Towards an Intelligent Intervertebral Disc Prosthesis for the Assessment of Spinal Loading

Pancholi, M. (2010). Towards an Intelligent Intervertebral Disc Prosthesis for the Assessment of Spinal Loading. (Unpublished Doctoral thesis, City University London)

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Abstract

Low back pain is an economic and social burden to society. Low back pain is considered to be a chronic problem when the causes are due degenerative disc diseases and damaged vertebrae. The main causes for degenerative disc are extremely complex and still not well understood, although in their majority are strongly related to the acute and frequent mechanical loading on the spine. Knowledge that might shed more light on such pathologies is the availability of in vivo human spinal disc loading data, which at the moment does not exist. Many efforts had been made by researchers to investigate and understand the in vivo loading of the human spinal disc. All such techniques were not true in vivo techniques and hence, their findings are questionable. Not only a full understanding of the in vivo loading of the human spine, but also the distribution of the loading on the spinal disc are of prime importance in order to comprehensively understand the biomechanics of the human spine. Such new knowledge will also be helpful in the treatment of vertebrae compression fractures and also aid in the further improvement of current implantable spinal technologies. The aim of this work was to engage in such investigation by developing a prototype intelligent artificial spinal disc with the capability of mapping the loads applied to the disc when it's loaded in an in vitro and ex vivo environment. In this research, for the first time a commercial artificial intervertebral disc prosthesis was used as a base for a load-cell. Following a critical review of possible suitable sensors to be embedded within the artificial spinal disc, it was concluded that strain gauges and piezoresistive thin layer sensors were the most appropriate for incorporation within the body of the artificial spinal disc. The loading cell has been successfully designed and developed comprising of eight strain gauges and two piezoresistive sensors encapsulated inside the body of the artificial spinal disc. Further instrumentation and software were developed in order to interface the loading cell with a data acquisition system. A universal testing machine was used for all loading experiments. In vitro and ex vivo (using an animal spine) experiments were conducted in order to evaluate the developed technology and also to rigorously investigate the loading behaviour of the new loading cell. Following the in vitro and ex vivo experiments, it can be concluded that all the sensors' outputs are almost identical in characteristics. All results are very much predictable with moderate level of tolerances, uncertainty, accuracy and repeatability. Such results suggest that this new intelligent artificial intervertebral disc prosthesis could allow the in vivo investigation of loading on the human spine in the lumbar region and therefore enable the continuous postoperative assessment of patients that had a spinal disc surgical intervention.

Item Type: Thesis (Doctoral)
Subjects: R Medicine
T Technology > TK Electrical engineering. Electronics Nuclear engineering
Divisions: School of Engineering & Mathematical Sciences
URI: http://openaccess.city.ac.uk/id/eprint/12072

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