The aim of this study was to devise a measurement method for the shoulder internal rotation with the elbow being extended using special plates that we developed, and compared the measured angles with those of conventional measurements. The subjects were 20 healthy volunteers (40 shoulders). In our new method, a rod was applied to the front of the elbow, and the internal rotation angles were measured using the plates with the elbow being extended, As the conventional method, internal rotation was expressed as thumb-distance from Jacoby's line. In addition, the external rotation angles were measured conventionally with the elbow flexed. Measurements were taken 3 times, each in the unit of 5 degrees or 1 cm in the sitting position. The angle of internal rotation was 80-120°in the new method and 17-41cm in the conventional method; there was a correlation (p<0.001), with a correlation coefficient of O.645. The differences of the values in the three times measurements were 0°(no difference) in 19 shoulders and 5°in 21 shoulders in the new measurement of the internal rotation. In the conventional measurement of the external rotation, tie difference was 0°,5°and 10°in 22,17 and 1 shoulder, respectively. The measurement of the shoulder internal rotation with elbow extended was easy to achieve, and the differences of the values in the three times measurements were almost identical with those of the conventional measurement of the shoulder external rotation. The new method is useful for measuring the range of internal shoulder rotation.
