title: Chiasma crurale: intersection of the tibialis posterior and flexor digitorum longus tendons above the ankle. Magnetic resonance imaging-anatomic correlation in cadavers.
abstract: OBJECTIVE
  To determine the precise anatomy and magnetic resonance (MR) imaging appearance of the chiasma crurale in cadavers, paying special attention to degenerative changes
  
  
  METHODS
  Twelve fresh human ankles were harvested from 11 nonembalmed cadavers (mean age at death 77 years) and used according to institutional guidelines. MR imaging and MR tenography were used to investigate the anatomy of the chiasma crurale using proton density-weighted sequences. The gross anatomy of the chiasma crurale was evaluated and compared to the MR imaging findings. Histology was used to elucidate further the structure of the chiasma crurale.
  
  
  RESULTS
  Above the chiasma, five specimens had a small amount of fat tissue between the tibialis posterior and flexor digitorum longus tendon. In all specimens both tendons had a sheath below the chiasma but not above it. At the central portion of the chiasma there was no soft tissue between the tendons, except in two specimens that showed an anatomic variant consisting of a thick septum connecting the tibial periosteum and the deep transverse fascia of the leg. In MR images, eight specimens showed what were believed to be degenerative changes in the tendons at the level of the chiasma. However, during gross inspection and histologic analysis of the specimens, there was no tendon degeneration visible.
  
  
  CONCLUSIONS
  At the central portion of the chiasma, there is no tissue between the tibialis posterior and flexor digitorum longus tendons unless there is an anatomic variant. At the chiasma crurale, areas with irregular tendon surfaces are normal findings and are not associated with tendon degeneration (fraying).
authors.affiliation: Department of Radiology, VA San Diego Medical Center, San Diego, CA, USA. florian.buck@gmail.com
authors.forename: Florian M
authors.initials: FM
authors.lastname: Buck
authors.forename: Ramon
authors.initials: R
authors.lastname: Gheno
authors.forename: Marcelo A C
authors.initials: MA
authors.lastname: Nico
authors.forename: Parviz
authors.initials: P
authors.lastname: Haghighi
authors.forename: Debra J
authors.initials: DJ
authors.lastname: Trudell
authors.forename: Donald
authors.initials: D
authors.lastname: Resnick
mesh_terms: D000368:Aged; D000843:Ankle Joint / Q000033:anatomy & histology*; D002102:Cadaver; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D013223:Statistics as Topic; D013710:Tendons / Q000033:anatomy & histology*