title: The effect of accuracy of implantation on range of movement of the Scandinavian Total Ankle Replacement.
abstract: When performing the Scandinavian Total Ankle Replacement (STAR), the positioning of the talar component and the selection of mobile-bearing thickness are critical. A biomechanical experiment was undertaken to establish the effects of these variables on the range of movement (ROM) of the ankle. Six cadaver ankles containing a specially-modified STAR prosthesis were subjected to ROM determination, under weight-bearing conditions, while monitoring the strain in the peri-ankle ligaments. Each specimen was tested with the talar component positions in neutral, as well as 3 and 6 mm of anterior and posterior displacement. The sequence was repeated with an anatomical bearing thickness, as well as at 2 mm reduced and increased thicknesses. The movement limits were defined as 10% strain in any ligament, bearing lift-off from the talar component or limitations of the hardware. Both anterior talar component displacement and bearing thickness reduction caused a decrease in plantar flexion, which was associated with bearing lift-off. With increased bearing thickness, posterior displacement of the talar component decreased plantar flexion, whereas anterior displacement decreased dorsiflexion.
authors.affiliation: Orthopaedics Biomechanics Laboratory, Department of Orthopaedics and Rehabilitation, University of Iowa, 2181 Westlawn, Iowa City, Iowa 52242-1100, USA. yuki-tochigi@uiowa.edu
authors.forename: Y
authors.initials: Y
authors.lastname: Tochigi
authors.forename: M J
authors.initials: MJ
authors.lastname: Rudert
authors.forename: T D
authors.initials: TD
authors.lastname: Brown
authors.forename: T E
authors.initials: TE
authors.lastname: McIff
authors.forename: C L
authors.initials: CL
authors.lastname: Saltzman
mesh_terms: D000368:Aged; D000843:Ankle Joint / Q000503:physiopathology / Q000601:surgery*; D019643:Arthroplasty, Replacement / Q000379:methods*; D001696:Biomechanical Phenomena; D002102:Cadaver; D005528:Foot / Q000503:physiopathology; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology; D007595:Joint Prosthesis; D008875:Middle Aged; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology*; D013314:Stress, Mechanical; D013628:Talus / Q000503:physiopathology; D016474:Weight-Bearing / Q000502:physiology