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Study Design: A prospective multicenter study., Objective: To investigate the effect of preoperative symptom duration on neurological recovery for the treatment of cervical ossification of the posterior longitudinal ligament (OPLL)., Summary of Background Data: The optimal timing to perform surgery in the setting of cervical OPLL remains unknown. It is important to know the influence of symptom duration on postoperative outcomes to facilitate discussions regarding the timing of surgery., Patients and Methods: The study included 395 patients (291 men and 104 women; mean age, 63.7 ± 11.4 yr): 204 were treated with laminoplasty, 90 with posterior decompression and fusion, 85 with anterior decompression and fusion, and 16 with other procedures. The Japanese Orthopedic Association (JOA) score and patient-reported outcomes of the JOA Cervical Myelopathy Evaluation Questionnaire were used to assess clinical outcomes preoperatively and 2 years after surgery. Logistic regression analysis was used to identify factors associated with the achievement of minimum clinically important difference (MCID) after surgery., Results: The recovery rate was significantly lower in the group with symptom duration of ≥5 years compared with the groups with durations of <0.5 years, 0.5 to 1 year, and 1 to 2 years. Improvement of JOA Cervical Myelopathy Evaluation Questionnaire in the upper extremity function score ( P < 0.001), lower extremity function ( P = 0.039), quality of life ( P = 0.053), and bladder function ( P = 0.034) were all decreased when the symptom duration exceeded 2 years. Duration of symptoms ( P = 0.001), age ( P < 0.001), and body mass index ( P < 0.001) were significantly associated with the achievement of MCID. The cutoff value we established for symptom duration was 23 months (area under the curve, 0.616; sensitivity, 67.4%; specificity, 53.5%)., Conclusions: Symptom duration had a significant impact on neurological recovery and patient-reported outcome measures in this series of patients undergoing surgery for cervical OPLL. Patients with symptom duration exceeding 23 months may be at greater risk of failing to achieve MCID after surgery., Level of Evidence: 3., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: A prospective multicenter study., Objective: The objective of this study was to investigate the incidence of loss of cervical lordosis after laminoplasty for cervical ossification of the posterior longitudinal ligament (OPLL). We also sought to determine associated risk factors and the relationship with patient-reported outcomes., Summary of Background Data: Loss of cervical lordosis is a sequelae often observed after laminoplasty, which may adversely impact surgical outcomes. Cervical kyphosis, especially in OPLL, is associated with reoperation, but risk factors and relationship to postoperative outcomes remain understudied at this time., Materials and Methods: This study was conducted by the Japanese Multicenter Research Organization for Ossification of the Spinal Ligament. We included 165 patients who underwent laminoplasty and completed Japanese Orthopaedic Association (JOA) score or Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaires (JOACMEQ), as well as Visual Analog Scales (VAS) for pain, with imaging. The participants were divided into two groups: those with loss of cervical lordosis of >10° or 20° after surgery and those without loss of cervical lordosis. A paired t test was applied to evaluate the association between changes in cervical spinal angles, range of motion, and cervical JOA and VAS scores before and at 2 years postoperatively. Mann-Whitney U test was used for JOACMEQ., Results: Postoperative loss of cervical lordosis >10° and >20° was observed in 32 (19.4%) and 7 (4.2%), respectively. JOA, JOACMEQ, and VAS scores were not significantly different between those with, and without, loss of cervical lordosis. Preoperative small extension range of motion (eROM) was significantly associated with postoperative loss of cervical lordosis, and the cutoff values of eROM were 7.4° [area under the curve (AUC): 0.76] and 8.2° (AUC: 0.92) for loss of cervical lordosis >10° and >20°, respectively. A large occupation ratio of OPLL was also associated with loss of cervical lordosis, with a cutoff value of 39.9% (AUC: 0.94). Laminoplasty resulted in functional improvement in most patient-reported outcomes; however, neck pain and bladder function tended to become worse postoperatively in cases with postoperative loss of cervical lordosis >20°., Conclusions: JOA, JOACMEQ, and VAS scores were not significantly different between those with, and without, loss of cervical lordosis. Preoperative small eROM and large OPLL may represent factors associated with loss of cervical lordosis after laminoplasty in patients with OPLL., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: A prospective multicenter study., Objective: The objective of this study is to compare the surgical outcomes of anterior and posterior fusion surgeries in patients with K-line (-) cervical ossification of the posterior longitudinal ligament (OPLL)., Summary of Background Data: Although laminoplasty is effective for patients with K-line (+) OPLL, fusion surgery is recommended for those with K-line (-) OPLL. However, whether the anterior or posterior approach is preferable for this pathology has not been