Collagen Fibril Morphological Study of Medial Patellar Ligament of Stifle Joint Affected with Patellar Luxation in Cattle

Abstract

Background: Upward fixation of patella is common clinical malady in cattle due to extensive movement of stifle joint during the locomotory activity because of unknown etiology. However, at certain peak point (overstretching of ligament) or due to occupational trauma (wear and tear), ligament become flaccid and weak leading to patellar displacement and lameness. Patellar ligaments play crucial role in stifle joint movement and any functional or structural alterations in the ligaments can lead to acute to chronic lameness in cattle. The present study was carried out to evaluate the structural changes in collagen fibril material in medial patellar ligament in cattle suffering with patellar luxation. Methods: Tissue specimens of medial patellar ligament of normal (control animal) and affected cattle (luxation of patella) were harvested and preserved for scanning electron microscopy (SEM) and transmission electron microscopic (TEM) study as per standard procedure at RUSKA Laboratories, College of Veterinary Science, PVNRTVU, Rajendranagar, Hyderabad, India. Result: The incidence of medial patellar luxation was higher in females as compared to male cattle and the duration of lameness was between 3-12 months (7.35±0.56 months) characterized by dragging of toe, outward jerky movement of affected limb, extension of limb and change in appearance of gait during walk and flexion of fetlock. Scanning electron study of normal ligament showed dense, uniformly and compact arrangement of collagen fiber bundles with morphometric thickness was 3.66±0.58 µm. whereas in luxated patella cases, medial ligament showed derangement in collagen fiber bundles. The collagen fibers were arranged irregular and wavy with morphometric thickness of collagen was 2.58±0.03 µm. Electron microscopy of the normal ligament showed presence of thick collagen fiber bundles packed in dense and compact arrangement. Electron microscopy of affected ligament had degenerative changes of the fibers characterized by thin collagen fiber bundles which were loosely and disorganized arranged fibrils. The present study concludes that, luxation of patella was common locomotory disorders in cattle due to derangement in collagen fiber bundles with drastic reduction in thickness of collagen fibers, increased gap between two collagen fibers, broken and overlapping fiber bundles and surface of collagen fibers appeared irregular rough via scanning and electron microscopy analysis.