Midterm results with a bipolar radial head prosthesis: radiographic evidence of loosening at the bone-cement interface.

BACKGROUND Metal prostheses are useful for restoring elbow and forearm stability when the radial head cannot be fixed after a fracture. Because the anatomy of the radial head is difficult to reproduce with a prosthesis, two different options have been proposed: a bipolar prosthesis with a fixed stem and a mobile head, and a monoblock prosthesis with a smooth stem that is intentionally fixed loosely in the neck of the radius. One concern with a fixed-stem implant with a mobile head has been the risk of osteolysis. The purpose of this study was to evaluate radiographic changes reflecting or suggesting progressive osteolysis in patients with a bipolar radial head prosthesis. METHODS The functional and radiographic outcomes following treatment of fifty-one comminuted fractures of the radial head with a bipolar radial head prosthesis in fifty-one consecutive patients were evaluated at a mean of 8.4 years postoperatively. There were eleven isolated comminuted fractures involving the entire radial head. Thirty-four fractures were associated with a posterior elbow dislocation, and six patients had a posterior Monteggia lesion. RESULTS According to the Mayo Elbow Performance Index, fourteen elbows were graded as excellent; twenty-five, as good; nine, as fair; and three, as poor. Radiographic changes reflecting or suggesting progressive osteolysis were present in thirty-seven patients. Complications occurred in ten patients, but only one underwent surgical treatment, for an ulnar neuropathy. CONCLUSIONS Although satisfactory midterm functional results were achieved in thirty-nine of the fifty-one patients, the high prevalence of adverse radiographic changes suggesting periprosthetic osteolysis should alert clinicians to this possible drawback of the use of bipolar radial head prostheses, especially in young and/or active patients.