effectively determined., Materials and Methods: A total of 478 patients with myelopathy due to cervical OPLL from 28 institutions were prospectively registered from 2014 to 2017 and followed up for two years. Of the 478 patients, 45 and 46 with K-line (-) underwent anterior and posterior fusion surgeries, respectively. After adjusting for confounders in baseline characteristics using a propensity score-matched analysis, 54 patients in both the anterior and posterior groups (27 patients each) were evaluated. Clinical outcomes were assessed using the cervical Japanese Orthopaedic Association and the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire., Results: Both approaches showed comparable neurological and functional recovery. The cervical range of motion was significantly restricted in the posterior group because of the large number of fused vertebrae compared with the anterior group. The incidence of surgical complications was comparable between the cohorts, but the posterior group demonstrated a higher frequency of segmental motor paralysis, whereas the anterior group more frequently reported postoperative dysphagia., Conclusions: Clinical improvement was comparable between anterior and posterior fusion surgeries for patients with K-line (-) OPLL. The ideal surgical approach should be informed based on the balance between the surgeon's technical preference and the risk of complications., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: A prospective multicenter study., Objective: This study aims to evaluate patient-reported outcomes using the Japanese Orthopedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ) and clarify clinical factors that affect the therapeutic effects for patients with cervical ossification of the posterior longitudinal ligament (OPLL)., Summary of Background Data: Although previous studies identified factors that affected the surgical outcomes, their assessment was mainly based on the Japanese Orthopedic Association score, which only includes neurological function. Investigating this pathology through multiple functions and quality of life (QOL) is pivotal to understanding the comprehensive clinical pictures of the cervical OPLL and its therapeutic outcomes., Materials and Methods: This study was performed by the Japanese Multicenter Research Organization for Ossification of the Spinal Ligament. A total of 478 patients with myelopathy caused by cervical OPLL from 28 institutions were prospectively registered from 2014 to 2017 and followed up for 2 years. Of the patients, 168 received laminoplasties and fully completed questionnaires. Demographic information, imaging findings, and clinical outcomes were collected. Patients were grouped according to effective or ineffective surgical outcomes as defined by the JOACMEQ using logistic regression analyses., Results: Laminoplasty resulted in functional improvement in the cervical spine and upper extremity around 40% of the patients, while QOL showed only 21.4% ( P <0.01). Multivariable analyses revealed that younger age and a postoperative decrease in arm or hand pain were correlated with significantly improved function of the upper extremities. A reduction in lower limb pain favorably affected the postoperative lower extremity function. A postoperative reduction in upper extremity pain enhanced the QOL recovery., Conclusions: Surgeons should recognize the diversity of surgical outcomes after laminoplasty and understand the necessity of pain management even after the surgery to enhance bodily functions and QOL in patients with cervical OPLL., Competing Interests: The authors report no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: A retrospective analysis of prospectively collected data., Objective: This study aimed to create a prognostic model for surgical outcomes in patients with cervical ossification of the posterior longitudinal ligament (OPLL) using machine learning (ML)., Summary of Background Data: Determining surgical outcomes helps surgeons provide prognostic information to patients and manage their expectations. ML is a mathematical model that finds patterns from a large sample of data and makes predictions outperforming traditional statistical methods., Methods: Of 478 patients, 397 and 370 patients had complete follow-up information at 1 and 2 years, respectively, and were included in the analysis. A minimal clinically important difference (MCID) was defined as an acquired Japanese Orthopedic Association (JOA) score of ≥2.5 points, after which a ML model that predicts whether MCID can be achieved 1 and 2 years after surgery was created. Patient background, clinical symptoms, and imaging findings were used as variables for analysis. The ML model was created using LightGBM, XGBoost, random forest, and logistic regression, after which the accuracy and area under the receiver-operating characteristic curve (AUC) were calculated., Results: The mean JOA score was 10.3 preoperatively, 13.4 at 1 year after surgery, and 13.5 at 2 years after surgery. XGBoost showed the highest AUC (0.72) and high accuracy (67.8) for predicting MCID at 1 year, whereas random forest had the highest AUC (0.75) and accuracy (69.6) for predicting MCID at 2 years. Among the included features, total preoperative JOA score, duration of symptoms, body weight, sensory function of the lower extremity sub-score of the JOA, and age were identified as having the most significance