Multimodal Deep Learning-based Radiomics Approach for Predicting Surgical Outcomes in Patients with Cervical Ossification of the Posterior Longitudinal Ligament.

STUDY DESIGN: A retrospective analysis. OBJECTIVE: This research sought to develop a predictive model for surgical outcomes in patients with cervical ossification of the posterior longitudinal ligament (OPLL) using deep learning and machine learning (ML) techniques. SUMMARY OF BACKGROUND DATA: Determining surgical outcomes assists surgeons in communicating prognosis to patients and setting their expectations. Deep learning and ML are computational models that identify patterns from large data sets and make predictions. METHODS: Of the 482 patients, 288 patients were included in the analysis. A minimal clinically important difference (MCID) was defined as gain in Japanese Orthopaedic Association (JOA) score of 2.5 points or more. The predictive model for MCID achievement at 1 year postsurgery was constructed using patient background, clinical symptoms, and preoperative imaging features (x-ray, CT, MRI) analyzed through LightGBM and deep learning with RadImagenet. RESULTS: The median preoperative JOA score was 11.0 (IQR: 9.0-12.0), which significantly improved to 14.0 (IQR: 12.0-15.0) at 1 year after surgery ( P < 0.001, Wilcoxon signed-rank test). The average improvement rate of the JOA score was 44.7%, and 60.1% of patients achieved the MCID. Our model exhibited an area under the receiver operating characteristic curve of 0.81 and the accuracy of 71.9% in predicting MCID at 1 year. Preoperative JOA score and certain preoperative imaging features were identified as the most significant factors in the predictive models. CONCLUSION: A predictive ML and deep learning model for surgical outcomes in OPLL patients is feasible, suggesting promising applications in spinal surgery. LEVEL OF EVIDENCE: 4.

Preoperative Symptom Duration Influences Neurological Recovery and Patient-Reported Outcome Measures After Surgical Treatment of Cervical Ossification of the Posterior Longitudinal Ligament.

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.

Factors Associated With Loss of Cervical Lordosis After Laminoplasty for Patients With Cervical Ossification of the Posterior Longitudinal Ligament: Data From a Prospective Multicenter Study.

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.

Comparison of Surgical Outcomes of Anterior and Posterior Fusion Surgeries for K-line (-) Cervical Ossification of the Posterior Longitudinal Ligament: A Prospective Multicenter Study.

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.

Deep learning-based prediction model for postoperative complications of cervical posterior longitudinal ligament ossification.

PURPOSE: Postoperative complication prediction helps surgeons to inform and manage patient expectations. Deep learning, a model that finds patterns in large samples of data, outperform traditional statistical methods in making predictions. This study aimed to create a deep learning-based model (DLM) to predict postoperative complications in patients with cervical ossification of the posterior longitudinal ligament (OPLL). METHODS: This prospective multicenter study was conducted by the 28 institutions, and 478 patients were included in the analysis. Deep learning was used to create two predictive models of the overall postoperative complications and neurological complications, one of the major complications. These models were constructed by learning the patient's preoperative background, clinical symptoms, surgical procedures, and imaging findings. These logistic regression models were also created, and these accuracies were compared with those of the DLM. RESULTS: Overall complications were observed in 127 cases (26.6%). The accuracy of the DLM was 74.6 ± 3.7% for predicting the overall occurrence of complications, which was comparable to that of the logistic regression (74.1%). Neurological complications were observed in 48 cases (10.0%), and the accuracy of the DLM was 91.7 ± 3.5%, which was higher than that of the logistic regression (90.1%). CONCLUSION: A new algorithm using deep learning was able to predict complications after cervical OPLL surgery. This model was well calibrated, with prediction accuracy comparable to that of regression models. The accuracy remained high even for predicting only neurological complications, for which the case number is limited compared to conventional statistical methods.

Residual Neuropathic Pain in Postoperative Patients With Cervical Ossification of Posterior Longitudinal Ligament.

