Posterolateral elbow joint instability: the basic kinematics.

Thirty-five osteoligamentous elbows were included in a study on the kinematics of posterolateral elbow joint instability during the pivot shift test (PST) before and after separate ligament cuttings in the lateral collateral ligament complex (LCLC). Division of the annular ligament or the lateral ulnar collateral ligament caused no laxity during the PST. Division of the lateral collateral ligament caused maximal laxity of 4 degrees and 23 degrees during forced PST in valgus and external rotation (supination), respectively. Cutting of the LCLC at the ulnar or the humeral insertion was necessary for any PST stressed elbow joint laxity to occur. Total division of the LCLC induced a maximal laxity of 7.9 degrees and 37 degrees during forced PST in valgus and external rotation (supination), respectively. This study suggests the lateral collateral ligament to be the primary soft tissue constraint to PST stress and the annular ligament and the lateral ulnar collateral ligament to be only secondary constraints. This study indicates that the integrity of the medial collateral elbow ligaments should be evaluated during forced valgus in pronation or neutral forearm rotation. Furthermore an isometric lateral collateral ligament reconstruction was shown to correct the joint laxity introduced by total LCLC transection.