Structural topography of the interosseous membrane of the human forearm

The aim of this study was to evaluate the morphology of the six different parts of the interosseous membrane (IOM) in 11 human cadaver forearms, including the distal oblique bundle (DOB), the distal accessory band (DAB), the central band (CB), the proximal accessory band (PAB), the dorsal oblique accessory cord (DOAC), and the proximal oblique cord (POC). Hematoxylin-eosin and Elastica van Gieson stained slices were used to investigate the tissue morphology. The DOB and DOAC were absent in one IOM and the POB in two IOMs, respectively. The CB and DAB were longer than all other structures except for each other. The DOAC was longer than the DOB. The DAB, CB, and PAB, were broader than the DOB, DOAC, and POC. No significant differences were observed regarding structure thickness. All structures were found to consist of densely packed parallel collagen fiber arrangement. The DOB and POC had a higher amount of elastic fibers in the fascicular collagen tissue than the other structures. Elastic fibers were more often equally distributed throughout the structures than condensed epifascicular or at the insertion into bone. The tight parallel collagen composition within the different structures reflects the central stabilizing role of the IOM in the forearm. The higher amount of elastic fibers within the DOB and POC can be attributed to their location close to the distal and proximal radioulnar joints, respectively. Here elastic fibers allow adaption to forearm rotation, whereas the structures of the central part of IOM have less elasticity reflecting the predominant stabilizing function.