Detection of Cervical Foraminal Stenosis from Oblique Radiograph Using Convolutional Neural Network Algorithm.

PURPOSE: This study was conducted to develop a convolutional neural network (CNN) algorithm that can diagnose cervical foraminal stenosis using oblique radiographs and evaluate its accuracy. MATERIALS AND METHODS: A total of 997 patients who underwent cervical MRI and cervical oblique radiographs within a 3-month interval were included. Oblique radiographs were labeled as "foraminal stenosis" or "no foraminal stenosis" according to whether foraminal stenosis was present in the C2-T1 levels based on MRI evaluation as ground truth. The CNN model involved data augmentation, image preprocessing, and transfer learning using DenseNet161. Visualization of the location of the CNN model was performed using gradient-weight class activation mapping (Grad-CAM). RESULTS: The area under the curve (AUC) of the receiver operating characteristic curve based on DenseNet161 was 0.889 (95% confidence interval, 0.851-0.927). The F1 score, accuracy, precision, and recall were 88.5%, 84.6%, 88.1%, and 88.5%, respectively. The accuracy of the proposed CNN model was significantly higher than that of two orthopedic surgeons (64.0%, p<0.001; 58.0%, p<0.001). Grad-CAM analysis demonstrated that the CNN model most frequently focused on the foramen location for the determination of foraminal stenosis, although disc space was also frequently taken into consideration. CONCLUSION: A CNN algorithm that can detect neural foraminal stenosis in cervical oblique radiographs was developed. The AUC, F1 score, and accuracy were 0.889, 88.5%, and 84.6%, respectively. With the current CNN model, cervical oblique radiography could be a more effective screening tool for neural foraminal stenosis.

Reoperation Rates According to Surgical Approach After Operation for Degenerative Cervical Pathology in Patients With Athetoid Cerebral Palsy: A Nationwide Cohort Study.

STUDY DESIGN: National population-based cohort study. OBJECTIVE: The overall complication rate for patients with athetoid cerebral palsy (CP) undergoing cervical surgery is significantly higher than that of patients without CP. The study was conducted to compare the reoperation and complication rates of anterior fusion, posterior fusion, combined fusion, and laminoplasty for degenerative cervical myelopathy/radiculopathy in patients with athetoid cerebral palsy. METHODS: The Korean Health Insurance Review and Assessment Service national database was used for analysis. Data from patients diagnosed with athetoid CP who underwent cervical spine operations for degenerative causes between 2002 and 2020 were reviewed. Patients were categorized into four groups for comparison: anterior fusion, posterior fusion, combined fusion, and laminoplasty. RESULTS: A total of 672 patients were included in the study. The overall revision rate was 21.0% (141/672). The revision rate was highest in the anterior fusion group (42.7%). The revision rates of combined fusion (11.1%; hazard ratio [HR], .335; P = .002), posterior fusion (13.8%; HR, .533; P = .030) were significantly lower than that of anterior fusion. Revision rate of laminoplasty (13.1%; HR, .541; P = .240) was also lower than anterior fusion although the result did not demonstrate statistical significance. CONCLUSION: Anterior fusion presented the highest reoperation risk after cervical spine surgery reaching 42.7% in patients with athetoid CP. Therefore, anterior-only fusion in patients with athetoid CP should be avoided or reserved for strictly selected patients. Combined fusion, with the lowest revision risk at 11.1%, could be safely applied to patients with athetoid CP.

Lateral Deviation of the Hyoid Bone and Thyroid Cartilage Influences Prevertebral Soft-Tissue Swelling and Dysphagia After Anterior Cervical Diskectomy and Fusion.

BACKGROUND AND OBJECTIVES: Prevertebral soft-tissue swelling (PSTS) after anterior cervical diskectomy and fusion (ACDF) is known to be influenced by several factors. We considered the effect of lateral deviation on the traction force and attempted to find a relationship with the PSTS. This study was designed to evaluate the preoperative lateral deviation of the hyoid bone and thyroid cartilage and its effect on PSTS, airway collapse, and clinical outcomes after ACDF. METHODS: Preoperative lateral deviations of the hyoid bone and thyroid cartilage at the superior cornu and inferior cornu were measured. To assess the effect of lateral deviation, patients who underwent 1 or 2 level ACDF with the left-sided approach were divided into a deviation group (left-sided deviation >5 mm or >10 mm) and a nondeviation group (left-sided deviation <5 mm or <10 mm). Difference of preoperative and postoperative PSTS (dPSTS), airway collapse, dysphagia score, and Neck Disability Index were compared between the 2 groups. RESULTS: Lateral deviation was measured in 290 patients, and 145 were enrolled to assess the effect of lateral deviation. Left-sided deviation was more common than right-sided deviation in all 3 structures (the hyoid bone, superior cornu, and inferior cornu of the thyroid cartilage). The deviation group demonstrated a significantly larger dPSTS at the C3 and C4 levels, more airway collapse at the C4 level, and a higher dysphagia score. There was no significant difference in the Neck Disability Index between the 2 groups. Lateral deviation significantly correlated with dPSTS (C3, C4, C5, and C6 levels) and airway collapse (C3 and C4 levels). CONCLUSION: A left-sided deviation of more than 5 mm of the hyoid bone or thyroid cartilage discouraged the left-sided approach for ACDF because of the aggravation of dPSTS, airway collapse, and dysphagia postoperatively.

