Studies find possible links between prolonged bisphosphonate treatments and atypical fractures in post-menopausal women
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, according to preliminary research presented today at the 2010 Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS).
Bisphosphonates are designed to slow or stop the bone loss that occurs during the body's bone remodeling cycle, or the natural process that involves removal and replacement of bone tissue.
Two separate studies by 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 potentially 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," said Brian Gladnick, BS, representing a team of investigators at HSS in New York.
Researchers at Columbia evaluated the bone structure of 111 postmenopausal women with primary osteoporosis, 61 of whom had been taking bisphosphonates for a minimum of four years and 50 controls taking calcium and vitamin D supplements.
This study found that bisphosphonate use improved structural integrity early in the course of treatment, but those gains were 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," said Melvin Rosenwasser, MD, orthopaedic surgeon for Columbia University Medical Center. "However, after four years of use, these trends reversed, revealing an association between prolonged therapy and declining cortical bone structural integrity."
Scientists at both institutions 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.