Читать книгу Fractures in the Horse - Группа авторов - Страница 157

Bisphosphonate therapy has come into the equine market in recent years, and its use in fracture management has been debated [48]. Bisphosphonates have a number of pharmacologic properties. Of principal interest in relation to fractures is their ability to suppress osteoclastic activity [49]. However, they also exert anti‐inflammatory and analgesic effects [50–52]. There is evidence in experimental animals that bisphosphonate administration may inhibit osseous adaption responses and result in mechanically weaker bones [53] and delay fracture healing [54–56]. This is logical when considering the role of osteoclasts in bone healing. The potential impact on fracture healing also depends on the time of administration [57]. In the early stages, bisphosphonates can inhibit the essential immune cascade (macrophages and monocytes) while later, since osteoclasts are essential in the remodelling phase, they can also have a negative effect. Studies in experimental animals have shown no delay in the formation of a hard callus (which in fact grows larger in the face of bisphosphonate therapy) but a significant delay in remodelling from woven to lamellar bone [58]. Despite the large callus size, these fractures have been shown to be mechanically equivalent but not superior to those found in untreated animals. It also appears that the timing of bisphosphonate administration does not influence healing. In humans, the results have been mixed and no clear conclusions can be made. There appears to be some positive response to bisphosphonate therapy in human osteoporotic patients suffering fractures, but this condition has not been recognized in horses. The established impact on osteoclastic function and bone remodelling suggest use should be avoided, and a recent review has suggested caution in young racehorses and in the presence of active bone remodelling [52]. There is also anecdotal evidence in horses that bisphosphonate use in the face of fracture repair may have a detrimental effect (L. R. Bramlage, personal communication).