Ossification of the coraco-acromial ligament.

Abstract

In july of 1956 we made our first observation of an abnormal bony projection arising from the antero-inferior aspect of the acromion process (Fig. 1). The finding was present bilaterally in a male patient examined because of pain and limitation of motion of both shoulders. Periarthritis or peritendinitis calcarea was suspected. Fifty cases have been seen in our offices and affiliated hospital departments since that time. A search of the world's medical reports revealed no such gross description. Gray (4) in 1942 described subacromial facets in 22.12 per cent of his material, including 1,085 scapulae. The possibility that we were demonstrating his so-called elevated facets was considered, but on review of some of our radiographs he felt that they did not represent this entity but, more probably, calcification or ossification of a ligament or tendon due to stress. Weissenbach (6) described the radiologic appearance of a subacromial osteophyte in one case, but no surgical or anatomical follow-up was obtained. Anatomic Material Dried scapulae were photographed and radiographed to demonstrate this bony projection. Also, the shoulders of 36 cadavers were examined radiographically in the Department of Anatomy, University of Buffalo Medical School. Anteroposterior 15° caudad angled projections and vertical anteroposterior projections were made of the abnormal shoulders for comparison. Abnormal processes were found in 3 of the cadavers. One, a male aged 52, had bilateral involvement (Fig. 2), the second, a male aged 72, had a unilateral process. Of the total of 36, 30 were white and 6 colored; 28 were males and 8 females; the youngest was thirty-six and the oldest ninety-one, with an average age of 67.3 years. Examination of 30 dried scapulae showed occurence of this bony projection in 7. The subacromial facets described by Gray were also frequent and when the two processes were present, the facet extended to involve the ligamentous ossification (Fig. 3). Two of the cadaver specimens were fully dissected and the abnormal projection was found to be an ossification of the acromial aspect of the coracoacromial ligament. This ossification (trabeculated bone) extended antero-inferiorly within the confines of the ligament and the inferior surface therefore appeared smooth and concave. The gross anatomic appearance is similar to ossification which occurs in the conoid and trapezoid ligaments. Radiographs of the specimens were made with an excellent arthrogram effect and visualization of the articular cartilage (Figs. 4 and 5). Microscopic examination revealed mature bone with all elements present including the marrow cavity and contents. Radiographic Technic The patients were studied for symptoms of peritendinitis, and a modified shoulder girdle examination was done.