Feasibility of Non-window Three-Dimensional-Printed Porous Titanium Cage in Posterior Lumbar Interbody Fusion: A Pilot Trial.

Background: The commercially available design of a three-dimensional (3D)-printed titanium (3D-Ti) cage can be divided into two types according to the presence of a window: a cage with a window that allows filling of bone graft materials and a non-window cage for stand-alone use. This prospective observational case series study aimed to explore the clinical feasibility of using a non-window type 3D-Ti cage in cases of combined window and non-window cage implantation. Furthermore, we evaluated the bone in growth patterns of non-window cages and their correlation with published fusion grading systems. Methods: A total of 31 consecutive patients who underwent single-level posterior lumbar interbody fusion surgery were included. Two 3D-Ti cages with different designs were inserted: a non-window cage on the left side and a window cage on the right side. Radiographic fusion was defined by the segmental angle between flexion and extension radiographs (F-E angle) and cage bridging bone (CBB) scores on computed tomography. The association between the F-E angle and osteointegration scoring system including the surface osteointegration ratio (SOR) score was analyzed. Results: Radiographic fusion was achieved in 27 of 31 patients (87%) at 12 months postoperatively. Among the non-window cages, 23 of 31 (74.2%) had fair SOR scores, while 19 of 31 (61.3%) window cages had fair intra-cage CBB scores. The higher the SOR score was, the smaller the flexion-extension angle (SOR 0 vs. SOR 1: 6.30° ± 2.43° vs. 1.95° ± 0.99°, p < 0.001; SOR 0 vs. SOR 2: 6.03° ± 2.43° vs. 0.99°± 0.74°, p < 0.001). Conclusions: The clinical feasibility of using a non-window 3D-Ti cage during lumbar interbody fusion might be acceptable. Furthermore, a newly suggested fusion criterion for the use of the non-window cage, the SOR score, showed a significant association with the published fusion grading systems, demonstrating its feasibility in determining interbody fusion in lumbar spinal surgery.

Preoperative Radiographic Simulation for Partial Uncinate Process Resection during Anterior Cervical Discectomy and Fusion to Achieve Adequate Foraminal Decompression and Prevention of Vertebral Artery Injury.

STUDY DESIGN: Retrospective radiographic study. PURPOSE: This study aims to demonstrate the proper resection trajectory of a partial posterior uncinate process resection combined with anterior cervical discectomy and fusion (ACDF) and evaluate whether foraminal stenosis or uncinate process degeneration increases the risk of vertebral artery (VA) injury. OVERVIEW OF LITERATURE: Appropriate resection trajectory that could result in sufficient decompression and avoid vertebral artery injury is yet unknown. METHODS: We retrospectively reviewed patients who underwent cervical magnetic resonance imaging and computed tomography angiography for preoperative ACDF evaluation. The segments were classified according to the presence of foraminal stenosis. The height, thickness, anteroposterior length, horizontal distance from the uncinate process to the VA, and vertical distance from the uncinate process baseline to the VA of the uncinate process were measured. The distance between the uncinate anterior margin and the resection trajectory (UAM-to-RT) was measured. RESULTS: There were no VA injuries or root injuries among the 101 patients who underwent ACDF (163 segments, mean age of 56.3±12.2). Uncinate anteroposterior length was considerably longer in foramens with foraminal stenosis, whereas uncinate process height, thickness, and distance between the uncinate process and VA were not significantly associated with foraminal stenosis. There were no significant differences in radiographic parameters based on uncinate degeneration. The UAM-to-RT distances for adequate decompression were 1.6±1.4 mm (range, 0-4.8 mm), 3.4±1.7 mm (range, 0-7.1 mm), 4.0±1.7 mm (range, 0-9.0 mm), and 4.5±1.2 mm (range, 2.5-7.5 mm) for C3-C4, C4-C5, C5-C6, and C6-C7, respectively. CONCLUSIONS: More than half of the uncinate process in the anteroposterior plane should be removed for adequate neural foramen decompression. Foraminal stenosis or uncinate degeneration did not alter the relative anatomy of the uncinate process and the VA and did not impact VA injury risk.

