Conference PaperPDF Available
Introduction
Musculo-skeletal (MS) models are emerging as potential tools
for the aid in orthopedic interventions, including Total Knee
Arthroplasty (TKA).
Recently, we presented and validated a subject-specific MS
model of TKA [1] that incorporates realistic contact, ligament
restraint and muscle activation.
Knee joint stability has previously not been evaluated.
Establishing realistic model predictions of kinematics as well
as joint stability is an essential step towards clinical use.
Objective
The aim of this study was to evaluate the model-predicted knee
joint stability, as obtained from simulations of knee joint laxity.
Material and Methods
Model. A previously validated model of TKA [1]. Only femur,
tibia and patella are included. The femur was constrained in
all directions except flexion-extension, which was being
driven. Tibia flexion-extension was constrained, leaving 11
patella and tibia degrees of freedom. These were solved using
Force-Dependent Kinematics [2]. Patellar ligament was
modeled with 3 elastic springs and overall ligament properties
were adapted from the literature.
Laxity simulation. We simulated anterior-posterior, varus-
valgus, and internal-external knee laxity, by applying specific
loads to the tibia (see Figure), and a neutral unloaded case as
reference. A constant pulling force of 200 N was applied to
the patella, and the femur was flexed from 0°-120°.
Evaluation. Knee kinematics were measured using Grood and
Suntays definition for the knee joint coordinate system [3].
Laxity in each direction was calculated as the difference
between the values of the loaded and reference case. The
results were then compared with experimental data [4].
Results
Posterior-Anterior tibial drawer laxity:
Valgus-varus laxity: Internal-external rotation laxity:
Discussion and Conclusion
Overall, the model followed the trends of reported knee joint
laxity for similar experiment and implant type.
Discrepancies may be due to differences in implant
characteristics, surgical technique, and ligament restraint.
In presence of subject-specific laxity test data, the knee joint
stability may be further calibrated on an individual basis.
Future work
We aim at studying the effect of variations in surgical
technique in TKA, such as tibial cut slope, varus-valgus
alignment, and orientation of the femoral component.
References:
[1] M. A. Marra, V. Vanheule, R. Fluit, B. H. F. J. M. Koopman, J. Rasmussen, N. J. J. Verdonschot, and M. S. Andersen, “A
Subject-Specific Musculoskeletal Modeling Framework to Predict in Vivo Mechanics of Total Knee Arthroplasty.,” J.
Biomech. Eng., Nov. 2014.
[2] M. S. Andersen, M. Damsgaard, and J. Rasmussen, “Force-dependent kinematics: a new analysis method for non-
conforming joints,” in XIII International Symposium on Computer Simulation in Biomechanics, 2011.
[3] E. Grood and W. Suntay, “A joint coordinate system for the clinical description of three-dimensional motions:
application to the knee.,” J. Biomech. Eng., 1983.
[4] A. M. J. Bull, O. Kessler, M. Alam, and A. A. Amis, “Changes in knee kinematics reflect the articular geometry after
arthroplasty.,Clin. Orthop. Relat. Res., vol. 466, pp. 24912499, 2008.
Evaluation of laxity tests with a musculo-
skeletal model of Total Knee Arthroplasty.
M.A. Marra¹, M. Strzelczak¹, S. van de Groes², P. Heesterbeek³, A. Wymenga⁴, H.F.J.M. Koopman⁵, D. Janssen¹, N. Verdonschot¹,
¹Orthopaedic Research Lab, Radboud university medical center, Nijmegen, The Netherlands, ²Orthopaedic Department, Radboud university medical center,
Nijmegen, The Netherlands, ³Research Department, Sint Maartenskliniek, Nijmegen, The Netherlands, ⁴Department of Orthopaedics, Sint Maartenskliniek,
Nijmegen, The Netherlands, ⁵Department of Biomechanical Engineering, University of Twente, Enschede, The Netherlands
Marco Marra, PhD student
Marco.Marra@radboudumc.nl
Orthopaedic Research Laboratory
Radboud university medical center
P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
www.biomechanics.nl
-10
-5
0
5
10
0 15 30 45 60 75 90
mm
Knee Flexion, deg
Bull et al.
Model
Anterior
Posterior
-5
-3
-1
1
3
5
0 15 30 45 60 75 90
deg
Knee Flexion, deg
-20
-10
0
10
20
0 15 30 45 60 75 90
deg
Knee Flexion, deg
Varus
Valgus
External rotation
Internal rotation
*adapted, averages over multiple experiments are shown
*
0°
6°
3°
+2 mm
+4 mm
9°
A
Tibial displacement during the
anterior laxity simulation
Acknowledgments:
This research is part of the ERC
project ‘BioMechTools, funded
by the European Commission
www.erc-biomechtools.eu
ResearchGate has not been able to resolve any citations for this publication.
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Musculoskeletal (MS) models should be able to integrate the patient-specific MS architecture and undergo thorough validation prior to their introduction into the clinical practice. We present a streamlined methodology to develop subject-specific models able to simultaneously predict body-level dynamics, muscle forces, ligament forces, knee joint contact forces and secondary knee kinematics. The MS architecture of a generic cadaver-based model was scaled using an advanced morphing technique to the subject-specific morphology of a patient implanted with an instrumented total knee arthroplasty available in the fifth "Grand Challenge Competition to Predict in Vivo Knee Loads" dataset. Inverse dynamics-like analyses of a hinge-like knee model and an 11-degree-of-freedom force-dependent kinematics (FDK) knee model were simulated for one gait, one right-turn and one unloaded leg-swing trial. Predicted tibiofemoral (TF) forces and secondary knee kinematics were evaluated using experimental data available in the Grand Challenge dataset. Total TF contact forces were predicted with a root-mean-square error (RMSE) and a coefficient of determination (R^2) smaller than 0.3 BW and higher than 0.9, respectively, for both gait and right-turn trials. Secondary knee kinematics from the leg-swing trial were overall better approximated using the FDK model (average Sprague and Geers' combined error C = 0.06) than when using a hinged knee model (C = 0.34). The proposed modeling approach allows detailed subject-specific scaling and personalization, and does not contain any non-physiological parameters. This modeling framework has potential applications in aiding the clinical decision-making in orthopedics procedures, and as a tool for virtual implant design.
Force-dependent kinematics: a new analysis method for nonconforming joints
  • M S Andersen
  • M Damsgaard
  • J Rasmussen
M. S. Andersen, M. Damsgaard, and J. Rasmussen, "Force-dependent kinematics: a new analysis method for nonconforming joints," in XIII International Symposium on Computer Simulation in Biomechanics, 2011.