Shock Attenuation of Various Protective Devices for Prevention of Fall-Related Injuries of the Forearm/Hand Complex

Shock Attenuation of Various Protective Devices for Prevention of Fall-Related Injuries of the Forearm/Hand Complex
First published on December 28, 2005, doi:10.1177/0363546505281800
This version was published on April 1, 2006
Kyu-Jung Kim, PhD*,, Ali M. Alian, MS, William S. Morris and Young-Hwa Lee, MS
The American Journal of Sports Medicine 34:637-643 (2006)

© 2006 American Orthopaedic Society for Sports Medicine

From the Department of Mechanical Engineering, California State Polytechnic University-Pomona, Pomona, California Department of Mechanical Engineering, University of WisconsinÒMilwaukee, Milwaukee, Wisconsin, and the Department of Factory Automation, Dongyang Technical College, Seoul, Korea

* Address correspondence to Kyu-Jung Kim, PhD, Department of Mechanical Engineering, California State Polytechnic University-Pomona, 3801 West Temple Avenue, Pomona, CA 91768 (e-mail: kyujungkim@csupomona.edu).

Background: Attenuation of the peak impact force is essential in any protective devices for prevention of fall-related injuries.

Hypothesis: Common wrist guards have limited effectiveness because of the multifaceted nature of wrist injury mechanisms, and other modalities may provide enhanced shock-absorbing functions.

Study Design: Controlled laboratory study.

Methods: A free-fall device was constructed using a mechanical surrogate to simulate falling impact. At 4 different falling heights, 5 different hand conditions were tested: bare hand, a generic-brand wrist guard, a Sorbothane glove, an air cell, and an air bladder condition. The impact force from the ground and the transmitted impact force to the forearm/hand complex were simultaneously measured.

Results: The falling height and hand condition significantly modulated the impact responses. The padded conditions always had significantly smaller peak impact forces compared with the bare-hand condition. The wrist guard became ineffective in impact force attenuation beyond the falling height of 51 cm. On the other hand, the air bladder condition maintained less than 45% of the peak impact force of the bare-hand condition and remained below the critical value, whereas other conditions were all ineffective.

Conclusion: It was reconfirmed that common wrist guard design could provide limited impact force attenuation, whereas damped pneumatic springs would provide substantially enhanced shock-absorbing functions.

Clinical Relevance: A wrist guard incorporating volar padding with the pneumatic spring design principle might be more effective at preventing injuries than are currently available designs.

Key Words: falling Ô biomechanics Ô fractures Ô prevention

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