How long should acute anterior dislocations of the shoulder be immobilized in external rotation?

BACKGROUND: Immobilization of the shoulder in external rotation has been shown to reduce the risk of recurrence after traumatic anteroinferior shoulder dislocation. It remains unclear how duration of immobilization affects labral coaptation.

HYPOTHESIS: Immobilization of the shoulder in 30 degrees of external rotation for 5 weeks allows better coaptation of the anteroinferior labrum than does an immobilization period of 3 weeks.

STUDY DESIGN: Cohort study; Level of evidence, 2.

METHODS: Twenty-two patients with traumatic anteroinferior dislocation of the glenohumeral joint were included in this study. Patients were divided into 2 groups. Group 1 consisted of the initial 11 patients (mean age, 37.4 years) immobilized for 3 weeks; group 2 consisted of the subsequent 11 patients (mean age, 29.7 years) immobilized for 5 weeks in 30 degrees of external rotation. With use of magnetic resonance imaging, displacement and separation of the glenoid labrum and anterior joint effusion were assessed in different arm positions (internal rotation, neutral rotation, 30 degrees of external rotation, maximum external rotation) within 3 days, 3 weeks, and 5 weeks after reduction.

RESULTS: Displacement and separation of the labrum and anterior joint effusion were significantly less, particularly with maximum external rotation compared with neutral and internal rotation, during the acute magnetic resonance imaging evaluation in both groups (P < .05). No statistically significant differences were found in all parameters comparing internal rotation with neutral rotation, 30 degrees of external rotation, and maximum external rotation in both groups after 5 weeks (P > .05). No statistically significant differences were found between both groups comparing the results of the measured variables during the acute, 3-week, and 5-week magnetic resonance imaging examinations (P > .05).

CONCLUSION: Immobilization of the shoulder in 30 degrees of external rotation seems to allow a similar coaptation of the glenoid labrum, regardless of duration of immobilization (3 vs 5 weeks). Clinical trials are needed to evaluate the effect of these results on recurrence rates. The optimum position of immobilization in external rotation has yet to be determined.