SYMPOSIA PAPER Published: 01 February 2011
STP153120120007

Mobility and Contact Mechanics of a Rotating Platform Total Knee Replacement

Despite their increasing clinical usage, mobile-bearing total knee replacements have not been well characterized biomechanically. An experimental and finite element analysis was done to asses the mobility and contact mechanics of a widely used rotating platform total knee replacement. Parameters that varied were axial load, condylar load allocation, flexion angle, and static versus dynamic loading. Similar results from the physical model and finite element model lend credence to the validity of the findings. The torque required to initiate rotation (static torque) was greater than that to sustain rotation (dynamic torque). At four times body weight axial load, peak resisting torque measured was 9.47 ± 0.61 and 5.51 ± 0.38 N-m, for static and dynamic torque, respectively. A 60–40 condylar load allocation produced slightly less resisting torque than the 50-50 load. For all practical purposes, the polyethylene insert rotated simultaneously with the femoral component, leading to maintenance of high contact area, desirable behavior clinically. Walking cycle simulations produced a total axial rotation range of motion of 6°. The high frictional torques observed at the mobile interface may explain why a percentage of these mobile-bearings fail to rotate under routine functional load.

Author Information

Otto, Jason, K.
Department of Biomedical Engineering, Univ. of Iowa, IA City, IA, US
Callaghan, John, J.
Department of Biomedical Engineering, Univ. of Iowa, IA City, IA, US Department of Orthopaedic Surgery, Univ. of Iowa, IA City, IA, US
Brown, Thomas, D.
Department of Biomedical Engineering, Univ. of Iowa, IA City, IA, US Department of Orthopaedic Surgery, Univ. of Iowa, IA City, IA, US
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Details
Developed by Committee: F04
Pages: 81–99
DOI: 10.1520/STP153120120007
ISBN-EB: 978-0-8031-9012-2
ISBN-13: 978-0-8031-7517-4