STUDY DESIGN: A prospective multi-institutional observational study. OBJECTIVE: To investigate and identify risk factors for residual neuropathic pain after surgery in patients with cervical ossification of posterior longitudinal ligament (c-OPLL). SUMMARY OF BACKGROUND DATA: Patients with c-OPLL often require surgery for numbness and paralysis of the extremities; however, postoperative neuropathic pain can considerably deteriorate their quality of life. METHODS: Out of 479 patients identified from multicenter c-OPLL registries between 2014 and 2017, 292 patients who could be followed up for 2 years postoperatively were reviewed, after excluding patients with nervous system comorbidities. Demographic details; medical history; radiographic factors including the K-line, spinal canal occupancy rate of OPLL, cervical kyphosis angle, and presence of spinal cord myelomalacia; preoperative Japanese Orthopaedic Association (JOA) score; surgical procedure (fusion or decompression surgery); postoperative neurological deterioration; and the visual analogue scale for pain and numbness in the upper extremities (U/E) or trunk/lower extremities (L/E) at baseline and at 2 years postoperatively were assessed. Patients were grouped into residual and non-residual groups based on a postoperative visual analogue scale ≥40 mm. Risk factors for residual neuropathic pain were evaluated by multiple logistic regression analysis. RESULTS: The prevalence of U/E and L/E residual pain in postoperative c-OPLL patients was 51.7% and 40.4%, respectively. The U/E residual group had a poor preoperative JOA score and longer illness duration, and fusion surgery was more common in the residual group than in non-residual group. The L/E residual group was older with a poorer preoperative JOA score. On multivariate analysis, risk factors for U/E residual pain were long illness duration and poor preoperative JOA score, whereas those for L/E residual pain were age and poor preoperative JOA score. CONCLUSIONS: The risk factors for residual spinal neuropathic pain after c-OPLL surgery were age, long duration of illness, and poor preoperative JOA score. LEVEL OF EVIDENCE: IV.

Clinical Indicators of Surgical Outcomes After Laminoplasty for Patients With Cervical Ossification of the Posterior Longitudinal Ligament: A Prospective Multicenter Study.

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.

Is anterior decompression and fusion more beneficial than laminoplasty for K-line (+) cervical ossification of the posterior longitudinal ligament? An analysis using propensity score matching.

OBJECTIVE: It is unclear whether anterior cervical decompression and fusion (ADF) or laminoplasty (LMP) results in better outcomes for patients with K-line-positive (+) cervical ossification of the posterior longitudinal ligament (OPLL). The purpose of the study is to compare surgical outcomes and complications of ADF versus LMP in patients with K-line (+) OPLL. METHODS: The study included 478 patients enrolled in the Japanese Multicenter Research Organization for Ossification of the Spinal Ligament and who underwent surgical treatment for cervical OPLL. The patients who underwent anterior-posterior combined surgery or posterior decompression with instrumented fusion were excluded. The patients with a follow-up period of fewer than 2 years were also excluded, leaving 198 patients with K-line (+) OPLL. Propensity score matching was performed on 198 patients with K-line (+) OPLL who underwent ADF (44 patients) or LMP (154 patients), resulting in 39 pairs of patients based on the following predictors for surgical outcomes: age, preoperative Japanese Orthopaedic Association (JOA) score, C2-7 angle, and the occupying ratio of OPLL. Clinical outcomes were assessed 1 and 2 years after surgery using the recovery rate of the JOA score. Complications and reoperation rates were also investigated. RESULTS: The mean recovery rate of the JOA score 1 year after surgery was 55.3% for patients who underwent ADF and 42.3% (p = 0.06) for patients who underwent LMP. Two years after surgery, the recovery rate was 53.4% for those who underwent ADF and 38.7% for LMP (p = 0.07). Although both surgical procedures yielded good results, the mean recovery rate of JOA scores tended to be higher in the ADF group. The incidence of surgical complications, however, was higher following ADF (33%) than LMP (15%; p = 0.06). The reoperation rate was also higher in the ADF group (15%) than in the LMP group (0%; p = 0.01). CONCLUSIONS: Clinical outcomes were good for both ADF and LMP, indicating that ADF and LMP are appropriate procedures for patients with K-line (+) OPLL. Clinical outcomes of ADF 1 and 2 years after surgery tended to be better than LMP, but the analysis did not detect any significant difference in clinical outcomes between the groups. Conversely, patients who underwent ADF had a higher incidence of surgery-related complications. When considering indications for ADF or LMP, benefits and risks of the surgical procedures should be carefully weighed.

Comparison of laminoplasty and posterior fusion surgery for cervical ossification of posterior longitudinal ligament.

