Tag: cervical disk arthroplasty

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Optimal Implant Sizing Using Machine Learning Is Associated With Increased Range of Motion After Cervical Disk Arthroplasty

Neurosurgery 95:627–633, 2024

Cervical disk arthroplasty (CDA) offers the advantage of motion preservation in the treatment of focal cervical pathology. At present, implant sizing is performed using subjective tactile feedback and imaging of trial cages. This study aims to construct interpretable machine learning (IML) models to accurately predict postoperative range of motion (ROM) and identify the optimal implant sizes that maximize ROM in patients undergoing CDA.

METHODS: Adult patients who underwent CDA for single-level disease from 2012 to 2020 were identified. Patient demographics, comorbidities, and outcomes were collected, including symptoms, examination findings, subsidence, and reoperation. Affected disk height, healthy rostral disk height, and implant height were collected at sequential time points. Linear regression and IML models, including bagged regression tree, bagged multivariate adaptive regression spline, and k-nearest neighbors, were used to predict ROM change. Model performance was assessed by calculating the root mean square error (RMSE) between predicted and actual changes in ROM in the validation cohort. Variable importance was assessed using RMSE loss. Area under the curve analyses were performed to identify the ideal implant size cutoffs in predicting improved ROM.

RESULTS: Forty-seven patients were included. The average RMSE between predicted and actual ROM was 7.6°(range: 5.8-10.1) in the k-nearest neighbors model, 7.8°(range: 6.5-10.0) in the bagged regression tree model, 7.8°(range: 6.210.0) in the bagged multivariate adaptive regression spline model, and 15.8°(range: 14.3-17.5°) in a linear regression model. In the highest-performing IML model, graft size was the most important predictor with RMSE loss of 6.2, followed by age (RMSE loss = 5.9) and preoperative caudal disk height (RMSE loss = 5.8). Implant size at 110% of the normal adjacent disk height was the optimal cutoff associated with improved ROM.

CONCLUSION: IML models can reliably predict change in ROM after CDA within an average of 7.6 degrees of error. Implants sized comparably with the healthy adjacent disk may maximize ROM.

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Incidence and Risk Factor of Implant Dislocation After Cervical Disk Arthroplasty: A Retrospective Cohort Analysis of 756 Patients

Neurosurgery 93:330–338, 2023

Implant dislocation after cervical disk arthroplasty (CDA) is obviously a critical complication, but no information about the incidence and associated risk factor has been reported.

OBJECTIVE: To investigate the incidence and risk factor of implant dislocation after CDA by a retrospective cohort analysis.

METHODS: A retrospective review of a consecutive series of CDA performed between January 2009 and March 2021 at a single institution was conducted. Analyses of chart records and radiological data established the incidence and associated risk factor of implant dislocation after CDA. A Kaplan-Meier survival estimation of implant survival was performed.

RESULTS: A total of 756 consecutive patients were included in this analysis. Five patients (0.7%) had a migration and even dropout of the artificial disk. The overall cumulative survival rate of the implant reached approximately 99.3% of the 756 patients. Preoperative kyphosis was significantly related to implant dislocation (P = .016), with an odds ratio of 15.013.

CONCLUSION: The incidence of implant dislocation after CDA is as low as 0.7% or 5/756 patients. Preoperative kyphosis significantly increases the risk of postoperative implant dislocation by a factor of 15. The migrating implants could be revealed on radiographs as early as 0.9 to 1.4 months postoperatively and were revised to anterior cervical diskectomy and fusion within half a year. No new event of implant dislocation occurred half a year postoperatively. The overall cumulative survival rate of the implant reached 99.3% of the 756 patients. In conclusion, CDA remains a safe and reliable procedure.

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Quality of Spinal Motion With Cervical Disk Arthroplasty. Computer-aided Radiographic Analysis

J Spinal Disord Tech 2010;23:89–95

Study Design: Kinematic study of a single site in an investigational device exemption trial.

Objective: Evaluate the center of rotation (COR) after Bryan cervical arthroplasty and compare adjacent segment motion after cervical disk arthroplasty and fusion using validated radiographic analysis.

Summary of Background Data: The goal of cervical arthroplasty is to reestablish spinal kinematics after anterior decompression. Excellent maintenance of range of motion has been reported for a variety of the prostheses; however, the manner the prostheses perform this task is different. A parameter that may be as important as range of motion is restoring the quality of motion. One of the important components is the COR that is easily studied biomechanically but has not been reported from in vivo studies. Furthermore, the effects on the quality of motion at adjacent levels have not been studied. The purpose of this study is to determine the quality of motion after Bryan cervical disk arthroplasty at the target level and the adjacent segments.

Methods: The first 48 patients diagnosed with single level cervical disk degenerative disease and associated myelopathy or radiculopathy from a single institution enrolled in the Bryan disk investigational device exemption trial were selected for inclusion. Twenty-two investigational patients and 26 anterior cervical discectomy and fusion controls were evaluated radiographically preoperatively and 3, 6, 12, and 24 months postoperatively. These results were analyzed using Quantitative Motion Analysis software manufactured by Medical Metrics Inc. Kinematic parameters included translation, sagittal rotation, anterior/posterior disk height, and the calculation of the COR both in the sagittal and coronal planes.

Results: At the arthroplasty level, the COR shifted more posterior (0.3 mm, 1% end plate width) and cephalad (4.9 mm, 20% end plate width) compared with the preoperative position, however, this change was not statistically significant (P=0.06). The variability of the COR, however, was less after arthroplasty compared with preoperative values. There was no significant difference in the short term between the adjacent levels after fusion compared with the prosthesis. At later time points (12 and 24 mo), however, the COR was significantly posterior at the level above arthroplasty compared with fusion (P<0.01). COR X was not significantly (P>0.3) different below fusions compared with arthroplasty. Sagittal rotation significantly increased at the level above for both the fusion and prosthesis groups. A trend was noted for increased translation (2.5% end plate width) at the level above a fusion compared with the Bryan disk at 24 months postoperatively, but this did not reach statistical significance.

Conclusions: Sagittal rotation increases above the level of the arthroplasty and fusion. In the long term, the arthroplasty group had a more posterior COR at the level above, compared with the level above a fusion. Translation at the level above a fusion was slightly increased but not statistically compared with the level above the arthroplasty with similar amounts of sagittal rotation (flexion/extension). Although not reaching statistical significance, the COR seemed to shift more posterior and cephalad at the arthroplasty level with less variability compared with the preoperative position.

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