Shock Wave Therapy for Horses

Don't worry; I am not going to talk about the shock therapy depicted in the 1970s Jack Nicholson film "One Flew Over the Cuckoo's Nest." Extracorporeal shock wave therapy (ESWT) isn't a cure for your horse's emotional or mental problems, but it might be a treatment option for a number of your equine athlete's orthopedic and soft tissue ailments.

ESWT has been around since the 1970s. In humans with urolithiasis (bladder stones), doctors use ESW lithotripsy to fracture stones within the bladder so they can pass without surgery. Since then, ESWT's use as a therapeutic tool in human and veterinary medicine has flourished. The first use of ESWT in the horse was reported in the late 1990s for treating proximal suspensory ligament desmitis (inflammation at the origin of the suspensory ligament) and osteoarthritis of the hock.

With the increasing popularity of ESWT, scientists have evaluated mechanisms of action and clinical efficacy and safety for use on equine bone and soft tissue. The effects of ESWT are apparent at gross anatomic and molecular levels. Recent studies revealed ESWT's ability to decrease inflammation; hasten healing time; enhance neovascularization (blood vessel formation) and cellular proliferation; improve fiber alignment in tendon repair; increase cellular bone morphogenic protein (BMP) production, leading to faster bone healing; and recruit stem cells to injured tissues. Scientists also showed it alleviates pain from degenerative diseases.

Currently, veterinarians treat an array of diseases and ailments with ESWT, including navicular syndrome, collateral ligament desmitis of the coffin joint, tendonitis, tendon avulsions (tearing), avulsion fractures, degenerative joint disease, muscle strains, dorsal spinous process impingements, sacroiliac disease, and stress fractures.

There are various ESWT generators for veterinary use, and the majority of clinical trials and research studies use focused units. Focused units deliver a specific amount of energy to a measurable "focused" tissue depth/area, so that the veterinarian can treat a specific area more precisely. Each unit has a variation in its waveform and a different effect on tissue.

Unfocused units (radial pressure wave therapy, or RPWT) vary greatly in waveform and energy distributed to tissues compared to the focused units. It's important to understand how each unit acts on tissue so the horse benefits properly.

Treatment protocols vary, and veterinarians use ESWT probes or trodes, depending on the depth of the injury. In general, a single ESWT treatment consists of 500-2,000 pulses or "shocks" to the area every seven days to four weeks, for an average of three total treatments (or as needed based on clinical signs/improvement).

In recent studies researchers have evaluated the effects of ESWT on equine wounds. They've shown that using ESWT on wounds results in blood vessel formation, which, in turn, decreases healing time. Another equine study revealed decreased healing time in lacerations of the distal limb by two weeks as compared to control groups. Diabetic people with foot ulcers and burn victims have had positive results as well. The use of ESWT on equine wounds is relatively new, and studies are still needed to determine proper treatment protocols to optimize and evaluate success.

More recently researchers evaluated ESWT's antibacterial effects. They found that as they increased the number of shock waves or total energy, the number of viable bacterial cells decreased because the cells' protective barriers weakened. ESWT could become a novel treatment for certain bacterial infections on the skin, or even of the bone and soft tissue structures within the body.

The future of ESWT and its use in the horse holds great promise. As an owner, expect to see your veterinarian's use of ESWT increase in the coming years to treat numerous ailments in your equine athlete.

Selected Readings:

Bischofberger, A.S.; Ringer, S.K.; Geyer, H.; Imboden, I.; Ueltschi, G.; Lischer, C.J. Histomorphologic evaluation of extracorporeal shock wave therapy of the fourth metatarsal bone and the origin of the suspensory ligament in horses without lameness. Am J Vet Res 67 (4): 577-582, 2006.

Gerdesmeyer, L.; von Eiff, C.; Horn, C.; Henne, M.; Roessner ,M.; Diehl, P.; Gollwitzer, H. Antibacterial effects of extracorporeal shock waves. Ultrasound Med Bio 31(1): 115-119, 2005.

Kersh, K.D.; McClure, S.R.; Van Sickle, D.; Evans, R.B. The evaluation of extracorporeal shock wave therapy on collagenase induced superficial digital flexor tendonitis. Vet Comp Orthop Traumatol 19: 99-105, 2006.

Ma, H.Z.; Zeng, B.F.; Li, X.L.; Chai, Y.M. Temporal and spatial expression of BMP-2 in subchondral bone of necrotic femoral heads in rabbits by use of extracorporeal shock waves. Acta Orthopaedica 79 (1): 98-105, 2008.

Martini, L.; Giavaresi, G.;Fini, M.; Torricelli, P.; de Pretto, M.; Schaden, W.; Giardino, R. Effect of extracorporeal shock wave therapy on osteoblastlike cells. Clin Orthop Rel Res 413: 269-280, 2003.

McClure, S.R.; Van Sickle, D.; White, M.R. Effects of extracorporeal shock wave therapy on bone: Vet Surg 33: 40-48, 2004.

Ravenuagh, M.S. Extracorporeal shock wave therapy for treatment of osteoarthritis in the horse: Clinical applications. Vet Clin Equine 21:609-625, 2005.

Sturtevant, B. Shock wave physics of lithotripters, in Smith A, Badlani GH, BagleyDH, et al:(eds) Smith's Textbook of Endourology. St. Louis, MO, Quality Medical Publishing, 1996, 529-552, 1996.

About the Author

Jeremiah Easley, DVM

Jeremiah Easley, DVM, is a large animal surgical resident at the University of Florida's Veterinary Teaching Hospital. He has a special interest in equine surgery, along with lameness, advanced diagnostic imaging, and dentistry.

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