OpenUCT :: Browsing by Author "Vaughan, Christopher Leonard (Kit)"

Browsing by Author "Vaughan, Christopher Leonard (Kit)"

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Open Access
Application of 3D imaging technology to anterior cruciate ligament surgery
(2006) Dawson, Sarah; Vaughan, Christopher Leonard (Kit); Fitzpatrick, D
Includes bibliographical references (leaves 155-160).
Open Access
Assessment of and improvements to a stereophotogrammetric patient positioning system for proton therapy
(1999) Hough, Jan K; Vaughan, Christopher Leonard (Kit)
This thesis describes the construction and use of the facemask at the National Accelerator Centre (NAC) as used to both immobilise and position patients for precision proton radiotherapy. The precision achieved using the stereophotogrammetric (SPG) positioning system is measured, and the shortcomings and errors in using the facemask by the SPG system are measured and analysed. The implementation of improvements made to the SPG system is reported upon, and alternative means of both supporting the fiducial markers and immobilising the patient are investigated and evaluated. The accuracy of positioning a facemask using the SPG system is 1.4 mm and of positioning a newly designed frame is 1.6 mm. These measurements were made without using a patient. It is estimated that the total uncertainty of positioning a patient's tumour at the isocentre is 1.6 (1SD) mm using the facemask and it is estimated that the precision using the frame will be less than this value. The largest component of this error (1.39 mm) is due to the error in obtaining the CT scanner co-ordinates. These results are comparable to those obtained by other investigators. The movement of patient bony landmarks within the facemask was measured to be 1.0 ± 0.8 mm. Three main recommendations are that the CT scanner co-ordinating procedure be improved, the SPG computer program be rewritten in parts to achieve greater speed and accuracy, and that the new frame be used. The frame is easier to manufacture than the facemask and allows real time monitoring of the position of the patient's head by the SPG system thus allowing faster throughput of patients and better positioning quality control.
Open Access
Assessment of spastic patients before and after selective posterior lumbar rhizotomy
(1988) Berman, Barbara; Vaughan, Christopher Leonard (Kit)
For many decades people working with spastic patients have searched for better methods of alleviating spasticity and its debilitating effects. Although many methods have been used, no single method has been completely successful. It was not until the nineteen seventies that Selective Posterior Lumbar Rhizotomy (SPLR) was used successfully with spastic patients. In 1980 Peacock started doing this procedure on a large number of spastic patients in South Africa. I became interested in SPLR after seeing the dramatic reduction in spasticity and the improvement in function in my patients who had undergone the procedure. Since observations of improvement up to this point had been subjective, I decided to measure and document the physical status of patients before and after surgery. Twenty-nine patients who underwent Selective Posterior Lumbar Rhizotomy in 1985 were studied. In order to be as objective as possible, crawling and gait analyses were done in addition. All the patients were assessed clinically two days prior to surgery and then between four and fourteen months after surgery. For both preoperative and postoperative assessments, resistance to passive movement, degree of joint stiffness, ability to initiate and inhibit voluntary movement, and the degree of abnormal function in the developmental positions (rolling, sitting, kneeling, crawling, standing and walking) were graded on rating scales. Analyses of gait and crawling were done using a digital camera system. Results of the study indicated that SPLR produced a statistically significant reduction in muscle tone and in joint stiffness. Improvements in voluntary movement and functional movement (rolling, sitting, kneeling, crawling, standing and walking) were also statistically significant. It was concluded that Selective Posterior Lumbar Rhizotomy is a useful method of reducing spasticity and results in improvement of the quality of life in patients with spastic cerebral palsy.
Open Access
The biomechanics of human locomotion
(2009) Vaughan, Christopher Leonard (Kit)
Includes bibliographical references. The thesis on CD-ROM includes Animate, GaitBib, GaitBook and GaitLab, four quick time movies which focus on the functional understanding of human gait. The CD-ROM is available at the Health Sciences Library.
