Background: Animal studies have demonstrated the efficacy of the use
of bisphosphonates to enhance screw fixation in bone. In this prospective,
randomized study of pertrochanteric fractures treated with external fixation,
we tested whether systemic administration of bisphosphonates would improve the
fixation of hydroxyapatite-coated screws implanted in osteoporotic bone.
Methods: Sixteen consecutive patients with a pertrochanteric
fracture were selected. Inclusion criteria were female gender, an age of at
least sixty-five years, and a bone mineral density T-score of less than
—2.5 standard deviations. Exclusion criteria included bisphosphonate
treatment during the two-year period prior to the fracture. Fractures were
fixed with a pertrochanteric fixator and four hydroxyapatite-coated pins. Two
pins were implanted in the femoral head (pin positions 1 and 2), and two were
placed in the femoral diaphysis (pin positions 3 and 4). The patients were
randomized either to therapy with alendronate for a three-month postoperative
period (Group A) or to no therapy (Group B). The Group-A patients received an
oral dose of 70 mg of alendronate per week. The fixators were removed after
three months.
Results: All of the fractures healed, and no loss of reduction,
nonunion, or delayed union was observed. The combined mean extraction torque
(and standard deviation) of the pins implanted at positions 1 and 2
(cancellous bone) was 2558 ± 1103 N/mm in Group A and 1171 ± 480
N/mm in Group B (p < 0.0005). The combined mean extraction torque of the
pins implanted at positions 3 and 4 (cortical bone) was 4327 ± 1720
N/mm in Group A and 4075 ± 1022 N/mm in Group B.
Conclusions: These data show that weekly systemic administration of
alendronate improves pin fixation in cancellous bone in elderly female
patients with osteoporosis. We observed a twofold increase in extraction
torque with the pins implanted in cancellous bone. These results support the
use of alendronate in the treatment of osteoporotic pertrochanteric fractures
to improve screw fixation in the femoral head.
Level of Evidence: Therapeutic Level I. See Instructions
to Authors for a complete description of levels of evidence.