Biomechanics of Wrist Guards – Efficient Usage in Preventing Forearm Injuries

Principal Investigator: Kyu-Jung Kim, Ph.D.

Institution: Mayo Foundation.

Project Title: Biomechanics of Wrist Guards – Efficient Usage in Preventing Forearm Injuries.

Resulting Publications:

  • SHOCK-ABSORBING EFFECTS OF VARIOUS PADDING CONDITIONS IN IMPROVING EFFICACY OF WRIST GUARDS. Il-Kyu Hwang and Kyu-Jung Kim, Journal of Sports Science and Medicine (2004) 3, 23-29
  • “Impact loading characteristics of the hand during backward fall arrests”, Kyu-Jung Kim, William P. Cooney, Kenton R. Kaufman, and Kai-Nan An. 1999 ASME Summer Bioengineering Conference, Big Sky, MT, June 1999.
  • “Three dimensional characteristics of the hand impact loading during forward and backward fall arrests using wrist guards”, Kyu-Jung Kim, William P. Cooney, Kenton R. Kaufman, and Kai-Nan An, Am. J. Sport. Med. (to be submitted).

Project Abstract: As recreational sports such as in-line skating (the fastest growing recreational sport in America) become more popular, there has been an alarming increase in the incidence of skate-related injuries. The Consumer Product Safety Commission reported that there were 76,116 in-line skating injuries in 1994, which increased more than twice than in 1993. Wrist and distal forearm injuries accounted for 59% of the injuries in 1994, with fractures being the most common form of injury, leading to a significant disability from joint stiffness, arthritis, and loss of strength. In-line skaters have injuries on their wrists despite wearing wrist guards. Although wrist guards appear to protect against wrist fracture, fractures may be higher up the arm due to the guard configuration and therefore less easily reduced. Many earlier studies based on cadaveric testing, however, failed to identify the possible injury mechanisms nor to recommend further guideline of the guard design and efficient usage.

The main hypothesis is that wrist guards make no differences in preventing forearm injuries. Performance measures include hand impact force, joint kinematics, and stresses and strains in the selected anatomical structures. This study will elucidate the forearm injury mechanisms during the foreword and backwards falls in terms of biomechanical parameters such as joint kinematics at touchdown, effective impact momentum, and joint forces and moments. Biomechanical design specification and effective usage of wrist guards can be suggested based on these findings.

In vivo impact force data from 30 young adults will be collected from the simulated fall experiment that subjects are leaned forward or backward to a specified angle into the lean control cable with hands at sides at the preset distance from the force plates. The existing experimental setup built for our earlier feasibility study will be used with minor modification. After a random time delay subjects will be suddenly released and fall. Fall arrests are made by putting the hands on the force plates, thus to isolate the roles of upper extremities. By varying location and inclination angle of the force plate, arm kinematics at contact can be controlled. Impact forces on each hand during fall arrests are measured by custom-made force plates using universal force sensors. Joint angles at touchdown are measured by a video-based motion analysis system. Using strain gauge sensors, loading at the splint of the wrist guard will be monitored. Each trial condition will be repeated with and without wrist guards. Subject safety will be ensured by wearing a harness, helmet, pelvis pad, chest protector, and joint pads. Three-dimensional finite element (FE) models of the forearm and hand will be constructed from the existing CAD models and used to simulate the impact at each different touchdown configuration. The stresses at each anatomical structure such as distal radius will be estimated from the FE impact simulation. The experimental and FE simulation parameters with and with wrist guards will be used in performance evaluation.