Cervical total disc arthroplasty

Primary Cervical Disc Arthroplasty Among Medicare Beneficiaries Versus Alternative Payers: Is It Time to Consider Nationwide Coverage?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

As of 2022, the Centers for Medicare and Medicaid Services does not provide nationwide coverage for cervical disc arthroplasty (CDA). The aim was to determine whether Medicare beneficiaries have differences in: (1) lengths of stay (LOS); (2) complications; (3) readmissions; and (4) costs of care.

METHODS

Using the 2010 to 2020 PearlDiver database, we queried patients undergoing primary CDA for degenerative disc pathology. Study groups patients were those undergoing CDA with Medicare coverage (n = 1467); patients without Medicare coverage were the comparison cohort (n = 15,389). Endpoints were to compare demographics and comorbidities within the Elixhauser comorbidity index (ECI), LOS, 90-day complications, 90-day readmissions, and 90-day reimbursements. A multivariate logistic regression was used to calculate odds (OR) of medical complications and readmissions within 90-days. A P-value less than .003 was significant.

RESULTS

Patients with Medicare coverage undergoing CDA had higher mean ECI compared to alternative payers (5.24 vs 3.26; P < .0001). Mean LOS was significantly higher for Medicare beneficiaries (2.20 vs 1.76 days; P < .010). There was no significant differences in odds of all medical complications (OR: 1.19, 95% CI: .98-1.44; P = .069) or readmission rates (1.77% vs 1.33%, OR:0.82, 95% CI: .50-1.29; P = .417) within 90-days following the index procedure among Medicare beneficiaries vs alternative payers. Non-Medicare beneficiaries had higher 90-day reimbursements compared to Medicare beneficiaries ($6,700 vs $7,086,P < .001).

CONCLUSIONS

Medicare beneficiaries despite having slightly longer lengths of stay did not have higher rates of medical complications or readmissions. Surgeons and policy makers may use this data to consider alternative treatments in Medicare patients.

Intervertebral kinematics during neck motion 6.5 years after fusion and artificial disc replacement

BACKGROUND

Arthroplasty with artificial disc replacement for surgical treatment of cervical spine degeneration was introduced with the notion that motion-preserving approaches would prevent development of adjacent segment disease. Though clinical outcomes favor arthroplasty over the commonly used anterior cervical discectomy with fusion approach, clinical studies confirming the biomechanical basis of these results are lacking. The aim of this study was to compare intervertebral kinematics between arthroplasty and fusion patients 6.5 years post-surgery during physiological motion of the neck.

METHODS

Using a biplane dynamic X-ray system, computed tomography imaging and model based tracking algorithms, three dimensional intervertebral kinematics were measured during neck axial rotation and extension in 14 patients treated for cervical radiculopathy with fusion (n = 8) or arthroplasty (n = 6). The measurements were performed at 2-year (baseline) and 6.5 year post-surgical time points, with the main interest being in the interaction between surgery types and time points. 3 translations and 3 rotations were investigated for the index (C5C6), and upper- (C4C5) and lower adjacent levels (C6C7).

FINDINGS

Surgery-time interaction was significant for axial rotation (P < 0.04) and flexion-extension rotation (P < 0.005) in C4C5 during neck axial rotation, left-right translation (P < 0.04) in C5C6 and anterior-posterior translation in C6C7 (P < 0.04) during neck extension. In contrast with the expectations, axial rotation and flexion-extension decreased in C4C5 during neck rotation and anterior-posterior translation decreased in C6C7 during neck extension for fusion.

INTERPRETATION

The findings do not support the notion that adjacent segment motion increases after fusion.

Top 100 Cited Articles on Spinal Disc Arthroplasty Research

STUDY DESIGN

A bibliometric review of current literature.

OBJECTIVE

The purpose of this study was to identify and analyze the 100 most cited articles in spinal disc arthroplasty (SDA) research.

SUMMARY OF BACKGROUND DATA

In the last several decades, SDA has been widely performed all over the world, with increasing popularity of cervical disc arthroplasty (CDA). While there is a large number of articles on this topic, to our knowledge, there is no bibliometric analysis yet.

METHODS

All databases from the Web of Science were searched in a three-step approach. The information of the 100 most cited studies was collected, including title, first and last author, year of publication, journal, total citations, geographic origin, subspecialty, and types of artificial intervertebral disc for further analysis.

RESULTS

The 100 most-cited articles were published from 1966 to 2015 in 9 different journals and were cited from 66 to 346 times. A total of 11 countries contributed to the 100 articles and the United States topped the list, with 54 articles, followed by Germany and France, with 10 and nine articles, respectively. There were more studies in CDA (n = 53) than lumbar disc arthroplasty (n = 35). Most of the studies reported clinical and radiographic outcomes (n = 33). The most productive periods were from 2006 to 2010. The majority of publications were in Spine, which published 43 articles. In total, 12 authors published more than two articles on the list.

CONCLUSION

Of the top 100 most cited articles on SDA, cervical papers outnumbered lumbar articles and the United States had 55 articles, with no other countries having more than 10. Our paper can help readers determine which of the thousands of articles on this topic are the most impactful and important ones to be familiar with.

LEVEL OF EVIDENCE

3.

