The suspensory apparatus of the coffin bone - Part 2: Clinical relevance of the suspensory apparatus and its fan-shaped reinforcement in chronic equine laminitis with coffin bone or hoof capsule rotation.

摘要

Acute laminitis is a serious equine disease resulting to degenerative changes of the suspensory apparatus of the coffin bone, ranging from severe disturbance to complete destruction. Metabolic or endocrinological laminitis is a progressive disease of domestication, as a consequence of continuous overfeeding and limited exercise, and of longevity. Traumatic laminitis is the result of inadequate hoof protection on hard surfaces or excessive exercise. Chronic laminitis is the condition that develops subsequently to any kind of laminitis, if not healed completely. The first part of the study focuses on the suspensory apparatus, particularly on its fan-shaped reinforcement at the tip of the coffin bone, while the aim of the second part of the study is to describe the ruptures within the suspensory apparatus in chronic laminitis and to suggest therapeutic measures. The present study was based on 20 hooves that were classified as laminitic according to adspectory examination or preliminary report. The hooves were analysed macroscopically via plastinated thin sections or microscopically via conventional histological methods. Chronic laminitis was manifested either in mild or severe coffin bone rotation on one hand, or in hoof capsule rotation on the other. Hoof capsule rotation resembles coffin bone rotation in mild cases. Coffin bone rotation is characterized by a dorsally broken toe axis in varying degree. Additionally, a prominent scar horn shield (tubulolamellary wedge) is developed between horn capsule and coffin bone in the toe region. Hoof capsule rotation is also observed at different degrees and appears similar to coffin bone rotation in the initial moderate cases, while the severe cases display a distinct bend of the hoof wall. Proximal to the bend the hoof wall displays physiological growth direction, but distal to the bend the hoof wall growth is disturbed resulting in iris disfigured lump hoof characteristic for laminitis. Removal of the superficial layers of the cornified lump exposes its composition of horn masses of the ectopic White Line. In chronic laminitis, predilection sites for ruptures within the suspensory apparatus were detected at the following locations: the initial anchorage at the coffin bone and the terminal anchorage within the hoof capsule, as well as the intermediate anchorage both at the basal membrane of the interlamellary bond and at the epithelial microstructure of the epidermis within the area of the stick-slip effect. The fan-shaped re-inforcement at the tip of the coffin bone was totally ruptured in severe coffin bone rolulian and grossly overexpanded in severe hoof capsule rotation. The orthopaedic measures should concentrate on the dorsal, middle; and palmar or plantar aspects of the hoof in coffin bone rotation. In severe hoof capsule rotation, the therapy focuses on resection of the pathologic horn masses (lump) produced by the White Line.