We carried out a cross-sectional study with analysis of the demographic, clinical and laboratory characteristics of patients with metal-on-metal hip resurfacing, ceramic-on-ceramic and metal-on-polyethylene hip replacements. Our aim was to evaluate the relationship between metal-on-metal replacements, the levels of cobalt and chromium ions in whole blood and the absolute numbers of circulating lymphocytes. We recruited 164 patients (101 men and 63 women) with hip replacements, 106 with metal-on-metal hips and 58 with non-metal-on-metal hips, aged < 65 years, with a pre-operative diagnosis of osteoarthritis and no pre-existing immunological disorders.

Laboratory-defined T-cell lymphopenia was present in13 patients (15%) (CD8⁺ lymphopenia) and 11 patients (13%) (CD3⁺ lymphopenia) with unilateral metal-on-metal hips. There were significant differences in the absolute CD8⁺ lymphocyte subset counts for the metal-on-metal groups compared with each control group (p-values ranging between 0.024 and 0.046). Statistical modelling with analysis of covariance using age, gender, type of hip replacement, smoking and circulating metal ion levels, showed that circulating levels of metal ions, especially cobalt, explained the variation in absolute lymphocyte counts for almost all lymphocyte subsets.

The biological significance of cobalt-chromium wear particles from metal-on-metal hip replacements may be different to the effects of the constituent metal ions in solution. Bacteria may be able to discriminate between particulate and ionic forms of these metals because of a transmembrane nickel/cobalt-permease. It is not known whether wear particles are bacteriocidal.

We compared the doubling time of coagulase negative staphylococcus, Staphylococcus aureus and methicillin resistant S. aureus when cultured in either wear particles from a metal-on-metal hip simulator, wear particles from a metal-on-polyethylene hip simulator, metal ions in solution or a control.

Doubling time halved in metal-on-metal (p = 0.003) and metal-on-polyethylene (p = 0.131) particulate debris compared with the control.

Bacterial nickel/cobalt-transporters allow metal ions but not wear particles to cross bacterial membranes. This may be useful for testing the biological characteristics of different wear debris. This experiment also shows that metal-on-metal hip wear debris is not bacteriocidal.

This study was conducted to assess the results in two subgroups:a) the effect of the PFC Sigma as compared to the PFC total knee replacement in lowering patella lateral release rates and b) the results of severe fixed flexion deformity correction with emphasis on some technical operative details.

Data is collected prospectively on all patients undergoing total knee replacements for an ongoing research programmer. As part of this project, we assessed the patella lateral release rate in 954 knees performed between April 1994 and January 2000.

Lateral release was reached in 55 out of 592 PFC knees compared with 25 out of 362 Sigma knees. The overall lateral release rate was 8.3%.

Using the Chi squared test, there is a statistically significant lower lateral release rate using the Sigma system and the study also demonstrated a low overall lateral release rate in our entire series. The biomechanics of the PFC Sigma system and some operative technical points will be discussed in the talk.

As regards the fixed flexion deformity group data was once again collected prospectively on the Knee Society Scoring form. The results are as follows:

Preoperative flexion deformity > 20 degrees = 53 knees, (Range 20 to 60 degrees),

Preoperative Mean Knee Score = 17.2,

Postoperative flexion deformity < 5 degrees=91%

Postoperative Mean Knee Score = 90.04.

These numbers and results are comparable to other large series and some technical operative details will be discussed in the talk.

An intact barrier between the hands of the surgeon and the patient remains the single most important factor in protection against infection for both. Increasing the awareness of possible glove perforation without skin penetration will decrease the risk of contamination.

We performed a prospective, randomised trial comparing the incidence of glove perforation using a new type of glove (Regent Biogel Reveal) and standard double-gloves in total hip and knee replacement. One or more perforations was detected in 14.6% of all gloves. The new gloves increased significantly the awareness of perforation. Multiple perforations at the base of the ring finger were found in surgeons who wore wedding rings during the operation and we recommend that rings be removed before undertaking surgery.