Crosslinking of UHMWPE markedly improves its wear resistance. However, Green et al. (JBMR 53, 490, 2000) have reported that the wear debris from crosslinked PE were smaller than from non-crosslinked PE, and that particles with a mean diameter of 0.24 μm diameter caused more osteolytic activity of mouse macrophages in vitro than 0.45 μm or 1.7 μm particles. In order to predict how a new PE will behave clinically, however, it is desirable to compare its particle morphology to that of the gamma-air sterilized PE that was used in the vast majority of acetabular cups over the past three decades. We compared PE wear debris that were generated in a hip simulator and recovered by digestion and filtration of the serum lubricants, from cups crosslinked at 2.7 Mrads in air (historical controls), and cups machined from extruded bars that had been pre-gamma crosslinked at 4.5 Mrads and remelted (to extinguish free radicals and stabilize against oxidation) prior to cup machining. The debris were 85% and 92% rounded particles, respectively, and the balance were fibrils. The diameters of most of the rounded particles were from 0.07 to 0.3 μm, with very similar distributions in this range for the two materials. The total number of round particles from the 4.5 Mrad remelted PE was 32% and 76% below that of the 2.7 Mrad gamma-air non-aged and aged cups, respectively, the number of fibrils was 66% and 88% lower, respectively, and the total volume of wear debris per million cycles was 71% and 90% lower with the 4.5 Mrad-remelted PE cups, respectively. Since there was little if any systematic change in particle morphology, the substantially reduced wear and high oxidation resistance of the cups fabricated from gamma crosslinked-remelted PE could markedly reduce the incidence of clinical osteolysis.

We compared the radiographic results of secondary total hip replacements, 99 following failed uncemented hemiarthroplasties and 21 following failed mould arthroplasties, with those of 825 primary cemented total hip replacements. The probability of occurrence of a number of radiological changes over time was calculated using survival analysis. The mean follow-up was 7.6 years (range one month to 20 years). The performance of the secondary total hip replacements varied with the preceding implant and was different for acetabular and femoral components. The incidence of radiological loosening was higher for femoral components implanted after failed hemiarthroplasties and for acetabular components after failed mould arthroplasties. However, the incidence of continuous radiolucent lines was lower for the acetabular components of converted hemiarthroplasties than for the primary replacements.

We reviewed the radiographs of 864 Charnley and STH (Zimmer) cemented total hip arthroplasties with a mean follow-up of seven years (maximum 16 years). Survivorship analysis was used to assess the correlation between radiographic performance and the bony containment or the coronal orientation of the acetabular cup. The cup orientation and containment were interrelated; all vertically oriented cups were completely contained, whereas 25% of more horizontal cups were only partially contained. Completely contained cups had significantly lower incidences of complete cement-bone radiolucency (p = 0.02) and of wear (p = 0.09). Vertically oriented cups had a lower incidence of continuous radiolucency than neutrally oriented cups, but this was not statistically significant (p = 0.25). Our results confirm the importance of complete bony containment, and also indicate that it is better to accept vertical orientation and obtain full bony coverage than to have a more horizontal orientation with partial containment.