The effect of metallic radial head arthroplasty on radiocapitellar joint contact area.

OBJECTIVE This study determined the effect of metallic radial head arthroplasty on radiocapitellar joint contact area. DESIGN The contact area of eight intact radiocapitellar joints was assessed during simulated compressive loading. Subsequently, the same experiments were repeated after reconstruction with three different radial head implant sizes. BACKGROUND There has been an increasing use of metal radial head implants relative to silicone implants. However, the contact characteristics with the metal reconstruction have not been determined. METHODS A 100 N compressive load was applied to the radiocapitellar joint at three different flexion angles for the native joint and three different sizes of a metal head implant. An impression material was employed to quantify joint contact area. RESULTS Following metallic radial head arthroplasty, the contact area decreased by approximately two-thirds relative to the native radiocapitellar joint (P<0.001). Smaller implant sizes resulted in slightly larger contact areas (P<0.05). In addition, contact area decreased as joint flexion angle increased (P<0.04). CONCLUSIONS Selection of radial head implant size is likely not a significant factor with regard to contact area mechanics of the radiocapitellar articulation. RELEVANCE The effect of radial head implant size on the contact area produced with the native capitellum is not known. This study shows that the design or selection of a metallic radial head implant from the viewpoint of size is likely not an important factor with regard to minimizing joint contact stresses.