Shock wave therapy for lameness
From outside the body (extracorporeal), the machine generates high-intensity shock or pressure waves, which pulse to a specific site within the injured tissue. Though its actual mode of action is still in dispute, it stimulates and accelerates the healing process, essentially combining an immediate analgesic effect with a reduction in inflammation, neovascularization in soft tissue and osteogenesis in bone. According to Dr. Scott McClure, DVM, Iowa State University, a leading researcher in the field, it can be used to treat various conditions, such as suspensory ligament desmitis, navicular disease, saucer fractures, bucked shins, bowed tendon, sesamoid fractures, stress fractures and vertebral spinal pain (kissing spine lesions).
The technique Though some of its initial use came with the need for general anesthesia, the most common units today are portable and able for use with a standing horse in the barn or at the racetrack.
Electrical energy is used to initiate the pressure wave. The energy settings and the number of pulses are important. Too low energy or too few pulses might not create the desired therapeutic effect. Excessive energy or pulses may result in tendon damage. The pressure waves penetrate fluid and soft tissue, and their effects occur at sites at the bone/soft tissue interface.
The mechanism by which shock waves stimulate healing is unknown. Theoretically, shock waves can increase cellular membrane permeability, cellular division, and stimulate cytokine production by bone marrow, neovascularization of soft tissue and osteogenesis in bone. Pressure waves might help physically break down or move a hematoma or fluid from the lesion to allow the fibroblasts to more rapidly fill the defect. At this time, the effect of ESWT on disease recurrence and future ligament strength has not been evaluated.
Though the horse is sedated, it can tolerate the pain, similar to hitting the funny bone, and there is some numbing effect as the shock waves are applied. Depending on the site and injury depth, the usage is usually 1,500 to 2,500 impulses. A small, defined area requires fewer impulses than a larger surface area. The more shallow and softer the tissue, fewer and milder impulses are required; the deeper and harder the tissue, the greater the number of impulses and energy required. Though shock wave therapy works with good results, there is need to define the procedural protocols, including how to treat, at what intensity, at what energy level and the proper number of impulses.
"During the procedure, we do sedate the horses and either use a twitch or sometimes use local anesthetic at the site," says David McCarroll, DVM with Interstate Equine Hospital in Goldsby, Okla.