Does local infiltration analgesia reduce peri-operative inflammation following total hip arthroplasty? A randomized, double-blind study

BACKGROUND: Postoperative inflammation following total hip arthroplasty (THA) can lead to delayed mobilization and return of hip function. Our primary aim was to assess whether local infiltration analgesia (LIA) during surgery can prevent postoperative inflammation. METHODS: This is a sub-analysis of data from a broader double-blind study where 56 patients received spinal anaesthesia for THA. Additionally, Group FNB (Femoral Nerve Block) received an ultrasound-guided femoral nerve block using 30 mL of ropivacaine 7.5 mg/mL (225 mg), and 151.5 mL of saline peri-articularly intra-operatively. Group LIA received 30 mL saline in the femoral nerve block and ropivacaine 2 mg/mL, 300 mg (150 mL) + ketorolac 30 mg (1 mL) + adrenaline 0.5 mg (0.5 mL) peri-articularly. After 23 h, the LIA mixture (22 mL) was injected via a catheter placed peri-articularly in Group LIA and 22 mL saline in Group FNB. A battery of pro- and anti-inflammatory cytokines was assessed using a commercially available kit preoperatively and after 4 h and 3 days postoperatively. Additionally, CRP, platelet count and white blood count was determined pre- and postoperatively. RESULTS: There was a general trend towards an increase in pro-inflammatory cytokines postoperatively, which returned to normal levels after 3 days. IL-6 concentration was significantly lower 4 h postoperatively in Group LIA compared to Group FNB (p = 0.015). No other significant differences were found between the groups in other cytokines. CRP levels were significantly higher in Group FNB compared to Group LIA 3 days postoperatively (p < 0.001). No other significant differences were seen between the groups. CONCLUSION: Local infiltration analgesia has a modest but short-lasting effect on postoperative inflammation in patients undergoing total hip arthroplasty. This is likely to be due to local infiltration of ketorolac and/or local anaesthetics in the LIA mixture. Future studies should be directed towards assessing whether the use of LIA translates into better patient outcomes. TRIAL REGISTRATION: EudraCT Number 2012-003875-20. Registered 3 December 2012