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ABSTRACT
This study assessed the importance of the anterior and posterior bundles of the medial collateral ligament in the elbow by measuring in situ strain in response to valgus loads at three positions of forearm rotation throughout a full arc of motion. Strain in the anterior bundle was significantly greater than in the posterior bundle and increased with more flexion. The anterior bundle developed strain at a lower flexion angle (30°) than the posterior bundle (60°). Strain ratio increased with load increase for all flexion angles. Forearm position minimally affected strain. These results indicate that the anterior bundle is important in resisting a valgus load, particularly in mid-flexion, while the importance of the posterior bundle increases as the elbow approaches full flexion.
Ligamentous injuries to the elbow are relatively common and can cause persistent pain and instability.1,2 In elbow dislocation, die exact injury mechanism is unknown; however, surgical exploration has revealed disruption of the medial collateral ligament in most cases.3
Tears of the medial collateral ligament are believed to occur from excessive valgus loading of the elbow. Such injuries may occur during acute traumatic events or as die result of repetitive microtrauma. The latter has been found in baseball pitchers, carpenters, and javelin throwers.4"6 If chronic instability of die joint develops, surgical intervention may be indicated.3,7
In addition to die inherent bony stability provided by the ulnohumeral articulation and radiocapitellar joint, die static stability of me elbow is provided by capsular and ligamentous structures.8,9 The major ligaments of the elbow are the lateral collateral ligament complex and the medial collateral ligament. The lateral collateral ligament complex is comprised of the radial collateral, lateral ulnar collateral, and annular ligaments. The medial collateral ligament consists of anterior, posterior, and transverse bundles.
Studies of the elbow ligaments have included anatomic dissections and ligamentous sectioning.6,814 Sojbjerg et al14 transected the different bands of die medial collateral ligament and observed me valgus laxity by measuring die angle of me forearm from the plane of normal flexion while under constant load. Case studies performed by Schwab et al6 showed injury to die anterior portion of the medial collateral ligament was responsible for severe valgus laxity of the joint. Other authors1013 have reported similar results indicating mat the anterior portion...