Quantitative analysis of the correlation between preoperative cervical degeneration and postoperative heterotopic ossification after cervical disc replacement: minimum 10-year follow-up data

Predictive Value of Cervical Degenerative Quantitative Scoring System on Postoperative Disc Height Loss After Cervical Disc Replacement

STUDY DESIGN

A retrospective study.

OBJECTIVE

In this study, a cervical degenerative quantitative scoring system was used to identify the risk factors for disc height loss after cervical disc replacement (CDR) and to verify their accuracy.

BACKGROUND

Disc height loss after CDR is drawing much attention. Preoperative cervical degeneration has been proven related to postoperative disc height loss but lacked quantitative verification.

PATIENTS AND METHODS

A total of 160 patients who underwent CDR with the Prestige-LP disc at our hospital between January 2011 and December 2016 were retrospectively reviewed. Disc height loss was defined as a reduction of more than 2 mm from postoperative to the final follow-up. A quantitative scoring system was used to evaluate preoperative degeneration on radiographs. Multivariate logistic regression was applied to determine predictive factors and calculate the logistic regression formula. Moreover, receiver operating characteristic curve analysis was conducted to obtain the optimal cutoff value and the area under the receiver operating characteristic curve [areas under the curve (AUC)].

RESULTS

Study subjects had a mean age of 43.51 ± 8.51 years, with a mean follow-up time of 60.14 ± 12.75 months. The overall incidence rate of disc height loss was 65.62%. Multivariate logistic regression analysis showed that endplate sclerosis ( P = 0.000) and low preoperative disc height ( P = 0.000) were independent risk factors for postoperative disc height loss. In addition, the calculated optimal cutoff point was 1 point of endplate sclerosis (AUC = 0.768) and 4.5 mm of preoperative disc height (AUC = 0.795). The regression formula established by multivariate logistic regression analysis was composed of preoperative disc height (odds ratio: 2.995, P = 0.000) and endplate sclerosis (odds ratio: 18.131, P = 0.000), with an AUC of 0.879.

CONCLUSIONS

Our findings suggest that a comprehensive preoperative assessment is essential when patients with apparent endplate sclerosis and low preoperative disc height are being considered for CDR.

Clinical and Radiological Outcomes of Cervical Disc Arthroplasty in Patients with Modic Change

OBJECTIVE

Modic change (MC) is defined as abnormalities observed in the intervertebral disc subchondral and adjacent vertebral endplate subchondral bone changes. Most studies on MC were reported in the lumbar spine and associated with lower back pain. However, MC has been rarely reported in the cervical spine, let alone in those who underwent cervical disc replacement (CDR). This study aimed to focus on MC in the cervical spine and reveal clinical and radiological parameters, especially heterotopic ossification (HO), for patients who underwent CDR. Furthermore, we illustrated the association between MC and HO.

METHODS

We retrospectively reviewed patients who underwent CDA from January 2008 to December 2019. The Japanese Orthopaedic Association (JOA), Neck Disability Index (NDI), and Visual Analog Scale (VAS) scores were used to evaluate the clinical outcomes. Radiological evaluations were used to conclude the cervical alignment (CL) and range of motion (ROM) of C2-7, functional spinal unit angle (FSUA), shell angle (SA), FSU height, and HO. Univariate and multivariate logistic regressions were performed to identify the risk factors for HO. The Kaplan-Meier (K-M) method was used to analyze potential risk factors, and multivariate Cox regression was used to identify independent risk factors.

RESULTS

A total of 139 patients were evaluated, with a mean follow-up time of 46.53 ± 26.60 months. Forty-nine patients were assigned to the MC group and 90 to the non-MC group. The incidence of MC was 35.3%, with type 2 being the most common. Clinical outcomes (JOA, NDI, VAS) showed no significant difference between the two groups. The differences in C2-7 ROM between the two groups were not significant, while the differences in SA ROM and FSUA ROM were significantly higher in the non-MC than in the MC group (p < 0.05). Besides, FSU height in MC group was significantly lower than that in non-MC group. Parameters concerning CL, including C2-7, FSUA, SA, were not significantly different between the two groups. The incidence of HO and high-grade HO, respectively, in the MC group was 83.7% and 30.6%, while that in the non-MC group was 53.3% and 2.2%, and such differences were significant (p < 0.05). Multivariate logistic regression analyses and Cox regression showed that MC and involved level were significantly associated with HO occurrence (p < 0.05). No implant migration and secondary surgery were observed.

CONCLUSION

MC mainly affected the incidence of HO. Preoperative MC was significantly associated with HO formation after CDR and should be identified as a potential risk factor for HO. Rigorous criteria for MC should be taken into consideration when selecting appropriate candidates for CDR.

The Effect of Preoperative Cervical Spondylosis on Heterotopic Ossification After Cervical Disc Replacement

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

This study aimed to explore the effect of preoperative cervical spondylosis on the heterotopic ossification (HO) formation in different locations after cervical disc replacement (CDR).

METHODS

The degree of preoperative cervical spondylosis was evaluated radiologically, including the intervertebral disc, uncovertebral joints, facet joints and ligaments. The effects of cervical spondylosis on the HO formation after CDR were analyzed according to the location of HO. Multivariate logistic regression was performed to identify the independent factors.

