Position of immobilization after dislocation of the glenohumeral joint - Astudy with use of magnetic resonance imaging

Background: Glenohumeral dislocations often recur, probably because a Banka rt lesion does not heal sufficiently during the period of immobilization. U sing magnetic resonance imaging, we assessed the position of the Bankart le sion, with the arm in internal and external rotation, in shoulders that had had a dislocation. Methods: Coaptation of a Bankart lesion was examined with use of magnetic r esonance imaging, with the arm held at the side of the trunk and positioned first in internal rotation (mean, 29 degrees) and then in external rotatio n (mean, 35 degrees), in nineteen shoulders. Six shoulders (six patients) h ad had an initial anterior dislocation, and thirteen shoulders (twelve pati ents) had had recurrent anterior dislocation. Fast-spin-echo T2-weighted ax ial images were made when the dislocation had occurred less than two weeks earlier, and spin-echo T1-weighted axial images after intra-articular injec tion of gadolinium-diethylenetriamine pentaacetic acid were made when the d islocation had occurred more than two weeks earlier. Separation and displac ement of the anteroinferior portion of the labrum from the glenoid rim were measured on the axial images, and coaptation of the anterior part of the c apsule to the glenoid neck was assessed by measurement of the detached area , opening angle, and detached length. Results: Separation and displacement of the labrum were both significantly less (p = 0.0047 and p = 0.0017, respectively) when the arm was in external rotation than when it was in internal rotation. The detached area and the opening angle of the anteroinferior portion of the capsule were both signif icantly smaller (p = 0.0003 and p < 0.0001, respectively), and the detached length was significantly shorter (p < 0.0001) with the arm in external rot ation. Conclusion: Immobilization of the arm in external rotation better approxima tes the Bankart lesion to the glenoid neck than does the conventional posit ion of internal rotation.