Effects of Population Variability on Knee Loading During Simulated Human Gait

Statistical-Shape Prediction of Lower Limb Kinematics During Cycling, Squatting, Lunging, and Stepping-Are Bone Geometry Predictors Helpful?

Purpose: Statistical shape methods have proven to be useful tools in providing statistical predications of several clinical and biomechanical features as to analyze and describe the possible link with them. In the present study, we aimed to explore and quantify the relationship between biometric features derived from imaging data and model-derived kinematics. Methods: Fifty-seven healthy males were gathered under strict exclusion criteria to ensure a sample representative of normal physiological conditions. MRI-based bone geometry was established and subject-specific musculoskeletal simulations in the Anybody Modeling System enabled us to derive personalized kinematics. Kinematic and shape findings were parameterized using principal component analysis. Partial least squares regression and canonical correlation analysis were then performed with the goal of predicting motion and exploring the possible association, respectively, with the given bone geometry. The relationship of hip flexion, abduction, and rotation, knee flexion, and ankle flexion with a subset of biometric features (age, length, and weight) was also investigated. Results: In the statistical kinematic models, mean accuracy errors ranged from 1.60° (race cycling) up to 3.10° (lunge). When imposing averaged kinematic waveforms, the reconstruction errors varied between 4.59° (step up) and 6.61° (lunge). A weak, yet clinical irrelevant, correlation between the modes describing bone geometry and kinematics was observed. Partial least square regression led to a minimal error reduction up to 0.42° compared to imposing gender-specific reference curves. The relationship between motion and the subject characteristics was even less pronounced with an error reduction up to 0.21°. Conclusion: The contribution of bone shape to model-derived joint kinematics appears to be relatively small and lack in clinical relevance.

Influence of the posterior cruciate ligament on kinematics of the knee during experimentally simulated clinical tests and activities of daily living

Clinical outcomes following posterior cruciate ligament (PCL) reconstruction are often suboptimal. A better understanding of the biomechanical contributions of the PCL to knee stability under physiologic, clinically-relevant loading conditions could improve reconstruction techniques and outcomes. We employed a servohydraulic joint motion simulator to investigate the kinematics of intact and PCL-deficient knees during simulated clinical tests and activities of daily living(ADL), including gait, stair ascent and descent. PCL transection caused the tibia to be displaced posterior, relative to the intact joint, throughout flexion. PCL transection also increased the amount of posterior tibial displacement measured during posterior laxity testing by up to 9.6 ± 1.7 mm at 75° (p = 0.001). During internal-external rotational laxity testing, PCL transection increased the allowable internal and external rotation of the tibia, by up to 2.9 ± 0.5°at90° (p = 0.001) and 1.0 ± 0.2° at45°(p = 0.001), respectively. PCL transection did not have a significant effect on abduction-adduction kinematics or laxity, regardless of flexion angle. PCL transection resulted in a relative posterior displacement of the tibia during the stance phase of gait when the knee was extended (2.2 ± 2.2 mm, p = 0.045), and when the knee was flexed during stair ascent (2.4 ± 2.2 mm, p = 0.035) and descent (1.6 ± 1.4 mm, p = 0.037). Our results support previous studies of the role of the PCL on neutral joint kinematics and laxity, and provide new data quantifying the effect of PCL transection on AP kinematics during simulated ADL.