RESULTS

149 patients with a total of 196 arthroplasty segments were involved in this study. HO, anterior HO (AHO), and posterior HO (PHO) developed in 59.69%, 22.96%, and 41.84% levels, respectively. The significant factors in univariate analysis for PHO after CDR included the disc height loss, anterior osteophytes, preoperative uncovertebral joint osteophytes and facet joint degeneration. The incidence of adjacent segment degeneration (ASD) was significantly higher in the PHO group compared to that without PHO at the last follow-up (P = .003). The disc height loss in high-grade HO was significantly more than that in low-grade group (P = .039). Multivariate analysis identified disc height loss was the only independent factor for PHO (P = .009). No significant degenerative factors related to the formation of AHO were found.

CONCLUSIONS

Preoperative cervical spondylosis predominantly affected the HO formation in the posterior disc space after CDR. The disc height loss was an independent risk factor for PHO formation. Rigorous criteria for the extent of preoperative disc height loss should be used when selecting appropriate candidates for CDR.

Current and Expanded Indications for Cervical Disc Arthroplasty: Beyond the FDA IDE Studies

The widespread success of cervical disc arthroplasty (CDA) has led to an interest in expanding indications beyond those outlined in the initial Food and Drug Administration investigational device exemption studies. Some of these off-label indications currently include 3-level and 4-level CDA, hybrid constructs with adjacent segment anterior cervical discectomy and fusion or corpectomy constructs, pre-existing kyphosis, revision of a failed anterior cervical discectomy and fusion to a CDA, CDA in the setting of significant degenerative disc disease and/or facet joint arthropathy, CDA for congenital cervical stenosis, and CDA in the presence of ossification of the posterior longitudinal ligament. This review article will summarize the current literature pertaining to the aforementioned indications.

Diversity in Orthopaedic Surgery Medical Device Clinical Trials: An Analysis of the Food and Drug Administration Safety and Innovation Act

INTRODUCTION

Demographic factors contribute markedly to orthopaedic surgery outcomes. However, women and minorities have been historically excluded from clinical trials. The United States passed the Safety and Innovation Act (Food and Drug Administration Safety and Innovation Act [FDA-SIA]) in 2012 to increase study diversity and mandate reporting of certain demographics. The purpose of this study was to investigate demographic reporting and analysis among high-risk orthopaedic medical device trials and evaluate the effectiveness of the FDA-SIA in increasing diversity of study enrollment.

METHODS

The premarket approval database was queried for all original submissions approved by the Orthopedic Advisory Committee from January 1, 2003, to July 1, 2022. Study demographics were recorded. Weighted means of race, ethnicity, and sex were compared before and after FDA-SIA implementation with the US population.

RESULTS

We identified 51 orthopaedic trials with unique study data. Most Food and Drug Administration device trials reported age (98.0%) and sex (96.1%), but only 49.0% and 37.3% reported race and ethnicity, respectively. Only 23 studies analyzed sex, six analyzed race, and two analyzed ethnicity. Compared with the US population, participants were overwhelmingly White (91.36% vs. 61.63%, P < 0.001) with a significant underrepresentation of Black (3.65% vs. 12.41%, P = 0.008), Asian (0.86% vs. 4.8%, P = 0.030), and Hispanic participants (3.02% vs. 18.73%, P < 0.001) before 2013. The FDA-SIA increased female patient enrollment (58.99% vs. 47.96%, P = 0.021) but did not increase the enrollment of racial or ethnic minorities.

CONCLUSION

Despite efforts to increase the generalizability of studies within the FDA-SIA, orthopaedic medical devices still fail to enroll diverse populations and provide demographic subgroup analysis. The study populations within these trials do not represent the populations for whom these devices will be indicated in the community. The federal government must play a stronger role in mandating study diversity, enforcing appropriate statistical analysis of the demographic subgroups, and executing measures to ensure compliance.

LEVEL OF EVIDENCE

I.

Effects of endplate coverage and intervertebral height change on heterotopic ossification following cervical disc replacement

Background

Heterotopic ossification (HO) is a common complication after cervical disc replacement (CDR). Biomechanical factors including endplate coverage and intervertebral disc height change may be related to HO formation. However, there is a dearth of quantitative analysis for endplate coverage, intervertebral height change and their combined effects on HO.

Methods

Patients who underwent single-level or two-level CDR with Prestige-LP were retrospectively reviewed. Clinical outcomes were evaluated through Japanese Orthopaedic Association (JOA) score, Neck Disability Index (NDI) score, and visual analogue scale (VAS) score. Radiological data, including the prosthesis-endplate depth ratio, intervertebral height change, posterior heterotopic ossification (PHO) and angular parameters, were collected. Logistic regression analysis was used to identify the potential risk factors. Receiver operating characteristic curves were plotted and the cut-off values of each potential factors were calculated.

Results

A total of 138 patients with 174 surgical segments were evaluated. Both the prosthesis-endplate depth ratio (P < 0.001) and post-operative disc height change (P < 0.001) were predictive factors for PHO formation. The area under the curve (AUC) of the prosthesis-endplate depth ratio, disc height change and their combined effects represented by the combined parameter (CP) were 0.728, 0.712 and 0.793, respectively. The risk of PHO significantly increased when the prosthesis-endplate depth ratio < 93.77% (P < 0.001, OR = 6.909, 95% CI 3.521–13.557), the intervertebral height change ≥ 1.8 mm (P < 0.001, OR = 5.303, 95% CI 2.592–10.849), or the CP representing the combined effect < 84.88 (P < 0.001, OR = 10.879, 95% CI 5.142–23.019).

Conclusions

Inadequate endplate coverage and excessive change of intervertebral height are both potential risk factors for the PHO after CDR. Endplate coverage less than 93.8% or intervertebral height change more than 1.8 mm would increase the risk of PHO. The combination of these two factors may exacerbate the non-uniform distribution of stress in the bone-implant interface and promote HO development.