Risk Factors for Postoperative Loss of Lordosis, Cervical Kyphosis, and Sagittal Imbalance After Cervical Laminoplasty.

OBJECTIVE: A retrospective cohort study was undertaken to elucidate the risk factors of loss of cervical lordosis (LCL), kyphotic deformity, and sagittal imbalance after cervical laminoplasty. METHODS: A total of 108 patients who underwent laminoplasty to treat cervical myelopathy and were followed for ≥2 years were included. Logistic regression analysis and multiple regression analysis were performed to identify preoperative risk factors of LCL, kyphotic deformity (cervical lordosis <0°), and sagittal imbalance (sagittal vertical axis >40 mm) at postoperative 2 years. RESULTS: Within multivariate multiple regression analysis, C2-C7 lordosis (P = 0.002), and C2-C7 extension capacity (P<0.001) showed significant association with LCL. Furthermore, age (P = 0.043) and C2-C7 lordosis (P = 0.038) were significantly associated with postoperative kyphosis. Receiver operating characteristic curve analysis for postoperative kyphosis showed that preoperative C2-C7 lordosis of 10.5° had a sensitivity and specificity of 81.3% and 82.4%, respectively. Preoperative K-line tilt (P = 0.034) showed a significant association with postoperative cervical sagittal imbalance at postoperative 2 years. Receiver operating characteristic curve analysis showed that a K-line tilt cutoff value of 12.5° had a sensitivity and specificity of 78.6% and 77.7%, respectively, for predicting postoperative sagittal imbalance. CONCLUSIONS: Higher preoperative C2-C7 lordosis and less preoperative cervical extension capacity were risk factors of LCL. Small preoperative C2-C7 lordosis <10.5° and younger age were risk factors of postoperative kyphosis. Furthermore, a greater K-line tilt would increase the risk of postoperative sagittal imbalance, with a cutoff value of 12.5°.

Comparison of Fusion, Subsidence, and Clinical Results Between 3D-Printed Porous Titanium Cage and Polyetheretherketone Cage in Posterior Lumbar Interbody Fusion: A Minimum of 2 Years Follow-Up.

OBJECTIVE: The occurrence of early osteointegration and reduced modulus of elasticity have been proved with 3-dimensinally (3D) printed porous titanium (3DP-titanium) cages used for posterior lumbar interbody fusion (PLIF). The present study was conducted to demonstrate the fusion rate, subsidence, and clinical outcomes for the 3DP-titanium cage in PLIF and to compare its results with those of the polyetheretherketone (PEEK) cage. METHODS: A total of 150 patients who underwent 1-2-level PLIF and were followed up for >2 years were retrospectively reviewed. The fusion rates, subsidence, segmental lordosis, visual analog scale (VAS) score for back pain, VAS score for leg pain, and Oswestry disability index were assessed. RESULTS: A higher 1-year (3DP-titanium, 86.9%; PEEK, 67.7%; P = 0.002) and 2-year (3DP-titanium, 92.9%; PEEK, 82.3%; P = 0.037) fusion rate could be achieved with 3DP-titanium cages for PLIF than with PEEK cages. The amount of subsidence (3DP-titanium, 1.4 ± 1.6 mm; PEEK, 1.9 ± 1.8 mm; P = 0.092) and incidence of significant subsidence (3DP-titanium, 17.9%; PEEK, 23.4%; P = 0.389) was not significantly different between the 2 materials. Furthermore, the VAS score for back pain and leg pain and Oswestry disability index were not significantly different between the 2 groups. On logistic regression analysis, cage material (P = 0.027) showed a significant association with fusion, and the number of levels fused (P = 0.012) was associated with subsidence. CONCLUSIONS: The 3DP-titanium cage resulted in a higher fusion rate than the PEEK cage when used for PLIF. The subsidence rate did not differ significantly between the 2 cage materials. Therefore, the 3DP-titanium cage can be safely used for PLIF, considering its stable construct.

Which Radiographic Parameter Can Aid in Deciding Optimal Allograft Height for Anterior Cervical Discectomy and Fusion?