in most of ML models., Conclusion: Constructing a prognostic ML model for surgical outcomes in patients with OPLL is feasible, suggesting the potential application of ML for predictive models of spinal surgery.Level of Evidence: 4., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: A prospective multicenter study., Objective: This study aims to investigate the postoperative complications of anterior decompression with fusion (ADF) for the treatment of cervical ossification of the posterior longitudinal ligament (OPLL)., Summary of Background Data: Surgical treatment for cervical OPLL has a high risk of various complications. ADF is reported to be effective for cervical OPLL, especially for massive OPLL. However, few studies have focused on the surgical complications of ADF., Methods: We prospectively included 102 patients undergoing ADF for severe cervical OPLL with average canal occupying ratio of 49.8%. We evaluated systemic and local complications, neurological complications, and risk factors related to the postoperative complications., Results: Frequently observed complications included graft/ implant complications (18.6%), neurological complications (11.8%), and cerebrospinal fluid leak (11.8%). Motor palsy involving only the upper extremity was found in nine patients (8.8%), and other motor palsies involving the lower extremities were found in three patients (2.9%). None of the preoperative factors were significantly associated with the occurrence of neurological palsies, whereas the number of operated levels was a significant factor related to the postoperative graft/implant complications (P = 0.003; odds ratio, 2.112). The incidence of graft/implant complications and related reoperation increased as the number of operated levels increased (especially four levels or more). Most motor palsies were observed immediately after surgery. Of the motor palsies in the bilateral upper extremities and palsies involving the lower extremities, 85.7% showed good recovery, whereas only 40% of unilateral upper extremity motor palsies showed good recovery during the follow-up period., Conclusion: In ADF for cervical OPLL, the number of operated levels was a significant factor related to the postoperative complication. Specifically, the incidence of graft/implant complications and reoperation rate increased in ADF with four or more levels.Level of Evidence: 3., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: A prospective multicenter study., Objective: To evaluate and compare the surgical outcomes after open-door (OD) and double-door (DD) laminoplasties in subjects with cervical ossification of the posterior longitudinal ligament (OPLL)., Summary of Background Data: Although previous studies compared clinical results after OD and DD laminoplasties, they were performed at a single institution with a relatively small sample size targeting mixed pathologies, including cervical spondylotic myelopathy., Methods: This study was performed by the Japanese Multicenter Research Organization for Ossification of the Spinal Ligament. A total of 478 patients with myelopathy caused by cervical OPLL from 28 institutions were prospectively registered from 2014 to 2017 and followed up for 2 years. Of these, 41 and 164 patients received OD and DD laminoplasties, respectively. Demographic information, medical history, and imaging findings were collected. Clinical outcomes were assessed using the cervical Japanese Orthopaedic Association, Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire, and visual analog scale scores., Results: Age, sex, symptom duration, and comorbidities were not significantly different between the groups. Segmental ossification was the most frequent in both the groups. No significant differences in K-line type, canal occupying ratio, C2 to C7 angles, and range of motion were found. Both the procedures reduced the cervical range of motion postoperatively. A comparable frequency of perioperative complications was observed between the groups. The cervical Japanese Orthopaedic Association scores showed a similar improvement at 2 years postopera- tively. The reduction in visual analog scale score for neck pain was favorable in the OD group (P = 0.02), while other pain assessments did not show any significant differences between the groups. The functional outcomes assessed using the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire presented equivalent effective rates., Conclusion: The results demonstrated almost comparable surgical outcomes between OD and DD laminoplasties. Lamino- plasty is a valuable technique as a therapeutic option for cervical OPLL.Level of Evidence: 2., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Prospective longitudinal study., Objective: The aim of this study was to evaluate temporal changes of bone turnover markers (BTMs) after lumbar spinal fusion in patients without osteoporosis., Summary of Background Data: Radiological studies are the standard method to monitor bony fusion, but they do not allow a timely assessment of bone healing. BTMs react rapidly to changes in bone metabolism during fusion process and could be an additional tool to monitor this process., Methods: A total of 78 nonosteoporosis patients who had undergone one- or two-level transforaminal lumbar interbody fusion were included. Fusion status was assessed using computed tomography sagittal and coronal images. Serum levels of