Incidence of Heterotopic Ossification at 10 years After Cervical Disk Replacement: A Systematic Review and Meta-analysis

Systematic review and meta-analysis. OBJECTIVE. This study aimed to assess the incidence of heterotopic ossification (HO) 10 years after cervical disk replacement (CDR). SUMMARY OF BACKGROUND DATA. HO is a common complication after CDR and may limit the range of motion of the artificial disk. As HO usually progresses slowly, a long-term follow-up is required to better understand its incidence. In recent years, the increasing number of original articles reporting 10-year outcomes gives us the opportunity to better understand the long-term incidence of HO. MATERIALS AND METHODS. We searched PubMed, Medline, Embase, and Cochrane Library databases to identify eligible studies. The incidence of HO was pooled, and subgroup analysis was performed. Meta-regression analyses were conducted to identify factors contributing to heterogeneity. RESULTS. Eleven studies with at least 10 years of follow-up comprising 1140 patients who underwent CDR were included. The pooled incidence of overall HO was 70% (95% CI, 60%–81%) at 10 years postoperatively, 60% (95% CI, 44%–75%) at five or six years postoperatively, and 50% (95% CI, 27%–72%) at one or two years postoperatively. The pooled incidence of severe HO (grade 3 or 4) was 37% (95% CI, 29%–45%), and mild HO (grade 1 to 2) was 30% (95% CI, 17%–44%) at 10 years of follow-up. Pooled range of motion decreased from 8.59° before surgery to 7.40° 10 years after surgery. Subgroup analysis showed that HO incidence differed according to the prosthesis type. The earlier publication was associated with a higher pooled incidence of severe HO in the meta-regression analysis. CONCLUSIONS. This is the first meta-analysis providing detailed information on the pooled 10-year incidence of HO after CDR. The incidence of HO seems to increase with the length of follow-up. LEVEL OF EVIDENCE. 3.