Severe heterotopic ossification after total hip arthroplasty in male patients under 70 years of age: effectiveness of prophylactic protocol

This study aims to evaluate the incidence of clinically significant heterotopic ossification (HO) in primary total hip arthroplasty (THA), comparing outcomes with and without the adoption of an HO prophylactic protocol in male patients under 70 years of age. The prophylactic protocol involved the administration of 50 mg of Indomethacin twice daily for 3 weeks. HO presence was classified according to the Brooker classification system, considering "severe" clinically significant HO (Brooker grade 3 and 4). Two hundred and seventy-nine patients were included in our study, and an overall HO rate of 68.2% versus a rate of 61.5% was found respectively in patients not subjected and subjected to prophylactic protocol, without significant difference (PR 0.062). However, patients not subjected to the HO prophylactic protocol exhibited a severe HO rate of 22.4% compared to 7.7% in the prophylactic group, with a statistically significant difference (P = 0.008). Our study demonstrated that prophylactic protocol adoption is significantly associated with lower rate of severe HO in male patients under 70 years of age. Currently, there are no orthopedic guidelines for the prevention and management of HO after THA, but in the absence of contraindications, the adoption of a prophylactic protocol for HO should always be considered in high-risk patients.