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: To identify preoperative radiographic parameters that can guide optimal allograft height selection for anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: Allograft height selection for ACDF depends on intraoperative assessment supported by trials; however, there is currently no radiographic reference parameter that could aid in allograft height selection for improved outcomes. METHODS: A total of 148 patients who underwent ACDF using allografts and were followed up for more than 1 year were retrospectively reviewed. Fusion rates, subsidence, segmental lordosis, and foraminal height were assessed. Segments were divided into 2 groups according to whether the inserted allograft height was within 1 mm from the following 3 reference radiographic parameters: (1) uncinate process height, (2) adjacent disc height, and (3) preoperative disc height +2 mm. RESULTS: This study included 101 patients with 163 segments. Segments with an allograft-uncinate height difference of ≤1 mm had a significantly higher fusion rate at 1-year follow-up compared with segments with allograft-uncinate height difference of >1 mm [85/107 (79.4%) vs. 35/56 (62.5%); P =0.025]. Subsidence, segmental lordosis, and foraminal height did not significantly differ between the groups when segments were divided according to uncinate height. Multivariate logistic regression analysis demonstrated that allograft-uncinate height difference of ≤1 mm and allograft failure were factors associated with fusion. CONCLUSIONS: The uncinate process height can guide optimal allograft height selection for ACDF. Using an allograft with an allograft-uncinate height difference of ≤1 mm resulted in a higher fusion rate. Therefore, the uncinate process height should be checked preoperatively and used in conjunction with intraoperative assessment when selecting allograft height.

Anterior Decompression and Fusion for the Treatment of Cervical Myelopathy Caused by Ossification of the Posterior Longitudinal Ligament: A Narrative Review.

Occasionally, ossification of the posterior longitudinal ligament (OPLL) causes cord compression, resulting in cervical myelopathy. OPLL differs from other causes of cervical spondylotic myelopathy in several ways, and the surgical strategy should be chosen with OPLL's characteristics in mind. Although both the anterior and posterior approaches are effective surgical methods for the treatment of OPLL cervical myelopathy, they each have their own set of benefits and drawbacks. Anterior decompression and fusion (ADF) may improve neurological recovery, restore lordosis, and prevent OPLL mass progression. The benefits can be seen in patients with a high canal occupying ratio or kyphotic alignment. We discussed the benefits, limitations, indications, and surgical techniques of ADF for the treatment of OPLL-induced cervical myelopathy in this narrative.

Foraminal Restenosis After Posterior Cervical Foraminotomy for the Treatment of Cervical Radiculopathy.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: To elucidate incidence, risk factor, and clinical effect of bone regrowth after posterior cervical foraminotomy (PCF). METHODS: Ninety-eight patients who underwent PCF for the treatment of cervical radiculopathy and were followed up for >2 years were retrospectively reviewed. Foraminal dimension, sagittal gap at resected area, facet thickness, lamina length, and cervical range of motion (ROM) were measured. Neck pain visual analogue scale (VAS), arm pain VAS, and neck disability index (NDI) were recorded. Radiographic measures were compared between segments with foraminal narrowing of ≥20% at the 2-years follow-up (restenosis segments) and foraminal narrowing of <20% (patent segments). RESULTS: Sixty-nine patients with 109 segments were included. 73.4% (80/109) of foramens demonstrated foraminal narrowing and decrease of foraminal dimension of ≥20% occurred in 30.3% (30/109). Foraminal dimension at postoperative 2-days was significantly higher in the restenosis segments (P = .047). Furthermore, increase of foraminal dimension was significantly associated with foraminal restenosis of ≥20% (P = .018). Facet thickness was significantly higher in the restenosis segments compared to patent segments at postoperative 2-years follow-up (P = .038). Neck pain VAS was significantly aggravated only in the restenosis group at postoperative 2-years follow-up (P < .001). CONCLUSIONS: Foraminal narrowing commonly occurs after PCF due to bone healing. Bone growth occurs in all directions while medial facet growth contributes more to foraminal restenosis. Greater widening of foramen during PCF is a risk factor for postoperative foramen restenosis. Therefore, amount of bone resection should be kept optimal and excessive resection should be avoided to prevent foramen restenosis.

Mid-term efficacy and safety of Escherichia coli-derived rhBMP-2/hydroxyapatite carrier in lumbar posterolateral fusion: a randomized, multicenter study.

