In vivo quantification of the laxity of normal and unstable glenohumeral joints.

The purpose of this study was to determine whether the magnitude of glenohumeral translation on clinical laxity tests could distinguish between clinically stable shoulders and shoulders with traumatic or atraumatic instability. Subjects included eight male volunteers with no history of symptoms of glenohumeral instability, eight patients with documented traumatic anterior instability and Bankart lesions, and eight patients with documented atraumatic multidirectional instability. The patients in the two instability groups had disabling instability that was refractory to nonoperative management and thus met the indications for surgical repair. All subjects were examined by an experienced shoulder surgeon using five standard manual tests: anterior drawer, posterior drawer, sulcus, push-pull, and fulcrum. The glenohumeral translations occurring during these laxity tests were quantitated with a spatial sensing system that had six degrees of freedom and was rigidly fixed to the scapula and humerus. The result showed substantial overlap in the translations found in members of the three groups for each of the laxity tests. Standard laxity tests demonstrate considerable translation in normal glenohumeral joints and do not reliably differentiate normal shoulders from those with two common forms of glenohumeral instability. This study suggests that assessment of the magnitude of glenohumeral translation on clinical laxity tests is not a specific test for the diagnosis of glenohumeral instability. Healthy subjects without symptoms may have as much translation as patients needing surgical repair for symptomatic shoulder instability. The need for and the type of surgical reconstruction for the unstable shoulder must be based on the patient's history and on duplication of the symptoms of instability on directed physical examination rather than on the magnitude of glenohumeral translation.