Bryan cervical disc prosthesis: 12-month clinical outcome

Prevalence of and Risk Factors for Heterotopic Ossification After Cervical Total Disc Replacement: A Systematic Review and Meta-Analysis

STUDY DESIGN

A systematic review and meta-analysis.

OBJECTIVES

The results from previous meta-analyses are limited by the small number of included studies. Moreover, the risk factors of heterotopic ossification (HO) have not been well studied. Therefore, this study aims to estimate the prevalence of HO after cervical total disc replacement (CTDR) at different follow-up time points and explore potential risk factors for HO.

METHODS

We searched databases to identify eligible studies that reported the rate of HO after CTDR. The pooled prevalence of HO, according to different grades of HO, length of follow-up and types of prosthesis, and 95% confidence intervals (CIs) were calculated. Multivariable meta-regression analyses were performed to identify factors that may contribute to the heterogeneity between estimates.

RESULTS

Of the 94 studies included, 82 studies reported an overall rate of HO, encompassing a total of 5861 cervical spinal levels that underwent CTDR. The overall pooled prevalence of HO was 32.5% (95% CI 26.7% to 38.4%). Single-level CTDR was associated with a higher overall rate of HO. When the rate of HO was stratified by McAfee/Mehren classification, the pooled prevalence of range of motion (ROM)-limiting HO was 11.0% (95% CI 9.2% to 12.8%). Latest publication, single-level CTDR, longer follow-up period, and studies published outside were associated with a higher rate of ROM-limiting HO.

CONCLUSIONS

We provide a comprehensive overview of the prevalence of different grades of HO. This meta-analysis also identifies and rules out some risk factors for HO after CTDR.

Cervical Total Disc Replacement and Heterotopic Ossification: A Review of Literature Outcomes and Biomechanics

Anterior cervical discectomy and fusion (ACDF) immobilizes surgical segments and can lead to the development of adjacent segment degeneration and adjacent segment disease. Thus, cervical total disc replacement (CTDR) has been developed with the aim to preserve the biomechanics of spine. However, heterotopic ossification (HO), a complication following CTDR, can reduce the segmental range of motion (ROM) and defects the motion-preservation benefit of CTDR. The pathological process of HO in CTDR remains unknown. HO has been suggested to be a self-defense mechanism in response to the non-physiological biomechanics of the cervical spine following CTDR. The current literature review is concerned with the association between the biomechanical factors and HO formation and the clinical significance of HO in CTDR. Endplate coverage, disc height, segmental angle, and center of rotation may be associated with the development of HO. The longer the follow-up, the higher the rate of ROM-limiting HO. Regardless of the loss of motion-preservation benefit of CTDR in patients with HO, CTDR confers patients with a motion-preservation period before the development of ROM-limiting HO. This may delay the development of adjacent segment degeneration compared with ACDF. Future clinical studies should explore the association between HO and changes in biomechanical factors of the cervical spine.

Cervical arthroplasty with ROTAIO® cervical disc prosthesis: first clinical and radiographic outcome analysis in a multicenter prospective trial

Background

Cervical Disc Arthroplasty (CDA) seems to be an alternative to Anterior Cervical Decompression and Fusion (ACDF) and was developed to minimize the risk of Adjacent Segment Disease (ASD). The ROTAIO Cervical Disc Prosthesis represents a new unconstrained implant with a variable centre of rotation which should enable physiological facet-guided movement. The aim of this current study was to evaluate the clinical outcomes after arthroplasty using ROTAIO Cervical Disc Prosthesis.

Method

Twenty-seven female and 18 male patients (n = 45) with a mean age of 43.7 ± 7.8 years were prospectively followed up for a maximum of 24 month. Clinical outcomes were assessed by Neck Disability Index (NDI), visual analogue scale (VAS) scores for neck and arm pain, patients´ overall satisfaction and the usage of analgesics. Additionally, radiographic information including ROM of the functional spinal unit (FSU) and signs of adjacent segment disease were recorded.

Results

NDI and VAS scores showed significant improvement 6 months after surgery and at last follow-up (p < 0.001). Concerning overall satisfaction 95.7 % of the patients showed good to excellent results at the last visit and a significant reduction of analgesic usage was observed (p < 0.001). Radiographic measurements showed a mean increase of ROM up to 8.40° in the treated FSU at last follow-up (p < 0.001). No signs of anterior migration or dislocation of the prosthesis and no subsidence was recorded radiographically. There were no major complications and a low rate of secondary procedures (2.2 %).

Conclusion

In the 24-months follow-up the ROTAIO Cervical Disc Prosthesis provided excellent clinical and radiographical results and seems to be safe and effective for the treatment of symptomatic single-level degenerative disc disease.

Cervical spine alignment in disc arthroplasty: should we change our perspective?

PURPOSE

The alignment at the cervical spine has been considered a determinant of degeneration at the adjacent disc, but this issue in cervical disc replacement surgery is poorly explored and discussed in this patient population. The aim of this systematic review is to compare anterior cervical fusion and total disc replacement (TDR) in terms of preservation of the overall cervical alignment and complications.

METHODS

A systematic review of the current literature was performed, together with the evaluation of the methodological quality of all the retrieved studies.

RESULTS

In most of the retrieved studies, a tendency towards a more postoperative kyphotic alignment in TDR was reported. The reported mean complication rate was of 12.5 % (0-66.2 %). Complications associated with cervical prosthesis included heterotopic ossification, device migration, mechanical instability, failure, implant removal, reoperations and revision.