This prospective multicenter study, established by the Japanese Ministry of Health, Labour and Welfare and involving 27 institutions, aimed to compare postoperative outcomes between laminoplasty (LM) and posterior fusion (PF) for cervical ossification of the posterior longitudinal ligament (OPLL), in order to address the controversy surrounding the role of instrumented fusion in cases of posterior surgical decompression for OPLL. 478 patients were considered for participation in the study; from among them, 189 (137 and 52 patients with LM and PF, respectively) were included and evaluated using the Japanese Orthopaedic Association (JOA) scores, the JOA Cervical Myelopathy Evaluation Questionnaire (JOACMEQ), and radiographical measurements. Basic demographic and radiographical data were reviewed, and the propensity to choose a surgical procedure was calculated. Preoperatively, there were no significant differences among the participants in terms of patient backgrounds, radiographical measurements (K-line or cervical alignment on X-ray, OPLL occupation ratio on computed tomography, increased signal intensity change on magnetic resonance imaging), or clinical status (JOA score and JOACMEQ) after adjustments. The overall risk of perioperative complications was found to be lower with LM (odds ratio [OR] 0.40, p = 0.006), and the rate of C5 palsy occurrence was significantly lower with LM (OR 0.11, p = 0.0002) than with PF. The range of motion (20.91° ± 1.05° and 9.38° ± 1.24°, p < 0.0001) in patients who had PF was significantly smaller than in those who had LM. However, multivariable logistic regression analysis showed no significant difference among the participants in JOA score, JOA recovery rate, or JOACMEQ improvement at two years. In contrast, OPLL progression was greater in the LM group than in the PF group (OR 2.73, p = 0.0002). Both LM and PF for cervical myelopathy due to OPLL had resulted in comparable postoperative outcomes at 2 years after surgery.

Long-term reoperation rates and causes for reoperations following lumbar microendoscopic discectomy and decompression: 10-year follow-up.

OBJECTIVE: To investigate the 10-year rates and causes of reoperations following lumbar microendoscopic discectomy for disc herniation (MEDH) and microendoscopic decompression for spinal stenosis (MEDS), as well as to define the reoperations at index and different lumbar levels. METHODS: Between June 2005 and May 2011, the same surgeon had been using MEDH and/or MEDS on 355 consecutive patients. The follow-up rate was 88.3%. The causes and rates of reoperations (RORs) were determined at 10 years after the initial operations. RESULTS: The 10-year reoperation rate for all patients combined was 22.1% (67/303). The 10-year reoperation rate for all cases that underwent repeat operations in the same segment was 16.5% (50/303); the most frequent reason for reoperation (FRR) was recurrence of disc herniation (ROR, 25/251 = 9.96%), the second FRR was an increase of postoperative spondylolisthesis and/or instability (ROR, 8/303 = 2.64%), and the third FRR was surgical site infection (ROR, 5/303 = 1.65%). Ten-year reoperation rate for all cases that underwent repeat operation at different lumbar levels was 5.61% (17/303); the most FRR was new disc herniation at another lumbar level (ROR, 10/303 = 3.30%), the second FRR was residual segmental stenosis (ROR, 4/303 = 1.32%), and the third FRR was new segmental stenosis at other lumbar levels (ROR, 2/303 = 0.66%). CONCLUSIONS: Three-fourths of all repeat operations were conducted in the same segment and one-fourth were performed at different lumbar levels. We believe that it is important to understand and prevent related problems.

Severity of Myelopathy is Closely Associated With Advanced Age and Signal Intensity Change in Cervical Ossification of the Posterior Longitudinal Ligament: A Prospective Nationwide Investigation.

