Comparison of the analgesic effect of an adductor canal block using a new suture-method catheter vs. standard perineural catheter vs. single-injection: a randomised, blinded, controlled study.

We performed a randomised, blinded, controlled study with adult patients scheduled for primary total knee arthroplasty under spinal anaesthesia. The aim was to investigate the analgesic effects of adductor canal block using catheter-based repeated boluses, either through a new suture-method catheter or a standard perineural catheter, compared with a single-injection technique. All patients received an adductor canal block after surgery with an initial bolus of 20 ml ropivacaine 0.75%, followed by 20 ml of ropivacaine 0.2% every 8 h in the standard and suture-method catheter groups, and sham boluses for the single-injection group. The primary outcome measure was total opioid consumption (intravenous morphine equivalents) from the end of surgery until 12:00 on postoperative day 2. Secondary outcomes were pain, muscle strength and ambulation. We randomly assigned (1:1:1) and analysed 153 patients. Total opioid consumption was median (IQR [range]) 24 (11-37 [0-148]) mg in the suture-method group, 38 (17-51 [0-123]) mg in the standard catheter group and 37 (14-57 [0-158]) mg in the single-injection group (p = 0.049). Differences were not statistically significant after Bonferroni correction (α = 0.05/3). There were no differences between groups on postoperative day 1. On postoperative day 2, there were no differences between catheter groups, but muscle strength and ambulation were improved compared with the single-injection group. We conclude that providing repeated boluses via a catheter did not decrease opioid consumption or pain compared with a single injection, but improved muscle strength and ambulation on postoperative day 2. The two types of catheters were similar.

Effect of adductor-canal-blockade on established, severe post-operative pain after total knee arthroplasty: a randomised study.

BACKGROUND: In this proof-of-concept study, we investigated the effect of the predominantly sensory adductor-canal-blockade on established pain in the early post-operative period after total knee arthroplasty (TKA). We hypothesised that the adductor-canal-blockade would reduce pain during flexion of the knee (primary end point) and at rest, as well as reducing morphine consumption and morphine-related side effects (secondary outcomes) compared with placebo. METHODS: We enrolled patients scheduled for elective TKA into this double-blind, placebo-controlled, randomised study. During general anaesthesia, we placed a catheter in the adductor canal, and after obtaining pre-block pain scores 30 min post-operatively, we injected 30 ml of ropivacaine 0.75% (n = 21) or saline (n = 20) according to randomisation. Clinicaltrials.gov Identifier: NCT01261897. RESULTS: Forty-two patients were randomised, and 41 were analysed. Mean (standard deviation) pain scores during flexion of the knee at 1 h post-operatively were 58 (22) mm and 67 (29) mm, ropivacaine and placebo group, respectively (P = 0.23) but was significantly reduced in the ropivacaine group when calculated as area under the curve for the interval 1-6 h (P = 0.02). There were no statistically significant differences regarding pain at rest (P = 0.08), morphine consumption (P = 0.06), nor morphine-related side effects, apart from nausea (P = 0.04). CONCLUSION: This proof-of-concept study shows promising results regarding the analgesic efficacy of adductor-canal-blockade in post-operative pain treatment after TKA, with a significant reduction in pain during flexion of the knee in the early post-operative period compared with placebo. However, the study was not sufficiently powered to permit final conclusions.