CONCLUSIONS

Even though cervical disc arthroplasty leads to similar outcomes compared to arthrodesis in the middle term follow-up, no evidence of superiority of cervical TDR is available up to date. We understand that the overall cervical alignment after TDR tends towards the loss of lordosis, but only longer follow-up can determine its influence on the clinical results.

Parameters that effect spine biomechanics following cervical disc replacement

Total disc replacement (TDR) is expected to provide a more physiologic alternative to fusion. However, long-term clinical data proving the efficacy of the implants is lacking. Limited clinical data suggest somewhat of a disagreement between the in vitro biomechanical studies and in vivo assessments. This conceptual paper presents the potential biomechanical challenges affecting the TDR that should be addressed with a hope to improve the clinical outcomes and our understanding of the devices. Appropriate literature and our own research findings comparing the biomechanics of different disc designs are presented to highlight the need for additional investigations. The biomechanical effects of various surgical procedures are analyzed, reiterating the importance of parameters like preserving uncinate processes, disc placement and its orientation within the cervical spine. Moreover, the need for a 360° dynamic system for disc recipients who may experience whiplash injuries is explored. Probabilistic studies as performed already in the lumbar spine may explore high risk combinations of different parameters and explain the differences between "standard" biomechanical investigations and clinical studies. Development of a patient specific optimized finite element model that takes muscle forces into consideration may help resolve the discrepancies between biomechanics of TDR and the clinical studies. Factors affecting long-term performance such as bone remodeling, subsidence, and wear are elaborated. In vivo assessment of segmental spine motion has been, and continues to be, a challenge. In general, clinical studies while reporting the data have placed lesser emphasis on kinematics following intervertebral disc replacements. Evaluation of in vivo kinematics following TDR to analyze the quality and quantity of motion using stereoradiogrammetric technique may be needed.

Artificial cervical disc arthroplasty: a systematic review

STUDY DESIGN

Systematic Review.

OBJECTIVE

(1) To qualitatively analyze the literature on the efficacy and effectiveness of artificial cervical disc arthroplasty (ACDA). (2) To highlight methodological and reporting issues of randomized controlled trials (RCT) reports on effectiveness of ACDA compared to cervical fusion.

SUMMARY OF BACKGROUND DATA

ACDA is an alternate surgical procedure that may replace cervical fusion in selected patients suffering from cervical degenerative disc disease.

METHODS

We searched seven electronic databases, including MEDLINE, Cochrane Library, and EMBASE, unpublished sources, and reference lists for studies on the efficacy and effectiveness of ACDA compared to cervical fusion--the surgical standard of care for patients with cervical degenerative disc disease.

RESULTS

A total of 622 studies were retrieved, of which 18 (13 case series, four RCT reports, one nonrandomized comparative study) met the inclusion criteria for this review. The four RCTs and the nonrandomized comparative study concluded that the effectiveness of ACDA is not inferior to that of cervical fusion in the short term (up to 2-yr follow-up). The safety profile of both procedures appears similar. The case series reviewed noted improved clinical outcomes at 1 or 2 years after one or multiple-level ACDA.

CONCLUSION

ACDA is a surgical procedure that may replace cervical fusion in selected patients suffering from cervical degenerative disc disease. Within 2 years of follow-up, the effectiveness of ACDA appears similar to that of cervical fusion. Weak evidence exists that ACDA may be superior to fusion for treating neck and arm pain. Future studies should report change scores and change score variance in accordance with RCT guidelines, in order to strengthen credibility of conclusions and to facilitate meta-analyses of studies.

A clinical analysis of 4- and 6-year follow-up results after cervical disc replacement surgery using the Bryan Cervical Disc Prosthesis

OBJECT

In this study, long-term results are presented from clinical studies of the Bryan Cervical Disc Prosthesis at University Hospital Gasthuisberg in Leuven, Belgium. A total of 98 patients (89 with 1-level and 9 with 2-level implantations) agreed to participate in follow-up studies for up to 10 years postoperatively. This article focuses on the 4- and 6-year results. Patients in one of the clinical studies had either radiculopathy or myelopathy associated with spondylosis and/or disc herniations that did not respond to conservative treatment. Patients from the other clinical study received commercially available Bryan devices and the study protocol did not have specific inclusion/exclusion criteria. More than 90% of the patients were considered to have radiculopathy.

METHODS

Clinical measurements discussed in the article include the 36-Item Short Form Health Survey, Neck Disability Index, numerical ratings of neck and arm pain, neurological outcomes, and Odom classification. Angular motion findings from lateral flexion-extension radiographs are also presented. The occurrence of adverse events and second surgeries are examined as an indicator of device safety.

RESULTS

The clinical outcomes at 4 and 6 years postoperatively appear consistent with the previously reported results at 1 and 2 years postoperatively. The mean angular motion results at 4 and 6 years postoperatively for 1-level patients were 7.3 and 7.7 degrees, respectively. Two-level patients had slightly less motion at 4 and 6 years postoperatively with mean caudad values of 5.7 and 6.0 degrees, respectively, and cephalad values of 4.2 and 6.2 degrees, respectively. Efforts were made to capture adverse events, regardless of their nature and relatedness to the study surgery. This effort resulted in a relatively high number of recorded events. However, only 6 patients experienced events that were judged by the investigator to be related, either possibly or definitely, to the Bryan device. These events included device migration, device removal, and hoarseness and vocal cord paralysis, as well as 3 cases involving pain and neurological symptoms. Eight patients underwent further neck surgery to treat symptoms.

CONCLUSIONS

The favorable clinical and angular motion outcomes that were previously noted at 1- and 2-years' follow-up after cervical disc replacement with the Bryan Cervical Disc Prosthesis appear to persist after 4 and 6 years of follow-up.