Experimental Flatfoot Model: The Contribution of Dynamic Loading

Abstract

The goal of this study was to determine if the application of muscle forces (simulating the dynamic phase of the midstance part of gait) had an effect on flatfoot deformity. We created a flatfoot model in each of seven cadaver foot specimens by grasping the Achilles, peroneus longus, peroneus brevis, flexor digitorum longus, and flexor hallucis longus tendons with soft-tissue vice clamps connected via wire cables to pneumatic cylinders. The experiment included four stages: 1) initial static axial loading; 2) axial loading after 3,000 load cycles (average, 735 N; range, 70 to 1400 N); 3) axial loading after releasing the spring ligament and plantar fascia; and 4) axial loading after an additional 3,000 load cycles. At each stage, both static (with axial loading only) and dynamic (axial loading with tensioning of the tendons to simulate the muscle forces at midstance) conditions were evaluated radiographically. No change was observed between the static and dynamic conditions in the first two phases of the experiment. After the third phase, changes in the talar-first metatarsal angle and the height of the medial cuneiform were noted, particularly in the dynamic condition. These and additional radiographic changes were magnified in the fourth phase, but only in the dynamic condition. We concluded that, to create an effective flatfoot model, the medial structures, including the spring ligament and possibly the plantar fascia, must be severed. Cyclic loading of the foot further increased the arch flattening, and this effect was magnified by dynamic loading.

Association between Height of the Forefoot Transverse Arch and Kinetics or Kinematics of Ankle Joint during Gait

“…It has been proposed that a factor of low MLA was related to plantar aponeurosis [26]. In addition Low FTA was related to plantar aponeurosis [27].…”

Plantar Pressures in the Forefoot After Lateral Column Lengthening: A Cadaver Study Comparing the Evans Osteotomy and Calcaneocuboid Fusion

“…3,9,13 The specific simulated muscle forces were Achilles, 400 N, posterior tibial tendon, 40 N, flexor digitorum longus, 20 N, flexor hallucis longus, 20 N, peroneus longus, 40 N, and peroneus brevis, 40 N. Plantar pressure measurements were obtained using the F-scan computerized gait analysis system (Tekscan, Inc., South Boston, MA). The sensor pad has a spatial resolution of four readings per square centimeter.…”

Posterior tibial tendon dysfunction and flatfoot: Analysis with simulated walking

“…(8) Others indicated that the posterior tibial tendon (PTT) plays a role in the dynamic support of the arch. (3) Most of these previous reports were in vitro studies with static loading of specimens. Recent gait analysis studies have revealed kinematics changes of the foot between normal and flatfoot.…”