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Scientific Articles   |    
Effect of Implantation Accuracy on Ankle Contact Mechanics with a Metallic Focal Resurfacing Implant
Donald D. Anderson, PhD1; Yuki Tochigi, MD, PhD1; M. James Rudert, PhD1; Tanawat Vaseenon, MD1; Thomas D. Brown, PhD1; Annunziato Amendola, MD1
1 Department of Orthopaedics and Rehabilitation, Orthopaedic Biomechanics Laboratory, The University of Iowa, 2181 Westlawn Building, Iowa City, IA 52242-1100. E-mail address for D.D. Anderson: don-anderson@uiowa.edu
View Disclosures and Other Information
Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants in excess of $10,000 from Arthrosurface, Inc., and the National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases (Grant P50 AR055533). In addition, one or more of the authors or a member of his or her immediate family received, in any one year, payments or other benefits of less than $10,000 or a commitment or agreement to provide such benefits from a commercial entity (Arthrosurface, Inc.).

Investigation performed at the Department of Orthopaedics and Rehabilitation, Orthopaedic Biomechanics Laboratory, The University of Iowa, Iowa City, Iowa

Copyright ©2010 American Society for Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2010 Jun 01;92(6):1490-1500. doi: 10.2106/JBJS.I.00431
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Abstract

Background: 

Talar osteochondral defects can lead to joint degeneration. Focal resurfacing with a metallic implant has shown promise in other joints. We studied the effect of implantation accuracy on ankle contact mechanics after focal resurfacing of a defect in the talar dome.

Methods: 

Static loading of seven cadaver ankles was performed before and after creation of a 15-mm-diameter osteochondral defect on the talar dome, and joint contact stresses were measured. The defect was then resurfaced with a metallic implant, with use of a custom implant-bone interface fixture that allowed fine control (in 0.25-mm steps) of implantation height. Stress measurements were repeated at heights of —0.5 to +0.5 mm relative to an as-implanted reference. Finite element analysis was used to determine the effect of implant height, post axis rotation, and valgus/varus tilt over a motion duty cycle.

Results: 

With the untreated defect, there was a 20% reduction in contact area and a 40% increase in peak contact stress, as well as a shift in the location of the most highly loaded region, as compared with the values in the intact condition. Resurfacing led to recovery of 90% of the contact area that had been measured in the intact specimen, but the peak contact stresses remained elevated. With the implant 0.25 mm proud, peak contact stress was 220% of that in the intact specimen. The results of the finite element analyses agreed closely with those of the experiments and additionally showed substantial variations in defect influences on contact stresses across the motion arc. Talar internal/external rotations also differed for the unfilled defect. Focal implant resurfacing substantially restored kinematics but did not restore the stresses to the levels in the intact specimens.

Conclusions: 

Focal resurfacing with a metallic implant appears to have the potential to restore normal joint mechanics in ankles with a large talar osteochondral defect. However, contact stresses were found to be highly sensitive to implant positioning.

Clinical Relevance: 

Resurfacing a talar osteochondral defect with an implant that restores the joint contour, that provides immediate stability, and that reproduces normal joint mechanics, without requiring biological potential, offers advantages over existing resurfacing techniques; however, restoration of normal joint mechanics is highly dependent on precise surgical implantation.

Figures in this Article

    Topics

    ankle ; cadaver ; cartilage
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    References

    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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