Effect of Lateral Femoral Cutaneous Nerve-block on Pain After Total Hip Arthroplasty: a Randomised, Blinded, Placebo-controlled Trial

Background: Total hip arthroplasty (THA) is a common procedure associated with moderate postoperative pain. No nerve block without loss of motor function has been documented for THA. We hypothesised that an ultrasound-guided lateral femoral cutaneous nerve (LFCN) block added to a multimodal postoperative pain regimen would reduce postoperative pain after THA.

Methods: One hundred patients who had a THA by the posterior approach were evaluated in this randomised, placebo-controlled, blinded, parallel-group trial comparing an ultrasound-guided LFCN-block with either 8 ml of ropivacaine, 7.5 mg/ml, (Group Ropivacaine) or 8 ml of saline (Group Placebo) given postoperatively. Surgery was performed under spinal anaesthesia. The primary outcome was pain (measured on a Visual Analogue Scale (VAS)) 4 h post-blockade during 30° flexion of the hip. Secondary outcomes were pain at rest, pain during movement, oxycodone consumption (0-24 h), time to mobilisation, ability to mobilise, and length of stay. Patients, assessors and all staff involved with patient care were blinded to the intervention.

Results: There was no difference in primary outcome between Group Ropivacaine and Group Placebo (VAS 27 mm vs. 31 mm, p = 0.41; difference -5 mm (95% CI: -15 mm - +5 mm). No differences in any of the secondary outcomes were observed. No adverse events, or harms, were observed during the trial.

Conclusion: Pain scores, opioid use, time to mobilisation, and length of stay were low in both Group Ropivacaine and Group Placebo. We found no added analgesic effect of a LFCN-block when combined with paracetamol and ibuprofen after THA by the posterior approach.

Trial Registration: EudraCT: 2013-004501-12 (December 16th 2013).