Medium-to-long term DEXA analysis of an uncemented (AML) femoral component

We present medium-to-long-term bone mineral density studies assessing bone resorption and remodelling around the cementless femoral component of a total hip arthroplasty (Depuy AML prosthesis). Bone mineral densities were compared with the unoperated side at a time interval of eight years between scans using dual energy X-ray absorptiometry. Initial proximal stress shielding is known but we show that this response continues into the medium to long term in relative terms. We have also found an overall trend for bone mineral density to increase around the prosthesis with the greatest changes occurring distally. The greatest real increase in bone mineral density occurred in Gruen zones 2, 3 and 5 with smaller increases in zones 1, 4, 6 and 7. However, when compared with the contralateral unoperated femur (thus considering systemic changes in bone mineral density), we found these changes only reached statistical significance in Gruen zones 5, 6 and 7.