Analgesic effect of single-shot ropivacaine at different layers of the surgical site in primary total hip arthroplasty: a randomised, controlled, observer-blinded study

The aim of this study was to evaluate the efficacy of local infiltration anaesthesia (LIA) during primary total hip arthroplasty (THA) via a posterolateral approach under general anaesthesia and to compare the efficacy of LIA in all layers with LIA in the deep and superficial fascia. One hundred twenty patients were randomised into three groups: LIA in the deep and superficial fascia (group A), LIA in all layers (group B) and the control (group C). The primary outcomes were the visual analogue scale (VAS) pain scores at rest and on movement within 72 h (h) postoperatively. The secondary outcomes included opioid consumption, patient satisfaction, range of motion (ROM), straight leg raise completion rate, length of hospital stay, opioid-related side effects and wound complications. We followed the patients until 6 months after discharge. At 2 and 6 h, groups A and B had lower resting VAS scores than group C (p < 0.01); at 12 h, group B had a lower resting VAS score than group C (p < 0.05). At 6 and 12 h, the movement VAS scores in groups A and B were lower than those in group C (p < 0.01). Groups A and B had similar VAS scores during the observation period. Groups A and B had higher levels of patient satisfaction than group C (p = 0.03 and p = 0.018, respectively). Opioid consumption was similar in the three groups. There were no significant differences in the other secondary outcomes amongst the three groups. No difference was found in hip rehabilitation or chronic pain during the follow-up period. Single-shot LIA with ropivacaine alone reduces the pain score during the first 12 postoperative hours and improves patients' satisfaction with THA. LIA in the deep and superficial fascia and LIA in all layers have similar analgesic effects. LIA in the deep and superficial fascia may be an alternative method to LIA in all layers.