STUDY DESIGN: Prospective, nationwide case series. OBJECTIVE: To identify preoperative factors associated with myelopathy and neurological impairment in patients with cervical ossification of the posterior longitudinal ligament (OPLL). SUMMARY OF BACKGROUND DATA: Various studies have reported clinical outcomes following the surgical treatment of OPLL. However, there has been no large-scale study of preoperative clinical features in patients with cervical OPLL. MATERIALS AND METHODS: Data were prospectively collected from 28 institutions nationwide in Japan. In total, 512 patients with neurological impairment caused by cervical OPLL requiring surgery were enrolled. Basic demographic and clinical data, including age, sex, diabetes status, body mass index, smoking history, and disease duration were collected. C2-7 lordotic angle, canal narrowing ratio, range of motion in flexion-extension at C2-7, and type of OPLL were evaluated on lateral radiographs to identify factors influencing the clinical features of patients with OPLL in whom surgery was planned. RESULTS: Complete documentation was available for 490 patients (362 male, 128 female). In total, 34 patients had the localized type, 181 had the segmental type, 64 had the continuous type, and 211 had the mixed type. Although there were no significant differences in age, body mass index, disease duration, Japanese Orthopedic Association (JOA) score, and lordotic angle at C2-7 according to the type of OPLL, significant differences were observed in a range of motion at C2-7 and the canal narrowing ratio among the 4 types. Multiple regression analysis revealed that the JOA score was significantly associated with age and signal intensity change on magnetic resonance imaging. CONCLUSIONS: This is the first large-scale, prospective, multicenter case series study to investigate factors influencing preoperative neurological status in patients with OPLL. Age and signal intensity change on magnetic resonance images were significantly associated with JOA score in patients requiring surgery. LEVEL OF EVIDENCE: Level II.

Histopathological characteristics of cervical extensor tissue in patients with dropped head syndrome.

BACKGROUND: To date, the histopathologic characteristics of dropped head syndrome (DHS) have not been reported sufficiently. The present study investigates the histopathology of biopsy specimens from the cervical paravertebral region in patients with DHS. METHODS: Histopathological parameters were evaluated in biopsy specimens of the cervical paravertebral soft tissue from 15 patients with DHS. RESULTS: Among the 15 cases of DHS examined, skeletal muscle was identified in 7 cases, all of which showed necrosis, microvessel proliferation and atrophy. The ligament was identified in 12 cases, 8 of which showed degeneration. The lag time between the onset of symptoms and the performance of a biopsy in all 8 cases, which showed degeneration was over 3 months. Microvessel proliferation in the ligament was observed in 1 of the 4 cases, in which the lag time between the onset of symptoms and the performance of a biopsy was less than 3 months (acute or subacute phase), and in 7 of the 8 cases, in which the lag time between the symptoms and the performance of a biopsy was over 3 months (chronic phase). Chronic inflammation in the ligament was identified in 1 of the 12 cases. CONCLUSIONS: The identification of necrosis, microvessel proliferation, and atrophy in the skeletal muscle of patients with DHS and the presence of ligament degeneration and microvessel proliferation in the chronic but not acute or subacute phases may suggest that persistent skeletal muscle damage of the cervical paravertebral region causes subsequent ligament damage in patients with DHS.

Factors Significantly Associated with Postoperative Neck Pain Deterioration after Surgery for Cervical Ossification of the Posterior Longitudinal Ligament: Study of a Cohort Using a Prospective Registry.

Postoperative neck pain has been reported as an unsolved postoperative complication of surgery for cervical ossification of the posterior longitudinal ligament (OPLL). The aim of the present study was to elucidate factors having a significant association with postoperative deterioration of neck pain in cervical OPLL patients. We studied a cohort of patients in a prospective registry of 478 patients who had undergone cervical spine surgery for cervical OPLL. We excluded those without evaluation of preoperative neck pain. Therefore, 438 patients were included in the present study. Neck pain was evaluated with the visual analogue scale (VAS, 0-100 mm). Postoperative neck pain deterioration was defined as a ≥20 mm increase of VAS neck pain. Patient factors, neurological status, imaging factors and surgical factors were assessed. Univariate analyses followed by multivariate analysis using stepwise logistic regression was performed. Six months after surgery, 50 (11.6%) patients showed postoperative neck pain deterioration and 76 (17.4%) patients showed postoperative neck pain deterioration 2 years after surgery. Six months after surgery, the rate of neck pain deterioration was significantly higher in patients who had undergone posterior surgery. Two years after surgery, the number of levels fused was significantly correlated with neck pain deterioration.

Perioperative Complications in Posterior Surgeries for Cervical Ossification of the Posterior Longitudinal Ligament: A Prospective Nationwide Investigation.

