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474 SIMULATION OF A HIGH-ARCH FOOT.
  1. S. B. Daines1,4,
  2. E. S. Rohr1,
  3. A. P. Pace1,4,
  4. M. J. Fassbind1,2,
  5. B. J. Sangeorzan1,3,
  6. W. R. Ledoux1,2,3
  1. 1RR&D Center of Excellence for Limb Loss Prevention and Prosthetic Engineering, VA Puget Sound, Seattle, WA; Departments of
  2. 2Mechanical Engineering
  3. 3Orthopaedics and Sports Medicine, University of Washington, Seattle, WA
  4. 4School of Medicine, University of Washington, Seattle, WA

Abstract

Purpose The term pes cavus describes several high-arch conditions. A precise definition is lacking, but common trends are mentioned in the literature, including hindfoot, midfoot, and forefoot inversion; forefoot adduction; first metatarsal and midfoot plantar flexion; and an increase in force on the lateral border. Pes cavus development has been linked to neurologic disease and muscle imbalance. Our goal was to create a cadaveric model of this important deformity in a normal foot by attenuating ligaments and generating muscle imbalances. A review of the literature found no previous cadaveric model.

Methods In this IRB-approved study, we tested nine freshly frozen human cadaver feet (mean age of 77.1 ± 8.3, range 65-90 years) on a frame capable of loading the extrinsic muscles and tibia/fibula. The feet were screened for osseous deformity by radiography. The tendons of the tibialis anterior (TA), peroneus longus (PL), peroneus brevis (PB), tibialis posterior (TP), flexor hallucis longus (FHL), and flexor digitorum longus (FDL) muscles as well as the Achilles tendon were exposed. We used Polhemus Fastrak electromagnetic sensors to track spatial orientation and rotations of the tibia, talus, calcaneus, navicular, medial cuneiform, cuboid, and first metatarsal. Force distribution was measured using the Novel Pedar insole pressure measurement system. The dorsal tarsometatarsal and intercuneiform ligaments were weakened by incision and cyclic loading. Data for physiologic midstance and three imbalanced conditions were collected and analyzed using linear mixed effects models.

Results Only one condition (overpull of the Achilles, TA, TP, FHL, and FDL) returned significant (p < .01) results consistent with the pes cavus deformity. These changes included plantar flexion of the midfoot and hindfoot, adduction of the forefoot, and inversion of the hindfoot, midfoot, and forefoot, as well as increased loading in the lateral forefoot and midfoot.

Conclusions We successfully created a cadaveric model of the pes cavus deformity. Future studies could focus on corrective procedures. The protocol of this experiment could be repeated before and after a procedure. An effective procedure should reduce the observed pes cavus characteristics.

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