Bisphosphonates may have minimal long-term impact on osteoporotic bone fracture healing

MANCHESTER — British researchers using an animal model determined that administering bisphosphonates for osteoporotic fractures can help increase the callus size, but the callus may be biomechanically inferior.

According to lead investigator Parag K. Jaiswal, MRCS, researchers have had conflicting opinions as to whether bone healing is affected by bisphosphonates as a treatment for osteoporosis. Using an animal model, “We wanted to see if and to what degree bisphosphonates influenced osteoporotic fracture healing and whether the timing of [drug] administration made a difference,” he said at the British Orthopaedic Association Annual Congress 2009, here.

The researchers performed a mid-diaphyseal femoral osteotomy on 36 female Wistar rats 6 weeks after ovariectomy. They were then divided into three groups: those that received no treatment (ie, the control group); those that received alendronate (ALN) starting 14 days after osteotomy; and those who received ALN from the time of osteotomy.

The researchers also assessed fracture repair weekly using standardized radiography, DEXA scan and in vitro peripheral quantitative computed tomography (pQCT), according to the abstract.

The rats were sacrificed 42 days post-osteotomy, and both the intact and osteotomized femora underwent mechanical testing.

The third group differed from the control in three respects: higher bone mineral content and density; larger callus; and lower torsional stiffness. Group 2 did not differ significantly from the control, according to Jaiswal.

“We also saw a significant positive correlation between stiffness and change in bone mineral content in the first group, but not for the second or third groups,” he said.

A similar trend existed for all radiographic parameters — such as volumetric density on pQCT, or change in area after line-profiling serial radiographs — among the three groups, Jaiswal added.

“Our results suggest that, using early bisphosphonate treatment, the callus size increased, but the callus was biomechanically inferior than the one that formed naturally,” he said. Also, “Administering bisphosphonates at either stage can compromise the relationship between radiographic and mechanical parameters used to assess fracture healing.”

Reference:
Jaiswal PK, Mangat N, Chenu C, et al. Fracture repair in osteoporosis: When are osteoclasts important? Presented at the British Orthopaedic Association Annual Congress 2009. Sept. 15-18, 2009. Manchester.