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February 6, 1997


The bone-building drug alendronate sodium may reduce the need for costly repeat surgeries by preventing the loosening of hip joints common after total hip replacement surgery, University of Pittsburgh Medical Center research shows.

The report, based on studies conducted at UPMC's Musculoskeletal Research Center, was presented by Arun S. Shanbhag, Carl T. Hasselman and Harry E. Rubash at the Orthopaedic Research Society meeting, in conjunction with the annual gathering of the American Academy of Orthopaedic Surgeons.

Nearly 500,000 joint replacement operations are done in the United States each year, including those for hips and knees, said Rubash, associate professor and chief of adult reconstructive surgery in UPMC's orthopaedic surgery department. About 10 percent of these operations require additional surgeries, each costing $40,000 to $60,000, to replace the components and surrounding bone that have broken down and loosened by an inflammatory process generated by the implanted materials.

"Based on our animal study with alendronate, we believe we may have found a way to control the bone destruction around failed joint implants, a previously un-solvable problem that has led to devastating consequences for the nearly 50,000 patients who must undergo joint replacement revision surgery each year in this country," said Shanbhag, assistant professor of orthopaedic surgery and medical engineering.

"Our biggest surgical problem is bone loss associated with the loosened implants," Rubash said. "If we could avoid the need for repeat surgeries by a mere 10 percent or decrease the complexity of the procedures by eliminating bone loss, an estimated $200 million would be saved." In total hip replacement, a plastic socket is implanted into the hip, joined by a metal ball anchored into the top of, and down through, the thigh bone. Although the ball-and-socket device that mimics hip joint movement is extremely smooth, tiny particles of wear debris still are released and remain within the space between the ball's anchor and the thigh bone. Within this space, the debris interacts with immune cells that, in turn, secrete bone resorbing substances. This process, called particle disease, can lead to erosion of the surrounding thigh bone, painful joint swelling and loosening and implant failure.

The UPMC research, which is the first study of the effect of alendronate on animal hip joint replacements, indicates that the oral prescription drug can prevent this destructive process.

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