Heterotopic bone formation after total hip arthroplasty.

Heterotopic bone formation is a common complication of total hip arthroplasty. A certain degree of heterotopic bone formation occurs in about one-half of the patients in degrees ranging from very mild to moderate involvement. The patients do not necessarily have any clinical disability; only 2 per cent of the patients developed severe heterotopic bone radiographically, and unsatisfactory functional results. There is no sex predilection for heterotopic bone formation except that the condition appears more severe in females. All ages are equally affected. The underlying disease process in the hip does not influence the occurrence of heterotopic bone. The incidence was significantly greater in patients who developed postoperative hematomas, prolonged wound drainage, or superficial infection. When surgical exposure is difficult and retraction of soft tissue aand soft tissue damage takes place, the incidence is much greater. Patients who have undergone previous surgical procedures about the hip present a greater risk in regards to development of disabling heterotopic bone formation. The etiology of heterotopic bone formation is not known. The following steps should be taken to avoid or greatly minimize the development of heterotopic bone: meticulous exposure with most careful retraction, copious irrigation with antibiotic solution, debridement of devitalized tissue prior to closure, instillation of drainage tubes, intraoperative and postoperative antibiotics, and carefully controlled postoperative anticoagulation.