title: Anatomical variations of the flexor hallucis longus and flexor digitorum longus in the chiasma plantare.
abstract: BACKGROUND
  The flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendon are routinely used in reconstructive foot and ankle surgery. The tendons cross in the chiasma plantare and show variable interconnections. This can complicate harvesting of the tendons. Previous anatomical studies were inconclusive and did not reference the connections to surgically relevant landmarks. The purpose of this study was to integrate these conflicting results, introduce a thorough classification system, and analyze the position of the interconnections relative to the surgically relevant bone landmarks.
  
  
  METHODS
  Sixty embalmed feet of 30 cadavers were analyzed anatomically with respect to the individual cross-links in the planta pedis. All feet were photo documented. The interconnections were classified in a modified classification system and distances to surgically relevant anatomic landmarks measured.
  
  
  RESULTS
  A proximal to distal connection from the FHL to the FDL was found in 95% of the feet (types I and III), in 3% there was a proximal to distal connection from the FDL to the FHL (type II) tendon only, and in 30% a crossed connection (type III) was found. The average point of branching of the FHL and FDL tendon was 5.3 and 4.6 cm distal to the medial malleolus, respectively.
  
  
  CONCLUSIONS
  Our modified classification system accommodated all found variations. In over 90% of the feet, a proximal to distal connection from the FHL to the FDL was found, which might contribute to the residual function of the lesser toes after FDL transfer.
  
  
  CONCLUSIONS
  The exact knowledge of the anatomy of the crossing of FDL and FHL in the plantar foot is essential to facilitate tendon harvesting, reduce morbidity and explain possible postoperative functional loss.
authors.affiliation: Department for Orthopedic Surgery, Hannover Medical School, Hannover, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Plaass
authors.forename: Ghassan
authors.initials: G
authors.lastname: Abuharbid
authors.forename: Hazibullah
authors.initials: H
authors.lastname: Waizy
authors.forename: Matthias
authors.initials: M
authors.lastname: Ochs
authors.forename: Christina
authors.initials: C
authors.lastname: Stukenborg-Colsman
authors.forename: Andreas
authors.initials: A
authors.lastname: Schmiedl
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D005528:Foot / Q000033:anatomy & histology*; D006801:Humans; D008297:Male; D013710:Tendons / Q000033:anatomy & histology*
keywords: Achilles tendon disorders; chiasma plantare; flexor digitorum longus; flexor hallucis longus; neuromuscular disorders; posterior tibial tendon dysfunction; tendon disorders; tendon transfer