POSTEROLATERAL ELBOW JOINT INSTABILITY - THE BASIC KINEMATICS

Thirty-five osteoligamentous elbows were included in a study on the ki nematics of posterolateral elbow joint instability during the pivot sh ift test (PST) before and after separate ligament cuttings in the late ral collateral ligament complex (LCLC). Division of the annular ligame nt or the lateral ulnar collateral ligament caused no laxity during th e PST. Division of the lateral collateral ligament caused maximal laxi ty of 4 degrees and 23 degrees during forced PST in valgus and externa l rotation (supination), respectively. Cutting of the LCLC at the ulna r or the humeral insertion was necessary for any PST stressed elbow jo int laxity to occur. Total division of the LCLC induced a maximal laxi ty of 7.9 degrees and 37 degrees during forced PST in valgus and exter nal rotation (supination), respectively. This study suggests the later al collateral ligament to be the primary soft tissue constraint to PST stress and the annular ligament and the lateral ulnar collateral liga ment to be only secondary constraints. This study indicates that the i ntegrity of the medial collateral elbow ligaments should be evaluated during forced valgus in pronation or neutral Forearm rotation. Further more an isometric lateral collateral ligament reconstruction was shown to correct the joint laxity introduced by total LCLC transection.