Fig 1 - uploaded by John Leicester Williams
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Model of an implanted left knee in a squat simulation. The quadriceps and hamstrings muscles and the posterior cruciate ligament and wrapping patellar tendon and ligament are shown. The capsular tissues and the collateral ligaments are not shown, but are present in the model.
Source publication
Computational mechanics methods, such as finite element analysis or multibody dynamics, are usually employed toward the end of the design phase of a total joint implant system. It is of greater benefit, however, to utilize these methods early in the design process as a benchmarking tool to compare competitive products, as a screening tool to elimin...
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... USA) was used to simulate a double-leg deep knee bend in a manner similar to the 'Pur- due Knee Simulator. Details of the KneeSIM program and many model parame- ters have been described elsewhere [6]. The model included tibio-femoral and pa- tello-femoral contact, ligaments (MCL, LCL and PCL, capsular tissues, and quadriceps and hamstring muscles (Fig. 1). The MCL, LCL and PCL, and capsular stiffness properties were modeled with point-to-point elements (multiple elements for the capsule, two elements for the MCL and single elements for the PCL and LCL). Ligament lengths were cal- culated using the distance between the attachments. Ligament force was calculated from the relation: F = k L ...
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... sert and the reduced radius at an earlier flexion angle than for a flat insert, 'roll- back' of the COP was correspondingly slowed earlier in the flexion cycle. For the design with a femoral radius increase on a flat insert: Both CLP and COP translat- ed posteriorly continuously and a slight acceleration of 'rollback' could be seen at 30 degrees (Fig. 10). For the design with a femoral radius increase from 25 mm to 30 mm at 30 de- grees on a curved insert: CLP 'rollback' accelerated after 30 degrees, especially on the lateral side, while COP 'rollback' preceded CLP rollback due to the addi- tional curvature of the insert (Fig. 11). At approximately 105 degrees the lateral condyle of the ...
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... and a slight acceleration of 'rollback' could be seen at 30 degrees (Fig. 10). For the design with a femoral radius increase from 25 mm to 30 mm at 30 de- grees on a curved insert: CLP 'rollback' accelerated after 30 degrees, especially on the lateral side, while COP 'rollback' preceded CLP rollback due to the addi- tional curvature of the insert (Fig. 11). At approximately 105 degrees the lateral condyle of the femur with the increasing radius rode up onto the posterior lip of the curved insert and reached the edge of the flat insert. At that point the COP of the lateral side remained on the rim, while the CLP continued past the physical boundary of the inserts (Figs. 10 & 11). ...
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... curvature of the insert (Fig. 11). At approximately 105 degrees the lateral condyle of the femur with the increasing radius rode up onto the posterior lip of the curved insert and reached the edge of the flat insert. At that point the COP of the lateral side remained on the rim, while the CLP continued past the physical boundary of the inserts (Figs. 10 & 11). ...
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Citations
Lack of ACL and non-anatomic articular surfaces in contemporary total knee implants result in kinematic abnormalities. We hypothesized that such abnormalities may be addressed with a biomimetic bi-cruciate retaining (BCR) design having anatomical articular surfaces. We used dynamic computer simulations to compare kinematics among the biomimetic BCR, a contemporary BCR and cruciate-retaining implant for activities of daily living. During simulated deep knee bend, chair-sit and walking, the biomimetic BCR implant showed activity dependent kinematics similar to healthy knees in vivo. Restoring native knee geometry together with ACL preservation provided these kinematic improvements over contemporary ACL-preserving and ACL-sacrificing implants. Further clinical studies are required to determine if such biomimetic implants can result in more normal feeling knees and improve quality of life for active patients.
Copyright © 2015. Published by Elsevier Inc.
