Relatively Low Rate of Heterotopic Ossification Following Primary Total Knee Arthroplasty: A Systematic Review and Meta-analysis

Heterotopic ossification (HO) is abnormal growth of ectopic bone and negatively affects the outcomes after total knee arthroplasty (TKA). This systematic review and meta-analysis were performed to characterize the prevalence and severity of HO after primary TKA. METHODS: A systematic review of the literature was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Patient demographics, publication year, and HO prevalence after a primary TKA were recorded. A meta-analysis was performed to determine the overall prevalence of HO formation, and a subanalysis compared the studies published in different timeframes to determine whether a temporal effect exists for HO prevalence. RESULTS: Two thousand nine hundred eighty-eight patients underwent primary TKA across the included studies. Fourteen percent of patients (9% to 20%; I(2): 93.68%) developed HO postoperatively during a mean follow-up of 40.1 months (11 to 108 months). HO rates seemed to decrease in studies published in more recent years, with a pooled HO prevalence of 5% (0% to 13%; I(2): 92.26%) among studies published in the past 15 years compared with 18% (12% to 25%; I(2): 92.49%) among studies published before then. CONCLUSION: Although studies reported a relatively low overall rate of HO after a primary TKA, the absence of a single, standardized classification system precludes the comparisons of HO severity between studies. Overall, HO prevalence seems to have decreased over time, likely reflecting the changes in perioperative medication protocols.