Prediction of Femoral Impact Forces in Falls on the Hip

[+] Author and Article Information
S. N. Robinovitch, W. C. Hayes

Orthopedic Biomechanics Laboratory, Department of Orthopedic Surgery, Charles A. Dana Research Institute, Beth Israel Hospital and Harvard Medical School, Boston, MA 02215

T. A. McMahon

Division of Applied Sciences, Harvard University, Cambridge, MA 02138

J Biomech Eng 113(4), 366-374 (Nov 01, 1991) (9 pages) doi:10.1115/1.2895414 History: Received August 10, 1990; Revised March 30, 1991; Online March 17, 2008


A major determinant of the risk of hip fracture in a fall from standing height is the force applied to the femur at impact. This force is determined by the impact velocity of the hip and the effective mass, stiffness, and damping of the body at the moment of contact. We have developed a simple experiment (the pelvis release experiment) to measure the effective stiffness and damping of the body when a step change in force is applied to the lateral aspect of the hip. Results from pelvis release experiments with 14 human subjects suggest that both increased soft tissue thickness over the hip and impacting the ground in a relaxed state can decrease the effective stiffness of the body, and subsequently reduce peak impact forces. Comparison between our fall impact force predictions and in-vitro measures of femoral fracture strength suggest that any fall from standing height producing direct, lateral impact on the greater trochanter can fracture the elderly hip.

Copyright © 1991 by The American Society of Mechanical Engineers
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