Incidence of heterotopic ossification in minimally invasive short-stem THA using the modified anterolateral approach.

Introduction: Heterotopic ossification (HO) is known to be a common complication after total hip arthroplasty (THA). The minimal invasive (MIS) modified anterolateral approach has become popular in combination with a short stem. We analysed the incidence of HO following short-stem THA using this approach in combination with a postoperative administration of nonsteroidal anti-inflammatory drugs (NSAIDs).
Materials and Methods: 216 short stems were implanted in 162 patients. NSAIDs were administered for 2 weeks after surgery in 154 patients (95.1%). Standardised pre- and postoperative radiographic imaging was done at 2-year follow-up. HO was analysed according to the Brooker classification. Influence of age, gender, body mass index (BMI), and blood transfusion were analysed. Harris Hip Score (HHS) and visual analogue scale (VAS) of satisfaction were assessed. Operation time and blood-transfusion rate was documented. Short-term gastrointestinal side effects were recorded.
Results: The overall incidence of HO was 7.8% (16 cases). HO Brooker type 3 and 4 occurred in only 1 case (0.5%). No correlation with age, gender or BMI was revealed. HHS improved largely from 45.8 (SD 15.9) before surgery to 98.1 (SD 4.7) after a minimum of 2 years. At that point VAS satisfaction was 9.7 (SD 0.9). Mean operative time was 45.8 minutes (SD 18.7). 12 patients (7.4%) received at least 1 blood-transfusion. Gastrointestinal side effects occurred in 13 of 154 patients (8.4%).
Conclusions: The combination of short-stem THA, the MIS modified anterolateral approach and a postoperative application of NSAIDs resulted in the effective prevention of HO and excellent clinical results.