Long Head of Biceps: Contributions to Glenohumeral Stabilization in Three Clinically Important Directions

The most frequently dislocated major joint of the body is the glenohumeral joint of the shoulder. While most dislocations are in the anterior direction, dislocations of the shoulder can occur in many directions. Many muscles help prevent unwanted translations of the joint by compressing and centering the humeral head into the glenoid socket via a mechanism known as concavity-compression (Lippitt, 1993). In addition, muscular stabilization may occur by direct resistance against the translating force (Itoi, 1993). This latter effect is often particularly sensitive to humeral position, the muscle’s origin and insertion, and arm loading. The aim of this study is to examine the specific role of the long head of biceps in preventing translations in the anterior, posterior, and inferior directions, in two humeral rotations.