THE FETLOCK TUNNEL-SYNDROME - A MACROSCOPIC AND MICROSCOPIC STUDY

Chronic changes of several structures in and around the fetlock tunnel can be a cause of the so-called fetlock tunnel syndrome (FTS) in the horse. Fourtynine annular ligaments (AL) from dead horses without a kn own history or clinical evidence of lameness and/or digital tendon she ath problems in these legs and 30 AL biopsies from horses suffering fr om FTS were studied macroscopically and microscopically. Macroscopical ly, the normal AL had a shiny white appearance, whereas the affected A L were often thicker and less white, Microscopically, the normal AL we re about +/- 1 mm thick and were composed of undulating, parallel bund les of collagen, Small blood vessels with a diameter of 0.03 - 0.12 mm were found, The affected AL showed an increased thickness of collagen bundles, a changed direction of longitudinal axis of collagen bundles , and irregularly dispersed fibroblast nuclei, The number of blood ves sels had increased, the external diameter of arteriolae could be up to 0.3 mm and arterial wall changes were observed, Possible relationship s between the histological findings and the aetiology of the FTS are d iscussed.