PURPOSE: This study aimed to evaluate the mid-term efficacy and safety of Escherichia coli-derived bone morphogenetic protein-2 (E.BMP-2)/hydroxyapatite (HA) in lumbar posterolateral fusion (PLF). METHODS: This multicenter, evaluator-blinded, observational study utilized prospectively collected clinical data. We enrolled 74 patients who underwent lumbar PLF and had previously participated in the BA06-CP01 clinical study, which compared the short-term outcomes of E.BMP-2 with an auto-iliac bone graft (AIBG). Radiographs and CT scans were analyzed to evaluate fusion grade at 12, 24, and 36 months. Visual analog scale (VAS), Oswestry disability index (ODI), and Short Form-36 (SF-36) scores were measured preoperatively and at 36 months after surgery. All adverse events in this study were assessed for its relationship with E.BMP-2. RESULTS: The fusion grade of the E.BMP-2 group (4.91 ± 0.41) was superior to that of the AIBG group (4.25 ± 1.26) in CT scans at 36 months after surgery (p = 0.007). Non-union cases were 4.3% in the E.BMP-2 and 16.7% in the AIBG. Both groups showed improvement in pain VAS, ODI, and SF-36 scores when compared to the baseline values, and there were no statistically significant differences between the two groups. No treatment-related serious adverse reactions were observed in either group. No neoplasm-related adverse events occurred in the E.BMP-2 group. CONCLUSIONS: The fusion quality of E.BMP-2/HA was superior to that of AIBG. E.BMP-2/HA showed comparable mid-term outcomes to that of AIBG in terms of efficacy and safety in one-level lumbar PLF surgery.

Efficacy and safety of oblique posterior endplate resection for wider decompression (trumpet-shaped decompression) during anterior cervical discectomy and fusion.

OBJECTIVE: Anterior cervical discectomy and fusion (ACDF) provides a limited workspace, and surgeons often need to access the posterior aspect of the vertebral body to achieve sufficient decompression. Oblique resection of the posterior endplate (trumpet-shaped decompression [TSD]) widens the workspace, enabling removal of lesions behind the vertebral body. This study was conducted to evaluate the efficacy and safety of oblique posterior endplate resection for wider decompression. METHODS: In this retrospective study, 227 patients who underwent ACDF for the treatment of cervical myelopathy or radiculopathy caused by spondylosis or ossification of the posterior longitudinal ligament and were followed up for ≥ 1 year were included. Patient characteristics, fusion rates, subsidence, and patient-reported outcome measures, including the neck pain visual analog scale (VAS) score, arm pain VAS score, and Neck Disability Index (NDI), were assessed. Patients who underwent TSD during ACDF (TSD group) and those who underwent surgery without TSD (non-TSD group) were compared. RESULTS: Fifty-seven patients (25.1%) were included in the TSD group and 170 patients (74.9%) in the non-TSD group. In the TSD group, 28.2% ± 5.5% of the endplate was resected, and 26.0% ± 6.1% of the region behind the vertebral body could be visualized via the TSD technique. The resection angle was 26.9° ± 5.9°. The fusion rate assessed on the basis of interspinous motion, intragraft bone bridging, and extragraft bone bridging did not significantly differ between the two groups. Furthermore, there were no significant intergroup differences in subsidence. The patient-reported outcome measures at the 1-year follow-up were also not significantly different between the groups. CONCLUSIONS: TSD widened the workspace during ACDF, and 26% of the region posterior to the vertebral body could be accessed using this technique. The construct stability was not adversely affected by TSD as demonstrated by the similar fusion and subsidence rates among patients who underwent TSD and those who did not. Therefore, TSD can be safely applied during ACDF when compressive lesions extend behind the vertebral body and are not limited to the disc space, enabling adequate decompression without disrupting the construct stability.

Factors affecting the prognosis of recovery of motor power and ambulatory function after surgery for metastatic epidural spinal cord compression.

