There is an increasing demand for spinal surgery and a growing number of new spinal implants and surgical procedures being offered by orthopaedic companies. However, the testing of spinal implants and spinal instrumentation is problematic, with testing in cadavers and animals becoming increasingly difficult and both having significant limitations. Thus the aim of this research is to develop an artificial laboratory spine that will have the same physical and biomechanical properties as the human spine. Validation of computer model is difficult hence an active artificial laboratory spine is being developed. A number of spinal elements have been produced and are being investigated, including an artificial intervertebral disc with different material properties to allow it to simulate different clinical conditions. The study is the first of its kind with the characteristics of the disc material that have been assessed in the laboratory, artificial muscles and spring elements and with normal physiological movements compared and validated from the reported literature. The model was used to investigate the potential of Shape Memory Alloy wires to act as artificial muscles and to control the movement of the spine. It is anticipated that the laboratory spine will have a number of other applications, in particular in the assessment of spinal instrumentation and testing. An actual geometry laboratory spine is also generated with suitable manufacturing technique for intervertebral disc, which has an accurate surface profile to fit between the two vertebral bodies above and below it, is discussed in this thesis.

Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (M.S.)--University of Toledo, 2009. / Typescript. "Submitted as partial fulfillment of the requirements for the Master of Science Degree in Mechanical Engineering." "A thesis entitled"--at head of title. Bibliography: leaves 92-98.

Interbody fusion cages are increasingly used in the treatment of spinal disease and injury in order to stabilize movement and promote arthrodesis of the vertebral bodies, but the micro-mechanics of the interaction between the cage and the adjacent host bone is not fully understood. This information has bearing on post-surgical therapy protocols, prediction of long-term bone tissue changes, and optimization of cage design. In order to gain insight into this problem, functional microCT imaging was used to directly evaluate implant micromotion and full-field vertebral body strains in an animal model implemented with various configurations of BAK interbody cages. It is believed that variations in cage design will produce variable implant success, functional fusion will be related to the extent of implant fixation, and specific strain fields will be associated with fused and unfused samples. We found that samples ranged from completely unfused (implant motion) to fully fused with organized trabecular bone (no motion). Strains concentrated at the implant interface in unfused samples, while fully fused samples exhibited uniformly distributed strains. / Graduation date: 2004

Thesis (Ph. D.)--Drexel University, 2004. / Includes abstract and vita. Includes bibliographical references (leaves 168-182).

Thesis (Ph. D.)--Drexel University, 2006. / Includes abstract and vita. Includes bibliographical references (leaves 170-193).

Pedicle screw breakage and loosening remain as clinical complications of short segment instrumentation procedures for spinal stabilization. This study has directly visualized and measured elastic, plastic and total vertebral pedicle trabecular bone full-field strains in the regions immediately surrounding the pedicle screw during pedicle screw insertion by utilizing functional microCT imaging and digital volume correlation. Human, porcine and polyurethane foam samples were analyzed and compared. Analysis showed that when osteoporotic human, normal human and porcine pedicle trabecular bone samples were compared, osteoporotic samples showed higher peak plastic strains and greater variability of these strains from their means. This suggests that osteoporotic human samples are non-uniformly elastic and plastic, while normal human and porcine samples are more uniformly elastic and plastic throughout the trabecular structure. PU-foams are not appropriate as models for pedicle trabecular bone in the in vivo environment since strain results showed dissimilar plastic and elastic strain magnitudes than human and porcine pedicle trabecular bone. This study may aid in the development of performance criteria for new PU-foams and improved pedicle screw designs. / Graduation date: 2004

Yes / Polyetheretherketone (or PEEK) is a thermoplastic polymer known for its high plasticity and toughness and has been widely employed as a material for a variety of load-bearing medical devices ranging from trauma implants to interspinal spacers and femoral stems. While being inherently chemically inert and therefore biocompatible and having very short lived post-radiation free radicals, PEEK presents different mechanical properties depending on its degree of crystallinity. It can be processed via extrusion, injection or compression moulding. However, these techniques do not allow high precision control over the fine morphological structure that strongly influences mechanical properties. Microinjection moulding, in contrast, makes it possible to produce fine details of medical implants with high precision and accuracy. Another advantage of this method is the controlled production of the material with heterogeneous structure due to variations in crystallinity. Having stiffness in the middle of the sample different from that at the edges enables a structure that mimics the bone/cartilage parts of an implant. This paper reports on the manufacturing of PEEK components by microinjection moulding, and their characterisation by physico-chemical (XRD, SAXS, TEM, FTIR, POM) and mechanical (tensile testing) means, in order to assess the suitability of use for biomedical application, such as spinal implants. We discuss the influence of such parameters as mould temperatures, injection speeds and hold pressures on the crystallinity and mechanical properties of the material. / Science Bridges: Bradford-China Programme for Pharmaceutical Sciences and Medical Technology, EP/G042365/1

Published Article / The link from medical scan images through data manipulation to additive manufacturing is well established. Various types of software are used to deliver the required .STL file(s). Often, the data manipulation will require the generation of new shapes around existing geometry, e.g. an implant that will replace missing bone tissue. This paper reports exploratory work undertaken to assess the feasibility of using haptic modelling and "virtual sculpting" software to generate novel designs of vertebrae implants for correction of spinal curvature. .STL data of several vertebrae, originating from CT scans, was imported into the Freeform system from SensAble technologies. It was used to create immutable "bucks" around which the user "sculpted" three-dimensional implant geometries. It must be noted that the designs have not been medically assessed and were for demonstration purposes only. However, the process route followed did prove to be feasible and offered some particular advantages, e.g. a precise fit between the implant and the vertebra and the possibility of enabling the direct intervention of medics in the implant design process.

Thesis (Ph. D. in Biomedical Engineering)--Vanderbilt University, May 2007. / Title from title screen. Includes bibliographical references.