Nerve transfer of the anterior interosseous nerve to the thenar branch of the median nerve - an anatomical and histological analysis.

Abstract

Nerve transfer has become a vital method in the reconstruction of hand function. Reconstructing the motor function to the thenar musculature has proven to be difficult and is rarely satisfactory following direct anatomic repair. The aim of this investigation was to describe the anatomic results obtained by transferring the anterior interosseous nerve to the thenar branch of the median nerve and analyze the histomorphometric results. Nerve transfers were performed in 15 fresh anatomic specimens. Nerve samples were excised from 13 fresh specimens and histologically investigated. The nerve diameter, fascicle number, and cross-sectional area of the individual fascicles were measured. The results of this investigation revealed that the anterior interosseous nerve and the thenar branch of the median nerve could be identified at their expected locations and a tension-free coaptation could be achieved. The anterior interosseous branch had a mean number of 606 ± 254 axons vs. 2160 ± 1326 in the thenar branch (p < 0.001). The anterior interosseous branch had a mean density of axons per fascicle mm² of 2398 ± 829 vs. 3012 ± 740 in the thenar branch (p = 0.390). The ratio of axons between the thenar branch of the median nerve and the anterior interosseous nerve yielded a mean of 1:4.16. Nerve transfer of the anterior interosseous nerve to the thenar branch of the median nerve should be considered as a viable option but remains a subject of investigation owing to its critical axon ratio. Furthermore, larger clinical studies will be required to validate or neglect this nerve transfer.