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.

Comparison of clinical outcomes between cervical disc arthroplasty and anterior cervical discectomy and fusion for the treatment of single-level cervical spondylosis: a 10-year follow-up study

The Spine Journal 23 (2023) 361−368

The theoretical advantage of cervical disc arthroplasty includes preserved motion at the cervical level, which may reduce degeneration of the adjacent segments. The long-term follow-up results are still controversial.

PURPOSE: The present study aimed to retrospectively study the long-term efficacy and complications of cervical disc arthroplasty using a single commercially-available device in a single center.

STUDY DESIGN: This was a propensity-score matched cohort study.

PATIENT SAMPLE: This study enrolled 148 single-level cervical degenerative disease patients from January 2009 to March 2012. After 1:1 propensity score matching, 39 patients remained in the ACDF or ACDR groups.

OUTCOME MEASURES: The outcome measures were neurological functions (Neck Disability Index (NDI) and Japan Orthopedic Association (JOA) scores), radiographic evaluations (cervical curvature, operative segment range of motion, degenerative condition of adjacent segments, heterotopic ossification (HO) of the surgical segment), and complications.

METHODS: NDI and JOA scores were used to evaluate patient neurological functions. Cervical curvature (C2-C7 Cobb angle) and operative segment range of motion (ROM) were compared between the two groups. Grading criteria for osteophyte formation were used to evaluate the degenerative condition of adjacent segments. HO after ACDR was graded according to the McAfee grading method.

RESULTS: The average follow-up time was 119.3 §17.2 months. Satisfactory improvements in neurological function were obtained for both the ACDR and ACDF groups. There were no significant differences in VAS or NDI scores between the two groups. In the ACDR group, the ROM of the operative segment increased from 6.7 §4.3˚ before the operation to 8.9 §3.5˚ on the second day after the operation (p<.001). The ROM of the operative segment was 8.1 §4.0˚ at the 1-year follow-up, 7.2 §3.6˚ at the 2-year follow-up, 5.7 §4.5˚ at the 5-year follow-up and 4.3 §3.9˚ at the last follow-up. ASD was more likely to develop in the caudal adjacent segments and progressed with the follow-up time. At the last follow-up, HO was present in 27 patients (69.23%), while high-grade HO (McAfee scores III and IV) was detected in 6 patients (15.38%).

CONCLUSIONS: Through nearly 10 years of follow-up, ACDR was as effective as ACDF for treating single-level degenerative cervical disc disease. However, HO and the role of ACDR in the protection of ASD remains to be further observed and followed up.

Long-term results of the NECK trial—implanting a disc prosthesis after cervical anterior discectomy cannot prevent adjacent segment disease

The Spine Journal 23 (2023) 350−360

Motion preserving anterior cervical disc arthroplasty (ACDA) in patients with cervical radiculopathy was introduced to prevent symptomatic adjacent segment disease as compared to anterior cervical discectomy and fusion (ACDF).

PURPOSE: To evaluate the long-term outcome in patients with cervical radiculopathy due to a herniated disc undergoing ACDA, ACDF or ACD (no cage, no plate) in terms of clinical outcome measured by the Neck Disability Index (NDI). Likewise, clinically relevant adjacent segment disease is assessed as a long-term result.

STUDY DESIGN: Double-blinded randomized controlled trial.

PATIENT SAMPLE: A total of 109 patients with one level herniated disc were randomized to one of the following treatments: ACDA, ACDF with intervertebral cage, ACD without cage.

OUTCOME MEASURES: Clinical outcome was measured by patients’ self-reported NDI, Visual Analogue Scale (VAS) neck pain, VAS arm pain, SF36, EQ-5D, perceived recovery and reoperation rate. Radiological outcome was assessed by radiographic cervical curvature and adjacent segment degeneration (ASD) parameters at baseline and up until five years after surgery.

METHODS: To account for the correlation between repeated measurements of the same individual Generalized Estimated Equations (GEE) were used to calculate treatment effects, expressed in difference in marginal mean values for NDI per treatment group.

RESULTS: Clinical outcome parameters were comparable in the ACDA and ACDF group, but significantly worse in the ACD group, though not reaching clinical relevance. Annual reoperation rate was 3.6% in the first two years after surgery, declined to 1.9% in the years thereafter. The number of reoperations for ASD was not lower in the ACDA group, while the number of reoperations at the index level was higher after ACD, when compared to ACDF and ACDA.

CONCLUSIONS: A persisting absence of clinical superiority was demonstrated for the cervical disc prosthesis five years after surgery. Specifically, clinically relevant adjacent level disease was not prevented by implanting a prosthesis. Single level ACD without implanting an intervertebral device provided worse clinical outcome, which was hypothesized to be caused by delayed fusion. This stresses the need for focusing on timely fusion in future research.

Longitudinal assessment of segmental motion of the cervical spine following total disc arthroplasty: a comparative analysis of devices

J Neurosurg Spine 37:556–562, 2022

Total disc arthroplasty (TDA) has been shown to be an effective and safe treatment for cervical degenerative disc disease at short- and midterm follow-up. However, there remains a paucity of literature reporting the differences between individual prosthesis designs with regard to device performance. In this study, the authors evaluated the longterm maintenance of segmental range of motion (ROM) at the operative cervical level across a diverse range of TDA devices.

METHODS In this study, the authors retrospectively evaluated all consecutive patients who underwent 1- or 2-level cervical TDA between 2005 and 2020 at a single institution. Patients with a minimum of 6 months of follow-up and lateral flexion/extension radiographs preoperatively, 2 months postoperatively, and at final follow-up were included. Radiographic measurements included static segmental lordosis, segmental range of motion (ROM) on flexion/extension, global cervical (C2–7) ROM on flexion/extension, and disc space height. The paired t-test was used to evaluate improvement in radiographic parameters. Subanalysis between devices was performed using one-way ANCOVA. Significance was determined at p < 0.05.

RESULTS A total of 85 patients (100 discs) were included, with a mean patient age of 46.01 ± 8.82 years and followup of 43.56 ± 39.36 months. Implantations included 22 (22.00%) M6-C, 51 (51.00%) Mobi-C, 14 (14.00%) PCM, and 13 (13.00%) ProDisc-C devices. There were no differences in baseline radiographic parameters between groups. At 2 months postoperatively, PCM provided significantly less segmental lordosis (p = 0.037) and segmental ROM (p = 0.039). At final follow-up, segmental ROM with both the PCM and ProDisc-C devices was significantly less than that with the M6-C and Mobi-C devices (p = 0.015). From preoperatively to 2 months postoperatively, PCM implantation led to a significant loss of lordosis (p < 0.001) and segmental ROM (p = 0.005) relative to the other devices. Moreover, a significantly greater decline in segmental ROM from 2 months postoperatively to final follow-up was seen with ProDiscC, while segmental ROM increased significantly over time with Mobi-C (p = 0.049).

CONCLUSIONS Analysis by TDA device brand demonstrated that motion preservation differs depending on disc design. Certain devices, including M6-C and Mobi-C, improve ROM on flexion/extension from preoperatively to postoperatively and continue to increase slightly at final follow-up. On the other hand, devices such as PCM and ProDisc-C contributed to greater segmental stiffness, with a gradual decline in ROM seen with ProDisc-C. Further studies are needed to understand how much segmental ROM is ideal after TDA for preservation of physiological cervical kinematics.


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