bone-specific alkaline phosphatase (BAP), procollagen type 1 amino-terminal propeptide (P1NP), and osteocalcin (OC) were measured to assess bone formation, and tartrate-resistant acid phosphatase 5b (TRACP-5b) was measured to assess bone resorption. Serum samples were obtained before surgery and at 1, 2, 4, 8, 13, 26, 39, and 52 weeks after surgery., Results: A solid fusion was achieved in 71 of 78 patients (91%), and seven patients resulted in pseudarthrosis. In the fusion group, the level of all BTMs once decreased at 1 postoperative week. Then, BAP and P1NP reached a peak at 4 weeks after surgery, and TRACP-5b and OC peaked at 8 weeks. Thereafter, the level of P1NP and TRACP-5b gradually got closer to the baseline over a year, and BAP kept high until 52 postoperative weeks. In the pseudarthrosis group, peak level of BTMs was significantly higher and the increased level of BAP and P1NP was kept until 52 weeks., Conclusion: The present study demonstrated dynamics of BTMs after lumbar spinal fusion in patients without osteoporosis. These normal population data contribute as a baseline to evaluate the effect of osteogenic agents on bone metabolism after spinal fusion.Level of Evidence: 2., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: A retrospective observational study., Objective: To clarify the exceptional conditions for a favorable neurological recovery after laminoplasty (LMP) for cervical myelopathy caused by K-line (-) ossification of the posterior longitudinal ligament (OPLL)., Summary of Background Data: The K-line-based classification of cervical OPLL was developed to predict insufficient neurological recovery after LMP. For patients with K-line (-) OPLL, LMP generally yields the least improvement because of inadequate decompression of the spinal cord; however, there are some exceptional cases wherein LMP promotes favorable neurological recoveries., Methods: We retrospectively reviewed the medical records of 106 consecutive patients who underwent LMP for cervical OPLL to determine the demographic data, radiographic findings, and neurological recoveries of the patients as assessed preoperatively and 2 years postoperatively by their Japanese Orthopedic Association (JOA) scores. The factors associated with favorable outcomes after LMP in patients with K-line (-) were then investigated., Results: Of 106 total patients, 31 were classified as K-line (-), of whom 21 achieved the least neurological recovery after LMP (JOA recovery rate <50%), while the remaining 10 patients achieved favorable outcomes (JOA recovery rate ≥50%). Among the K-line (-) group patients, those with ext-K-line (+), which changed to K-line (+) in the neck-extended position, and the patients with up-K-line (-), in whom the lesion responsible for myelopathy in the upper cervical spine (C3 or above), showed favorable neurological recoveries after LMP., Conclusion: Our data shows that, even for patients with K-line (-) OPLL, a favorable neurological recovery can be expected after LMP in cases in which the OPLL is in the upper cervical spine or the K-line changes to (+) in the neck-extended position. This means that K-line-based predictions of surgical outcomes after LMP should be indicated for patients with OPLL in the middle and lower cervical spine with limited extension mobility.Level of Evidence: 4., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Cohort study (level 3)., Objective: The aim of this study was to identify independent risk factors for residual low back pain (LBP) following osteoporotic vertebral fracture (OVF)., Summary of Background Data: Nonunion has been proposed as the primary cause of residual LBP following OVF. However, LBP can occur even when union is maintained. Other reported causes of LBP after OVF include vertebral deformities and spinopelvic malalignment., Methods: Sixty-seven patients with single-level thoracolumbar OVF who had not received previous osteoporotic treatment were enrolled. Conservative treatment was conducted using a soft lumbosacral orthosis plus osteoporosis drugs, either weekly alendronate (bisphosphonate) or daily teriparatide. Pain scores, kyphosis angle of fractured vertebra (VKA), and spinopelvic alignment, including pelvic incidence minus lumbar lordosis (PI-LL), were assessed periodically during treatment. Radiographic union was evaluated independently by three specialists at 24 weeks post-admission. Patients were divided by pain scores >40% at 24 weeks into the LBP (n = 36) and non-LBP (n = 31) groups. Temporal changes and statistical associations were examined to identify risk factors for LBP at 24 weeks., Results: At 24 weeks, 25% of OVFs failed to achieve union. The LBP group consisted of 71% of nonunion and 48% of union cases. Stepwise multinomial regression analysis showed VKA at 24 weeks >25° was significant risk factor for the LBP group (odds ratio: 6.24, 95% confidence interval: 1.77-22.02, P = 0.004). Significant differences in VKA emerged during treatment in the LBP group, but PI-LL showed the tendency not to change throughout the treatment period. Non-union was correlated with VKA (area under the curve: 0.864)., Conclusion: Although spinopelvic malalignment is considered as a preexisting factor for LBP, VKA exacerbated by nonunion predominantly led to LBP after a new OVF. Each incidence of OVF should be treated to limit further morphological changes to the fractured vertebra., Level of Evidence: 3.