OBJECTIVE: Metastatic epidural spinal cord compression (MESCC) causes neurological deficits that may hinder ambulation. Understanding the prognostic factors associated with increased neurological recovery and regaining ambulatory functions is important for surgical planning in MESCC patients with neurological deficits. The present study was conducted to elucidate prognostic factors of neurological recovery in MESCC patients. METHODS: A total of 192 patients who had surgery for MESCC due to preoperative neurological deficits were reviewed. A motor recovery rate ≥ 50% and ambulatory function restoration were defined as the primary favorable endpoints. Factors associated with a motor recovery rate ≥ 50%, regaining ambulatory function, and patient survival were analyzed. RESULTS: About one-half (48.4%) of the patients had a motor recovery rate ≥ 50%, and 24.4% of patients who were not able to walk due to MESCC before the surgery were able to walk after the operation. The factors "involvement of the thoracic spine" (p = 0.015) and "delayed operation" (p = 0.041) were associated with poor neurological recovery. Low preoperative muscle function grade was associated with a low likelihood of regaining ambulatory functions (p = 0.002). Furthermore, performing the operation ≥ 72 hours after the onset of the neurological deficit significantly decreased the likelihood of regaining ambulatory functions (p = 0.020). Postoperative ambulatory function significantly improved patient survival (p = 0.048). CONCLUSIONS: Delayed operation and the involvement of the thoracic spine were poor prognostic factors for neurological recovery after MESCC surgery. Furthermore, a more severe preoperative neurological deficit was associated with a lesser likelihood of regaining ambulatory functions postoperatively. Earlier detection of motor weaknesses and expeditious surgical interventions are necessary, not only to improve patient functional status and quality of life but also to enhance survival.

Assessment of Fusion After Anterior Cervical Discectomy and Fusion Using Convolutional Neural Network Algorithm.

BACKGROUND: A convolutional neural network (CNN) is a deep learning (DL) model specialized for image processing, analysis, and classification. OBJECTIVE: In this study, we evaluated whether a CNN model using lateral cervical spine radiographs as input data can help assess fusion after anterior cervical discectomy and fusion (ACDF). STUDY DESIGN: Diagnostic imaging study using DL. PATIENT SAMPLE: We included 187 patients who underwent ACDF and fusion assessment with postoperative one-year computed tomography and neutral and dynamic lateral cervical spine radiographs. OUTCOME MEASURES: The performance of the CNN-based DL algorithm was evaluated in terms of accuracy and area under the curve. MATERIALS AND METHODS: Fusion or nonunion was confirmed by cervical spine computed tomography. Among the 187 patients, 69.5% (130 patients) were randomly selected as the training set, and the remaining 30.5% (57 patients) were assigned to the validation set to evaluate model performance. Radiographs of the cervical spine were used as input images to develop a CNN-based DL algorithm. The CNN algorithm used three radiographs (neutral, flexion, and extension) per patient and showed the diagnostic results as fusion (0) or nonunion (1) for each radiograph. By combining the results of the three radiographs, the final decision for a patient was determined to be fusion (fusion ≥2) or nonunion (fusion ≤1). By combining the results of the three radiographs, the final decision for a patient was determined as fusion (fusion ≥2) or nonunion (nonunion ≤1). RESULTS: The CNN-based DL model demonstrated an accuracy of 89.5% and an area under the curve of 0.889 (95% confidence interval, 0.793-0.984). CONCLUSION: The CNN algorithm for fusion assessment after ACDF trained using lateral cervical radiographs showed a relatively high diagnostic accuracy of 89.5% and is expected to be a useful aid in detecting pseudarthrosis.

Anatomical considerations for appropriate mini-plate positioning in open-door laminoplasty to avoid plate impingement and screw facet violation.

This study aimed to describe a safe zone for mini-plate positioning that can avoid instrument-related complications in laminoplasty. Fifty-one patients who underwent laminoplasty and were followed up for at least 1 year were retrospectively reviewed. The posterior surface length and inferior pole angle of the lateral mass were measured at each level using computed tomography. The safe zone was defined based on these measurements. Incidences of screw facet violation and plate impingement were recorded. Patient-reported outcome measures were compared between the appropriate position (AP) and inappropriate position (IP) groups. Among 40 patients included, 15 (37.5%) had inappropriate plate positioning, causing screw facet violation or plate impingement, which more commonly occurred at distal (C5, C6) and proximal (C3, C4) levels, respectively. Lateral mass posterior surface length was shorter at the proximal levels, and the inferior pole angle of the lateral mass was smaller at the distal levels, signifying that the lateral mass became thin and long at the distal levels. Patient-reported outcome measures were not significantly different between the two groups. However, cervical range of motion at the final follow-up was significantly less in the IP group (p = 0.01). The suggested safe zone demonstrates that inserting the mini-plate with plate-to-lateral mass inferior pole distances of 4-5 mm and 5-6 mm at the C3-C5 and C6-C7 levels, respectively, would avoid instrument-related complications. The risk of plate impingement was higher at the proximal level, whereas the risk of screw facet violation was higher at the distal level in open-door cervical laminoplasty. These risks coincide with anatomical differences at each level. Despite inappropriate positioning of the mini-plate, clinical outcomes were not adversely affected.

