Clinical significance of variations in the interconnections between flexor digitorum longus and flexor hallucis longus in the region of the knot of Henry.

Tendon transfer of the flexor digitorum longus tendon (FDLT) or the flexor hallucis longus tendon (FHLT) into the tibialis posterior tendon is carried out in patients with tibialis posterior dysfunction. FDLT and FHLT are connected in the region of the knot of Henry. The present study has investigated the anatomical variations of this tendinous interconnection. The results could be used to determine which of the two tendons should be transected proximal to the region of the knot of Henry in the surgical treatment of tibialis posterior dysfunction. In over two-thirds of cadaver specimens investigated, tension applied solely to FHLT resulted in flexion of all digits and the hallux. On the basis of these results, we propose that identification of the tendon to be transected should be decided at the time of surgery depending on the anatomical pattern. Based on the evidence provided by 16 cadaveric dissections, transection of FDLT proximal to the region of the knot of Henry for the repair of tibialis posterior dysfunction would result in retention of function of the hallux and lesser digits in the majority of cases.