Abstract
To study glenohumeral rhythm, ball roll (B), rotational movement of the humeral head, and gliding (G), its parallel translation by sliding, were measured in 60 healthy subjects during elevation of the arm, using an image analyzing system.
The B value reached a maximum at 0°-10°and the G value at 10°-20°. As the arm was elevated, the G value decreased and the B value tended to gradually stabilize after some decrease. The B+G value reached a maximum in the early range of elevation, and superior migration of the humeral head was most notable during this period. Although the value decreased until 400, the humeral head continued to rise. The value alternated between positive and negative after 300, and the amplitude of the fluctuation increased after 900. The |G|/B ratio was always below 1.0 between 0° and 300 and remained at about 1.0 until 900, but above that the rhythm was disturbed. Glenohumeral movement was divided into 3 phases by the B +G value and the |G| /B ratio, as follows; 1st (0°- 30°), ball roll>gliding; 2nd (30°- 90°), stable phase, and 3rd (90°-150°), unstable phase.
