title: Systematic Quantification of Stabilizing Effects of Subtalar Joint Soft-Tissue Constraints in a Novel Cadaveric Model.
abstract: BACKGROUND
  Distinguishing between ankle instability and subtalar joint instability is challenging because the contributions of the subtalar joint's soft-tissue constraints are poorly understood. This study quantified the effects on joint stability of systematic sectioning of these constraints followed by application of torsional and drawer loads simulating a manual clinical examination.
  
  
  METHODS
  Subtalar joint motion in response to carefully controlled inversion, eversion, internal rotation, and external rotation moments and multidirectional drawer forces was quantified in fresh-frozen cadaver limbs. Sequential measurements were obtained under axial load approximating a non-weight-bearing clinical setting with the foot in neutral, 10° of dorsiflexion, and 10° and 20° of plantar flexion. The contributions of the components of the inferior extensor retinaculum were documented after incremental sectioning. The calcaneofibular, cervical, and interosseous talocalcaneal ligaments were then sectioned sequentially, in two different orders, to produce five different ligament-insufficiency scenarios.
  
  
  RESULTS
  Incremental detachment of the components of the inferior extensor retinaculum had no effect on subtalar motion independent of foot position. Regardless of the subsequent ligament-sectioning order, significant motion increases relative to the intact condition occurred only after transection of the calcaneofibular ligament. Sectioning of this ligament produced increased inversion and external rotation, which was most evident with the foot dorsiflexed.
  
  
  CONCLUSIONS
  Calcaneofibular ligament disruption results in increases in subtalar inversion and external rotation that might be detectable during a manual examination. Insufficiency of other subtalar joint constraints may result in motion increases that are too subtle to be perceptible.
  
  
  CONCLUSIONS
  If calcaneofibular ligament insufficiency is established, its reconstruction or repair should receive priority over that of other ankle or subtalar periarticular soft-tissue structures.
authors.affiliation: Department of Orthopaedic Surgery, Hospital Clinico Universidad de Chile, Santiago, Chile mpellegrini@hcuch.cl.
authors.forename: Manuel J
authors.initials: MJ
authors.lastname: Pellegrini
authors.affiliation: Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina r.r.glisson@duke.edu.
authors.forename: Richard R
authors.initials: RR
authors.lastname: Glisson
authors.affiliation: Department of Orthopedic and Trauma Surgery, University Hospital Basel, Basel, Switzerland markus.wurm@usb.ch.
authors.forename: Markus
authors.initials: M
authors.lastname: Wurm
authors.affiliation: Department of Radiology, Deventer Ziekenhuis, Deventer, the Netherlands pousema@gmail.com.
authors.forename: Paul H
authors.initials: PH
authors.lastname: Ousema
authors.affiliation: Sports Medicine and Orthopaedic Surgery, Orthopedic Foot and Ankle Center of Hampton Roads, Chesapeake, Virginia orthofoot@cox.net.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Romash
authors.affiliation: Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina james.nunley@duke.edu.
authors.forename: James A
authors.initials: JA
authors.lastname: Nunley
authors.affiliation: Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina mark.e.easley@duke.edu.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Easley
mesh_terms: D000328:Adult; D000368:Aged; D000843:Ankle Joint / Q000502:physiology* / Q000503:physiopathology; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D017844:Lateral Ligament, Ankle / Q000502:physiology* / Q000503:physiopathology; D008023:Ligaments, Articular / Q000502:physiology* / Q000503:physiopathology; D008875:Middle Aged; D008953:Models, Anatomic; D016059:Range of Motion, Articular; D013380:Subtalar Joint / Q000502:physiology* / Q000503:physiopathology