Study Design: Prospective cohort study., Objective: To characterize a patient population with nonunion after acute osteoporotic vertebral fractures (OVFs) and compare the union and nonunion groups to identify risk factors for nonunion., Summary of Background Data: While OVFs are the most common type of osteoporotic fracture, the predictive value of a clinical assessment for nonunion at 48 weeks after OVF has not been extensively studied., Methods: This prospective multicenter cohort study included female patients aged 65 to 85 years with acute one-level osteoporotic compression fractures. In the radiographic analysis, the anterior vertebral body compression percentage was measured at 0, 12, and 48 weeks. Magnetic resonance imaging (MRI) was performed at enrollment and at 48 weeks to confirm the diagnosis and union status. The patient-reported outcome measures included scores on the European Quality of Life-5 Dimensions (EQ-5D), a visual analogue scale for low back pain, and the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) at 0, 12, and 48 weeks., Results: In total, 166 patients completed the 12-month follow-up, 29 of whom had nonunion. Patients with nonunion at 48 weeks after OVF had lower EQ-5D and JOABPEQ walking ability, social life function, mental health, and lumbar function scores than those with union at 48 weeks after injury. The independent risk factors for nonunion after OVF in the acute phase were a diffuse low type pattern on T1-weighted MRI and diffuse low and fluid type patterns on T2-weighted MRI. The anterior vertebral body compression percentage and JOABPEQ social life function scores were independent risk factors at 12 weeks., Conclusion: A diffuse low type pattern on T1-weighted MRI and diffuse low and fluid type patterns on T2-weighted MRI were independent risk factors for nonunion in the acute phase. Patients who have acute OVFs with these risk factors should be carefully monitored for nonunion., Level of Evidence: 2.

Study Design: Prospectively collected, multicenter, nationwide study., Objective: The aim of this study was to investigate recent surgical methods and trends, outcomes, and perioperative complications in surgery for thoracic ossification of the ligamentum flavum (T-OLF)., Summary of Background Data: A prospective multicenter study of surgical complications and risk factors for T-OLF has not been performed, and previous multicenter retrospective studies have lacked details for these items., Methods: Surgical methods, pre- and postoperative thoracic myelopathy (Japanese Orthopedic Association [JOA] score), symptoms, and intraoperative neurophysiological monitoring were investigated prospectively in 223 cases. Differences in these factors between fusion and nonfusion procedures for T-OLF were examined. The minimum follow-up period was 2 years after surgery RESULTS.: The mean JOA score was 6.2 points preoperatively, and 7.9, 8.2, and 8.2 points at 6 months, 1, and 2 year postoperatively, giving mean recovery rates of 35.0%, 40.9%, and 41.4% respectively. Posterior decompression and fusion with instrumentation was performed in 109 cases (48.9%). There were 45 perioperative complications in 30 cases (13.5%), with aggravation of motor disturbance in the lower extremities being most common (4.0%, n = 9). Patients treated with fusion had a significantly higher BMI, rate of gait disturbance, ossification occupation rate of OLF at computed tomography, and intramedullary high intensity area at magnetic resonance imaging (P < 0.01). The preoperative JOA score was lower (P < 0.05) and the JOA recovery rate at 1 year after surgery was significantly higher in cases treated without fusion (44.9% vs. 37.1%, P < 0.05)., Conclusion: The high rate of surgery with instrumentation of 48.9% reflects the current major trend toward posterior instrumented fusion surgery for T-OLF. Fusion surgery with instrumentation may be appropriate for patients with severe OLF and preoperative myelopathy. A further prospective study of long-term outcomes is required with a focus on optimal surgical timing and the surgical procedure for T-OPLL., Level of Evidence: 3.

Study Design: Basic science., Objective: This study aimed to compare the techniques of surgical repair of dural tear using bioabsorbable material and fibrin glue., Summary of Background Data: Cerebrospinal fluid (CSF) leakage caused by dural tear can often be difficult to manage even after repair when the same materials are used in a similar manner., Methods: Burst pressure was measured for repaired porcine dura with holes of different diameters using spray of combined fibrinogen and thrombin solution (fibrin spray) alone as a control and the 5-mm hole following different methods using fibrinogen and thrombin solutions plus polyglactin 910 sheet (PGS). For group 1, fibrinogen was applied on the dura followed by PGS and thrombin. For group 2, thrombin was followed by PGS and fibrinogen. For group 3, fibrinogen was followed by PGS and fibrin spray. For group 4, thrombin was followed by PGS and fibrin spray. Microscopic observation was conducted for each specimen., Results: Repair using fibrin spray alone was successful for the 0.3-mm diameter pinhole (breakdown pressure: 27.8 ± 8.6 mmHg), but was not able to cover the 2.7- and 5-mm holes. For a 5-mm diameter hole, the breakdown pressure was 54.4 ± 38.8 mmHg in group 1, 26.3 ± 19.4 mmHg in group 2, 147.7 ± 65.0 mmHg in group 3, and 35.5 ± 23.4 mmHg in group 4 (P < 0.001). There was little fibrin glue in the burst layer between the dural surface and PGS with thrombin on the dural surface (group 2 and group 4)., Conclusion: Suppression of excessive CSF leakage could be successful by performing several cycles of the group 1 method (fibrinogen was applied on the dura followed by PGS and thrombin), followed by the group 3 method (fibrinogen was applied on the dura followed by PGS and fibrin spray), with thrombin solution wash each time., Level of Evidence: 4.

