Fibrous Bands Around the Ulnar Nerve Distal to the Cubital Tunnel: Their Real Presence and Anatomical Importance

Introduction: Fibrous bands (FB) are structures believed to cross the ulnar nerve (UN), distal to the cubital tunnel (CT). They are located within the fascia of the flexor digitorum profundus (FDP) muscle, deep to the flexor carpi ulnaris (FCU). Previous anatomical and surgical studies have suggested that such bands are a potential additional source of nerve compression. Surgical decompression of the UN in the elbow region, by endoscopy, has been considered a viable option for treating UN-related compressive neuropathies, like cubital tunnel syndrome. However, during endoscopy, these FB significantly impact UN visibility5.

Objectives: The aim of the current study was to characterize the anatomical characteristics of these FB, proximal and distal to the CT.

Methodology: Eighteen formalinized upper limbs were dissected, nine right and nine left, within the Department of Anatomy at the Biomedical Institute of the Federal University of the State of Rio de Janeiro (UNIRIO). None of the dissected limbs exhibited any type of lesion within the area of interest. The dissections were performed with micro techniques under a magnifying glass with 3.5x magnification, and under a microscope with 6–10x magnification, photographed using a Kodak Easy Share M531 camera. Classical UN exposure was established within the elbow region.

Results: Of the 18 upper limbs studied, 50% lacked any FB. There was not found any FB proximal to the CT. When present, both the number and location of the FB varied between the different limbs, as near to the cubital tunnel as 3 cm past the UN’s entrance into the tunnel, and as far away as almost 11 cm distal to it. There was some consistency in the location range occupied by the different FB whenever multiple FB were present, with relatively little overlap between the first and second, second and third, and so on. Overall, across the nine dissected cadavers, there were no FB on either the left or right side in three cadavers (33.3%), FB on both the left and right side in three; and FB only on the left in three, meaning that FB were twice as common in left limbs (n = 6) as on the right (n = 3).

Conclusions: Our study identified FB in 50% of the dissected limbs, all within 3–11 cm of the CT, though their number and location varied. Further studies are necessary to describe variations in the presence of these FB and identify their associations with clinically-significant compressive neuropathies of the UN distal to the CT.

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