Development Of An Anthropomorphic Thigh For Impact Assessment

Abstract

Modelling of body segments allows predictions to be made of their response characteristics during interactions with the environment. Once the segment or whole body has been replicated, their response to impact can be investigated. This along with an injury tolerence level provides an opportunity to assess the effectiveness of protective equipment. Head/neck models are used by the helmet industry to assess the effectiveness of crash and sport helmets. Wholebody models are used in the automotive and aircraft industries. No instrumented physical thigh model has been designed to assess soft tissue strain as a result of transverse impacts to the longitudinal axis. There is no appropriate means to assess the protection from injury of the numerous thigh pads used in sport. The aims of this study are: i) Determine the response of the human thigh (and its components) to transverse impacts to the longitudinal axis. ii) Select injury tolerence levels for thigh contusions. iii) Select synthetic materials with similar mechanical properties to those of the human thigh (muscle, skin and fat). iv) Design an instrumented physical model of the leg capable of predicting thigh contusions. The subjects will be seated with their thigh horizontal and a knee angle of 120 degrees. An ankle strap will be attached to a load cell. Testing will be performed at a given percent of maximal voluntary isometric cantraction for knee extension. A hemispherical striker under guided free-fall will impact the anterior mid thigh. An accelerometer will be mounted to the striker. Various drop heights may be employed dependinq on subject discomfort. Subjects have volunteered to an impact which will result in a thigh contusion. Testing will be carried out under medical supervision. Thigh skinfold and girth measurements will be taken. To estimate the internal force and the amount of dampening offerred by the biological components, cadaver material will be tested at drop heights which produced contusions in living subjects. Intact anterior thigh tissue (muscle, fascia, fat and skin) will be placed on a force platform and drop tests performed. The components (muscle, skin and fat) will also be assessed separately. Synthetic materials to represent muscle and skin and fat should display similar dampening properties as determined from cadaver impact tests. A force transducer positioned under the synthetic materials can then estimate the internal force and predict contusions.