Study Design: Retrospective analysis of a prospectively collected, consecutive, nonrandomized series of patients., Objective: To assess the surgical outcomes of the simultaneous double-rod rotation technique for treating Lenke 1 thoracic adolescent idiopathic scoliosis (AIS)., Summary of Background Data: With the increasing popularity of segmental pedicle screw spinal reconstruction for treating AIS, concerns regarding the limited ability to correct hypokyphosis have also increased., Methods: A consecutive series of 32 patients with Lenke 1 main thoracic AIS treated with the simultaneous double-rod rotation technique at our institution was included. Outcome measures included patient demographics, radiographical measurements, and Scoliosis Research Society questionnaire scores., Results: All 32 patients were followed up for a minimum of 2 years (average, 3.6 yr). The average main thoracic Cobb angle correction rate and the correction loss at the final follow-up were 67.8% and 3.3°, respectively. The average preoperative thoracic kyphosis (T5-T12) was 11.9°, which improved significantly to 20.5° (P < 0.0001) at the final follow-up. An increase in thoracic kyphosis was significantly correlated with an increase in lumbar lordosis at the final follow-up (r = 0.42). The average preoperative vertebral rotation angle was 19.7°, which improved significantly after surgery to 14.9° (P = 0.0001). There was no correlation between change in thoracic kyphosis and change in apical vertebral rotation (r =-0.123). The average preoperative total Scoliosis Research Society questionnaire score was 3.0, which significantly improved to 4.4 (P < 0.0001) at the final follow-up. Throughout surgery and even after, there were no instrumentation failures, pseudarthrosis, infection of the surgical site, or clinically relevant neurovascular complications., Conclusion: The simultaneous double-rod rotation technique for treating Lenke 1 AIS provides significant sagittal correction of the main thoracic curve while maintaining sagittal profiles and correcting coronal and axial deformities., Level of Evidence: 4.

Study Design: Retrospective review., Objective: To assess the long-term outcomes of anterior spinal fusion (ASF) for treating thoracic adolescent idiopathic scoliosis (AIS)., Summary of Background Data: Although ASF is reported to provide good coronal and sagittal correction of the main thoracic (MT) AIS curves, the long-term outcomes of ASF is unknown., Methods: A consecutive series of 25 patients with Lenke 1 MT AIS were included. Outcome measures comprised radiographical measurements, pulmonary function, and Scoliosis Research Society outcome instrument (SRS-30) scores (preoperative SRS-30 scores were not documented). Postoperative surgical revisions and complications were recorded., Results: Twenty-five patients were followed-up for 12 to 18 years (average, 15.2 yr). The average MT Cobb angle correction rate and the correction loss at the final follow-up were 56.7% and 9.2°, respectively. The average preoperative instrumented level of kyphosis was 8.3°, which significantly improved to 18.6° (P = 0.0003) at the final follow-up. The average percent-predicted forced vital capacity and forced expiratory volume in 1 second were significantly decreased during long-term follow-up measurements (73% and 69%; P = 0.0004 and 0.0016, respectively). However, no patient had complaints related to pulmonary function. The average total SRS-30 score was 4.0. Implant breakage was not observed. All patients, except 1 who required revision surgery, demonstrated solid fusion. Late instrumentation-related bronchial problems were observed in 1 patient who required implant removal and bronchial tube repair, 13 years after the initial surgery., Conclusion: Overall radiographical findings and patient outcome measures of ASF for Lenke 1 MT AIS were satisfactory at an average follow-up of 15 years. ASF provides significant sagittal correction of the main thoracic curve with long-term maintenance of sagittal profiles. Percent-predicted values of forced vital capacity and forced expiratory volume in 1 second were decreased in this cohort; however, no patient had complaints related to pulmonary function.

Study Design: Retrospective multicenter study., Objective: To review the clinical characteristics of traumatic cervical spinal cord injury (SCI) associated with ossification of the posterior longitudinal ligament (OPLL)., Summary of Background Data: Despite its potentially devastating consequences, there is a lack of information about acute cervical SCI complicated by OPLL., Methods: This study included consecutive patients with acute traumatic cervical SCI (Frankel A, B, and C) who were admitted within 48 hours of injury to 34 spine institutions across Japan. For analysis of neurologic outcome, patients who had completed at least a 6-month follow-up were included. Neurologic improvement was defined as at least one grade conversion in Frankel grade., Results: A total of 453 patients were identified (367 men, 86 women; mean age, 59 years). OPLL was found in 106 (23%) patients (87 men, 19 women; mean age, 66 years). Most of the patients with OPLL (94 of 106) were without bone injury, presenting with incomplete SCI. The prevalence of OPLL reached 34% in SCI without bone injury. The cause of SCI was predominantly falls (74%). Only 25% of the patients were aware of OPLL. Half of the OPLL patients reported gait disturbance before injury. Forty-eight (52%) OPLL patients without bone injury underwent surgery (median, 13.5 days after injury), mostly laminoplasty. Overall, no significant difference was noted in neurologic improvement between surgery group and conservative group. However, further stratification showed that surgery was associated with greater neurologic recovery in patients who had gait disturbance before injury (P = 0.04)., Conclusion: Prevalence of OPLL among cervical SCI was alarmingly high, especially in those without bone injury. Most of cervical SCI associated with OPLL were incomplete, without bone injury, and caused predominantly by low-energy trauma. The majority of the patients were unaware of OPLL. Surgery produced better neurologic recovery in patients who had gait disturbance before injury.

