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.