PURPOSE:
To characterize and compare the histological structure of the proximal, central, and distal bands of the interosseous membrane (IOM) of the human forearm in fresh-frozen specimens.

METHODS:
The IOMs from 16 fresh-frozen left forearm specimens were carefully dissected and examined. The footprint areas of the proximal, central, and distal IOM bands were measured in 6 specimens. The histological characteristics of the IOM bands were evaluated using hematoxylin-eosin and Masson trichrome staining protocols in 10 specimens as histological analysis necessitated an intact footprint. The footprint areas of the IOM were measured using an image processing program. The insertion complex was assessed using a light microscope.

RESULTS:
Histological assessment revealed that the IOM structure demonstrated similarities with ligament structure. The average footprint areas of the proximal, central, and distal bands at the radial site were 11.1 ± 0.8, 180.4 ± 30.4, and 10.7 ± 1.3 mm2, respectively. At the ulnar site, they were 11.0 ± 1.1, 171.8 ± 30.1, and 10.7 ± 1.2 mm2, respectively. The insertion complex of the IOM into the bone comprised 4 layers: (1) interwoven collagen, (2) oblique collagen, (3) mineralized fibrocartilage (tidemark), and (4) lamellar bone. The average tidemark zone thicknesses of the proximal, central, and distal bands were 20.1 ± 6.3, 107.8 ± 22.9, and 20.6 ± 4.7 μm, respectively at the radial site and 12.0 ± 4.5, 85.7 ± 23.2, and 13.5 ± 6.9 μm, respectively at the ulnar site.

CONCLUSIONS:
In this study, we confirm that the histological characteristics of the IOM are similar to those of ligaments. Compared with the proximal and distal bands, the central band has a greater footprint area and thicker tidemark zone.

CLINICAL RELEVANCE:
If surgical reconstruction is performed, the size and histological characteristics of the graft should be similar to those of the native ligaments.





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