Aims: To determine the usefulness of preoperative CRP, ESR, WCC and joint aspirate in the diagnosis of infective loosening before revision TKA.

Methods and Materials: Retrospective review of patients undergoing revision TKA for the period May 1998 to May 2008 was performed, examining the results of preoperative CRP, ESR, WCC, joint aspirate and intra-operative microbiological samples. Positive results were CRP ≥10 mg/dL, ESR ≥ 22mm/hr, WCC ≥11 g/dL and positive growth on culture unless stated as contaminant. The data was analysed to determine sensitivity, specificity, negative and positive predictive values of the tests for single stage and staged revisions.

Results: 51 patients underwent single stage revision with 10 positive cultures. CRP and WCC were highly specific for infection (84%, 98%) with low sensitivities (10%). ESR was 66% specific and 25% sensitive. All had high negative predictive values (76–86%).

23 patients underwent staged revision. 17 cases had positive cultures at 1st stage and 8 at 2nd stage. 1st stage CRP, ESR and WCC had low sensitivity (67%, 59%, 17%). WCC was 80% specific whereas CRP and ESR had low specificity (25%, 20%). All had high positive predictive value (71–80%). 2nd stage CRP and ESR were specific for infection (71%) but had low sensitivities (22 and 44%). WCC was 0% sensitive but 87% specific. Negative predictive values of CRP, ESR and WCC were 63, 71 and 62%.

For both single stage and 1st stage staged revisions, pre-operative joint aspirate was 100% specific with sensitivities of 0% for single stage and 50% in staged revisions.

Conclusion: All patients undergoing both staged and single stage revision arthroplasty should routinely have preoperative inflammatory markers and joint aspirate. However, positive intraoperative cultures may still be obtained despite negative preoperative investigations.

Aims: To determine the rate of early and late infection amongst patients with renal disease undergoing TKA.

Methods and Materials: Review was undertaken of the Scottish National Arthroplasty Project data for the period from April 1985 to March 2008. Data was examined for the rate of infection amongst patients under-going TKA with a diagnosis of renal transplant, renal dialysis or renal failure. Early infection was classed as occurring within 90 days of the index procedure and late infection as occurring after 90 days. Renal failure, dialysis and transplant were identified using ICD 9 and 10 codes. The 4th revision of the OPCS codes was used to search for renal transplant, renal dialysis and knee arthroplasty.

Results: In total, 59288 TKAs were performed in Scotland over the period analysed. There were 651 early infections and 1296 late infections giving overall early and late infection rates of 1.1% and 2.2% respectively. 10 patients had renal transplant prior to TKA with 1 early infection (infection rate 1%) and no late infections. 44 patients had a renal transplant before or after TKA with 1 early and 6 late infections giving an early infection rate of 2.27% and late infection rate of 13.64% for this group. 17 patients undergoing renal dialysis underwent TKA with no early infections but a single late infection, giving a late infection rate of 5.8%. 2920 patients had a diagnosis of renal failure prior to or after TKA with 48 early and 138 late infections. Infection rates for this group were 1.64% early and 4.73% late.

Conclusions: TKA patients with renal transplant, renal failure or undergoing dialysis are at increased risk of infection. In particular, renal transplant patients are most at risk of late infection. Renal patients must be counselled of these increased risks prior to orthopaedic or transplant surgery.