Open Access
Cerebral Palsy and Rhizotomy: A ten year follow-up study with Gait Analysis
(1997) Subramanian, Nivedita; Vaughan, Christopher Leonard (Kit)
In 1985, a cohort of 14 children with cerebral palsy underwent a neurosurgical procedure - selective posterior rhizotomy - in an effort to reduce their spasticity. They were part of a prospective study in which their gait was analysed before surgery and at one and three years' post-operatively. In 1995, ten years after surgery, there were important questions that needed to be addressed: would their gait be different from the findings before surgery and three years after surgery and how would they compare with age-matched normal subjects? Three of the original subjects were lost to follow-up and 11 were invited to participate in this long-term study. Their ages ranged from 12 to 24 years at this time of evaluation. Their gait was studied in the sagittal plane by taping retro-reflective markers onto the greater trochanter, lateral femoral epicondyle and lateral malleolus and having the subjects walk in a direction perpendicular to a video camera recording their gait. The data were digitised and analysed making use of custom written software and all relevant gait parameters were calculated. The parameters evaluated were the ranges of motion and midrange values of the knee and thigh, and the spatial-temporal parameters, namely cadence, stride length and velocity. Data were also obtained from twelve age-matched normal control subjects. The ten-year results were compared to the pre-operative data, the data obtained from the three-year study and the normal controls. A statistical analysis was performed on these parameters by using multiple analysis of variance (MANOVA) and post hoc comparisons were performed with a Scheffe test and a significance level set at p < 0.05. Results indicated that after ten years, the joint ranges of motion and mid-range values did not differ significantly from the normal values. The values also did not vary significantly from the values obtained in the three-year follow-up study, suggesting that functional changes acquired due to rhizotomy were of long term duration. The spatial-temporal parameters, however, did differ significantly from the normal range. Although this finding may have been influenced by the environment and subject motivation, the reduced cadence and stride length meant that the cerebral palsy subjects walked slower than their normal counterparts. This project, while confirming the results of the previous subjective studies, provides the first long-term objective data that establishes the effectiveness of selective posterior rhizotomy in improving and maintaining locomotor function for children with spastic cerebral palsy.
Open Access
A comparison of 3D gait models based on the Helen Hayes Hospital marker set
(2000) Tabakin, Dudley; Vaughan, Christopher Leonard (Kit)
This study compares three commercial gait analysis packages, Vicon Clinical Manager (VCM), GaitLab 2.0 (GL) and Peak Motus 2000 (PM) with a standard model developed using the Vicon BodyBuilder (BB) software package. All these packages use the same modified Helen Hayes Hospital marker set for external marker placement.
Open Access
The design and Manufacture of an accelerated fatigue testing machine for coronary stents
(2007) Hoole, Martin Philip Hereford; Vaughan, Christopher Leonard (Kit)
Open Access
The design, construction and testing of a hermetically sealed breast platfrom for dual-modality mammography
(2014) Smith, Raphael V; Vaughan, Christopher Leonard (Kit)
When ultrasound is used as an adjunct to X-ray mammography in either hand-held or automated mode, the patient typically lies in a prone position. The disadvantages of this approach include: variable image quality; poor co-registration of X-ray and ultrasound images; and increased costs and patient anxiety. In response to these shortcomings, the Aceso full-field digital mammography and automated breast ultrasound (FFDM+ABUS) system aims to acquire both X-ray and 3D ultrasound images simultaneously. The Aceso has been developed by the Cape Town based company CapeRay Medical (Pty) Ltd. The focus of this thesis is the design, construction and testing of a novel breast platform wherein the challenges of combining FFDM and ABUS have been addressed, in a clinically suitable package.
Open Access
Development of biomechanical models that represent members of the South African National Defence Force
(2010) Bredenkamp, Karen; Vaughan, Christopher Leonard (Kit)
Open Access
Ergonomics of single-handed pulling : a biomechanical and psychophysical assessment
(2003) MacKinnon, Scott Netson; Vaughan, Christopher Leonard (Kit)
The description of biornechanical events measured during manual materials handling (MMH) activities has been a major focus for ergonomists attempting to understand the relationships between performance factors and injury mechanisms. Pulling exertions, while being frequently observed in occupational settings, requires more attention from researchers. The purpose of this work was to elucidate the inﬂuences of task-simulated factors upon subject performance while exerting pull forces within a stationary workstation.
Open Access
Feasibility of using an industrial robot with the LODOX technology
(2002) Flash, Gregory Henry; Vaughan, Christopher Leonard (Kit)
DebTech Pty(LTD), a subsidiary of De Beers South Africa, has designed a low dosage digital X-ray machine called LODOX. This innovative machine has been commissioned in Groote Schuur Hospital in Cape Town, South Africa. It is capable of performing standard radiological scans, producing high quality images quickly and in a digital form.
Open Access
Feasibility of using LODOX technology for mammography
(2001) Lease, Alyson; Vaughan, Christopher Leonard (Kit); Beningfield, Steve
Bibliography: leaves 94-99.
Open Access
Finite element tool for modelling stent deployment to aid stent design
(2004) Keevy, Pieter-André; Vaughan, Christopher Leonard (Kit)
Includes bibliographical references (leaves 141-143).
