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Cadaveric simulation models allow researchers to study native tissues in situ. However, as tests are conducted using donor specimens with unmatched kinematics, techniques that impose population average motions are subject to deviation from true physiologic conditions. This study aimed to identify factors which explain the kinetic variability observed during robotic simulations of a single human gait motion using a sample of human cadaver knees. Twelve human cadaver limbs (58 ± 16 years) were subjected to tibiofemoral geometrical analysis and cyclical stiffness testing in each anatomical degree of freedom. A simulated gait motion was then applied to each specimen. Resulting kinetics, specimen geometries, and various representations of tissue stiffness were reduced to functional attributes using principal component analysis and fit to a generalized linear prediction model. The capacity of knee topography to generate force was the largest contributor to kinetic variation in compression. Overall joint size, femoral notch height, translational laxity, and ad/abduction stiffness significantly contributed to kinetic variation in medial/lateral and anterior/posterior forces and associated torques. Future studies will investigate customizing kinematic paths to better simulate native conditions and reduce sampling variation, improving biomechanical test methods and evaluation strategies for future orthopedic techniques.

Robotic testing offers researchers the opportunity to quantify native tissue loads for the structures of the knee joint during activities of daily living. These loads may then be translated into design requirements for future treatments and procedures to combat the early onset of knee degeneration following an injury. However, high knee loads during testing have the potential to deflect a robotic end effector and cause inaccuracies in the applied kinematics. Furthermore, bone bending could also induce kinematic change. This study aimed to quantify the effects of robotic compliance and bone bending on the accuracy of simulated in vivo kinematics in a KUKA KRC210 serial robotic system. Six (6) human cadaver knees were subjected to cyclic human gait motion while 6 DOF forces and torques were recorded at the joint. A Vicon T-Series camera system was used to independently record the applied kinematics. Periods of highest kinematic deviation occurred during instances of low joint loading, suggesting negligible levels of forced deflection for simulations of moderate levels of activity while results of this small study indicate that high physiologic loading poses low risk of deviation from target kinematics, further testing is necessary to confirm.