Degeneration of the Second Joint of the Shouledr: An anatmical study

This study was undertaken to elucidate the relationship between degenerative changes of the acromion and the anatomical size of the second joint of the shoulder.We used 41 bleached skeletal bones, 78 shoulder joints (37 right, 41 left) which had been stored in the Department of Anatomy Section 2, Nagasaki University. The aveage age was 59.1 years (range, 20-79) in 18 males, 61.5 years (range, 31-77) in 23 females.Osteophytes in the anterior portion of the acromion and wear on the undersurface were observed macroscopically, and we measured the anatomical size of the scapula and humerus with slide calipers. Scapular Y-view radiographs were then obtained to carry out measurements which included the acromial angle, and the coraco-acromial triangle area.There were 25 joints (32.1%) with osteophytes and 13 joints (16.7%) had a worn undersurface of the acromion. The incidence of right shoulder's osteophyte formation was statistically higher than on the left. The average age of the large osteophyte group and that of the non-osteophyte group was 71.8 and 59.3 years, respectively. This showed that the degree of osteophyte formation increased with increasing age. We could find no statistical relationship between degenerative changes of the acromion and the anatomical size of the second joint of the shoulder. The average inclination of the acromial angle was 56.7 in the large osteophyte group and 49.3 of the non-osteophyte group. This showed that osteophyte formation accelerated with iscreasing acromial angle, that is, as the slope of the acromion became flat.These results may be useful in solving pathogenesis of degenerative disease of the second shoulder joint and it's therapy.