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Keywords:

  • mummified ligament;
  • subacromial extension;
  • subacromial bursa;
  • enthesophytes;
  • arthroscopy

Abstract

According to a largely forgotten statement in the anatomical literature, the coraco-acromial ligament is frequently attached to the undersurface of the tip of the acromion as well as to its medial margin. Surgeons, now able to examine this region via an arthroscope, support this observation. Raised impingement facets on the tip region of the undersurface of the acromion, sometimes eburnated because of actual contact with the proximal humerus, commonly complicate disorders of the shoulder-joint complex and are often associated with ossification extending into the attachment of the coraco-acromial ligament. Such enthesophytes thus appear to preserve in ossified form the morphology of the attachment; many seem to arise from the subacromial surface as continuations of impingement facets. Two early 19th century scapulas are described in which much of the soft tissue covering the subacromial surfaces was preserved in mummified form. One had a large enthesophyte apparently extending into the coraco-acromial ligament; the other included some of the superior layer of the subacromial bursa. In both, a tissue containing prominent fibrous strands orientated in the plane of the ligament covered the tip region of the subacromial surface. Short immersion in a solution of sodium orthophosphate softened the dried tissue sufficiently to enable its components to be separated. The fibrous strands had a firm attachment near the lateral acromial margin and passed free across the surface like a sling supposedly into the coraco-acromial ligament. The sling-like character was emphasized in one specimen by the attachment of some fibres to the tip of the enthesophyte. It is postulated that the sling-like character would assist the main ligament to buffer pressures exerted by the proximal humerus in normal function. © 1998 John Wiley & Sons, Ltd.