Bone mineral density after the removal of intramedullary nails: a cross-sectional and longitudinal study

We measured bone mineral density (BMD) using dual X-ray absorptiometry (DXA) at several sites in both fractured and nonfractured limbs in eight patients with femoral shaft fracture and six with tibial shaft fracture at the time of the intramedullary (IM) nail removal. Seven patients were followed up for an average of 13 months. The BMD at the proximal part of the femur and tibia was from 3% to 11% lower in the fractured side as compared to the nonfractured side. The greatest bone loss (13%-21%) was found in the operated distal tibia of the patients with tibial shaft fractures. At the fracture site of the femur, BMD was 10.5% ( P < 0.05) higher, possibly owing to fracture callus formation, whereas tibial shaft BMD was not increased. However, a calculated apparent volumetric BMDvol at the fracture site was 15%-16% decreased. Although BMDs of the fractured side almost reached the baseline level of the nonfractured side (96.9%-102.1%) by the final follow-up (>12 months), the absolute deficit was still 3%-9%. Surprisingly, significant BMD increases (5%-6%) were also detected in all proximal femoral measurement sites of the contralateral limb, which indirectly suggests that the uninjured limb may also suffer from bone loss after lower-extremity trauma. We conclude that clinically important bone loss exists in the proximal femur and proximal and distal tibia of the fractured limb at the time of IM nail removal. Although areal BMD was higher at the femoral fracture site, the lower apparent volumetric BMDvol suggests decreased mineralization and reduced strength of the fracture site. Although the present results do not suggest special recommendations for restricted weight bearing after the removal of IM nails, the relationship between decreased bone density and increased risk of fractures should be borne in mind.