Open Access
The influence of a hip extension strengthening programme on gait performance in individuals following stroke
(2002) Busse, Monica; Vaughan, Christopher Leonard (Kit)
Gait difficulties experienced by individuals following a stroke may be related to the commonly observed reduced hip extension in the stance phase of gait. The aim of this initial exploratory study was to evaluate the effects of a home-based strengthening programme on hip muscle strength and gait performance in individuals following stroke. Six chronic stroke patients (> 9 months duration) participated in this pretest-posttest group design which was composed of two six week phases, A and B, where B immediately followed A. No training or advice was given to the six subjects during phase A. During Phase B, the same six subjects participated in a "hip extension focused" home exercise programme aimed at improving hip extensor muscle strength and the range of anterior hip structures. The exercise programme consisted of functional strengthening, task related activities and stretching. At the end of this sixweek period, the subjects were re-tested in order to evaluate the effects of the exercise programme. The outcome measures included isometric muscle strength, walking speed and range of the anterior structures of the hip. The walking section of the Motor Assessment Scale for Stroke and the Nottingham Extended Activities of Daily Living were also employed. In addition, clinical gait analysis was used to gather measures of gait velocity, step length and hip joint excursion. Statistically significant increases were found in the study group (n = 6) for the identified parameter of hip extensor strength after the intervention (p = 0.05), although this change could not necessarily be attributed to intervention effects alone. Hip extension strength was significantly correlated with (1) step length (r = 0.82; p = 0.04) and (2) joint excursion (r = 0.8; p = 0.05) after the intervention. These correlations, although tentative and not conclusive, suggest that hip extensor strength may influence gait performance and therefore warrants further investigation. While the results obtained from this exploratory study appear to suggest that the hip extensors play an important role in providing stability for the lower limb during gait, a randomised controlled study with a larger cohort of patients would be necessary to make any definitive conclusions.
Open Access
Investigating the effect of size on gait using a bipedal robot
(2004) Karbanee, Nazir A; Vaughan, Christopher Leonard (Kit)
Includes bibliographical references (leaves 157-168).
Open Access
Knee joint contact stresses : the influence of deformity and muscle activity
(1991) Schmotzer, Hans; Vaughan, Christopher Leonard (Kit); Learmonth, I D
Studies have shown that the alignment of the knee in the coronal plane has a significant effect on the joint contact stress. However, gait analysis demonstrated that factors other than alignment contributed significantly to the outcome of corrective surgery. It was therefore hypothesized that muscle contraction can alter the stress distribution within the knee joint and that overloading can occur in the absence of a deformity. Six normal knees were harvested from different donors. The exact orientation of all muscle groups was recorded and their tendinous insertions carefully preserved. Custom built pressure transducers (6 per compartment, 0.5 mm thick, 10 mm diameter) were inserted through 2 small, posterior, capsular incisions and placed on the tibial surface and the menisci. The knees were mounted in a loading system which allowed free self-alignment of the joint under load. All muscles were replaced by wire cables instrumented with force transducer, tensioner and grip. Several alignment models (5, 10 degree varus, neutral, 5 degree valgus and 15 degree of flexion) as well as the effect of contraction of all major muscles crossing the knee joint were tested. An even pressure distribution was seen in neutral alignment. In a varus deformity the peak pressure shifted medially and laterally in valgus. Unloading of the opposite compartment was seen for deformities as small as 5 degrees. A flexion deformity produced a postero-lateral shift of the peak pressure area. Muscle contraction increased the pressure significantly in a region next to the muscle. Generally, unloading - though less significant - was seen in a region diagonally across the joint. These results suggest that muscular hyperactivity may considerable increase the contact stresses. However, muscle weakness or lack of muscular contraction may indirectly play a significant role in affecting the contact pressure distribution. If the muscle force is insufficient to counterbalance the external moment condylar lift-off occurs. This increases the angulation between femur and tibia thereby overloading the compartment where contact takes place; One can therefore conclude that abnormal gait patterns or neuromuscular control mechanisms may result in unphysiologically high contact stresses which may cause the development of unicompartmental osteoarthritis and subsequently, a deformity.
Open Access
Localising discrete points in 3D space using stereo pairs of digital slot-scanning X-rays
(2006) Wynne, Susan M; Vaughan, Christopher Leonard (Kit); Douglas, Tania S
Includes bibliographical references (p. 104-111).
Open Access
The long-term sequelae of Selective Dorsal Rhizotomy in patients with Spastic Diplegia
(2009) Langerak, Nelleke Gertrude; Vaughan, Christopher Leonard (Kit); Fiegen, A Graham; Peter, Jonathan C
Includes abstract. Includes bibliographical references.
Open Access
Reconstruction of three dimensional coordinates of multiple targets using linear sensors
(2003) Georgiev, Roumen H; Vaughan, Christopher Leonard (Kit)
Bibliography: leaves 200-204.
Open Access
Rotational laxity of the knee following reconstruction of the anterior cruciate ligament using single vs double-bundle surgery
(2009) Hemmerich, Andrea; Vaughan, Christopher Leonard (Kit)
Includes abstract. Includes bibliographical references (leaves 172-196).