Abstract
The purpose of this investigation is to document postmortem radiologic and histologic changes of the undersuface of the acromion and to elucidate the pathogenesis of so-called Neer's spur.
A part of the acromion with the coracoacromial ligament inserted into the undersurface of the acromion, was obtained from 76 autopsy specimens (mean age 69.3 years). The specimens were radiographed in A-P direction. The insertion of the ligament at the acromion was macro-and microscopically examined.
In 18.4% of the specimens a downward beaklike bony projection of the acromion was noted. In 9.2% of the cases an inferior spur at the ligament insertion into the acromion was observed. 4% of the specimens demonstrated localized sclerosis inferiorly.
Degenerative changes were staged from grade 1 to grade 4. Hypertrophic change of the fibrocartilaginous layer was a characteristic finding in grades 1 and 2, and wear and tear of the undersurface of the acromion was typical of grades 3 and 4. Neer's spur which was always surrounded by a hypertrophied fibrocartilagionus layer, was found at the anteroinferior corner of the acromion.
From this study it is felt, that 1) a bony variant can predispose an impingement syndrome, and 2) the hypertrophied fibrocartilaginous layer plays an important role in the degenerative process of the acromial insertion of the coraco-acromial ligament.
