Saturday February 24, 1996

New bone paste heals fractures faster than traditional methods

Orthopaedic researchers have found that a bone paste compound injected through the skin into a wrist fracture will heal bones faster than traditional methods, according to the results of a study presented Thursday in scientific paper 31.

The Norian SRS bone paste provides internal stabilization of the fracture with little morbidity, said co-author Jesse Jupiter, MD, director of orthopaedic hand service, Massachusetts General Hospital, Boston.

Norian SRS is a fast-setting, biocompatible bone mineral substitute, composed of carbon, calcium, hydrogen, and phosphorus, that forms a carbonated apatite of low crystallinity and small grain size.

"The patient's bone reacts to the compound as if it were really bone and does not reject it as foreign matter," said Dr. Jupiter. Osteoclast cells tunnel through the bone paste similarly to the way they do when remodeling bone, he said.

Dr. Jupiter studied the bone paste's effects on fracture healing and functional restoration among women age 49-57 years who had slipped on the ice and broken their wrist.

After injecting the moldable 'toothpaste-like' compound into the fracture site, Dr. Jupiter let the bone paste harden for 15 minutes, and then immobilized the patient's wrist in a short arm cast for six weeks.

"Prior to surgery, patients experienced minimal to moderate swelling and moderate to severe limitation of motion in their hand, wrist, and forearm," Dr. Jupiter said. "After cast removal, all patients freely used the affected wrist."

At one-year follow-up, the grip strength in a hand that was conventionally treated ranged between 60 and 85 percent that of the other uninjured hand. The grip strength of a hand that had the bone paste treatment was about 98 percent of the other uninjured hand.

Three, six, and 12 months after surgery, manual dexterity was normal for all patients who received the bone paste treatment.

These patients lost about 1 mm of radial bone length, compared to length losses of up to 10 mm with conventional treatment. X-rays of patient wrists were taken throughout the year.

"Range of motion improved by 50 percent at three months and further improved through 12 months," Dr. Jupiter said.

Bone paste-treated patients had a mean pronation of 100 percent; a mean supination of 93 percent; a mean wrist extension of 95 percent; a mean flexion of 85 percent, a radial deviation mean of 88 percent; and an ulnar deviation mean of 89 percent.

"At one year follow-up, Norian SRS equaled or exceeded the results of standard treatment methods," said Dr. Jupiter. There were no side effects or complications.

Bone paste achieved anatomic restoration of the affected wrist in four of five patients.

The plasticity of Norian SRS during implantation allows it to penetrate the interstices of bone and fill irregular voids, Dr. Jupiter said. Norian SRS occupies the space in between the broken bones, preventing them from slipping back into the fracture position.

Dr. Jupiter said that the compound appears to be especially well-suited for treating older people's fractures because osteopenic bone often makes repositioning and stabilizing difficult.

"It could prove useful for hip fracture cases where the normal hip screw will not hold in place due to osteoporotic bone," Dr. Jupiter said. "The bone paste theoretically will supply stability to the fracture so the hip won't have to be replaced.

"What we don't know yet is whether the bone paste will work on compressive loads, such as in the knee."

The bone paste is now undergoing multicenter clinical trials for approval by the U.S. Food and Drug Administration. Norian SRS was created and is manufactured by Norian Corp., a biomedical technology company headquartered in Cupertino, Calif.

Co-authors of the study with Dr. Jupiter are Steven C. Winters, MD, of Poplar Bluff, Mo.; Scott Sigman, MD, of Los Angeles;

Colleen Lowe, occupational therapist, Massachusetts General Hospital; Charles Pappas, MD, assistant professor of radiology, department of orthopaedics and rehabilitation, University of Vermont College of Medicine, Burlington, Vt.; and Amy Ladd, MD, assistant professor of hand and orthopaedic surgery, Stanford University Medical Center, Stanford, Calif.

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