Cervical disc arthroplasty versus anterior cervical discectomy and fusion: a meta-analysis of rates of adjacent-level surgery to 7-year follow-up

Background

Anterior cervical discectomy and fusion (ACDF) is an effective treatment for cervical spondylosis. A limitation of ACDF is the risk of adjacent-segment degeneration (ASD), owing to arthrodesis of a motion segment. Cervical disc arthroplasty (CDA) has hence garnered significant attention; yet, compelling evidence of reduction in ASD requiring surgery is lacking. This systematic review and meta-analysis sought to compare long-term longitudinal adjacent-level operation rates with CDA versus ACDF.

Methods

An electronic literature search was conducted. Eligible studies were multi-center randomized controlled trials (RCTs) comparing CDA with ACDF for one- or two-level symptomatic cervical spondylosis. The primary outcome was adjacent-level operation. Index-level reoperation was a secondary outcome. Outcomes were evaluated at 1-year intervals from the index operation to last reported follow-up by random-effects meta-analyses.

Results

Eleven RCTs met criteria. For one-level spondylosis, there was no difference in the rate of adjacent-level operation between CDA (2.3%) and ACDF (3.6%) at 2 years. However, a large difference favoring CDA became evident at 5 years and persisted at 7 years (4.3% vs. 10.8%, P<0.001). Significantly fewer patients who underwent CDA required index-level reoperation at all time points out to 7 years (5.2% vs. 12.7%, P<0.001). Similar to one-level operations, there was no significant difference in adjacent-level operations with two-level CDA (1.7%) versus two-level ACDF (3.4%) at 2 years. At 7 years, a significant difference favoring CDA became apparent (5.1% vs. 10.0%, P=0.014). Two-level CDA resulted in fewer index-level reoperations out to 7 years (4.2% vs. 13.5%, P<0.001).

Conclusions

In this meta-analysis, the short-term rate of adjacent-level operation was similar with CDA or ACDF. However, around 5 years, a statistically significant divergence emerged, where the rate of adjacent-level surgery rose steeply for ACDF. Index-level reoperations were less frequent with CDA in both the short- and long-term. These data indicate CDA may have a superior longevity to ACDF with regard to need for subsequent adjacent-level operation.

NuNec™ Cervical Disc Arthroplasty Improves Quality of Life in Cervical Radiculopathy and Myelopathy: A 2-yr Follow-up

BACKGROUND

Anterior cervical disc replacement is an alternative to fusion for the treatment of selected cases of radiculopathy and myelopathy. We report clinical and radiological outcomes after disc replacement with the NuNec™ artificial cervical disc (Pioneer® Surgical Technology, Marquette, Michigan) with subgroup analysis.

OBJECTIVE

To review clinical and radiological outcomes after anterior cervical disc replacement with the NuNec™ artificial cervical disc.

METHODS

A consecutive case series of patients undergoing cervical disc replacement with the NuNec™ artificial disc was conducted. Clinical outcomes were assessed by questionnaires preoperatively and up to 2 yr postoperatively including neck and arm pain, Neck Disability Index, Euroqol 5-dimensions, and Short Form-36; x-rays from the same period were analyzed for range of movement and presence of heterotopic ossification.

RESULTS

A total of 44 NuNec™ discs were implanted in 33 patients. Clinical improvements were seen in all outcomes; significant improvements on the Neck Disability Index, Euroqol 5-dimensions, and physical domain of the Short Form-36 were maintained at 2 yr. There was a mean of 4° range of movement at the replacement disc level at 2 yr, a significant reduction from baseline; there was also progression in levels of heterotopic ossification. Complications included temporary dysphagia (10%) and progression of disease requiring foraminotomy (6%); no surgery for adjacent level disease was required. There was no significant difference in the outcomes of the radiculopathy and myelopathy groups.

CONCLUSION

Clinical outcomes using the NuNec™ disc replacement are comparable with other disc replacements. Although the range of movement is reduced, the reoperation rate is very low.

Current practice of cervical disc arthroplasty: a survey among 383 AOSpine International members

OBJECTIVE

The use of cervical disc arthroplasty (CDA) in spinal practice is controversial. This may be explained by the lack of studies with a large sample size and long-term outcomes. With this survey the authors aimed to evaluate the opinions of spine surgeons on the use of CDA in the current treatment of cervical disc herniation (CDH).

METHODS

A web-based survey was sent to all members of AOSpine International by email using SurveyMonkey on July 18, 2016. A single reminder was sent on August 18, 2016. Questions included geographic location; specialty; associated practice model; number of discectomies performed annually; the use of CDA, anterior cervical discectomy (ACD), and anterior cervical discectomy and fusion (ACDF); and the expectations for clinical outcomes of these procedures.

RESULTS

A total of 383 questionnaires were analyzed. Almost all practitioners (97.9%) were male, with a mean of 15.0 ± 9.7 years of clinical experience. The majority of responders were orthopedic surgeons (54.6%). 84.3% performed ACDF as the standard technique for CDH. 47.8% of the surgeons occasionally used CDA, whereas 7.3% used CDA as standard approach for CDH. The most common arthroplasty device used was the ProDisc-C. Low evidence for benefits and higher costs were the most important reasons for not offering CDA. The risk of adjacent-level disease was considered smaller for CDA as compared with ACDF. However, ACDF was expected to have the highest effectiveness on arm pain (87.5%), followed by CDA (77.9%), while ACD had the least (12.6%).

CONCLUSIONS

In this survey, CDA was not considered to be the routine procedure to treat CDH. Reported benefits included the reduced risk of adjacent-level disease and preservation of motion of the neck. Lack of enough evidence on its effectiveness as well as higher costs were considered to be disadvantages of CDA. More research should be conducted on the implementation impact of CDA and the cost-effectiveness from society's perspective.