Characterization of the tissue crossing the supratrochlear aperture of the humerus using histochemical techniques

The supratrochlear aperture (STA) is the opening observed in the septum that separates the olecranon from the coronoid fossae. Numerous studies have shown that there is considerable variation in the occurrence of this feature within and among populations.

Cadavers (n = 43) were assessed for the presence of the STA by means of X-ray. Ten samples of STA-bearing bones and an equal number of controls without STA were obtained from cadavers using a hole saw. These samples were decalcified, fixed in formalin and processed for histological assessment in differing (ascending) grades of alcohol before being embedded in paraffin wax. Sections (10 µm thick) were stained with haematoxylin and eosin (H&E) for general architecture as well as the rapid one-step Mallory-Heidenhain stain for bone and connective tissue.

The STA samples exhibited an abundance of connective tissue arranged in regular bundles of fibers across the STA. In contrast, the controls showed only bone tissue in the septum.

The arrangement of connective tissue fibers organized in regular bundles is a characteristic of strength, which may indicate that the STA is under sustained stress or pressure from the olecranon and coronoid processes of the ulna. It remains debatable whether the STA should continue to be considered as a foramen in life as we demonstrate that it is obliterated by connective tissue. It contains no neurovascular structures, making it unlike other structures defined as foramina.