Review Question - QID 2948

The patient has post-traumatic heterotopic ossification (HO). HO can occur about the hip following acetabular and hip fractures as well total hip arthroplasties (THA). Comprehensive Orthopaedic Review puts the incidence as high as 80% in THA patients and Miller's states that it is seen most with the direct lateral approach in THA and extensile approaches for acetabular fractures. The presence of a head injury makes an orthopedic trauma patient high risk for HO.

Board et al conducted a review of HO following THA and found that in high risk individuals 700-800 cGY delivered less than 4 hours preoperatively or within 72 hours postoperatively appeared to be more effective than indomethacin 75mg daily for 6 weeks.

Ayers et al also conducted a review of the literature and concluded that localized radiation was the treatment of choice to prevent heterotopic ossification following cementless total hip arthroplasty in high risk individuals.

Irradiation prevents proliferation and differentiation of primordial mesenchymal cells into osteoprogenitor cells that can form osteoblastic tissue. Oral bisphosphonates are not effective for prophylaxis as they inhibit mineralization of osteoid, but do not prevent the formation of osteoid matrix and when bisphosphonate therapy is discontinued, mineralization with formation of HO may occur. VAC (Answer 3) is a chemotherapy regimen used in Ewings sarcoma treatment. Recombinant PTH 1,34 (Answer 2) has been shown to increase bone mineral density.