Reproduction of In Vivo Motion Using a Parallel Robot

Abstract

Although alterations in knee joint loading resulting from injury have been shown to influence the development of osteoarthritis, actual in vivo loading conditions of the joint remain unknown. A method for determining in vivo ligament loads by reproducing joint specific in vivo kinematics using a robotic testing apparatus is described. The in vivo kinematics of the ovine stifle joint during walking were measured with 3D optical motion analysis using markers rigidly affixed to the tibia and femur. An additional independent single degree of freedom measuring device was also used to record a measure of motion. Following sacrifice, the joint was mounted in a robotic/universal force sensor test apparatus and referenced using a coordinate measuring machine. A parallel robot configuration was chosen over the conventional serial manipulator because of its greater accuracy and stiffness. Median normal gait kinematics were applied to the joint and the resulting accuracy compared. The mean error in reproduction as determined by the motion analysis system varied between 0.06 mm and 0.67 mm and 0.07 deg and 0.74 deg for the two individual tests. The mean error measured by the independent device was found to be 0.07 mm and 0.83 mm for the two experiments, respectively. This study demonstrates the ability of this system to reproduce in vivo kinematics of the ovine stifle joint in vitro. The importance of system stiffness is discussed to ensure accurate reproduction of joint motion.

A comparison of passive flexion–extension to normal gait in the ovine stifle joint

“…Gross mechanical functions of joint tissues have been defined by a series of anatomic observations over the past few decades (Markolf et al, 1976;Blankevoort et al, 1988;Beynnon et al, 1994;Xerogeanes et al, 1998) and refined by increasingly sophisticated direct measurements of their functions in vivo and in vitro (Livesay et al, 1995;Fujie et al, 1996Fujie et al, , 2004Rudy et al, 1996;Thornton et al, 1997;Beynnon and Fleming, 1998;Ma et al, 2000Ma et al, , 2003Debski et al, 2002;Darcy et al, 2003Darcy et al, , 2006Darcy et al, , 2007Gabriel et al, 2004;Tapper et al, 2004;Taylor et al, 2006;Howard et al, 2007). It is now widely recognized that each joint tissue has unique biomechanical properties, including structure specific load-deformation behaviors that are dependent on their exact loading conditions (loading direction, loading rate, zero reference position, etc.)…”

Knee Abduction Affects Greater Magnitude of Change in ACL and MCL Strains Than Matched Internal Tibial Rotation In Vitro

“…Within the past 20 years, robotic methods of joint articulation have allowed investigators to examine the underlying mechanical behaviors through more physiologic simulations of activities of daily living on cadaveric specimens [12,23,26,39]. These in vitro data would be unobtainable in vivo as a result of the invasive nature of biomechanical testing.…”

Design and Validation of a General Purpose Robotic Testing System for Musculoskeletal Applications

“…Loading generally increased error magnitude but was not pronounced for the center range of motion. The error values were less than those found in other studies, [10] and therefore, are adequate for in vitro reproduction of certain motions.…”

“…In contrast, in vitro testing with cadavers under simulated loading conditions can comple ment these other techniques and offers additional advantages. Musculoskeletal simulators and loading devices have been devel oped [5][6][7][8][9][10] to study the lower extremities. By reproducing vary ing degrees of the target kinematics and kinetics in vitro, investi gators have acquired meaningful and clinically relevant data.…”