The present study was undertaken to investigate the histological and histochemical characteristics of the deltoid and major pectoral muscles in the normal shoulder, the loose shoulder and recurrent dislocation of the anterior shoulder joint for the better understanding of the pathophysiology of these diseases.
1. Human deltoid and major pectoral muscles were obtained from 7 cases with the loose shoulder (age 14 to 22), and 14 cases with recurrent dislocation of the anterior shoulder joint (age 17 to 48). As a control, deltoid and major pectoral muscles were also obtained from 8autopsy cases (age 17 to 73) within a few hours after their death.
2. All the samples were frozen in isopentane, and cool e d in liquid nitrogen. Cryosections were stained with hematoxylin-eosin, Gomori-trichrome, oil-red 0, NADH-TR and myosin ATPase (pH 9.4,4.6,4.3).
3. In all muscles of the lo o se shoulder and recurrent dislocation of the anterior shoulder joint, there were marked variations of fiber size and endomysial fibrosis as compared with normal shoulders.
4. A ll muscles, particularly in the loose shoulder, showed predominance of type 1 fiber and atrophy of type 2 fiber.
5. The grades of histological and histochemical abnormalities correlated approximately with the clinical features in the loose shoulder and recurrent dislocation of the anterior shoulder joint