Abstract
BackgroundOpenSim musculoskeletal models provide an accurate simulation environment that eases limitations of in vivo and in vitro studies. In this work, a biomechanical knee model was formulated with femoral articular cartilages and menisci along with 25 connective tissue bundles representing ligaments and capsules. The strain patterns of the connective tissues in the presence of femoral articular cartilage and menisci in the OpenSim knee model was probed in a first of its kind study.MethodsThe effect of knee flexion (0°–120°), knee rotation (− 40° to 30°) and knee adduction (− 15° to 15°) on the anterior cruciate, posterior cruciate, medial collateral, lateral collateral ligaments and other connective tissues were studied by passive simulation. Further, a new parameter for assessment of strain namely, the differential inter-bundle strain of the connective tissues were analyzed to provide new insights for injury kinematics.ResultsACL, PCL, LCL and PL was observed to follow a parabolic strain pattern during flexion while MCL represented linear strain patterns. All connective tissues showed non-symmetric parabolic strain variation during rotation. During adduction, the strain variation was linear for the knee bundles except for FL, PFL and TL.ConclusionsStrains higher than 0.1 were observed in most of the bundles during lateral rotation followed by abduction, medial rotation and adduction. In the case of flexion, highest strains were observed in aACL and aPCL. A combination of strains at a flexion of 0° with medial rotation of 30° or a flexion of 80° with rotation of 30° are evaluated as rupture-prone kinematics.
Highlights
OpenSim musculoskeletal models provide an accurate simulation environment that eases limitations of in vivo and in vitro studies
A base musculoskeletal model of Xu et al was adopted from https://simtk.org/home/ kneemodel/. It was further developed by incorporating menisci, articular cartilages that tallied with the boundary femoral condyle, transverse ligament (TL), menisco-femoral ligaments (MFL), patella-tibial ligament (PT), capsules (CAP), popliteofibular ligament (PL), fibular ligaments (FL), and patello-femoral ligaments (PFL) [10, 11]
The strain plots of aFL, pFL, cPT, mPT, lPT and TL during flexion, rotation and adduction are shown in Additional file 1: Figure S3 for reference
Summary
OpenSim musculoskeletal models provide an accurate simulation environment that eases limitations of in vivo and in vitro studies. A biomechanical knee model was formulated with femoral articular cartilages and menisci along with 25 connective tissue bundles representing ligaments and capsules. The strain patterns of the connective tissues in the presence of femoral articular cartilage and menisci in the OpenSim knee model was probed in a first of its kind study. Though the information provided by these studies are quite valuable, there are limitations such as differences in sources of cadaveric tissues, preservation modes of tissues, in vitro conditions, experimental design and loading parameters etc., [15]. The mechanical behaviour of ACL and other ligaments in-line with real-life kinematics and loading conditions shall help us in a better understanding of the stress–strain relationship, injury mechanisms etc
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