A surgeon plans total hip arthroplasty through a direct lateral approach in a 54-year-old man with ankylosing spondylitis, a recognised risk factor for heterotopic ossification. Which prophylactic regimen is appropriate?
- A Single fraction external beam radiation of about 700 cGy delivered within 72 hours after surgery ✓
- B Low molecular weight heparin continued for six weeks after surgery
- C Post-operative bisphosphonate therapy started at two weeks
- D Continuous passive motion beginning on day one
Correct answer: A. Single fraction external beam radiation of about 700 cGy delivered within 72 hours after surgery
Explanation
Prophylaxis against heterotopic ossification is either a single low dose of external beam radiation (about 700 cGy) given preoperatively or within 72 hours postoperatively, or an NSAID such as indomethacin. Radiation prevents differentiation of pluripotent mesenchymal cells into osteoblasts. LMWH prevents venous thromboembolism, not ectopic bone. Bisphosphonates inhibit resorption of formed bone rather than new ectopic formation, and continuous passive motion has no effect on HO development.
Reference: Campbell's Operative Orthopaedics, 14th ed.
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