MRI examination of the glenohumeral joint after traumatic primary anterior dislocation. A descriptive evaluation of the acute lesion and at 6-month follow-up.

Primary traumatic anterior dislocation of the shoulder in young patients has a high recurrency rate. There are varying opinions on the pathology behind the recurrences. The aim of this study was to describe the MRI characteristics of the acute lesion, and at 6-month follow-up. Thirty patients aged 18-30 years with primary traumatic anterior dislocation of the shoulder were randomized into two groups. One group was treated with acute arthroscopic lavage within 10 days. The control group was treated with traditional non-operative therapy. All patients underwent acute MRI within 10 days and before the arthroscopic lavage, and again at the 6-month follow-up, for evaluation of the lesions. The acute MRI verified Hill-Sachs lesions in all patients. At the 6-month follow-up MRI, there was no change in the size of the Hill-Sachs lesion. This was also the case with the six patients in the control group with recurrent dislocations during the first 6 months. Twenty-nine patients (97%) had joint effusion at the acute MRI, which was very useful for evaluation of the soft tissue pathology. The glenohumeral ligaments were detached in 20/30 patients (66%), and the labrum in 22/30 patients (70%). A capsulolabral detachment classified as a Baker 3 lesion was seen in 16/30 (53%) of the patients, including all six patients with recurrent dislocation. At the 6-month control only 3/30 (10%) of the patients had joint effusion for adequate evaluation of the labrum and ligamentous pathology. A Hill-Sachs lesion was found in 100% of the patients after primary dislocation, and recurrent dislocations did not change the size of the lesion. The study supports the opinion that this lesion is overlooked in the clinical situation. The joint effusion at the acute MRI was of utmost importance for evaluation of the soft tissue pathology. The 6-month MRI control was therefore considered inconclusive when evaluating capsulolabral lesions, due to lack of effusion. MRI arthrography with contrast administration would have been very helpful at the 6-month examination.