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Sunday, February 07, 1999

Ultrasound heals tibial nonunions

An outcomes study of treatment of tibial nonunions finds that low-intensity pulsed ultrasound produces similar results as surgery.

Co-author Victor H. Frankel, MD, professor of orthopaedic surgery, New York University (NYU) School of Medicine, New York City, presented the research in scientific paper 92 Friday. For an average of 90 days, 174 patients (131 tibia nonunions, 43 tibia/fibula nonunions) in a multicenter study were treated with low intensity ultrasound for 20 minutes a day. Healing was assessed by clinical and radiographic criteria.

"Overall, 84 percent of ultrasound-treated patients healed at an average of 167 days," said Dr. Frankel, noting that males and females had the same healing rate, but females had, by 24 days, a longer healing time (182 days plus or minus 16.5 vs. 158 days plus or minus 10.1). Among all patients with tibial nonunions, 85 percent healed; among those with concurrent fibula nonunions, 81 percent healed.

"The success rate of ultrasound compares with other treatment techniques such as intramedullary nailing and bone grafting, which succeed 80 to 95 percent of the time," Dr. Frankel said.

"Length of nonunion before treatment and smoking have a negative effect on healing," he said. "Only 63 percent of nonunions of duration greater than three years healed; and only 68 percent of smokers healed."

Initial fracture types were 109 closed cases; 41 open cases; 15 osteotomies; eight stress fractures; one distraction procedure. All had similar healing rates. "However, as expected, the nonunion location affected the healing rate," said Dr. Frankel.

Eighty percent of the distal shaft nonunions healed; 87 percent of the metaphyseal nonunions healed; and 100 percent of the proximal shaft nonunions healed.

Prior surgical treatment of the fracture impacted the outcomes of these cases. Dr. Frankel noted that 92 percent of the 54 nonunion cases with only conservative treatment healed in contrast to 74 percent of the 27 nonunion cases that had three or more failed surgical procedures.

Six nonunion cases were infected and all six healed with ultrasound treatment in a mean of 278 days.

For this study patients used the ultrasound device at home. It consists of three components: a plastic retaining and alignment fixture (RAF); a battery-operated treatment module which supplies the ultrasound signal to the skin at the site of the fracture; and a control unit.

"The prescribing physician marked the skin at the nonunion site to assist the patient in positioning the RAF with a Velcro‚ strap or, if a cast was used, windowed the cast for attachment of the RAF," said Dr. Frankel. The patient applied ultrasonic coupling gel to the transducer surface of the treatment head module and attached it to the skin at the nonunion site by the use of the RAF.

Dr. Frankel said that the ultrasound pressure-wave signal was composed of a pulse burst width of 200 microseconds containing approximately 300 sine-wave pressure pulses, each approximately 0.67 nanosecond in duration (frequency of 1.5 megahertz). The 200-mi-crosecond burst of pressure pulses was followed by an off-time of 800 microseconds and therefore, repeated every millisecond (repetition rate of one kilohertz).

"The nonthermal intensity of the pressure wave applied to the skin at the site of the fracture was 30 milliwatts per square centimeter, which is two orders of magnitude below thermal conventional physical therapy ultrasound intensity levels," he said. "A visible and au-di-ble signal alerted the patient when the daily treatment was complete."

All participants in the study met specific criteria: minimum nine months after initial injury; no surgical intervention in the previous three months; and two orthogonal radiographic views showing the fracture line and gap clearly visible. Patients (111 males, 63 females) ranged in age from 18 to 69 (average: 43.4 years).

"A short-leg cast or functional brace was applied during treatment and patients were allowed to weight bear as tolerated," said Dr. Frankel.

"Treatment was well-tolerated by the patients, and no serious complications were identified. No patient had skin irritation or edema as a result of using the device."

From the Hospital for Joint Diseases, co-authors of the study with Dr. Frankel are Kenneth J Koval, MD, associate professor of orthopaedic surgery, NYU School of Medicine; and Fredrick J Kummer, PhD, research professor, NYU School of Medicine.

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Last modified 07/February/1999