbell-shaped schwannoma (DS). Methods: Seventy-three patients with DS who were followed up for at least 2 years were included. The Eden classification was used to designate the types of DS. The CSA and range of motion (ROM) were analyzed using radiographs. The clinical outcomes were assessed using the Japanese Orthopaedic Association (JOA) score and JOA cervical myelopathy questionnaire. Results: The CSA in the neutral, flexion, and extension position and cervical ROM were not significantly reduced in the follow-up period. The JOA scores showed significant improvement after surgery. The postoperative radiographic parameters and clinical outcomes of Eden type II or III DS, which needed facetectomy for the resection, did not show any statistically significant difference compared with those of Eden type I tumor, which was resected without facetectomy. Fifty-two cases (71.2%) achieved gross total resection, whereas 21 cases (28.8%) remained in partial resection (PR). One case underwent reoperation due to the regrowth of the remnant tumor whose margin was at the entrance of the intervertebral foramen. Conclusions: Tumor resection using the posterior unilateral approach preserved CSA and resulted in favorable clinical outcomes in patients with DS. When the resection ends in PR, the proximal margin of the remnant tumor should be located distally away from the entrance of the foramen to prevent regrowth.

Study Design: Prospective multicenter cohort study. Objectives: To determine the incidence and risk factors for postoperative complications following cervical spine surgery and to explore their association with long-term clinical outcomes. Methods: A total of 1482 patients with degenerative cervical disorders who underwent surgery at 10 high-volume institutions in Japan were prospectively enrolled. Perioperative complications were defined as events occurring within 30 days postoperatively. Risk factors were analyzed using univariate and logistic regression analyses. Clinical outcomes were assessed using the cervical Japanese Orthopaedic Association (JOA) score and the Physical Component Summary (PCS) of the SF-36 at baseline and 2 years postoperatively. Results: Perioperative complications occurred in 5.5% of patients: segmental motor paralysis (2.3%), neurological deficit (0.6%), dural tear (0.5%), CSF leakage (0.3%), epidural hematoma (0.9%), and surgical site infection (0.8%). Male sex (OR 3.049; 95% CI 1.045-8.929) and posterior fusion (OR 4.016; 95% CI, 1.518-10.620) were significant risk factors for segmental motor paralysis, while respiratory disease (OR 5.500; 95% CI, 1.462-20.694) was associated with surgical site infection. At 2 years, patients with complications showed variable neurological recovery, with many failing to reach the minimum clinically important difference. Conclusions: Male sex, posterior fusion, and respiratory disease were identified as significant risk factors for major complications. Awareness of these factors may support improved surgical planning and perioperative management. However, interpretation of long-term outcomes should be made with caution because of the limited number of cases and potential selection bias associated with incomplete follow-up.

Study Design. Retrospective comparative study. Objective. The aim of this study was to evaluate the changes in global spinal sagittal alignment (GSSA) following selective anterior spinal fusion (ASF) in patients with Lenke type 5 adolescent idiopathic scoliosis (AIS). Summary of Background Data. Few studies have assessed the changes in postoperative GSSA, including cervical, thoracic, and lumbosacral sagittal alignment in AIS patients with major thoracolumbar/lumbar (TL/L) curve who underwent selective ASF. Methods. Fifty-two patients with Lenke type 5 AIS (two males and 50 females, mean age at surgery of 16.4±3.1years) were included in this study. The average final follow-up was 8.3±3.1years after surgery. The variations of outcome variables were analyzed in various spinal sagittal profiles using radiographic outcomes (pre-operation, immediate post-operation, and final follow-up). The clinical outcomes at the final follow-up were assessed using Scoliosis Research Society (SRS)-22 and Oswestry Disability Index (ODI) questionnaires. Results. The mean Cobb angle of the main TL/L and minor thoracic curve was significantly improved after selective ASF, which was maintained up to the final follow-up. However, in all cases, the various sagittal parameters examined (sagittal vertical axis [SVA], C2–7 SVA, C2–7 lordosis, T1 slope, thoracic kyphosis, T10-L2 kyphosis, lumbar lordosis, pelvic incidence, pelvic tilt, and sacral slope), did not significantly change in the immediate postoperative period, and all GSSA parameters were maintained up to the final follow-up. Furthermore, the magnitude of coronal curve correction and fused levels did not affect each GSSA parameter postoperatively. During the period up to the final follow-up, no significant clinical symptoms were observed. The final SRS-22 global score was 4.5±0.3, and ODI scored 0.8±2.4. Conclusion. Selective ASF did not influence various GSSA parameters postoperatively and could maintain excellent correction for coronal deformity with satisfactory final functional and clinical outcomes confirmed by long-term follow-up.