Morphologic Change of CorticoCancellous Allograft Used for Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The aim of this study was to evaluate the incidence and clinical implications of graft morphologic changes in corticocancellous allografts used for anterior cervical discectomy and fusion (ACDF), such as graft resorption or fracture. SUMMARY OF BACKGROUND DATA: Although cortico-cancellous allograft is one of the most commonly used interbody spacer for ACDF, clinical implications of allograft resorption or fracture is unclear. METHODS: One-hundred and thirty-eight consecutive patients who underwent ACDF for degenerative cervical myelopathy or radiculopathy were retrospectively reviewed. Patients with allograft morphologic changes, including graft resorption and fracture (morphologic change group), were compared with patients without morphologic changes (unchanged group). Furthermore, operated segments with morphologic changes were compared with unchanged segments. Patient characteristics, cervical lordosis, segmental lordosis, fusion, subsidence, neck pain visual analogue scale (VAS), arm pain VAS, and neck disability index (NDi) scores were evaluated. RESULTS: Ninety patients (149 segments) were included in the study. Allograft resorption or fracture was detected in 46 (51.1%) patients and 81 (54.3%) segments, respectively. The fusion rate of morphologic change segments was significantly lower than that of the unchanged segments (P < 0.001). Furthermore, segments with morphologic changes had significantly higher rates of subsidence compared to unchanged segments ( P < 0.001). Segmental lordosis at the final follow-up was significantly smaller in the morphologic change segments ( P < 0.001). Neck pain VAS, arm pain VAS, and NDI scores did not demonstrate significant intergroup differences. CONCLUSION: Corticocancellous allograft demonstrated a high rate of graft morphologic change (54.3%). Graft resorption or fracture was associated with increased pseudarthrosis, subsidence, and decreased postoperative segmental lordosis; however, the clinical results were not significantly affected. Caution is needed when choosing to use corticocancellous allografts for ACDF due to the high rate of graft resorption or fracture and the negative implications of these risks.

Significance of Vertebral Body Sliding Osteotomy as a Surgical Strategy for the Treatment of Cervical Ossification of the Posterior Longitudinal Ligament.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: Vertebral body sliding osteotomy (VBSO) has previously been reported as a technique to decompress ossification of the posterior longitudinal ligament (OPLL) by translating the vertebral body anteriorly. This study aimed to evaluate the radiological and clinical efficacies of VBSO and clarify the surgical indications of VBSO for treating myelopathy caused by OPLL. METHODS: Ninety-seven patients with symptomatic OPLL-induced cervical myelopathy treated with VBSO or laminoplasty who were followed up for more than 2 years were retrospectively reviewed. Cervical alignment, range of motion, fusion, modified K-line (mK-line) status, and minimum interval between ossified mass and mK-line (INT(min)), and the Japanese Orthopaedic Association (JOA) score were assessed. Patients in the VBSO group were compared with those who underwent laminoplasty. RESULTS: Cervical lordosis and INT(min) significantly increased in the VBSO group. All patients in the VBSO group assessed as mK-line (-) preoperatively were assessed as mK-line (+) postoperatively. However, in the LMP group, the mK-line status changed from (+) preoperatively to (-) postoperatively in 3 patients. Final JOA score (p = 0.02) and JOA score improvement (p = 0.01) were significantly higher in the VBSO group. JOA recovery ratio (p = 0.03) and proportion of patients with a recovery rate ≥50% were significantly higher in the VBSO group (p < 0.01). CONCLUSIONS: VBSO is an effective surgical option for OPLL-induced myelopathy, demonstrating favorable neurological recovery and lordosis restoration with low complication rates. It is best indicated for kyphotic alignment, OPLL with a high space-occupying ratio, and OPLL involving ≤3 segments.

The Kappa Line as a Regional Modification of the K-line: A Predictor of Neurological Outcome and Indicator of the Adequate Level of Decompression in Selective Laminoplasty.

