Abstract
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.
Correspondence should be addressed to: BASK c/o BOA, at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London, WC2A 3PE, England.
