Relative osteopenia after femoral implant removal in children and adolescents.

Radiographic osteopenia is regularly observed after implant removal from a fracture or femoral osteotomy but has not been objectively quantified. Hardware removal is generally performed months to years after the index event (fracture or osteotomy) when full activity has been resumed. Objectively demonstrable bone mineral deficiency affects fracture risk. Hardware removal may facilitate the return to normal bone mineral density. Children who had dual-energy X-ray absorptiometry scans following femoral implant removal were retrospectively reviewed to assess the percent of change in bone mineral density and change in Z-scores. The femoral neck and the lateral distal femora were scanned, comparing the operated side with unaffected femur as a control. Sixteen children were included. Patients demonstrated up to 15.4% (average, 4.8%) less bone mineral density in the femoral neck region, up to 43% less (average, 16.5%) in the metabolically active distal metaphyseal region, and up to 18.1% less (average, 6.3%) in the transitional region. No statistical difference was noted in the diaphy-seal region. A statistically significant decrease in Z-score was noted when plate and screw constructs (average change, -0.97 SD) as compared with intramedullary nail constructs (average change, -0.33 SD) were used. Children can exhibit statistically significant decreases in bone mineral density in the femoral neck and distal femur following femoral implant removal, with plate and screw constructs demonstrating a greater effect than intramedullary (load sharing) devices. This has implications for return to activity and suggests that implant removal may be important in restoration of bone strength in children.