Differences in Heterotopic Ossification Rates Between Implant Types After Cervical Disc Arthroplasty

Introduction: Cervical disc arthroplasty (CDA) is widely used in patients with degenerative spine disease to preserve cervical motion, a key advantage over traditional fusion. However, heterotopic ossification (HO), the abnormal formation of bone in soft tissue, is an adverse complication that can mitigate this advantage. Despite the variety of implant types available to surgeons, there is limited knowledge about the differences in HO rates among them. Therefore, this study evaluated overall and clinically significant HO rates in CDA patients between implant types.

Methods: The PubMed, Google Scholar, and EBSCO databases were queried for studies evaluating HO rates by implant type. Eligible studies focused on overall and clinically significant HO (McAfee Grades III and IV) with 2-5 years of postoperative follow-up in single- and/or two-level CDA patients. Data was aggregated and analyzed using a random effects model on a computerized manager and reported as odds ratios (OR) with a 95% confidence interval (CI). Outlier rates greater than three standard deviations from the mean were excluded.

Results: Final analysis included 20 studies with over 2,000 patients and 4 implant types. For overall HO, rates of HO in the Bryan CDA implant (OR: 0.02; 95% CI: 0.004-0.083) were markedly lower compared to the Prestige (OR: 0.18; 95% CI: 0.087-0.335) and Discover (OR: 0.12; 95% CI: 0.082-0.173) implant, which both had statistically similar rates. For clinically significant HO, the Bryan CDA implant (OR: 0.006; 95% CI: 0.001-0.036) had the lowest rate followed by the Mobi-C implant (OR: 0.21; 95% CI: 0.168- 0.256) and the Prestige Implant (OR: 0.35; 95% CI: 0.303-0.398)

Conclusion : These findings suggest that the Bryan CDA implant demonstrates lower rates of HO compared to other implant types. Further research is warranted to explore mechanisms by which factors, such as implant material and surgical techniques, may influence the differing rates of HO among various implants.