Metallic radial head arthroplasty improves valgus stability of the elbow

The stabilizing influence of radial head arthroplasty was studied in eight medial collateral ligament deficient anatomic specimen elbows. An elbow tes ting apparatus, which used computer controlled pneumatic actuators to apply tendon loading, was used to simulate active elbow flexion. The motion path ways of the elbow were measured using an electromagnetic tracking device, w ith the forearm in supination and pronation, As a measure of stability, the maximum varus to valgus laxity over the range of elbow flexion was determi ned From the difference between varus and valgus gravity loaded motion path ways. After transection of the medial collateral ligament, the radial head was excised and replaced with either a silicone or one of three metallic ra dial head prostheses. Medial collateral ligament transection caused a signi ficant increase in the maximum varus to valgus laxity to 18.0 degrees +/- 3 ,2 degrees, After radial head excision, this laxity increased to 35.6 degre es +/- 10,3 degrees, The silicone implant conferred no increase in elbow st ability, with a maximum varus to valgus laxity of 32.5 degrees +/- 15.5 deg rees, All three metallic implants improved the valgus stability of the medi al collateral ligament deficient elbow, providing stability similar to the intact radial head. The use of silicone arthroplasty to replace the radial head in the medial collateral ligament deficient elbow must be questioned. Metallic radial head arthroplasty provides improved valgus stability, appro aching that of an intact radial head.