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The Rate of Heterotopic Ossification Following Cervical Disc Arthroplasty: A Systematic Review and Comparison of Data.

STUDY DESIGN
Systematic Review.


OBJECTIVES
The purpose of the current study is to determine the overall incidence of HO following CDA as well as per annum rates.


SUMMARY OF BACKGROUND DATA
CDA is a well-established surgical modality for treatment of one- and two-level degenerative disc disease that has failed conservative treatment. Despite its proven mid-term clinical success, the potential for accelerated HO following CDA remains an area of clinical concern.


METHODS
A MEDLINE literature search was performed using PubMed, the Cochrane Database of Systematic Reviews, and Embase from January 1980 to February 2018. We included studies involving adult patients, who underwent CDA, documentation of HO, with >12 month follow up. The pooled results were obtained by calculating the effect size based on the logit event rate. Per annum rates were determined based on weighted averages according to average follow-up period.


RESULTS
The initial database review resulted in 230 articles, with 19 articles that met inclusion and exclusion criteria. These pooled results included 2,151-disc levels and 1,732 patients (50% men and 50% women) that underwent CDA and were evaluated for postoperative HO. The mean age was 45 years with a mean follow-up of 60 months. Sixteen studies reported the occurrence of severe HO resulting in 22.8% of disc levels developing severe HO. When stratifying these studies based on funding type, severe HO was reported at a rate of 21.6% by IDE studies and 27.9% by independent studies.


CONCLUSION
The findings of the pooled data show the incidence of severe HO following CDA to be 22.8%. However, there is a significant difference in reported rates of mild and severe HO between IDE and independent data. This alludes to possible underreporting of HO and severity of HO in the industry sponsored IDE studies when compared to independent studies.


LEVEL OF EVIDENCE
2.