Computational wear simulation of patellofemoral articular cartilage during in vitro testing

Abstract

Though changes in normal joint motions and loads (e.g., following anterior cruciate ligament injury) contribute to the development of knee osteoarthritis, the precise mechanism by which these changes induce osteoarthritis remains unknown. As a first step toward identifying this mechanism, this study evaluates computational wear simulations of a patellofemoral joint specimen wear tested on a knee simulator machine. A multi-body dynamic model of the specimen mounted in the simulator machine was constructed in commercial computer-aided engineering software. A custom elastic foundation contact model was used to calculate contact pressures and wear on the femoral and patellar articular surfaces using geometry created from laser scan and MR data. Two different wear simulation approaches were investigated – one that wore the surface geometries gradually over a sequence of 10 one-cycle dynamic simulations (termed the “progressive” approach), and one that wore the surface geometries abruptly using results from a single one-cycle dynamic simulation (termed the “non-progressive” approach). The progressive approach with laser scan geometry reproduced the experimentally measured wear depths and areas for both the femur and patella. The less costly non-progressive approach predicted deeper wear depths, especially on the patella, but had little influence on predicted wear areas. Use of MR data for creating the articular and subchondral bone geometry altered wear depth and area predictions by at most 13%. These results suggest that MR-derived geometry may be sufficient for simulating articular cartilage wear in vivo and that a progressive simulation approach may be needed for the patella and tibia since both remain in continuous contact with the femur.

Effect of Tibial Posterior Slope on Knee Kinematics, Quadriceps Force, and Patellofemoral Contact Force After Posterior-Stabilized Total Knee Arthroplasty

“…Computer simulations can apply large loads and duplicate weight-bearing activities using musculoskeletal models that can diminish the limitations of clinical and cadaveric experimental studies. Several previous papers used simulations to predict postoperative flexion angle, knee kinematics, joint load, and damage to the insert [18][19][20][21]. These results were validated by clinical data [20] and implant retrieval findings [21].…”

The 2014 ABJS Nicolas Andry Award: The Puzzle of the Thumb: Mobility, Stability, and Demands in Opposition

“…We are pursuing these with collaborations at Brown University and University of Auckland, including the potential use of high-resolution registration with dual fluoroscopy [73,104]. The computational methods employ either statistical shape modeling [5,41,66] or rigid body dynamics [41], integrating 3-D data to develop subject-specific models to predict changes over time, such as patterns of joint degeneration, response to fracture, or ligament disruption.…”

Results of automatic image registration are dependent on initial manual registration

“…This suggests that initial configuration of registration volumes may be important and should be carefully considered for acquiring contact data using image registration. Li et al (2011) demonstrated changes in femoral and patellar wear contact areas of up to 5% with variations in pose. Fregly et al (2008) showed variations in contact parameters after knee replacement of up to 1157% with errors in translation and rotation.…”

“…However, when using registration to acquire transformations from image sets such as MRI, the initial configuration of the registration volumes may potentially influence the final outcome. Contact mechanics simulations may be subsequently affected and studies have shown contact parameters to be sensitive to variations in initial alignment (Li et al 2011). It is possible that the results of automatic registration are sensitive to initial alignment of the images, and that the further apart the registration volumes, the less likely that automatic registration provides a good solution.…”