A preliminary study on the measurement of static and dynamic motion at the glenohumeral joint.

Measurement of glenohumeral joint motion has, for the most part, been performed with the simple goniometer. The purpose of this paper is to describe a method for measuring and recording static and dynamic external rotation of the glenohumeral joint using the Cybex II Isokinetic Dynamometer and an MFE model 815 X-Y plotter. Static range of motion was assessed at 60 deg/sec using a slow arm action externally from a 90 degree abduction position. Dynamic motion was recorded at 300 deg/sec using a rapid rotational whipping action from a 90 degree abducted position. Measurements were recorded on three groups of athletes, and the influences of sex, hand dominance, overarm activity, and surgery were analyzed. The subjects in the first two groups were divided according to sex and their participation in overarm versus nonoverarm (control) activities. Static and dynamic motion in both groups was significantly influenced by sex and hand dominance (P less than 0.05). Although there was no overall difference in the motion measurements between the control and overarm groups, the interaction of this factor with sex and type of measurement was significant. Males who participated in overarm activities had, on the average, more static range of motion than males in the control group. A third group that had undergone a modified Bristow procedure for recurrent dislocation/subluxation of the shoulder demonstrated that static and dynamic range of motion were significantly reduced by the surgery (P less than 0.05). The average differences in static and dynamic motion between the surgical arm and its nonsurgical counterpart were 17.5 degrees and 21 degrees, respectively, resulting in an overall range of motion difference of 19 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)