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.
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