We randomly allocated 50 total knee replacements to scrub teams wearing body-exhaust suits (BES) or Rotecno occlusive clothing. The effectiveness of the clothing was assessed using air and wound bacterial counts.

Bacteria were recovered from 62% of wounds (64% BES, 60% Rotecno). The mean air count was 0.5 CFU/ m³ with BES and 1.0 CFU/m³ with Rotecno (p = 0.014). The mean wound counts were 14 bacteria/wound with BES and eight bacteria/wound with Rotecno (p = 0.171). There was no correlation between the air and wound counts (r = −0.011, Spearman’s).

The higher air counts suggest that Rotecno occlusive clothing is less effective than BES, but wounds were equally contaminated with both types of clothing suggesting that at very low levels of air contamination the contribution of bacteria to the wound from the air is irrelevant. Even doubling the air counts from 0.5 to 1.0 CFU/m³ had no detectable effect on the wound.

This allows a reassessment to be made of other sources of contamination the effect of which would previously have been overwhelmed by contamination from air.

Matrix metalloproteinases (MMPs) may have a role in the process of aseptic loosening. Doxycycline has been shown to inhibit MMPs. Our aim was to investigate the potential pharmacological effect of doxycycline on aseptic loosening. We used radiolabelled mouse calvariae cultured with human interface membrane cells from aseptically loosened hips.

Bone resorption was confirmed in this model. The effect of doxycycline was assessed by culturing dead radiolabelled bone discs with cells from the interface membrane with doxycycline. The control group consisted of the same culture system without doxycycline. Supernatant ⁴⁵calcium and the total ⁴⁵calcium remaining in the bone discs at the completion of the culture were used to measure osteolysis.

We found that doxycycline can inhibit osteolysis at the interface membrane of aseptically loosened hips. This may have therapeutic implications for the treatment of patients with aseptic loosening of total joint replacements.

This study in UCA (ultra clean air) during TKR (total knee replacement) quantified wound bacterial counts, assessed the relationship to air counts and compared BES (body exhaust suits) with Rotecno occlusive clothing.

Fifty TKR were randomly allocated to scrub teams wearing BES or Rotecno occlusive clothing. Air bacterial counting within 30cm of a wound is the established methodology to define air cleanliness. Reliable wound bacterial counting should be a more precise index of infection risk however, to date, there is no established accurate method. The TSMI (tetrazolium stained membrane imprint) method of bacterial wound counting has been validated in a tissue model and human surgical wounds in conventionally ventilated theatres.

This method remains to be assessed in UCA where wounds may be too clean for bacteria to be detected accurately. We used air counts within 30cm of the wound and tested the TSMI method in wounds.

Bacteria were recovered from 62% of the wounds. The mean air count wearing BES was 0. 5 cfu/m3 compared with 1. 0 cfu/m3 with Rotecno. The air counts were significantly higher with Rotecno clothing (p=0. 014, Toeplitz covariance analysis). The mean wound count was 14 bacteria/ wound with BES and 8 bacteria/wound with Rotecno. Although the counts were higher with BES the difference was not significant (p=0. 7, MannWhitney U test). There was no significant correlation between air and wound counts (r = 0. 108, Spearman’s).

On first impression Rotecno occlusive clothing would appear to be less effective than BES on account of the higher air counts. However wounds were equally contaminated with both clothing types. As there is no relationship between wound and air counts, this suggests that at very low levels of air contamination the contribution of bacteria to the wound from the air is irrelevant. Even doubling of air counts from 0. 5 to 1. 0 cfu/m3 had no detectable effect on the wound.

The use of ultraclean air (UCA) in operating theatres reduces the infection rate after joint replacement but some cases of infection still occur. We investigated one possible source of contamination, namely the setting up of instruments in a conventional plenum-ventilated preparation room.

We measured bacterial fallout using agar settle plates and compared instruments set up in the preparation room with those set up in the UCA theatre, assessed the effect of covering instruments after preparation and compared fallout during their preparation with total fallout throughout the operation.

Our findings showed that covering the instruments reduced total bacterial fallout fourfold by reducing the exposure time, particularly during periods of increased activity and bacterial dispersal. Preparation in the UCA theatre and subsequent covering of the instruments reduced total fallout 28-fold. All measurable bacterial fallout occurred during the setting up and not during surgery.

Despite the use of ultraclean air, there are still cases of infection in total joint arthroplasty. One possible route by which bacteria may enter the wound is indirectly by contamination of instruments during skin preparation and draping.

We found that bacterial air counts were 4.4 times higher during preparation and draping for hip or knee arthroplasty using an unscrubbed, ungowned leg holder than during the operation itself. With the leg holder scrubbed and gowned during preparation and draping, the air counts were reduced but were still 2.4 fold greater than intraoperatively. On some occasions, the air counts during preparation and draping exceeded the standards for ultraclean air irrespective of the attire of the leg holder.

We recommend that the leg is held by a scrubbed and gowned member of the team. More importantly, we consider that instrument packs should be opened only after skin preparation and draping have been completed.