[Initial results of shoulder MRI in external rotation after primary shoulder dislocation and after immobilization in external rotation]

Abstract

Purpose: A change in the strategy for treating primary anterior traumatic dislocation of the shoulder has occurred. To date, brief fixation of internal rotation via a Gilchrist bandage has been used. Depending on the patient's age, a redislocation is seen in up to 90 % of cases. This is due to healing of the internally rotated labrum-ligament tear in an incorrect position. In the case of external rotation of the humerus, better repositioning of the labrum ligament complex is achieved. Using MRI of the shoulder in external rotation, the extent of the improved labrum-ligament adjustment can be documented, and the indication of immobilization of the shoulder in external rotation can be derived. The aim of this investigation is to describe the degree of position changing of the labrum-ligament tear in internal und external rotation.

Materials and methods: 10 patients (9 male, 1 female, mean age 30.4 years, range 15 - 43 years) with a primary anterior dislocation of the shoulder without hyper laxity of the contra lateral side and labrum-ligament lesion substantiated by MRI were investigated using a standard shoulder MRI protocol (PD-TSE axial fs, PD-TSE coronar fs, T2-TSE sagittal, T1-TSE coronar) by an axial PD-TSE sequence in internal and external rotation. The dislocation and separation of the anterior labrum-ligament complex were measured. The shoulders were immobilized in 10 degrees external rotation for 3 weeks. After 6 weeks a shoulder MRI in internal rotation was performed.

Results: In all patients there was a significantly better position of the labrum-ligament complex of the inferior rim in external rotation, because of the tension of the ventral capsule and the subscapular muscle. In the initial investigation, the separation of the labrum-ligament complex in internal rotation was 0.44 +/- 0.27 mm and the dislocation was 0.45 +/- 0.33 mm. In external rotation the separation was 0.01 +/- 0.19 mm and the dislocation was - 0.08 +/- 0.28 mm. After 6 weeks of immobilization in 10 degrees external rotation, the separation of the labrum was - 0.10 +/- 0.14 mm and the dislocation was - 0.23 +/- 0.21 mm.

Conclusion: In anterior labrum-ligament tears, the axial MRI of the shoulder in external rotation demonstrates a more physiologic position of the glenoid. This may indicate an immobilization of the shoulder in external rotation, which results in a more anatomical healing of the glenoidal tear. Thus, in the case of labrum-ligament tears, MRI in external rotation is becoming indispensable.