Article

Many biomechanical studies investigated pathology of flatfoot and effects of
operations on flatfoot. The majority of cadaveric studies are limited to the
quasistatic response to static joint loads. This study examined the unconstrained
joint motion of the foot and ankle during stance phase utilizing a dynamic
foot-ankle simulator in simulated stage 2 posterior tibial tendon dysfunction
(PTTD). Muscle forces were applied on the extrinsic tendons of the foot using six
servo-pneumatic cylinders to simulate their action. Vertical and fore-aft shear
forces were applied and tibial advancement was performed with the servomotors.
Three-dimensional movements of multiple bones of the foot were monitored with a
magnetic tracking system. Twenty-two fresh-frozen lower extremities were studied
in the intact condition, then following sectioning peritalar constraints to
create a flatfoot and unloading the posterior tibial muscle force. Kinematics in
the intact condition were consistent with gait analysis data for normals. There
were altered kinematics in the flatfoot condition, particularly in coronal and
transverse planes. Calcaneal eversion relative to the tibia averaged 11.1+/-2.8
degrees compared to 5.8+/-2.3 degrees in the normal condition. Calcaneal-tibial
external rotation was significantly increased in flatfeet from mean of 2.3+/-1.7
degrees to 8.1+/-4.0 degrees . There were also significant changes in
metatarsal-tibial eversion and external rotation in the flatfoot condition. The
simulated PTTD with flatfoot was consistent with previous data obtained in
patients with PTTD. The use of a flatfoot model will enable more detailed study
on the flatfoot condition and/or effect of surgical treatment.
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Langue : ANGLAIS