Backside Wear in Modern Total Knee Designs


Timothy Wright, PhD

Senior Scientist, Hospital for Special Surgery
F.M. Kirby Chair, Orthopaedic Biomechanics

Prakash Jayabalan, MBBS
Laboratory for Biomedical Mechanics & Materials, Hospital for Special Surgery

Bridgette D. Furman, BS
Laboratory for Biomedical Mechanics & Materials, Hospital for Special Surgery

Jocelyn M. Cottrell, BS
Laboratory for Biomedical Mechanics & Materials, Hospital for Special Surgery

Abstract
While modularity affords various options to the orthopaedic surgeon, these benefits come at a price.  The unintended bearing surface between the back surface of the tibial insert and the metallic tray results in micromotion leading to polyethylene wear debris.  The objective of this study was to examine the backside wear of tibial inserts from three modern total knee designs with very different locking mechanisms: Insall-Burstein II® (IB II®), Optetrak®, and Advance®.  A random sample of seventy-one inserts were obtained from our institutions retrieval collection and examined to assess the extent of wear, depth of wear, and wear damage modes.  Patient records were also obtained to determine patient age, body mass index, length of implantation, and reason for revision. Modes of wear damage (abrasion, burnishing, scratching, delamination, 3rd body debris, surface deformation, and pitting) were then scored in each zone from 0 to 3 (0=0%, 1>0%-10%, 2=>10%-50%, 3>50%). The depth of wear was subjectively identified as removal of manufacturing identification markings stamped onto the inferior surface of the polyethylene. Both Advance® and IBII® polyethylene inserts showed significantly higher scores for backside wear than the Optetrak® inserts. All IB II® and Advance® implants showed evidence of backside wear, whereas 17% (5 out of 30) of the retrieved Optetrak® implants had no observable wear.  There were no significant differences when comparing the depth of wear score between designs.  The locking mechanism greatly affects the propensity for wear and should be considered when choosing a knee implant system.

This article appears in HSS Journal: Volume 3, Number 1.
View the full article at springerlink.com.


About the HSS Journal
HSS Journal, an academic peer-reviewed journal, is published twice a year, February and September, and features articles by internal faculty and HSS alumni that present current research and clinical work in the field of musculoskeletal medicine performed at HSS, including research articles, surgical procedures, and case reports.


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