Type and location of flexor hallucis longus musculotendinous junctions and its tendinous interconnections with flexor digitorum longus tendon: pertinent data for tendon harvesting and transfer

Abstract

Background: Anatomy of flexor hallucis longus (FHL) is essential for the achievement of tendon transfer and several procedures performed in the foot and ankle. The aim of this study was to evaluate the anatomical knowledge of FHL including the type and location of musculotendinous junction (MTJ), tendinous interconnections (TIC) morphology, its location related to Master Knot of Henry (MKH), and the pattern of TIC distribution. Materials and methods: One hundred and sixty-six legs from 52 embalmed and 31 soft cadavers were assessed. The medial and lateral bellies of FHL (MB and LB) were identified and traced until the end of the most distal muscle fiber to determine the medial and lateral MTJs. MTJ was classified into 4 types based on the existence and length of MB and LB: Type 1, long LB and shorter MB; Type 2, equal length of both bellies; Type 3, only LB and no MB; Type 4, long MB and shorter LB. Low lying muscle belly was defined as muscle extending beyond the zero point (the point of intersection between distal osseous part of tibia and FHL tendon). The distance between MTJ and zero point was measured. TIC was classified into seven types based on the direction and number of slip: Type I, one slip from