Abstract
Cineradiographical shoulder evaluations were done on 15 healthy volunteers and 60 unstable shoulders (20 cases of recurrent anterior dislocation, 20 of recurrent anterior subluxation, and 20 of multidirectional instability) . Cineradiographical analysis was performed on each shoulder in elevation and depression from 0°to 90°elevated position. Also, each function of the rotator cuff muscles and the scapulothracic joint were examined using EMG and an original roentogenograph named the Scapula-45. Unstable shoulders had cuff dysfunction and/or abnormal movement of the scapulothoracic joint and demonstrated abnormal micromovement of the humeral head on glenoid during elevation and depression, named “skid slip”, was found under cineradiographical examination. Furthermore, cases with dysfunction of the scapulothoracic joint had variable abnormal reactions of the scapula, showing the socalled skid slip phenomenon. The results of this study show that unstable shoulders showed skid slip and had dysfunction of the rotator cuff muscle and/or the scapulothoracic joint.
