(Ivanhoe Newswire) -- Bisphosphonate treatments, proven to enhance bone
density and reduce fracture incidence in post-menopausal women, may adversely
affect bone quality and increase risk of atypical fractures of the femur when
used for four or more years. Bisphosphonates are designed to slow or stop the
bone loss that occurs during the body's bone remodeling cycle, the natural
process that involves removal and replacement of bone tissue.
Researchers from Hospital for Special Surgery (HSS) and Columbia University
Medical Center revealed data suggesting that long-term suppression of bone
remodeling by bisphosphonate treatments may alter the material properties of
bone, potentially affecting the bone's mechanical integrity and possibly
contributing to the risk of atypical fractures.
"Although bisphosphonates have demonstrated an improvement in bone quantity,
little if anything is known about the effects of these drugs on bone quality,"
Brian Gladnick, BS, representing a team of investigators at HSS in New York, was
quoted as saying.
Researchers at Columbia evaluated the bone structure of 111 postmenopausal women
with primary osteoporosis. Sixty-one of them had been taking bisphosphonates for
a minimum of four years, and 50 controls had been taking calcium and vitamin D
supplements.
The study found that bisphosphonate use improved structural integrity early in
the course of treatment, but those gains diminished with long-term treatment.
"In the early treatment period, patients using bisphosphonates experienced
improvements in all parameters, including decreased buckling ratio and increased
cross-sectional area," Melvin Rosenwasser, MD, orthopedic surgeon for Columbia
University Medical Center, was quoted as saying. "However, after four years of
use, these trends reversed, revealing an association between prolonged therapy
and declining cortical bone structural integrity."
Scientists noted that the culprit behind the diminishing results may be the fact
that bisphosphonates suppress the body's natural process of remodeling bone.
"Recent research suggests that suppressed bone remodeling from long-term
bisphosphonate use might result in brittle bone that is prone to atypical
fractures," said Gladnick.
The investigators added that more research is needed to determine the true
efficacy of the long-term clinical use of bisphosphonates for the treatment of
osteoporosis, and that the results of their studies will not likely affect
clinical practice in the near future.
"Bisphosphonate use still is a very effective solution that prevents bone loss
in most patients and no one is recommending that physicians avoid prescribing
these," said Dr. Rosenwasser. "However, as baby boomers age and continue to
remain active, it is important that we conduct more research and develop
sustainable, safe and effective treatments for osteoporosis."
In a second unrelated study conducted at HSS, researchers evaluated the bone
composition of 21 post-menopausal women who were treated for femoral fractures.
Of these, 12 patients had a history of bisphosphonate treatment for an average
of 8.5 years, while nine had not had bisphosphonate treatment.
"Patients who had been treated with bisphosphonates showed a reduction in tissue
heterogeneity, specifically with mineral content and crystal size compared with
the control group," Gladnick said. "This tells us that there may be some
measurable differences in bone quality parameters in patients on long-term
bisphosphonate therapy, which might contribute to the development of atypical
fractures."
SOURCE: Presented at the Annual Meeting of the American Academy of Orthopedic
Surgeons (AAOS), March 10, 2010
