No pain, no gain

May 23, 2001

The shock wave gravy train derailed more than a decade ago, when minimally invasive surgery all but took over the gallstone market. Vendors had hoped gallstone treatments would boost this technology, popularized by its ability to smash kidney stones, to

The shock wave gravy train derailed more than a decade ago, when minimally invasive surgery all but took over the gallstone market. Vendors had hoped gallstone treatments would boost this technology, popularized by its ability to smash kidney stones, to new heights, but it was not meant to be. Now vendors are hoping to breath new life into extracorporeal shock wave therapy by using sound waves to treat pain.

Several vendors, including Healthtronics and Siemens Medical Solutions, have fashioned systems that promise to treat heel spurs, tennis elbow, and golfer’s elbow. Extracorporeal shock wave therapy might even speed the healing of bone fractures. Rather than focusing on stones, this newest generation of ESWT systems is taking aim at soft tissues, such as ligaments and cartilage, as well as bone. Lower power shock waves aimed at shallower depths trigger the body’s healing process, say vendors. The exact process is not known.

“It’s kind of like aspirin,” said Cathy Anne Pinto, clinical manager of regulatory affairs at Siemens. “It’s a fact that pain relief occurs, but as to the exact mechanism, there are still some questions.”

Renal lithotripsy, with its ability to smash kidney stones into sand, marked the beginning of extracorporeal shock wave therapy, which (by definition) is administered from outside the body. Radiologists fought for control of these systems, citing the need for adjunctive imaging technologies-ultrasound or x-ray-as justification for why they should control this new product type.

As the market for lithotripters began to saturate in the mid- to late 1980s, biliary lithotripsy was proposed as the means for propelling the technology onward. But gallstones are more elastic than kidney stones and, therefore, more resistant to shock waves. Shock waves broke the stones into pieces, but the remains needed to be dissolved by drugs. In light of these shortcomings, laparoscopic cholecystectomy, a procedure in which the gallbladder is pulled from the patient through a small opening, became the preferred treatment.

At least one company, Medstone, has refused to give up on biliary lithotripsy. This company and others, including Siemens, Dornier, and Healthtronics, continue to sell kidney stone lithotripters. Despite the persistence of vendors, sales of ESWT products have languished.

A new treatment niche, however, has opened up-plantar fasciitis, better known as heel spurs. Healthtronics was the first, last October, to gain FDA approval for a product designed specifically to treat this problem, which gives rise to 6.5 million reported new cases each year. About 10% of patients typically undergo surgical intervention annually to resolve their heel pain. Healthtronics’ OssaTron appears to provide a noninvasive, safe, and effective treatment alternative. In a multicenter, randomized, placebo-controlled study, the system achieved success in 60% of some 300 patients.

“We are creating, through the use of shock waves, a controlled subclinical injury that prompts a healing response,” said Howard Smith, director of marketing for OssaTron.

Healthtronics is pursuing two other indications, tennis elbow and nonunion, or delayed healing, of bone fractures. Tennis elbow affects between 1% and 3% of the U.S. population. Symptoms range from minor to extreme pain and complete loss of arm mobility. The OssaTron is already being used in Europe to treat patients with this condition and is in clinical trials in the U.S. to generate data to support a PMA submission to the FDA.

Fractures that fail to heal properly are believed to affect about 200,000 people annually in the U.S. Treatment includes bone grafts, internal or external fixation of the bone, electrical stimulation, and casting. The OssaTron promises to resolve the problem by inducing microfractures and bleeding that lead to bone growth around the fracture. The system is already on the market for this application outside the U.S., reportedly healing nonunion fractures in the tibia, humerus, metacarpals, and metatarsals in up to 80% of cases. Clinical trials are under way in the U.S. in preparation for an FDA submission. Other potential applications that may be addressed in clinical trials include avascular necrosis of the hip and shoulder tendinitis.

Siemens is also pursuing new indications, and several of these are in pain therapy as well.

“We are focusing mostly on tennis elbow, but there are other indications,” said Anne Marie Keevins, division manager for Siemens special products business unit. “Overseas we have done shoulder treatments for pain, and in Canada we have looked at heel spurs.”

Although based on the same principle, the ESWT products built to address new applications differ from those designed to blast stones. One obvious difference is the lack of an imaging system, either ultrasound or x-ray, which originally attracted the radiology community to shock wave therapy.

“We shock until the patient feels pain,” Keevins said. “Then the doctors know they are on the source of the problem.”

The OssaTron, when used to treat patients with nonunion of fractures, is the exception. Smith noted that the product works in tandem with an orthopedic C-arm.

“You have to localize the fracture site and make sure that you are in proper anatomical alignment with it,” Smith said. “You have to be sure you don’t create additional damage.”

Although the U.S. typically represents the most lucrative market for high-technology products, foreign countries often get them first. Like the OssaTron, Siemens’ Sonocur shock wave product is being sold in Europe, as well as in Canada, for the treatment of chronic pain disorders. But because the FDA has designated Sonocur and other such products as class III devices, companies seeking approval to market the systems in the U.S. must go through clinical trials to prove safety and efficacy.

“Our experience (at foreign clinical sites) will not be used as pivotal data in getting FDA marketing clearance, but it may give (reviewers) some comfort to know that the system has been available outside the U.S. and there haven’t been any serious adverse events,” Pinto said.

Studies regarding tennis elbow at U.S. institutions in Virginia, North Carolina, and Georgia are now under way. All 114 patients deemed necessary to generate the data to support an FDA application have been enrolled. Data from the treatments will be evaluated and updated at three- and 12-month follow-up periods, Pinto said.

“The three-month follow-up is the most critical for us,” she said. “Those are really the data that will support our primary end points in terms of pain relief.”

These applications are attractive because they open a new marketing avenue for lithotripter vendors. To date, most lithotripters have been sold to urologists or radiologists. Pain therapy products will be sold to orthopedists.