Customized surface-guided total knee replacement for natural kinematics and deep flexion
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Date
2016
Authors
Pejhan, Shabnam
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Abstract
Total knee replacements (TKRs) are developed to improve the quality of the life of patients by relieving pain and restoring normal knee function. The motivation of this dissertation was to develop and evaluate a TKR that provides close to normal kinematics for all flexion ranges, including deep flexion. The objective was to determine the design features of a customized surface-guided knee implant so that no intercondylar motion guiding cam and post is required. In this design concept, specially shaped asymmetric articulating surfaces aim to guide the motion through a predefined target pattern of motion. The novel design features of the tibiofemoral articulation surfaces were generated based on patient-specific anatomic measurements of the reference landmarks and axes. Principal component analysis along with parametric analytical optimization was used to define the combination of design variables that can reach a high range of flexion, with the least deviation from the desired pattern of motion. This analysis showed that the location and orientation of the flexion-extension axis and the tibial sagittal slope were the most influential parameters on the kinematic performance.
Virtual simulations and experimental testing were used to verify the capability of the customized surface-guided TKR in reproducing the desired tibiofemoral pattern of motion. The load-controlled tests using a knee wear simulator made it possible to examine the kinematic behavior, considering the geometric design variables alone. The new surface-guided TKR can achieve a high range of flexion while following the design target pattern of motion. Experiments on the optimized TKR design show that the tibial insert rotated about 23° internally around a center on the medial condyle, as the joint bent up to 140° of flexion. Such rotation occurred as a result of posterior translation of the lateral condyle in comparison to that of the medial side.
The findings of this study prove that a customized surface-guided TKR with a lateral motion guiding articulation and a medial pivot center restores close to normal kinematics. This research is another step in the ongoing process of developing artificial knee joints that allow normal functionality and higher range of motion, and thereby improve the patients’ satisfaction.
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Keywords
Total Knee Replacement, Surface-guided, Kinematics
Citation
Shabnam Pejhan, Eric Bohm, Jan-Mels Brandt, and Urs Wyss. "Design and Virtual Evaluation of a Customized Surface-Guided Knee Implant." 2016, Proc IMechE Part H: J Engineering in Medicine 230 (10): 949-961.