In a randomised study, 28 patients with a mean age of 62.2 years (32 to 81) with osteoarthritis or avascular necrosis of the hip received either a ceramic-on-ceramic or a metal-on-metal total hip replacement. Apart from the liners the acetabular and femoral components were made of Ti-Al-Nb alloy. The serum aluminium and cobalt levels were measured before, and at one year after surgery.

The 15 patients in the ceramic-on-ceramic group had a median pre-operative aluminium level of 1.3 μg/l (0.25 to 8.4) and a cobalt level below the detection limit. At one year the aluminium level was 1.1 μg/l (0.25 to 2.3) and the cobalt level was 0.4 μg/l (0.15 to 0.7). The 13 patients in the metal-on-metal group had a median pre-operative aluminium level of 1.9 μg/l (0.25 to 4.4) and a cobalt level below the detection limit. At one year the median aluminium level was 0.9 μg/l (0.25 to 3.9) whereas the cobalt level was 1.4 μg/l (0.5 to 10.5). This increase in the cobalt level at one year was significant (p < 0.001).

Our findings indicate that ceramic-on-ceramic bearings do not cause elevated levels of serum aluminium in the first post-operative year.

We investigated prospectively the bone mineral density (BMD) of the proximal femur after implantation of a tapered rectangular cementless stem in 100 patients with a mean age of 60 years (16 to 87). It was determined using dual energy x-ray absorptiometry, performed one week after surgery and then every six months until the end-point of five years.

The BMD increased significantly in Gruen zones 2, 4 and 5 by 11%, 3% and 11% respectively, and decreased significantly in Gruen zones 1, 6 and 7 by 3%, 6% and 14% respectively, over the five-year period. The net mean BMD did not change over this time period. The changes in the BMD were not confined to the first 12 months after surgery. This investigation revealed no change in the overall periprosthetic BMD, but demonstrated a regional redistribution of bone mass from the proximal to distal zones.