title: The role of the interosseous talocalcaneal ligament in subtalar joint stability.
abstract: BACKGROUND
  Injury of the interosseous talocalcaneal ligament (ITCL) has been recognized as a cause of subtalar instability, though lack of an accepted clinical test has limited the ability of clinicians to reliably make the diagnosis. Clinical effects of ITCL failure remain unclear because of insufficient understanding of the role of the ligament.
  
  
  METHODS
  Load-displacement characteristics of the subtalar joint were studied in six cadaver specimens using an axial distraction test and a transverse multi-direction drawer test. In all tests, cyclic loading (+/-60 N) was applied, and load-displacement responses were collected before and after sectioning of the ITCL. Two parameters were used to analyze the data: neutral-zone laxity as a measure of joint play, and flexibility as a measure of resistance to applied force.
  
  
  RESULTS
  In the axial distraction test, sectioning increased both neutral-zone laxity and flexibility (p =.01 and.02, respectively). In the transverse test, sectioning caused increase of both neutral-zone laxity and flexibility (p <.001, for each). Neutral-zone laxity increased most greatly along an axis defined roughly by the posterior aspect of the fibula and the central region of the medial malleolus. Flexibility increased most in the medial direction (p <.05, for each).
  
  
  CONCLUSIONS
  Results confirmed the role of the ITCL in maintaining apposition of the subtalar joint, as well as suggested its role in stabilizing the subtalar joint against drawer forces applied to the calcaneus from lateral to medial. The dominant direction of increased neutral-zone laxity described above suggests the optimal direction for detecting subtalar instability involved with ITCL injury.
  
  
  CONCLUSIONS
  ITCL failure may result in subtalar instability and should be examined with a drawer force along the preferential axis roughly from the posterior aspect of the fibula to the central region of the medial malleolus. Further clinical evaluation is required to determine whether ITCL failure is reliably detectable.
authors.affiliation: Department of Orthopaedics and Rehabilitation, University of Iowa, USA. yuki-tochigi@uiowa.edu
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tochigi
authors.forename: Annunziato
authors.initials: A
authors.lastname: Amendola
authors.forename: M James
authors.initials: MJ
authors.lastname: Rudert
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Baer
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Brown
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Hillis
authors.forename: Charles L
authors.initials: CL
authors.lastname: Saltzman
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D008023:Ligaments, Articular / Q000293:injuries* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D013380:Subtalar Joint / Q000503:physiopathology*; D013640:Tarsal Joints / Q000503:physiopathology