Development of a synthetic wrist impact surrogate for sports applications

Leslie, Gemma Elizabeth ORCID: https://orcid.org/0000-0001-6411-1808 (2022) Development of a synthetic wrist impact surrogate for sports applications. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Wrist injuries are common in snowboarding. Snowboarding wrist protectors are available, but there is limited research on their effectiveness. Previous research has explored tests for assessing the performance of wrist protectors, including bend tests and impact tests. BS EN ISO 20320:2020 was recently published as a standard for snowboarding wrist protectors. Performance testing of wrist protection typically use a wrist surrogate. The surrogate in BS EN ISO 20320:2020 consists of a simple representation of a hand and forearm, made from stiff materials and connected with a hinge joint. It is expected that a wrist surrogate utilising soft tissue simulants, rather than just stiff materials, would give a better prediction of human response under impact. Two styles of wrist protector, short and long, were chosen for testing with a developed compliant surrogate and an equivalent stiff one. A compliant surrogate with a 3 mm thick silicone outer layer and a stiff core was developed for use in a bend test for wrist protectors. Adding silicone to the surrogate increased the measured stiffness of both protectors. Finite element modelling and experiments were then used to inform the thickness of the soft tissue simulant on the palm of a wrist surrogate intended for impact testing. Impact tests against BS EN ISO 20320:2020 were conducted to determine the ability of the protector’s palmar region to limit force, and the effect of introducing an anvil shaped like a hand, and compliance in the form of a layer of silicone. Both protectors' palmar regions were better at limiting force when impacted on an anvil shaped more like a hand, and further so, when adding a silicone layer to the anvil. A compliant surrogate with a 7 mm thick silicone layer over the palmar side of the hand, and a 3 mm thickness elsewhere, was then developed for use in a pendulum impact test, which tested the entire protector. Adding compliance to the surrogate reduced the peak force and increased the time to reach this peak. This PhD project has demonstrated that testing with a biofidelic wrist surrogate can affect the measured performance of wrist protectors. Future work could further develop the biofidelity of the surrogate, such as by including a bone simulant, instrumentation and adding stiffness to the joint, to further our knowledge of wrist injury mechanisms and the effectiveness of wrist protectors.