C-reactive protein as marker of post-operative analgesic quality after primary total knee arthroplasty

To study the correlation between the level of C-reactive protein (CRP) and the severity of pain in the post-operative period with primary total knee arthroplasty and to conduct a comparative assessment of these indicators with various methods of pain relief. The primary hypothesis of the investigation was that post-operative CRP level is likely to be correlated with the severity of post-operative pain after total knee arthroplasty. The secondary points were the evaluation of CRP and pain syndrome in the groups, as well as the identification of the correlation between the level of CRP and the method of analgesia.

Peri-operative levels of CRP and pain syndrome (10-point visual analogue scale) studied 160 patients with grade III gonarthrosis who have underwent primary total knee arthroplasty under conditions of subarachnoid anaesthesia in the period from years 2017 to 2019. Depending on the method of post-operative analgesia, patients were divided into five groups: group 1 had only systemic multimodal analgesia (SMA, n = 56), group 2 were treated with the epidural analgesia (EDA, n = 20), group 3 had local high-volume infiltration anaesthesia (LHVIA, n = 20), group 4 were getting LHVIA with a wound catheter (LHVIAc, n = 48), and group 5 had a single blockade of the femoral nerve (FNB, n = 16).

A direct strong correlation was obtained between the level of CRP and the severity of pain syndrome in the knee joint during movement in four to six hours after surgery (n = 160, Kendall coefficient τ = 0.230, p = 0,000) and on the first post-operative day (n = 160, τ = 0.21, p = 0.001). The increase in CRP (the difference between pre-operative and post-operative CRP levels) also was positively correlated with the severity of pain in the post-operative period (n = 160, τ = 0.257, p = 0.000 and τ = 0.187, p = 0.001, respectively). CRP level significantly has increased in the post-operative period (p = 0,000). The lowest CRP indicators in the first post-operative day were recorded during the infiltrative anaesthesia (3rd and 4th groups);, the highest were during the administration of SMA group (1st group).

The results confirm the correlation between the level of CRP and the severity of pain syndrome in the early post-operative period after total knee arthroplasty, its dependence on the method of analgesia, and allow to use it as a criterion for evaluating of the effectiveness of analgesia.