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Design, development and testing of a non-invasive spinal rod system to treat scoliosis

Rodríguez Arévalo, A.C.; (2009) Design, development and testing of a non-invasive spinal rod system to treat scoliosis. Doctoral thesis, University of London.

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Abstract

ldiopathic scoliosis is a tri-dimensional deformity of the spine surgically corrected by means of instrumentation such as the Harrington rod. This correction can be of two types: vertebral fusion and fusionless correction. During vertebral fusion, the spinal deformity is corrected, a metal implant fixed to several vertebrae and morsellised bone used to promote fusion. However, if performed in children and adolescents, it can hinder their trunk height affecting the growth of the ribcage and internal organs. Fusionless correction addresses this by performing a staged correction of the spine allowing for vertical growth, but it increases the risk of deep infection and trauma due to repeated surgeries. A non-invasive system based on a growing endoprosthesis, which permits staged correction and minimizes infection risk, was designed and its systems tested. This device provides a distraction force to overcome the natural soft tissue response which amounts to a maximum of 6OON. The drive unit providing this extension is comprised of a commercially available micro-motor, gear-head and encoder combination, attached to a specially designed gearbox which transforms the rotation into vertical extension via a threaded stainless steel rod attached to the uppermost vertebra of the deformity. The implant is sealed within a stainless steel chamber and controlled with an inductive link. The inductive link has been designed and tested for operation at increasing distance between its coils. This system provides the necessary power for the implant and transmits data from the drive unit which is used to perform automatic control with a closed-loop system. The control system maintains the power of the motor so that the extension is stable and comfortable to the patient. This thesis presents the design and testing of the inductive link, measurement of spinal forces, testing of the miniature motor and gearbox and mechanical implant fatigue testing.

Type:Thesis (Doctoral)
Title:Design, development and testing of a non-invasive spinal rod system to treat scoliosis
Language:English
UCL classification:UCL > School of Life and Medical Sciences > Faculty of Medical Sciences > Surgery and Interventional Science (Division of) > Institute of Orthopaedics and Musculoskeletal Science

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