Morphological and histochemical analysis of a case of superficial digital flexor tendon injury in the horse

This report compares the morphology and the concentrations of glycosaminogl ycans (GAGs) in an injured superficial digital flexor tendon (SDFT) of a ho rse with those of a normal tendon. An injured 6-year-old male Thoroughbred exhibited heat and swelling around the SDFT of the right forelimb. On histo pathological examination, exuberant granulation was observed in the affecte d tendon, with activated tenocytes, angiogenesis, haemorrhage; and infiltra tion of small numbers of leucocytes. The collagen fibres were loosely packe d and irregularly arranged. The diameter of control collagen fibrils was 20 -360 nm and that of affected collagen fibrils 20-240 nm. In the analysis of GAGs in the matrix, hyaluronic acid (HA), dermatan sulphate (DS), and chon droitin sulphate (CS) were found to be major components in both control and affected tendons. Increases in DS in the affected tendon were striking. Ou r observations suggest that fibrillogenesis was activated by increases in D S and decreases in HA and CS. It is also assumed that absence of collagen f ibrils of normal thickness and in a parallel arrangement reflected the morp hological and biochemical characteristics of fibrillogenesis in the injured tendon. If the inflammatory features of an injured tendon could be altered ! it might return eventually to its normal structure. (C) 1999 W.B. Saunder s Company Limited.