The use of sclerosing agents in tendon repair of racehorses.

Abstract: Most practitioners will have experienced the frustration encountered in the treatment of sprains of the flexor tendons and suspensory ligaments of racehorses. After apparent recovery, the damaged structure will often break down again when the horse returns to hard training. Milne (1960), Reed (1962), Jubb and Kennedy (1963) and Hickman (1964) have written detailed ac- counts of the pathology of tendon injuries and the mechanism of repair of tendon tissue. These writers substantiate that when a tendon is sprained, there is a tearing or rupture of some of the tendon fibres, varying in number in propor- tion to the severity of the sprain. Proctor (1963) disagrees with this view maintaining that most cases of bowed tendons involve changes only in the peri-tendinous structures and not the tendon tissue itself. This observation was based on gross appearances, however, and the histological work of Wheat (1963) affirms that the important lesion is in the tendon tissue itself. Being a specialised tissue, tendon fibres heal by a special process of fibroblastic repair, wherein the torn fibres are replaced by connective tissue. This infiltration of scar tissue does not fully restore the original strength of the tendon. Weak spots remain in the continuity of the fibres predisposing them to a recurrence of the injury when the tendon is again stressed. For many years now the recognised forms of treatment for tendon injuries have been various forms of counter-irritation. Milne (1960) has shown that both blistering and firing (superficial or penetrating) and combinations of both fail to produce inflammatory changes in deep structures, but merely in the skin and subcutaneous tissues. Such treatments possibly produce beneficial re- sults mainly by enforcing rest of the affected limb. Some authorities feel that the subcutaneous ban- dage effect of the thickened subcutis explains the good results such forms of treatment may some- times obtain. If a damaged tendon is to heal strongly enough to withstand the strain of racing, treatment must produce a deep-seated hyperaemia in the ten- don tissue to promote better healing of the damaged fibres; if the treatment can also pro- mote an excessive deposition of new connective tissue in the damaged area (that is, more than would be laid down in the normal healing pro- cess), the strength of the tendon when healed should approximate more closely its original strength prior to injury. Asheim (1964) ob- tained better vascular activity in the damaged ten- dons by surgical intervention. He made a longitu- dinal saggital incision in the tendons, closing the incision with stainless steel sutures. Fey (1947) as cited by Milne (1960) speaks of the better healing response in such tissues when hyperaemia plus tissue destruction are induced by the treat- ment process, as compared with a mere hyper- aemic state without tissue destruction. Davis (1967) reported the successful use of sclerosing agents for ligament and tendon injuries in racing greyhounds, and J. R. Gannon (per- sonal communication 1967) reported favourable results with the use of monoethanolamine oleate" in tendon injuries in horses. This paper describes a technique used on Thoroughbred and Standard-bred horses suffer- ing from sprained flexor tendons, sprained sus- pensory ligaments and, in one case, sprained sesamoidean ligaments.