Plasma endocannabinoid behaviour in total knee and hip arthroplasty.

Endocannabinoids are a class of lipid mediators involved in a wide range of physiological pathways including pain perception, and immunological defences. In particular, the involvement of endocannabinoids in bone metabolism and bone resorption has recently been studied. Moreover, one study on total knee arthroplasty describes the probable role of endocannabinoids in pain perception after surgery. The aim of the present study was to evaluate variations of endocannabinoid concentrations in patients undergoing total hip or total knee arthroplasty before and after surgery. Sera from 23 patients were collected at three different times: before surgery and at two different times during rehabilitation, and endocannabinoids were quantified by HPLC-MS/MS analysis. Mean values of endocannabinoids in presurgical serum samples were: 6.11±0.5 ng/ml for N-palmitoylethanolamide, 1.39±0.08ng/ml for N-stearoylethanolamide, 4.84±0.04 ng/ml for N-oleoylethanolamide, 0.44±0.03ng/ml for N-arachidonoylethanolamide, 0.84±0.05ng/ml for N-linoleoylethanolamide, 0.17±0.01ng/ml for N-α-linolenoylethanolamide. Statistical analysis showed a significant decrease of all the endocannabinoids after surgery, while there were no remarkable differences between total hip and total knee arthroplasties or between genders. Moreover, the results show no significant correlation between endocannabinoid concentrations and C-reactive protein and Erythrocyte sedimentation rate. The present study shows for the first time a specific and univocal behaviour of six endocannabinoids and N-acylethanolamides in orthopaedic surgery, suggesting the endocannabinoid system as a possible pharmacological target for presurgical therapeutics.