A new wave in equine medicine

Shock-wave therapy shows early potential for treating some orthopedic problems

Lithotripsy was a great discovery. Anyone who has suffered with kidney stones or bladder stones knows the intense pain associated with these conditions. The development of lithotripsy allowed doctors to focus pressure or shock waves on the stones to break them apart. The patient then passes much smaller stone particles, reducing or eliminating pain and avoiding surgery.

In the course of investigating the broader effects of shock-wave therapy, researchers have made a few other discoveries. In the early 1980s, researchers were concerned about the possible effects of lithotripsy on the surrounding tissue.

They knew the shock waves would gently break apart the stones in the kidney or bladder, but what would those pressure waves do to surrounding tissue such as blood vessels, kidney cells, and the bone of the pelvis?

The first experiments on shock-wave side effects, as they were then considered, were carried out on the pelvic bones of rabbits. Shock waves were applied as they would be for lithotripsy, and the pelvic bones were then examined under a microscope.

Researchers discovered small ruptures in the bone tissue. Bleeding and microdamage to the bone cells resembled, on a cellular level, what would occur in a fresh fracture. At first, this was of great concern. This new, wonderful procedure that could remove kidney stones without pain and surgery was also likely to cause blood-vessel damage and local microfractures. Was this going to be another situation where the problems associated with a cure were as bad or worse than the original condition?

Stimulate repair

Researchers followed the progress of the damage to the bone tissue, however, and found that, after the shock-wave trauma occurred, the osteocytes and osteoblasts of the affected bone showed increased activity. These cells are responsible for repairing damage to bone and for producing new bone to heal the damage. It is exactly these cells that the body needs to heal fractures and to heal any type of stress to the bone.

Shock waves seem to stimulate these cells, and the result is increased growth. Researchers then began to think of ways to apply this new information to conditions where bone growth was desirable.

Studies began in Bulgaria in the mid-1980s on the effects of shock waves on pseudoarthrosis, a disorder in the fracture-healing process where the body forms only a cartilage-like link between the fractured bone ends, but real stable bone callus does not form. Nonunion fractures fall into this category as well.

The first medical paper reporting on the use of shock-wave therapy for the healing of pseudoarthrosis was published in 1991, and other researchers soon confirmed the results.

They found that shock waves provided an effect similar to a fresh fracture on a tissue level. The body then seemed to recognize that healing in this area was still required and in many cases a bony link was formed. These studies showed that 60%-to-80% of all pseudoarthrosis cases could be healed completely with shock-wave therapy.

This information in turn caused other human orthopedic researchers to investigate shock-wave therapy use for a number of other conditions. Researchers in Hamburg, Germany, discovered that shock waves caused a decrease in pain in areas associated with bone-tendon connections. Shock waves seemed to relieve pain associated with shoulder injuries, tennis elbow, and heel spurs.

Further research indicated that shock waves might actually reduce the bony growths that develop at the areas where tendons and ligaments are inserted onto bone. In conditions such as tennis elbow and heel spurs, repeated trauma causes the bone to produce small, irregular growths known as osteophytes.

The body produces this bone material in an attempt to deal with the stress at that particular location. The buildup of this bone tissue causes more pain in the tendon or ligament, which must now move over these irregularly shaped, often irritating bone spurs. Shock waves reduce the pain in these areas and seem to resolve some of the excessive bone growth.