Study Design: Case report., Objective: To report an extremely rare case of hematoma derived from the ligamentum flavum within the thoracic spine., Summary of Background Data: Only one previous case has been reported of a hematoma derived from the ligamentum flavum in the thoracic spine. METHODS.: A 61-year-old man presented with gait disturbance and numbness below the navel. Magnetic resonance imaging on the 16th day after the onset of the symptoms showed spinal cord compression at the T10-T11 level caused by a round mass. This intraspinal, extradural space occupying lesion, continuous with ligamentum flavum was centrally hypointense and marginal hyperintense on a T1-weighted image and central heterogeneous and marginal hypointense on a T2-weighted image. The wall of the lesion was slightly enhanced after use of a contrast medium., Results: The patient underwent a T10 laminectomy and the mass was carefully resected from the dura mater. Histologic examination showed that the wall of the mass comprised fibrous connective tissue that contained elastic fibers derived from a degenerative ligamentum flavum tear. It also revealed that evidence of previous hemorrhagic events within the mass. There was no evidence of neoplastic nor synovial tissue. After surgery, the patient's numbness and gait disturbance disappeared., Conclusion: This report identifies an extremely rare case of spinal cord compression by a hematoma from the ligamentum flavum within the thoracic spine.

Study Design: A retrospective review., Objective: This study examined the clinical outcomes of circumferential spinal cord decompression through a posterior approach for thoracic ossification of posterior longitudinal ligament (OPLL), to determine the efficacy of this procedure and the incidence of complications., Summary of Background Data: Since posterior decompressive laminectomy is not always effective in the treatment of thoracic myelopathy caused by OPLL, circumferential spinal cord decompression through a single posterior approach seems to offer an effective treatment option. However, this procedure is technically demanding and has a high risk of postoperative neurologic deterioration. Long-term clinical outcome data and complication rates of this procedure are not well covered in the literature., Methods: Medical records of sequentially treated 30 patients, who had undergone circumferential spinal cord decompression through a single posterior approach, were reviewed to determine demographic data, neurologic examination, imaging findings, surgical procedure, and follow-up data. The Japanese Orthopedic Association (JOA) score was used to assess physical dysfunction and neurologic impairment., Results: The mean follow-up period was 8 years; the average operative time was 389 minutes; the mean blood loss was 1883 mL. An average of 4-level spinal cord decompression was performed on all 30 patients. Posterior spinal fusion was performed on 26 of the 30 patients. The mean preoperative JOA score was 3.4/11, and it improved to an average of 7.1/11 at final evaluation. Clinical symptoms and the JOA score improved in 24 patients, but were unchanged or worsened in the other 6 patients compared to the preoperative conditions. Surgical complications included dural tear in 12 patients (40%), deep infection in 3 (10%), and postoperative neurologic deterioration in 10 (33%). Statistical analysis showed that a risk factor associated with the unfavorable surgical outcomes was multiple level circumferential spinal cord decompression of 5 or more vertebral levels., Conclusion: Despite circumferential spinal cord decompression through posterior approach for thoracic OPLL providing effective neurologic recovery, there was a high rate of complications such as postoperative neurologic deterioration. Risk factor analysis shows that multiple level circumferential decompression of 5 or more vertebral levels to be associated with unfavorable surgical outcome.

