抄録
The purpose of this study is to clarify the factors which advance an initial shoulder dislocation to a recurrent shoulder dislocation using MR imaging.
Eighty-nine shoulders of 82 patients with traumatic anterior dislocations (40 shoulders of initial dislocations,49 shoulders of recurrent dislocations) were examined. The patients with an initial dislocation were checked upon redislocation and instability and given a personal examination or answered a questionnaire on the telephone. Twenty initial dislocations that had been treated conservatively and had observed for over 6 months were divided into two groups. The shoulders of group R were young patients (<30 years old) without a fracture or cuff tear. The shoulders of group N were older patients (>30 years old), with a fracture of the greater tuberosity of the humerus or with a cuff tear, The axial sections of T2* weighted or 3D-STAGE images were obtained using a superconductive MR imager (Shimadzu). The differences of Bankart lesions between the initial and recurrent dislocations were evaluated using Horii's classifications.
Among the initial dislocations, there were 37 out of 40 shoulders in grade 1 with a distinct labrum (92.5%). Of the recurrent dislocations, there were 32 out of 49 (65.3%). There was a statistical difference between the two groups (P<0.01). In R group, all the shoulders with a detached Bankart lesion (>2 mm; 5 shoulders) had a feeling of instability. But only one of four shoulders with an undetached Bankart lesion (<2mm) had it. There was a statistical difference between the two groups (P<0.05)too.
We speculate that an initial dislocation with a detached Bankart lesion (>2mm) will advance to a recurrent dislocation.
