Elective total hip replacement surgery may be a poor model of the inflammatory response to trauma

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Abstract Background One of the many problems associated with studying the inflammatory response to major trauma is the variability of injuries and their severity. To overcome this problem, an assessment was made of whether elective total hip replacement (THR) surgery, which includes skeletal and muscle trauma, might provide a reliable model of the inflammatory response to trauma. Methods Serial venous blood samples were taken from ten patients before, during and for 24 h after THR. Sandwich immunoassays were performed to detect free and receptor-bound interleukin (IL) 6 and tumour necrosis factor (TNF) α. Whole blood was also taken from nine of the patients for in vitro incubation with endotoxin to assess white cell responsiveness. Results None of the patients had a measurable TNF-α response during or after surgery. Only two patients had raised IL-6 during and after surgery (maximum 145 pg ml−1). Incubation of preoperative blood samples with endotoxin resulted in TNF-α and IL-6 production. The median for TNF-α was 710 (range 416–2800) pg ml−1 and that for IL-6 was 1050 (range 121–2350) pg ml−1. Some 24 h after surgery the median for TNF-α was only 450 (range 75–1760) pg ml−1. The median IL-6 production was 950 (range 124–1840) pg ml−1. There was a reduction in in vitro TNF-α production in all nine patients (mean reduction 57 per cent; P < 0·05) at 24 h. There was no significant change in in vitro IL-6 production before and after surgery. The reduction in TNF-α response indicated downregulation, which was not apparent for IL-6. Conclusion In this study THR did not produce the typical inflammatory response described for other forms of elective surgery. THR may not be a reliable model for studying the inflammatory response to trauma. The cement used to secure the prosthesis may have an effect on the inflammatory response.