Anatomical Variation of Tendinous Interconnection between Flexor Hallucis Longus and Flexor Digitorum Longus Tendon and Its Location regarding Master Knot of Henry

Abstract

Tendinous interconnections between flexor hallucis longus (FHL) and flexor digitorum longus (FDL) have functional importance in toe movement and act as a natural tenodesis after harvesting FHL tendon proximal to master knot of Henry (MKH). This anatomical study aimed to clarify the type, location and distribution to lesser toes of tendinous interconnection between FHL and FDL tendons in 102 embalmed and 62 soft cadaveric feet. According to the classification of Beger et al., three types of interconnection (type I, II, V) were found in 85.4 %, 0.6%, and 7.9% of specimen, respectively. In addition, a new type of connection (6.1%) in which is FHL tendon bifurcated into one tendon to the first toe and the other tendon fused with FDL tendon. The tendinous interconnection was located either proximal (−) or distal (+) to MKH. The mean distance from MKH in type I was1.38±10.40 mm (from −59.47 to 20.52 mm). The proximal and distal interconnection slips in type V were located at 6.61±4.69 mm (from 0.00 to 12.47mm) and 12.95±3.48mm (from 7.05 to 16.13 mm) from MKH. In the new type, the interconnection slip was located at −6.59±8.93 mm (from −20.81 to 5.48 mm) from MKH. The distribution of tendinous slip to lesser toes was determined by pulling the FHL tendon and observing the lesser toes’ movement. According to the classification of Plaass et al., the prevalence of distribution of tendinous slip to lesser toes in type a, b, c and d was 19.5%, 67.7%, 11.0%, and 1.8%, respectively. Knowledge of the tendinous interconnection and its location are important for enhancing the clinical efficacy of FHL tendon transfer and minimizing of the functional loss of toes in post‐operative period.Support or Funding Information1. The ๑ ๐ ๐ th Anniversary Chulalongkorn University Fund for Doctoral Scholarship from the Graduate School, Chulalongkorn University 2. Overseas Academic Presentation Scholarship for Graduate Students from the Graduate School, Chulalongkorn University