The valgus stabilizers of the elbow have been identified anatomically, but their relative importance has not been quantified. The purpose of this study was to analyze the acute changes of the torque-displacement curve to valgus stress following (a) section of the posterior portion of the medial collateral ligament; (b) excision of the radial head; (c) prosthetic replacement of the radial head; and (d) excision of the anterior portion of the medical collateral ligament. Thirty cadaver specimens underwent load-displacement testing in three positions: 0 degrees, 45 degrees, and 90 degrees of flexion. The anterior portion of the medial collateral ligament was the primary stabilizer of the elbow to valgus stress. The relative contribution of the posterior ligament was minimal. After excision of the radial head alone, the slope of the load-displacement curve decreased an average of 30%. Silicone rubber radial head replacement did not significantly improve the stability to valgus stress after radial head excision.