Study Design: The accuracy of pedicle screw placement was evaluated in posterior scoliosis surgeries with or without the use of computer-assisted surgical techniques., Objective: In this retrospective cohort study, the pedicle screw placement accuracy in posterior scoliosis surgery was compared between conventional fluoroscopic and computer-assisted surgical techniques., Summary of Background Data: There has been no study systemically analyzing the perforation pattern and comparative accuracy of pedicle screw placement in posterior scoliosis surgery., Methods: The 45 patients who received posterior correction surgeries were divided into 2 groups: Group C, manual control (25 patients); and Group N, navigation surgery (20 patients). The average Cobb angles were 73.7 degrees and 73.1 degrees before surgery in Group C and Group N, respectively. Using CT images, vertebral rotation, pedicle axes as measured to anteroposterior sacral axis and vertebral axis, and insertion angle error were measured. In perforation cases, the angular tendency, insertion point, and length abnormality were evaluated., Results: The perforation was observed in 11% of Group C and 1.8% in Group N. In Group C, medial perforations of left screws were demonstrated in 8 of 9 perforated screws and 55% were distributed either in L1 or T12. The perforation consistently occurred in pedicles in which those axes approached anteroposterior sacral axis within 5 degrees . The average insertion errors were 8.4 degrees and 5.0 degrees in Group C and Group N, respectively, which were significantly different (P < 0.02)., Conclusion: The medial perforation in Group C occurred around L1, especially when pedicle axis approached anteroposterior sacral axis. This consistent tendency was considered as the limitation of fluoroscopic screw insertion in which horizontal vertebral image was not visible. The use of surgical navigation system successfully reduced the perforation rate and insertion angle errors, demonstrating the clear advantage in safe and accurate pedicle screw placement of scoliosis surgery.

Study Design: Ceramic anterior lumbar interbody arthrodesis was performed using an in vivo sheep model. Observations of fusion status and the load-sharing of spinal instrumentation were studied at sequential intervals for 1 year after surgery., Objectives: To elucidate the healing process of spinal arthrodesis performed with a bioactive ceramic spacer and the change in load-sharing of anterior spinal instrumentation., Summary of Background Data: With the improved development of spinal instrumentation, anterior spinal arthrodesis has become a standard spinal reconstruction technique; however, the mechanistic basis underlying the healing process is not well documented. Moreover, it remains unclear how load-distribution through the fusion mass and spinal instrumentation change throughout the healing process., Methods: Using 24 sheep, a two-level anterior lumbar interbody fusion (L2-L3, L4-L5) was performed using a smooth surface and a porous surface-modified bioactive ceramic, with each segment instrumented using a one-rod anterior spinal instrumentation system. Four animals each were killed at 2, 4, 8, 12, 24, and 52 weeks after surgery. Postmortem analysis included quantification of anterior rod strain under multidirectional flexibility testing and radiographic and histologic analyses of the arthrodesed segments., Results: From 0 to 8 weeks after surgery, the bending strain of the rod gradually decreased despite no obvious bone formation. From 8 to 24 weeks after surgery, the rod strain markedly decreased with the development of bridging trabeculated bone formation between vertebral bodies. After 24 weeks after surgery, minimal changes were observed in rod strain; however, the fusion mass volumetrically increased with corresponding facet joint atrophy. The porous surface-modification of ceramic did not influence the histologic healing process, despite the improvement of interface osseous union rate., Conclusions: In anterior spinal arthrodesis, spinal instrumentation is mainly exposed to bending stress, with decreased load-sharing with corresponding development of the spinal fusion. Continuous bone remodeling of the anterior fusion mass results in concurrent decreases in spinal instrumentation and posterior spinal element load-transmission. The principal healing mechanism of ceramic anterior interbody spinal fusion is not an osseous union between the ceramic and vertebral body, but bridging bone formation around the ceramic, which directly connects the vertebral bodies above and below the disc.

Study Design: The bone-bonding characteristic of the new artificial intervertebral disc consisting of bioceramic-coated three-dimensional fabric was evaluated mechanically and histologically in an in vivo sheep model., Objectives: To investigate the mechanical properties and the histologic appearance of the interface between the three-dimensional fabric disc and the vertebral body, and to evaluate these alterations in vivo under a spinal segmentally mobile condition., Summary of Background Data: Bone ingrowth to the bioceramic-coated three-dimensional fabric surface had been demonstrated already under a stable environment in preliminary animal studies., Methods: For this study, 20 sheep underwent two-level lumbar intervertebral disc replacement with three-dimensional fabric discs (Group I) or bioceramic spacers as a comparative material (Group II). All operative segments were stabilized temporarily with spinal instrumentation for the initial ingrown phase. Four animals each were killed at 4, 6, 15, and 24 months in Group I and at 6 months in Group II, and the operative segments were subjected to either a detachment test or histologic evaluation., Results: The interfacial tensile strength at 6 months was significantly higher in Group I than in Group II. No significant decrease in tensile strength was detected until 24 months after surgery in Group I. Histologically, bone ingrowth to the three-dimensional fabric surface was observed 4 months after surgery, and no aseptic loosening occurred until 24 months after surgery., Conclusions: The findings show that the three-dimensional fabric disc was firmly fixed to the vertebral body by bone ingrowth, and that this biologic fixation was preserved even under the spinal segmentally mobile condition.