STUDY DESIGN: This was a prospective multicenter study. OBJECTIVE: The aim of this study was to investigate the perioperative complications of posterior surgeries 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. Laminoplasty (LAMP) and posterior decompression and instrumented fusion (PDF) are effective for multilevel cervical OPLL; however, few studies have focused on the surgical complications of these 2 procedures. MATERIALS AND METHODS: We prospectively included 380 patients undergoing posterior surgeries for cervical OPLL (LAMP: 270 patients, PDF: 110 patients), and investigated the systemic and local complications, including neurological complications. We further evaluated risk factors related to the neurological complications. RESULTS: Motor palsy was found in 40 patients (10.5%), and motor palsy in the upper extremity was most frequent (8.9%), especially in patients who received PDF (14.5%). Motor palsies involving the lower extremities was found in 6 patients (1.6%). Regarding local complications, dural tears (3.9%) and surgical site infections (2.6%) were common. In the univariate analysis, body mass index, preoperative cervical alignment, fusion surgery, and the number of operated segments were the factors related to motor palsy. Multivariate analysis revealed that fusion surgery and a small preoperative C2-C7 angle were the independent factors related to motor palsy. Motor palsy involving the lower extremities tended to be found at early time points after the surgery, and all the patients fully recovered. Motor palsy in the upper extremities occurred in a delayed manner, and 68.8% of patients with PDF showed good recovery, whereas 81.3% of patients with LAMP showed good recovery. CONCLUSIONS: In posterior surgeries for cervical OPLL, segmental motor palsy in the upper extremity was most frequently observed, especially in patients who received PDF. Fusion and a small preoperative C2-C7 angle were the independent risk factors for motor palsy. LEVEL OF EVIDENCE: Level III.

Impact of Diabetes Mellitus on Cervical Spine Surgery for Ossification of the Posterior Longitudinal Ligament.

Ossification of the posterior longitudinal ligament (OPLL) is commonly associated with diabetes mellitus (DM); however, the impact of DM on cervical spine surgery for OPLL remains unclear. This study was performed to evaluate the influence of diabetes DM on the outcomes following cervical spine surgery for OPLL. In total, 478 patients with cervical OPLL who underwent surgical treatment were prospectively recruited from April 2015 to July 2017. Functional measurements were conducted at baseline and at 6 months, 1 year, and 2 years after surgery using JOA and JOACMEQ scores. The incidence of postoperative complications was categorized into early (≤30 days) and late (>30 days), depending on the time from surgery. From the initial group of 478 patients, 402 completed the 2-year follow-up and were included in the analysis. Of the 402 patients, 127 (32%) had DM as a comorbid disease. The overall incidence of postoperative complications was significantly higher in patients with DM than in patients without DM in both the early and late postoperative periods. The patients with DM had a significantly lower JOA score and JOACMEQ scores in the domains of lower extremity function and quality of life than those without DM at the 2-year follow-up.

Neurological improvement is associated with neck pain attenuation after surgery for cervical ossification of the posterior longitudinal ligament.

Although favourable surgical outcomes for myelopathy caused by cervical ossification of the posterior longitudinal ligament (OPLL) have been reported, factors significantly associated with post-operative neck pain attenuation still remain unclear. The primary aim of the present study was to determine factors significantly associated with post-operative neck pain attenuation in patients with cervical OPLL using a prospective multi-centre registry of surgically treated cervical OPLL. Significant postoperative neck pain reduction (50% reduction of neck pain) was achieved in 31.3% of patients. There was no significant difference in neck pain attenuation between surgical procedures. Statistical analyses with univariate analyses followed by stepwise logistic regression revealed neurological recovery as a factor having a significant positive association with post-operative neck pain attenuation (p = 0.04, odds ratio 5.68 (95% confidence interval: 1.27-22.2)). In conclusion, neurological recovery was an independent factor having a significant positive association with post-operative neck pain attenuation in patients with cervical myelopathy caused by OPLL who underwent cervical spine surgery.

Machine Learning Approach in Predicting Clinically Significant Improvements After Surgery in Patients with Cervical Ossification of the Posterior Longitudinal Ligament.

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.

The impact of sagittal imbalance on walking in patients with lumbar spinal canal stenosis.

