Weekly alendronate treatment can improve screw fixation in osteoporotic bone

Alendronate patients had significantly higher mean extraction torque for pins inserted into cancellous femoral heads, but not for pins in the cortical bone of the femoral diaphysis.

Weekly administration of alendronate can significantly improve screw fixation in the cancellous bone of osteoporotic women, a prospective study found.

Antonio Moroni, MD, and colleagues at the University of Bologna, Italy, randomly assigned 16 consecutive women with a pertrochanteric hip fracture to treatment either with or without Fosamax (alendronate, Merck & Co.) after undergoing surgical reduction with external fixation of the fracture.

No patients had received treatment with a bisphosphonate for at least 2 years before study enrollment, the authors noted.

Patients in the study group averaged 83 years of age and received weekly treatment with 70 mg of oral alendronate beginning the first postoperative week. Six patients had an AO/OTA type-A1 fracture and two patients had an AO/OTA type-A2 fracture; bone mineral density averaged 493 mg/cm².

The control group included three patients with an AO/OTA type-A1 fracture and five patients with an AO/OTA type-A2 fracture. These patients averaged 86 years of age; bone mineral density averaged 490 mg/cm², according to the study, published in the American edition of the Journal of Bone and Joint Surgery.

In all cases, surgeons fixed the fractures using an Orthofix pertrochanteric fixator and four tapered hydroxyapatite-coated pins (Orthofix); two pins were placed in the femoral head and two were placed in the femoral diaphysis.

Investigators measured the screw torque when mounting the fixators and when the fixators were removed at 3 months follow-up.

The researchers found that all fractures healed and no patients had a loss of reduction, nonunion or delayed union, nor were there any cases of pin loosening or infection. Also, no alendronate-treated patients experienced drug-related adverse events, the authors said.

Both groups had similar pin insertion torque. However, alendronate-treated patients had significantly higher combined mean extraction torque for pins inserted into the cancellous bone of the femoral heads. For these pins, the extraction torque averaged 2,558 N/mm for alendronate-treated patients vs. 1,171 N/mm for control patients (P<.0005), according to the study.

"In Group A (alendronate group), fixation of the pins implanted [in the femoral heads] improved over time as shown by the mean pin extraction torque, which was higher than the corresponding insertion torque," the authors said.

"In Group B (control group), fixation of the pins ... was maintained over time, but it did not improve, as no significant difference was detected between the mean pin extraction and insertion torque," they said.

No significant differences in mean extraction torque were noted between alendronate-treated and control patients for pins inserted into the cortical bone of the femoral diaphysis.

For more information:
Moroni A, Faldini C, Hoang-Kim A, et al. Alendronate improves screw fixation in osteoporotic bone. J Bone Joint Surg Am. 2007;89-A:96-101.