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Title: Biomechanics of limb prostheses directly attached to bone
Author: Newcombe, Lindsay Kathleen
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2009
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The technique of attaching a limb directly to the skeleton has clear benefits, when compared with socket-attachment, for the many amputees who encounter skin problems. A potential risk of attaching a limb to the skeleton is the wound where the implant breaches the skin. At the Centre for Biomedical Engineering in the Institute of Orthopaedics and Musculoskeletal Science at UCL, a method has been devised which enhances epithelial attachment to the implant, resisting infection, and this has been used to develop a system for attaching a limb to the skeleton: Intraosseous Transcutaneous Amputation Prosthesis, or ITAP. In a transfemoral prosthesis, protection of bone from external loading is anticipated and in this thesis a fail-safe component is designed to prevent fracture. It has adjustable activation levels and has been tested to the appropriate International Standards. In order to determine loads that are to be allowed and prevented, normal loading of the femur during ordinary activities is researched failure modes of femoral bone are investigated. Finite element analysis is employed to investigate the stress distribution throughout the femur with the attachment of a prosthetic leg. A cylindrical model is used to assess the effect of varying geometry and material properties of the bone and implant. An anatomical model, derived from a CT scan, is used to analyse the effect of stump length. There are three risk groups that the amputee can be allocated depending on the level of amputation, the size of the bone, and the amount of bone contact with the implant. At the beginning of rehabilitation the fail-safe is set low to protect the poorer bone and bone-implant interface. The settings are gradually increased during rehabilitation to 60Nm, 80Nm or 100Nm in bending and 10Nm, 15Nm and 25Nm in torsion for high, medium and low risk amputees respectively.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available