Measurement of the inflammatory response in the early postoperative period after hip and knee arthroplasty

The aim of this study was to identify an inflammatory marker with fast and predictable kinetics to enable future discrimination between normal postoperative inflammation and potential infection after total hip and knee arthroplasty cases. Changes in serum levels of C-reactive protein (CRP), interleukins (IL) 1β, 6 and 8 and NT-proCNP peptide were measured before and during first 5 postoperative days in 100 patients undergoing total hip or knee arthroplasty. We also compared two methods to describe the magnitude of inflammation – applying separate two sample tests at each time point, and summary measures – area under the curve (AUC). IL-6 showed a similar kinetics pattern to the CRP in response to surgical trauma. Significantly greater level changes in all markers but NT-proCNP were observed in knee patients. Persisting high levels of CRP, but not other markers, were observed in obese hip patients. IL-6 was found to be an adjunct to routine CRP use. IL-6 has faster kinetics and is less influenced by patient weight, therefore it seems to be more useful in clinical practice. Summary measures describe the inflammatory response well and are easier to analyze than multiple analyses of single time points.