Study design: Retrospective comparative study. Objectives: The present study investigated radiographical changes in global spinal sagittal alignment (GSSA) and clinical outcomes following tumor resection using spinous process-splitting laminectomy (SPSL) approach without fixation in patients with conus medullaris (CM) or cauda equina (CE) tumor. Methods: Forty-one patients with CM or CE tumor (19 males, 22 females, mean age at surgery of 52.9 ± 13.0 years) were included in this study. The variations of outcome variables were analyzed in various GSSA profiles using radiographic outcomes. The clinical outcomes were assessed using Japan Orthopaedic Association (JOA) score and JOA back pain evaluation questionnaire (JOABPEQ). Results: In all cases, the various GSSA parameters (sagittal vertical axis, C2–7 lordosis, T1 slope, thoracic kyphosis, T10–L2 kyphosis, lumbar lordosis [LL; upper, middle, and lower], sacral slope, pelvic incidence, and pelvic tilt) did not significantly change in the 2-years postoperative period. Moreover, age at surgery, the number of resected laminae, preoperative T12–L2 kyphosis, or LL did not affect the postoperative changes in T12–L2 kyphosis or LL, and had no statistically significant correlation among them. The scores of each postoperative JOA domain and the Visual Analogue Scale included in the JOABPEQ were significantly improved. There was no statistical significant group difference in each sagittal profile or clinical outcomes between CM and CE groups postoperatively. Conclusions: Tumor resection using SPSL approach did not affected the various GSSA parameters examined and resulted in satisfactory clinical outcomes, indicating that SPSL approach is a suitable surgical technique for patients with CM or CE tumor.

Study Design: Retrospective comparative study. Objectives: To compare the surgical and clinical outcomes of ventral intradural extramedullary (IDEM) schwannomas to those of dorsal/lateral IDEM schwannomas. Setting: The single institution in Japan. Methods: This study included 94 patients with cervical or thoracic IDEM schwannomas who underwent tumor resection via a posterior approach between 2012 and 2022. Patients were categorized into Ventral (n = 12) and Dorsal/Lateral (n = 82) groups based on tumor localization. Demographic and surgical data, including surgical time and intraoperative motor evoked potential (MEP) changes, as well as clinical outcomes such as Japanese Orthopaedic Association (JOA) scores and gait function (modified McCormick scale, MMCS), were evaluated. Results: The Ventral group had a significantly longer surgical time (p = 0.039) and was more likely to experience a temporary decrease in intraoperative MEP waveforms (p = 0.008) compared to the Dorsal/Lateral group. However, there were no significant differences between the groups in age at surgery, sex, level, tumor size, estimated blood loss, JOA score improvement, JOA recovery rate, or gait function at the final follow-up. Gross total resection (GTR) was achieved in all cases. Conclusions: Despite longer surgical times and more likely to experience a temporary decrease in intraoperative MEP waveforms, ventral IDEM schwannomas do not result in significantly worse surgical or clinical outcomes compared to dorsal/lateral IDEM schwannomas. These findings suggest that even if the surgical procedure requires longer, gross total resection of ventral schwannomas via a posterior approach is resulting in favorable treatment outcomes.