Redislocation of the shoulder during the first six weeks after a primary anterior dislocation: risk factors and results of treatment.

BACKGROUND

After an anterior dislocation, shoulder instability may occur with disruption of the soft-tissue or osseous restraints, leading to early redislocation. The aim of the present study was to clarify the risk factors for this complication within the first six weeks after a first-time anterior traumatic dislocation and to assess the outcome of treatment with immediate operative stabilization.

METHODS

A three-year, prospective, observational cohort study of 538 consecutive patients with a first-time anterior dislocation of the shoulder was carried out. Reassessment of shoulder function was performed at a dedicated shoulder clinic, and suspected early redislocations were assessed with additional radiographs. All medically fit patients with a confirmed acute redislocation were treated with repeat closed reduction under anesthesia. Patients with unstable reductions were treated operatively. Functional and radiographic assessment of outcome was carried out during the first year after dislocation.

RESULTS

Seventeen (3.2%) of the 538 patients sustained an early redislocation within the first week after the original dislocation. Patients at increased risk of early redislocation included those who sustained the original dislocation as the result of a high-energy injury (relative risk = 13.7), those who had a neurological deficit (relative risk = 2.0), those in whom a large rotator cuff tear occurred in conjunction with the dislocation (relative risk = 29.8), those in whom the original dislocation was associated with a fracture of the glenoid rim (relative risk = 7.0), and those who had a fracture of both the glenoid rim and the greater tuberosity (relative risk = 33.5). Following operative reconstruction, the outcome at one year after the injury was favorable in terms of function, general health, and radiographic findings. None of the patients had a redislocation or symptoms of instability at one year.

CONCLUSION

All patients who have substantial pain, a visible shoulder deformity, or restriction of movement at one week after reduction of a first-time dislocation should be evaluated with repeat radiographs to exclude a redislocation. Patients in whom this complication develops usually have either (1) severe disruption of the soft-tissue envelope due to a large rotator cuff tear or (2) disruption of the normal osseous restraints to dislocation due to either an isolated fracture of the glenoid rim or fractures of both the glenoid rim and the greater tuberosity. Early operative stabilization is justified for patients in whom the dislocation is associated with these coexisting conditions and who have evidence of gross instability.