Fracture after bisphosphonate treatment in children with cerebral palsy: the role of stress risers

Abstract

In the nonambulatory cerebral palsy (CP) population with a prior history of fracture, the use of pamidronate is not always effective in preventing further fractures. To test the hypothesis that when fractures occur after cyclic pamidronate, they will be at the proximal or distal end of a pamidronate band. Retrospective review of our CP patient database revealed 53 children who had received one or more complete courses of pamidronate therapy (five cycles over 12 months). Medical records were screened to identify children who had sustained a fracture or fractures after completing treatment. Of 53 patients treated with pamidronate, only 14 sustained fractures after treatment. Radiographs were available for 11 patients, showing 19 fractures. Sixty-three percent of these fractures were located at a junction with pamidronate bands but not within the bands. We propose stress risers as the mechanism for fractures that have occurred where bone mineral density abruptly changes as a result of cyclic administration of pamidronate. We show a theoretical example of how alternative dosing might reduce the ratio and therefore decrease the chance of formation of a stress riser.