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Screw fixation of implants to the spine

Patel, Purvi Shantilal (2010)
Ph.D. thesis, University of Birmingham.

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Bone screws are used to fix various implants to the human spine. Screw fixation can be difficult in osteoporotic bone because of its reduced strength. This research aimed to investigate screw fixation techniques in the spine. A questionnaire study, representing British and Irish spine surgeons, confirmed the potential for a simple screw positioning device and identified the need for an improved screw for osteoporotic bone. Determination of the compressive mechanical properties of 0.32\(^{-3}\), 0.16\(^{-3}\) and 0.09\(^{-3}\) polyurethane foam enabled them to be used as models for normal, osteoporotic and very low density osteoporotic, human cancellous bone, respectively. The screw pullout force from these bone models decreased with polyurethane foam density, implying that the quality of bone principally influences the strength of screw fixation. The angle of screw insertion and thread design was also found to affect screw pullout force, but not a small amount of screw toggling prior to axial pullout. No benefits in pullout strength were found when placing screws at 40° in a normal bone model or when using closely placed multiple screws in an osteoporotic bone model.

Type of Work:Ph.D. thesis.
Supervisor(s):Shepherd, Duncan E. T. and Hukins, David W. L.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Mechanical Engineering
Subjects:TJ Mechanical engineering and machinery
RD Surgery
Institution:University of Birmingham
ID Code:849
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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