Biomechanical analysis of falls onto the outstretched hand

Gittens, Nicola Jane. 2005. Biomechanical analysis of falls onto the outstretched hand. PhD Thesis, Cardiff University.

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Abstract

Research has shown that the installation of Impact Absorbing Playground Surfaces (LAPS) in play areas in Cardiff has reduced the amount of serious head injuries. However, even though head injuries have been greatly reduced in severity, arm fractures have not reduced in severity or frequency. This confirms that the current strategies for the assessment and prevention of head injury potential have been shown to be highly successful, yet totally ineffective for preventing upper limb fractures. A need therefore exists to develop a method for the assessment of playground surfaces for their ability to alleviate arm fractures. The force required to fracture the arm during a fall in a playground is currently unknown. The overall aims of the study were to investigate the forces that are produced in the arm during a fall onto the outstretched hand at a non-injurious level and to then utilize the data to aid in the development of a mechanical arm fracture model that could be used, alongside a British Standard head impact testing device, to additionally test LAPS for their ability to alleviate arm fractures. A study was conducted, using motion analysis equipment, to investigate the forces produced during a fall onto the outstretched hand. Thirty-five volunteers of mixed gender, age and weight were dropped through a height of 3 and 5 cm onto force plates, and from 5 cm onto a domestic surface and a playground surface. A further study was conducted to assess the mechanism of the arm prior to and during impact using high-speed video (HSV) equipment. Electromyography (EMG) equipment was also used to record the activation of certain muscles throughout the falls. These tests were completed with five volunteers at heights of 1 and 5 cm onto force plates, and further tests were conducted on one volunteer at heights of 10 and 20 cm, and two volunteers from standing height. The results showed that falls onto the outstretched hand produce an impact force characterised by an initial force peak, Fl, followed by two further force peaks, F2 and F3. The magnitude of force peak Fl was found to be generally higher than the subsequent force peaks F2 and F3. Force peak F3 was not prevalent in all force time curves and it was suggested from the results that when it did occur it was not significantly different to force peak F2. A positive linear relationship was found between force peaks Fl and F2 (as Fl increases, F2 increases). The increase of force peak F2 was not as great as the increase of force peak Fl, confirming the suggestion that the magnitude of force peak Fl is generally greater than F2. Gender, fall height and effective mass were found to be important factors when assessing the impact forces found during a fall onto the outstretched hand. The mechanism of the arm prior to and during impact was found to be similar regardless of the fall height and falls were found to not generally occur onto a fully extended elbow. A shock wave was produced in the arm on impact with a surface and the initiation of arm muscles in response to a fall was found to be due to motor vestibular reflexes and not an intentional cerebral decision as to when was best to arrest the fall. Using the information from the experimental fall studies, a computer model was developed to enable falls from a higher height, such as those that occur during a playground fall, to be investigated. The model was developed and a series of simulations were performed at heights of 1 and 2 cm. Despite an overestimation of the magnitude of force peak Fl, the computer model was found to correlate well with the results found from the experimental studies. Force peak Fl was influenced by fall height and force peak F2 was influenced by effective mass (in male volunteers). Data from the experimental falls and computer modelling conducted in this study, along with data from a playground injury study can be used to further develop and validate an arm fracture model to investigate playground injuries and also for application to domestic falls and non-accidental injury investigation for a range of ages.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Engineering
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
ISBN:	9781303205200
Date of First Compliant Deposit:	30 March 2016
Last Modified:	19 Jul 2023 14:02
URI:	https://orca.cardiff.ac.uk/id/eprint/56084

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