PURPOSE: Gait and posture disorder severely impedes the quality of life of affected patients with lumbar spinal canal stenosis (LSCS). Despite the major health concern, there is a paucity of literature about the relationships among spatiotemporal gait parameters and spinal sagittal parameters. This is a cross sectional study performed in a single tertiary referral center to determine the relationships among spatiotemporal gait parameters and spinal sagittal parameters in patients with LSCS. METHODS: A total of 164 consecutive patients with LSCS, 87 men and 77 women with mean age of 70.7 years, were enrolled. Spatiotemporal gait parameters were studied using a gait analysis system. Spinal sagittal parameters were studied including sagittal vertical axis (SVA), thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic inclination (PI), and pelvic tilt (PT) both in the neutral and stepped positions. RESULTS: SVA was significantly larger in the stepped position than in the neutral position (neutral position, 72.5 mm; stepped position, 96.8 mm; p = 0.003). Parameters regarding the pelvis exhibited significant differences, which could represent pelvic anteversion in the stepped position. By stepwise multiple regression analysis, the prediction models, containing SVA (neutral) and PT (stepped) for double supporting phase, exhibited statistical significance, and accounted for approximately 50% of the variance. CONCLUSIONS: The present study provides statistically established evidence of correlation among spatiotemporal gait parameters and spinal sagittal parameters. Differences between sagittal parameters in neutral and stepped position may stand for the postural control during gait cycle, and increased SVA in neutral position and increased PT in stepped position may correlate with prolonged double supporting phase.

Cervical sagittal alignment in patients with dropped head syndrome.

BACKGROUND: Dropped head syndrome (DHS) can be divided into two types, the positive sagittal vertical axis (SVA) type and the negative SVA type. However, the cervical sagittal alignment of DHS including global sagittal spinal alignment and the typical cervical alignment of the types of DHS is still unclear. The purpose of this study was to clarify the character of cervical sagittal alignment of DHS and analyze the relationship between cervical sagittal alignment and global sagittal spinal alignment. METHODS: The subjects were 35 DHS patients (10 men, 25 women, mean 71.1 years old). They were divided into two groups: negative DHS (N-DHS group, SVA < 0 mm) and positive DHS group (P-DHS group, SVA ≥ 0 mm). As control, 28 age-matched cervical spondylosis patients (CS, 21 men, 7 women, mean 67.4 years old) were analyzed. The following parameters were measured on lateral global-spine standing radiographs: cervical SVA (C2-C7SVA), O-C2A (O-C2 angle), C2 slope (C2S), C2-7A (C2-7 angle), T1 slope (T1S) and C7SVA. RESULTS: The results of measurements of each of the averaged sagittal alignment parameters were (CS, P-DHS, N-DHS): C2-7SVA(26.2 mm, 47.3 mm, 44.5 mm), O-C2 angle (35.0°, 37.1°, 39.3°), C2S (16.5°, 31.4°, 33.8°), C2-7A (9.3°, 9.9°, -16.6°), T1S (22.9°, 39.7°, 25.7°), C7SVA (35.3 mm, 51.0 mm, -43.1 mm). C2-C7SVA and C2S were significantly larger in both types of DHS compared to CS. Comparing P-DHS with N-DHS, C2-C7A and T1S were significantly smaller in N-DHS. CONCLUSIONS: O-C2A did not differ significantly among CS, P-DHS and N-DHS. In DHS patients, C2-7SVA and C2S were significantly larger than those of CS regardless of the type of DHS. The typical cervical sagittal alignment of DHS was different between P-DHS and N-DHS. In P-DHS, C2-7A and T1S were larger than those in N-DHS and the imbalance of thoraco-lumbar alignment should be noted.

Eight cases of sudden-onset dropped head syndrome: patient series.

BACKGROUND: As the proportion of elderly people continues to increase, the number of patients with dropped head syndrome (DHS) also grows. However, the relationship between onset and clinical course of DHS has hardly been studied, particularly, that of sudden-onset DHS has not been reported and remains unclear. OBSERVATIONS: Sudden-onset DHS was defined as presenting with chin on chest deformity within 3 days from the time of awareness of cervical weakness. Sixty-six patients with DHS visited our facility. Among them, 8 of the total cases (12.1%) had experienced sudden onset DHS (6 females and 2 males; average age: 71.9 ± 10.9 years). Six of 8 cases showed recovery by conservative treatment, whose first interventions were from 0.1 to 12 months, but 3 experienced recurrence. Diffuse spinal kyphotic-type DHS was seen in 2 cases, and both had recurring horizontal gaze disturbance after initial recovery. Two unimproved cases underwent surgery of combined anterior and posterior cervical fixation, and their first interventions were at 5 and 24 months. After surgery, cervical sagittal alignment was improved, and they could walk maintaining horizontal gaze. LESSONS: Sudden-onset DHS can be expected to have a better outcome, but recurrence is possible in global imbalanced-type DHS.