Radiocapitellar joint stability with bipolar versus monopolar radial head prostheses.

Background: Bipolar and monopolar designs are both available for replacement of the radial head. Few data exist comparing the biomechanical characteristics of these 2 quite different prostheses. This study evaluated the relative contribution to radiocapitellar stability by concavity compression with these 2 types of radial head prostheses.

Methods: The study used 12 fresh frozen elbow cadavers. The capitellum of the distal humerus and 3 different conditions of radial head (native, monopolar and bipolar) were tested for radiocapitellar joint stability.

Results: The monopolar metallic head and the native radial head behaved similarly regarding resistance to subluxation. The bipolar head behaved in an entirely opposite manner than the native and monopolar head and actually acted to facilitate subluxation.

Conclusions: Mobility of radial head components, such as in the bipolar radial head, has a compromising effect on the concavity compression stability of the radiocapitellar joint. A monopolar implant is more effective in stabilizing the radiocapitellar joint than a bipolar radial head prosthesis.