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

Abstract

Study design: 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.

Figure 1

Flow diagram of the selection of the studies. HO indicates heterotopic ossification.

Figure 2

The pooled incidence of overall heterotopic ossification at 10 years postoperatively (A), five or six years postoperatively (B), and one or two years postoperatively (C).

Figure 3

The pooled incidence of severe HO (A) and mild HO after 10 years of follow-up (B). HO indicates heterotopic ossification.

Figure 4

Subgroup analyses of the incidence of overall heterotopic ossification based on study design (A), prosthesis type (B), and funding source 10 years postoperatively (C).

Figure 5

Funnel plots of the meta-analysis for overall heterotopic ossification (HO) (A) and severe HO (B).