Doctoral Degrees (Industrial Engineering)

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Browsing Doctoral Degrees (Industrial Engineering) by Author "De Beer, Neal"

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    Development of a process chain for digital design and manufacture of patient-specific intervertebral disc implants with matching endplate geometries
    (Stellenbosch : University of Stellenbosch, 2011-03) De Beer, Neal; Van der Merwe, A. F.; Scheffer, C.; Dimitrov, D. M.; University of Stellenbosch. Faculty of Engineering. Dept. of Industrial Engineering.
    ENGLISH ABSTRACT: Back pain is a common concern amongst a growing population of people across the world today, where in most cases the pain can become unbearable resulting in major lifestyle adjustments. Seventy to eighty percent of the population of the Western world experiences low-back pain at one time or another. Pain can be produced as a worn disc becomes thin, narrowing the space between the vertebrae. Pieces of the damaged disc may also break off and cause irritation to the nerves signalling back pain. Depending on the severity of a patient’s condition, and after conservative treatment options have been exhausted, a disc replacement surgery (arthroplasty) procedure may be prescribed to restore spacing between vertebrae and relieve the pinched nerve, while still maintaining normal biomechanical movement. Typical complications that are however still observed in some cases of disc implants include: anterior migration of the disc, subsidence (sinking of disc) and lateral subluxation (partial dislocation of a joint). Issues such as function, correct placement and orientation, as well as secure fixation of such a disc implant to the adjacent vertebrae are highly important in order to replicate natural biomechanical behaviour and minimise the occurrence of the complications mentioned. As various imaging and manufacturing technologies have developed, the option for individual, patientspecific implants is becoming more of a practical reality than it has been in the past. The combination of CT images and Rapid Manufacturing for example is already being used successfully in producing custom implants for maxilla/facial and cranial reconstructive surgeries. There exists a need to formalise a process chain for the design and manufacture of custom-made intervertebral disc implants and to address the issues involved during each step. Therefore this study has investigated the steps involved for such a process chain and the sensible flow of information as well as the use of state-of-the-art manufacturing technologies. Strong emphasis was placed on automation of some of the processes as well as the user-friendliness of software where engineers and surgeons often need to work together during this multi-disciplinary environment. One of the main benefits for customization was also investigated, namely a reduction in the risk and potential for implant subsidence. Stiffness values from pressure tests on vertebrae were compared between customized implants and implants with flat endplate designs. Results indicated a statistically significant improvement of customized, endplate matching implants as opposed to flat implant endplates. Therefore it may be concluded that the use of customized intervertebral disc implants with patient specific endplate geometry may decrease the risk and potential for the occurrence of subsidence.