Abstract
Finite element (FE) analysis has become an increasingly popular technique in the study of human joint biomechanics, as it allows for detailed analysis of the joint/tissue behavior under complex, clinically relevant loading conditions. A wide variety of modeling techniques have been utilized to model knee joint ligaments. However, the effect of a selected constitutive model to simulate the ligaments on knee kinematics remains unclear. The purpose of the current study was to determine the effect of two most common techniques utilized to model knee ligaments on joint kinematics under functional loading conditions. We hypothesized that anatomic representations of the knee ligaments with anisotropic hyperelastic properties will result in more realistic kinematics. A previously developed, extensively validated anatomic FE model of the knee developed from a healthy, young female athlete was used. FE models with 3D anatomic and simplified uniaxial representations of main knee ligaments were used to simulate four functional loading conditions. Model predictions of tibiofemoral joint kinematics were compared to experimental measures. Results demonstrated the ability of the anatomic representation of the knee ligaments (3D geometry along with anisotropic hyperelastic material) in more physiologic prediction of the human knee motion with strong correlation (r ≥ 0.9 for all comparisons) and minimum deviation (0.9º ≤ RMSE ≤ 2.29°) from experimental findings. In contrast, non-physiologic uniaxial elastic representation of the ligaments resulted in lower correlations (r ≤ 0.6 for all comparisons) and substantially higher deviation (2.6° ≤ RMSE ≤ 4.2°) from experimental results. Findings of the current study support our hypothesis and highlight the critical role of soft tissue modeling technique on the resultant FE predicted joint kinematics.
Highlights
The knee is the largest and one of the most complex joints within the human body, consisting of both patellofemoral and tibiofemoral articulations
During the past three decades, a large number of knee Finite element (FE) models with varying degrees of complexity, accuracy and functionality have been reported in the literature [1,2,3,4,5,6,7,8,9,10,11,12]
More recent studies have used a 3D representation of knee ligaments with various degrees of anatomical and constitutive model complexity [5,6,8,9,11,12,28]
Summary
The knee is the largest and one of the most complex joints within the human body, consisting of both patellofemoral and tibiofemoral articulations Anatomical structures such as ligaments, menisci and articular cartilage provide stability across the knee joint during functional daily activities. Due to inherent challenges associated with experiments (in vivo and ex vivo) and the associated high cost and time, FE analysis has long been recognized and trusted as a reliable alternative method in the study of human joints. Primary advantage of this numerical approach lies in precise control over boundary conditions, material properties and structural alterations in parametric studies. The ligament forces/strains, contact forces/areas, and stress/strain distribution across soft and hard tissue structures are invaluable products of such a numerical approach, which are challenging, if not impossible, to obtain experimen-
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