Biomechanics of Calcaneal Fractures: A Model for the Motor Vehicle
Supported in part by the Department of Transportation,
National Highway Traffic Safety Administration Grand DTNH22-93-Y-17028 and the Department of Veterans Affairs Medical Research

Robert C. Seipel, MD
Medical College of Wisconsin
Department of Orthopaedic Surgery

Frank A. Pintar, PhD
Medical College of Wisconsin
Department of Neurosurgery

Narayan Yoganandan, PhD
Medical College of Wisconsin
Department of Neurosurgery

Melbourne D. Boynton, MD
Vermont Orthopaedic Clinic

Corresponding Author:
Frank A. Pintar, PhD
Medical College of Wisconsin
Department of Neurosurgery

Abstract: Changes in legislation, availability of passive or active restraint systems or both, together with increased public awareness for safety and the need for use of restraint, have shifted the spectrum of trauma in motor vehicle crashes from the head and torso to other regions. Lower extremity trauma in motor vehicle crases continues to be a significant problem. The objective of this study was to investigate the biomechanics of the human foot and ankle complex under impact loading and replicate calcaneal fractures routinely seen in motor vehicle crashes. Twenty-two unembalmed cadaver lower extremity specimens were subjected to dynamic loads using a mini-sled pendulum device. Input and output forces and results of pathologic analysis were obtained using load cell data, radiographs obtained before and after testing, and gross dissection. The intraarticular fracture patterns produced were similar to those seen clinically and described in the literature. Maximum forces ranged from 3.6 to 11.4 kN for the fracture, and 0.5 to 7.3 kN for the nonfracture groups. Logistic regression analysis revealed a 50% probability of calcaneal fracture at 5.5 kN and a 25% probability at 4.0 kN. These studies will lead to an understanding of the tolerance of the lower extremity in sustaining calcaneal fractures under impact. Implications of the work are in the design of crash test dummies, data acquisition, and modifications in motor vehicle design and safety.