Differences in peri-operative serum inflammatory markers between normoponderal and obese patients undergoing large joint replacement for osteoarthritis-a descriptive study.

Purpose: The occurrence, evolution and treatment outcome of osteoarthritis are influenced by a series of factors, including obesity. Assessing how chronic inflammation present in obesity changes the values of peri-operative biological tests could facilitate a clearer interpretation of laboratory examinations for the proper management of possible complications.
Methods: This descriptive study compared biological and clinical factors during the peri-operative period in patients undergoing total hip/knee replacement, in order to identify the special characteristics of the inflammatory status in obese compared to normal weight patients. In the two groups (71 normoponderal, 74 obese), serum levels of fibrinogen, high-sensitivity C-reactive protein (hsCRP), tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were determined 24 hours pre- and post-operatively.
Results: Our results found significant post-operative increases in serum levels of IL-6 and hsCRP in both groups (p = 0.0001), with inter-group differences in pre-operative hsCRP (p = 0.02) and post-operative IL-6 levels (p = 0.013). Interestingly, TNF-alpha levels were much higher in the obese pre-operatively than post-operatively (p = 0.002) and higher than the normoponderals (p = 0.003), decreasing to levels similar to those of the normal weight patients on day two.
Conclusions: Because of its important clinical implications, an appropriate comprehension of the peri-operative changes in a patient's inflammatory status has the potential to influence therapeutic attitude. We failed to observe any significant post-operative differences in the mean values of the markers assessed, except those of IL-6, implying that serum levels of fibrinogen, hsCRP and TNF-alpha within 24 hours after large joint replacements are not influenced by the patient's ponderal status.