Functionally induced alteration of adult scapular morphology.

The dependence of the growth and development of the scapula on its functional matrix has been clearly defined by a number of experimental studies. Early modifications of this functional matrix may result in an altered scapular morphology [Howell, 1917]. Further, extreme developmental muscular hypofunction results in an increase in scapular breadth and a decrease in length [Riesenfeld, 1966; Doyle, 1976]. However, these studies have been confined to the scapular growth period and no findings have been published on the effect of scapular hypofunction in adults. The present paper addresses this problem. Adult scapular hypofunction in the rat was produced by unilateral amputation of the upper arm. Statistically significant (p less than 0.001) differences in intraindividual scapular breadth dimensions are reported. Further, an increase in the relative instability of the scapular length dimension was observed. No differences in gross scapular morphology resulted from the hypofunctional condition. It is concluded that the functional matrix of the scapula determines a unique morphology during the course of development. Once established, scapular morphology is relatively fixed and only unstable dimensions such as breadth are predictably responsive to a changed matrix.