Assessment of rotation in proximal humeral osteotomy.

The correlation between the shift measured on bone surface in rotatory osteotomy and the radiologic change of the retroversion angle was analyzed. The humeral head retroversion was measured radiographically in 7 isolated humeri by means of a semiaxial projection. All bones were then osteotomized and the humeral head rotated in order to increase and decrease the retroversion. The retroversion was measured radiographically for each new rotational position of the head. The relationship between the measured shift in rotatory osteotomy and the change of retroversion was found to be linear. Twelve patients with recurrent anterior shoulder joint dislocations and a small humeral head retroversion were operated on in order to increase the retroversion. In all patients the increase of retroversion angle was smaller (57%) than expected on the basis of the shift in osteotomy and humeral diameter. The mean increase of retroversion was 2 degrees/mm shift (range 1.3-3.0 degrees/mm).