Although anterior shoulder dislocations may be documented, the basic mechanism involved in the dislocation remains controversial.
We have several patients who fe l l and struck their shoulder on the ground and dislocated it anteriorly. However according to the textbooks, direct force is only rarely the cause of dislocation and we can not find any reports about the mechanism of a dislocation by direct force. We experienced a 17-year-old boy who had a fracture dislocation of the humeral head. We wish to present this case and discuss the mechanism of the dislocation. He was thrown off his motorbike and got injured. In the operation, there was an ecchymosis over the middle portion of the deltoid muscle, which implied the blow was at this point. There was no tear of the cuff muscles, but there was a Bankart lesion. Mild traction toward the lateral direction reduced the dislocation easily. The fragment was fixed stably with a screw. The Bankart lesion was repaired with pull-out sutures. Afterward, he got good results. Discussion: Anatomically the plane of the gleno-humeral joint locates obliquely forward about 30 degrees. Should the compression force come from a more laterall than vertical line of the joint line, the humeral head would be pushed out anteriorly.
Since a scapula is very mobile, a strong direct force and gear effect between the humeral head and the glenoid, move it medially, anteriorly and inferiorly. Anterior dislocation could occur by direct force not only posteriorly, but also laterally. We wish to examine the precise mechanism of the damage for its correct diagnosis and treatment.
