Innervation of the Flexor Digitorum Profundus: A Systematic Review

The aim of this study was to review the innervation of the flexor digitorum profundus (FDP).

In PubMed and Scopus, terms (Flexor digitorum profundus OR FDP) AND (innervation OR nerve) were used, resulting in 233 and 281 papers, respectively. After excluding 142 duplicates, 73 abstracts were reviewed. Forty-seven abstracts were excluded, 26 full papers were reviewed, and 17 papers were analyzed.

In most cases (97.6%), the index FDP was innervated by the anterior interosseous nerve (AIN). Dual innervation from the AIN and ulnar nerve (UN) was observed in 2.4% of papers. In majority (76.8%), the middle FDP received dual innervation from the AIN and the UN. The rest was innervated by the AIN only (22.0%) or the UN only (1.2%). In most cases (85.4%), the ring FDP was innervated by the UN only. The rest (14.6%) received dual innervation from the AIN and the UN. In majority of cases (64.6%), the little FDP was innervated by the UN only. The rest (35.4%) received dual innervation from the AIN and the UN. The AIN entered the FDP at 107.63 (8.80) mm from the elbow, corresponding to 26.75% (2.17%) of the forearm length, measured proximally. The average number of AIN branches to the FDP was 2.27 (1.33). The average number of UN branches to the FDP was 1.37 (0.94). In 8.8% of limbs, a communicating branch supplied the FDP. Among the limbs with a communicating branch, 32.3% had branches supplying the FDP.

The results of this study may be useful in managing nerve injury patients.