Do Bankart lesions heal better in shoulders immobilized in external rotation?

Abstract

Background and purpose: Immobilization in external rotation (ER) for shoulder dislocation has been reported to improve the coaptation of Bankart lesions to the glenoid. We compared the position of the labrum in patients treated with immobilization in ER or internal rotation (IR). A secondary aim was to evaluate the rate of Bankart lesions.

Patients and methods: 55 patients with primary anterior shoulder dislocation, aged between 16 and 40 years, were randomized to immobilization in ER or IR. Computer tomography (CT) and magnetic resonance imaging (MRI) were performed shortly after the injury. After the immobilization, MRI arthrography was performed. We evaluated the rate of Bankart lesions and measured the separation and displacement of the labrum as well as the length of the detached part of the capsule on the glenoid neck.

Results: Immobilization in ER reduced the number of Bankart lesions (OR = 3.8, 95% CI: 1.1 -13; p = 0.04). Separation decreased to a larger extent in the ER group than in the IR group (mean difference 0.6 mm, 95% CI: 0.1 - 1.1, p = 0.03). Displacement of the labrum and the detached part of the capsule showed no significant differences between the groups.

Interpretation: Immobilization in ER results in improved coaptation of the labrum after primary traumatic shoulder dislocation.

Figure 1.

Flow chart of the prospective randomized multicenter study. Immobilization in internal versus external rotation after primary anterior traumatic shoulder dislocation. Age group 16–24 years: n = 82. Age group 25–40 years: n = 106. Total: 188 patients included. 67 patients were diagnosed and treated at Oslo casualty ward (Oslo University Hospital, Ullevaal). 3 patients were diagnosed and treated at Akershus University Hospital. Patients from these 2 hospitals were also recruited to the CT/MRI/MRI arthrography study.

Figure 2.

The definition of ‘separation’, ‘displacement’ and ‘detached length’ was done according to the method of Eiji Itoi. Figures are reproduced (by permission of the author and the Journal of Bone and Joint Surgery) from the original article of Itoi in JBJS (AM) Number 5. May 2001. Separation (S) was defined as the distance (in mm) between the inner margin of the labrum and the anterior aspect of the glenoid neck. Displacement (D) was defined as the distance (in mm) between the tip of the labrum and the tip of the glenoid rim. The value was positive when the labrum was displaced medial to the rim of the glenoid.

Figure 3.

Measurements of the capsule: The detached length (A to B) is the length between the anterior glenoid rim and the anterior capsular attachment (in mm). The figure is reproduced (by permission of the author and the Journal of Bone and Joint Surgery) from the original article of Itoi in JBJS (AM) Number 5. May 2001. In our study the detached area (lined area) and the opening angle θ were not measured.