Incidence and risk factors for heterotopic ossification following periprosthetic joint infection of the hip

Introduction Heterotopic ossifications (HOs) commonly occur following total hip arthroplasty. Data regarding the appearance of HO after periprosthetic joint infection (PJI) of the hip are rare. Therefore, the aim of this study was to analyze the incidence and potential risk factors for the development of HO in patients with PJI of the hip. Materials and methods We performed a single-center, retrospective study including patients treated with a two- or multistage operation and patients undergoing salvage procedure in cases of PJI of the hip with a minimum follow-up of 6 months. A total of 150 patients were included in the analysis. The Brooker-scale was used to classify HO. Patients were divided in three groups: (1) No HO, (2) HO Brooker type 1-4, and (3) high-grade HO (HO Brooker type 3 and 4). In each group, we checked possible risk factors for the development of HO for statistical significance. Results Patients included in our study had a mean age of 70.4 +/- 12.1 years. Of all patients, 75 were women (50%). HOs could be found in 70 patients (46.7%). Twenty-seven patients showed HO Brooker type 1, 23 type 2, 15 type 3 and 5 type 4. Male gender [odds ratio (OR) 2.14; p = 0.022], smoking (OR 5.75; p = 0.025) were significant risk factors for HO. A chronic infection (OR 3.54; p = 0.029) and a higher number of procedures (p = 0.009) were significant risk factors for the development of high-grade HO. Conclusions HOs often occur following surgical care of PJI. Male gender, smoking, a chronic infection and high number of operations are risk factors for developing HO after PJI.