STUDY DESIGN: This is a retrospective cohort study. OBJECTIVE: The aim was to introduce Kappa line (modification of K-line) for the prediction of postoperative neurological recovery after selective cervical laminoplasty (LMP) and use in determining the decompression level. SUMMARY OF BACKGROUND DATA: The K-line is a radiographic marker that can predict prognosis and aid in surgical planning for patients undergoing LMP through C3 to C7. However, its efficacy in LMP involving limited segments is unclear. Furthermore, no specific radiographic marker to predict the prognosis of selective LMP has been reported. MATERIALS AND METHODS: Fifty-one consecutive patients with a minimum 2-year follow-up after selective LMP for cervical myelopathy caused by ossification of posterior longitudinal ligament were retrospectively reviewed. The Kappa line was defined as a straight line connecting the midpoints of the spinal canal made by remaining bony structure after decompression procedures on a plain lateral radiograph in the neutral position. Patients were classified as K-line (+) or (-) and Kappa line (+) or (-) based on whether the ossified mass crossed the indicator line. RESULTS: The Kappa line (+) group demonstrated significantly higher Japanese Orthopaedic Association (JOA) recovery rate (P=0.01), final JOA score (P<0.01), and dural sac diameter (P<0.01) postoperatively than the Kappa line (-) group. Cord compression grade was significantly lesser in the Kappa line (+) group. However, the K-line-based classification did not demonstrate significant difference in JOA recovery rate, final JOA score, and cord compression grade between the (+) and (-) groups; the dural sac diameter was significantly higher in the K-line (+) group (P<0.01). CONCLUSIONS: The Kappa line showed better correlation with ossification of posterior longitudinal ligament size and cervical alignment, providing better prediction of neurological recovery and remaining cord compression following selective LMP. Therefore, the Kappa line can aid in determining the level of decompression in selective LMP.

Segmental Height Decrease Adversely Affects Foraminal Height and Cervical Lordosis, But Not Clinical Outcome After Anterior Cervical Discectomy and Fusion Using Allografts.

OBJECTIVE: This study was conducted to elucidate the clinical significance of postoperative segmental height decrease (SHD) in anterior cervical discectomy and fusion (ACDF) using allografts. METHODS: We reviewed 88 patients who underwent ACDF using allografts as interbody spacers. Cervical lordosis, segmental lordosis, segmental height, foraminal height, fusion, allograft fracture, and resorption were assessed. Significant SHD was defined as that ≥2 mm. Neck pain visual analog scale (VAS) score, arm pain VAS score, and Neck Disability Index (NDI) score were also recorded. Significant segmental height decreased (SH-D) segments were compared with segmental height maintained (SH-M) segments. RESULTS: Thirty-two patients (36.4%) and 34 segments (23.1%) demonstrated significant SHD. SH-D segments demonstrated significantly lower segmental lordosis (3.7 ± 4.1 vs. 0.9 ± 4.8°; P < 0.01), foraminal height (9.6 ± 1.1 vs. 8.7 ± 0.9 mm; P < 0.01), and fusion rate (88 [77.9%] vs. 20 [58.9%]; P = 0.04) than SH-M segments at the final follow-up, respectively. Furthermore, global lordosis was significantly lower in the SH-D group (18.3 ± 8.5 vs. 13.9 ± 8.9°, respectively; P = 0.02). However, neck and arm pain VAS scores and NDI score did not demonstrate a significant difference between patients with and without significant SHD. Logistic regression analysis demonstrated that higher allograft height (P = 0.03), greater allograft anteroposterior length (P = 0.04), and allograft resorption or fracture (P < 0.01) were associated with increased risk of significant SHD. Logistic regression analysis also demonstrated that allograft resorption or fracture (P < 0.01) was associated with risk of nonunion. CONCLUSIONS: Significant SHD was associated with decreased segmental lordosis, global cervical lordosis, and foraminal height. However, significant SHD did not result in worsening of clinical symptoms. Larger allograft size was associated with risk of significant SHD. This study demonstrates provisional results that suggest allograft resorption or fracture may be a factor that adversely affects fusion or SHD.

Comparison between selective caudal fixed screw construct and all variable screw construct in anterior cervical discectomy and fusion.

This retrospective comparative study aimed to compare the efficacy of selective caudal fixed screw constructs with all variable screw constructs in anterior cervical discectomy and fusion (ACDF). Thirty-five patients who underwent surgery using selective caudal fixed screw construct (SF group) were compared with 44 patients who underwent surgery using all variable constructs (AV group). The fusion rate, subsidence, adjacent level ossification development (ALOD), adjacent segmental disease (ASD), and plate-adjacent disc space distance were assessed. The one-year fusion rates assessed by computed tomography bone bridging and interspinous motion as well as the significant subsidence rate did not differ significantly between the AV and SF groups. The ALOD and ASD rates and plate-adjacent disc space distances did not significantly differ between the two groups at both the cranial and caudal adjacent levels. The number of operated levels was significantly associated with pseudarthrosis in the logistic regression analysis. The stability provided by the locking mechanism of the fixed screw did not lead to an increased fusion rate at the caudal level. Therefore, the screw type should be selected based on individual patient's anatomy and surgeon's experience without concern for increased complications caused by screw type.