Which two strategies are commonly used to prevent heterotopic ossification after hip arthroplasty?

• A. Meticulous soft tissue handling and minimizing periarticular trauma.
• B. Early aggressive physical therapy and high-dose steroids.
• C. Prophylactic NSAIDs and/or postoperative radiotherapy.
• D. Prolonged bed rest and immobilization.

Answer: (C)

Heterotopic ossification after hip arthroplasty is driven by inflammatory processes that promote bone formation in soft tissues around the joint. The most effective and commonly used preventive approaches target these pathways: using prophylactic NSAIDs to blunt inflammatory prostaglandin signaling, and delivering postoperative radiotherapy to inhibit the activity of cells that would form ectopic bone. NSAIDs (for example, indomethacin) reduce prostaglandin synthesis, which lowers the stimulus for osteogenesis in periarticular tissues. Radiotherapy, typically a single perioperative dose delivered within a few days after surgery, interferes with mesenchymal cell proliferation and osteoblastic differentiation in the periarticular space, decreasing both the incidence and severity of HO. While good surgical technique and early rehabilitation are important for overall outcomes, they do not constitute the same targeted prophylaxis with strong evidence as NSAIDs and radiotherapy. Prolonged bed rest or high-dose steroids are not standard, effective HO prevention strategies.