IN VITRO SIMULATION OF THE STANCE PHASE IN HUMAN GAIT

Abstract

The purpose of this study is to develop an electromechanical system for dynamic simulation of the stance phase of a human gait using cadaveric foot specimens. The system can be used for quantification of foot and ankle pathomechanics and design of foot and ankle reconstructive surgeries. Servo-pneumatic systems were used for application of the tibial weight loading and muscle loadings. A four-bar mechanism was constructed to provide the progressive motion of a tibia during the simulation while the external loadings were simultaneously applied. Muscle loadings were estimated based on the physiological cross-sectional area and normal electromyography (EMG) data with the assumption of the linear EMG–force relationship. Ad hoc tuning of the unknown muscle gains was conducted until a reasonable match with the normal vertical ground reaction force profile, center of pressure advancement, and characteristic foot motion events (heel strike, foot flat, heel rise and toe-off) could be made. Three cadaver feet and an artificial foot were tested with five repeated trials. The simulator reproduced the stance phase of a human gait in the sagittal plane with reasonable accuracy and consistency without compromising either kinematics or kinetics of the foot and ankle complex.

An in vitro approach to the evaluation of foot-ankle kinematics: Performance evaluation of a custom-built gait simulator

“…In particular we assume the knee and ankle joint axis to be fixed and all segments to be rigid. Furthermore, the set-up has limited degrees of freedom to control knee movement as is the case in existing gait simulators [1,[3][4][5]. In particular, our set-up lacks to simulate the fontal and transverse plane motion that occurs at the knee and which was observed to be quite significant [23].…”

“…In order to investigate foot function under dynamic conditions representative for gait, several groups have developed a set-up for dynamic in vitro gait simulation using cadaveric feet [1,[3][4][5][6][7], all applying forces to the tendons and controlling tibial kinematics, in some cases supplemented with ground reaction forces. Since the first publication on in vitro gait simulation [1], each group has focused on improving several aspects of the existing approaches, being mainly the limited degrees of freedom of the mechanism controlling the kinematics of the tibia, the low gait speed, the limited forces applied to the tendons and the limited ground reaction force magnitudes.…”

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

“…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.…”

An Innovative Testing Protocol to Study Foot and Ankle Kinetics during Early Stance Phase of Gait

“…Few testing platforms can evaluate lower limb kinetics [8,9,10,11,12], and of those the instantaneous axis of rotation (IAR ) is approximated or forced to follow a set IAR pathway that is not its own. Even with strong evidence that the ankle behaves according to a system with an instantaneous axis, many still approximate a single point of rotation for the ankle during rotation [13] or use overly simplified techniques as graphically tracking landmarks over large angles [14] on an x-ray.…”

“…The results are tight and consistent per results from the repeatability study. While many still estimate the IAR of the ankle complex as a single point [14] or poorly approximated [9][10][11][12][13]15], this method would offer better insight into the kinetics of the foot and ankle complex.…”