MORPHOMETRICAL STUDY OF BONY ELEMENTS OF THE FORELIMB FETLOCK JOINTS IN SOME EQUINE BREEDS

Date

2009-1

Type

Master Thesis

Thesis title

Melbourne University

Author(s)

Abdulrhman Mohamed Salah Alrtib

Abstract

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

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