Veterinary Science - Theses

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    Radiographic bone morphology of the equine metacarpophalangeal joint and relationships to the incidence of pathology in thoroughbred
    Alrtib, Abdulrhman Mohamed ( 2013)
    Pathological conditions of the bones of the metacarpophalangeal joint (MCPJ) are common amongst racehorses. These conditions are of a great economic cost to the horse industry as well as being detrimental to the welfare of the horses themselves. This study aimed to: 1. develop reliable and repeatable radiological measurements of the MCPJ bones in Thoroughbreds; 2. investigate possible relationships between bone morphometry and the pathological incidences in this breed; and 3. identify correlations between these measurements and specific performance requirements in the breed. The centre of a circle best fit onto lateromedial radiographs of the most dorsal region of the lateral condyle of three MCPJs was assumed to approximate the centre of MCPJ motion and was found to be located on the lateral eminence of the lateral collateral ligament. Using this anatomical landmark, MCPJ angles were measured in cadaver limbs and then in live horses before and after lifting the contralateral limb. Angles were significantly less with the contra-lateral limb lifted. The goniometer repeatability coefficient was 4.7° (95% CI 3.9° to 6.0°) and was similar in horses standing squarely and with the contra-lateral limb lifted. Marked MCPJs, filmed in different head positions showed no significant effect of head position on the MCPJ angles. MCPJ angles measured before and after treadmill exercise showed the right MCPJ angle decreased significantly with exercise. Gross and radiographic studies established a set of MCPJ parameters that could be consistently identified on radiographs. Nine individual angular, 3 derived angular, and 16 linear parameters were developed, and used to derive 18 ratios. There was almost perfect agreement, with a CCC of more than 0.99, among all the parameters in tests of repeatability. In order to assess the effect of the MCPJ angle on MCPJ parameters, forelimbs from adult horses were loaded in a load frame to specific MCPJ angles within the normal range. Parameters measured on standard dorsopalmar and lateromedial radiographs showed that the ratio parameters were less affected than the angular parameters when the MCPJ angle was changed. An 11° change in the MCPJ angle was considered potentially acceptable for all these parameters. The effect of the orientation angle was determined on measurements obtained from 3D models of CT scan images of forelimbs from adult horses. Generally, the ratio parameters were less affected than the angular parameters during MCPJ rotation. An MCPJ rotation of 5° was considered as potentially acceptable for all these parameters. Radiographs from horses with MCPJ problems were collected from clinics along with their radiological reports. DP and LM radiographs were also taken from 18 experienced racehorses with no MCPJ problems. Significant differences were reported between normal and damaged horses in four parameters measured from those radiographs including two angles and two ratios. These parameters were B13, B14, H1/H3 and H2/H3. The study identified specific measures of the equine MCPJ bones that may be made using radiological methods. In addition, it identified some basic morphological measures that were associated with specific pathology in the MCPJ in Thoroughbred racehorses.
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    Morphometrical study of bony elements of the forelimb fetlock joints in some equine breeds
    Alrtib, Abdulrhman Mohamed ( 2009)
    Many pathologic lesions and several types of fractures in the equine forelimbs involved the bony elements of the metacarpophalangeal joints (fetlock joints) especially the third metacarpal bones and the proximal sesamoid bones. Although the bones of the fetlock joint have been described in a general manner, the variations between equine breeds are still insufficient and differences within the breeds are not completely covered. Therefore, the aim of the current study was to identify the morphometrical variations of these bones between and within some different equine breeds. Right and left metacarpal, proximal phalangeal and proximal sesamoid bones were collected from 23 horses (10 Thoroughbreds, 5 Standardbreds and 8 Ponies) euthanized for non-orthopaedic reasons. The bones were boiled between 95°C and 99°C for 30 hours, then cleaned and left for 24 hours at room temperature for air drying. Finally, the bones were dried in the drying cabinet at 49.5°C for 8 hours. A number of dimensional parameters were measured using a custom-built apparatus, calliper and plastic tape. These measurements included proximodistal height, lateromedial width, and dorsopalmar depth. All the statistical data were analysed using the ANOVA test and SPSS statistic software except the repeatability data which were analysed by calculating the repeatability coefficient. This study showed that there were significant variations between the medial and lateral sides of all bones in all breeds. The length to the lateral condyle of Mc3 was greater than the length to the medial condyle of Mc3 in all breeds. The width and depth of the medial condyle was greater than the lateral condyle in all breeds. The lengths of the lateral sides of the P1 bones were greater than the lengths of the medial sides in the right forelimbs of Thoroughbreds and Standardbreds. The width of the medial articular cavity of P1 was greater than the width of the lateral articular cavity except in the left limb of Ponies. The depth of the medial articular cavity of P1 was greater than the depth of the lateral articular cavity except in the left limb of Standardbreds. The lateral sesamoid bones in both limbs of Thoroughbreds and Ponies were significantly longer or tended to be longer than the medial sesamoid bones. The lateral sesamoid bones were wider than the medial sesamoid bones in both limbs of Ponies. The depths of the lateral sesamoid bones were the significantly greater or tended to be greater than those of the medial sesamoid bones in both limbs of Thoroughbreds and Standardbreds. There were many morphometrical variations in the bony elements of the equine fetlock joints of Thoroughbreds, Standardbreds and Ponies. Further studies are needed to identify the reasons and mechanical effects of these differences.