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Journal of Bone and Joint Surgery - British Volume, Vol 87-B, Issue 5,
736-740.
doi: 10.1302/0301-620X.87B5.14872 Copyright © 2005 by British Editorial Society of Bone and Joint Surgery The effect of accuracy of implantation on range of movement of the Scandinavian Total Ankle ReplacementY. Tochigi, MD, Visiting Assistant Professor; M. J. Rudert, PhD, Associate Research Engineer; T. D. Brown, PhD, Professor; T. E. McIff, PhD, Research Assistant Professor; and C. L. Saltzman, MD, ProfessorOrthopaedics Biomechanics Laboratory, Department of Orthopaedics and Rehabilitation, University of Iowa, 2181 Westlawn, Iowa City, Iowa 52242-1100, USA, Section of Orthopaedic Surgery, University of Kansas Medical Center, 5002 Eaton Hall, 3901 Rainbow Boulevard, Kansas City, Kansas 66160, USA, Department of Orthopaedics and Rehabilitation University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242-1088, USA. Correspondence should be sent to Dr Y. Tochigi; e-mail: yuki-tochigi{at}uiowa.edu
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.
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