title: Effect of adductor canal block on pain in patients with severe pain after total knee arthroplasty: a randomized study with individual patient analysis.
abstract: BACKGROUND
  Total knee arthroplasty (TKA) is associated with varying degrees of pain. A considerable proportion (25-40%) of patients experience severe pain, despite a comprehensive multimodal analgesic regimen. We hypothesized that adductor canal block (ACB) would reduce pain in this patient category compared with placebo.
  
  
  METHODS
  Fifty patients with severe pain, defined as having a visual analogue scale (VAS) pain score of >60 during active flexion of the knee on the first or the second postoperative day after TKA, were included in this randomized, double-blind, placebo-controlled trial. All the patients had received a comprehensive multimodal analgesic regimen. Group A received an ACB with ropivacaine 0.75%, 30 ml at time 0 and isotonic saline after 45 min. Group B received an ACB with isotonic saline at time 0 and ropivacaine 0.75%, 30 ml after 45 min.
  
  
  RESULTS
  A 32-mm difference in VAS pain score, during active flexion of the knee (primary endpoint), was observed in favour of Group A, 95% confidence interval (CI): 23-42, P<0.0001. At rest, the difference in VAS pain score was 15 mm in favour of Group A, 95% CI: 8-23 mm, P=0.0001. Individual patient analysis revealed that 25% of the patients had no effect during active flexion. At rest, however, only 8% had more than mild pain after ACB compared with 57% at inclusion.
  
  
  CONCLUSIONS
  ACB reduced VAS with 32 mm, during active flexion of the knee, in patients with severe pain after TKA, but a large proportion (78%) still had at least moderate, movement-related pain. Clinical trial registration www.clinicaltrials.gov, NCT01549704.
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine, Copenhagen University Hospital, Gentofte Hospital, Niels Andersens Vej 65, 2900 Hellerup, Denmark.
authors.forename: U
authors.initials: U
authors.lastname: Grevstad
authors.forename: O
authors.initials: O
authors.lastname: Mathiesen
authors.forename: T
authors.initials: T
authors.lastname: Lind
authors.forename: J B
authors.initials: JB
authors.lastname: Dahl
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000577:Amides; D000779:Anesthetics, Local; D019645:Arthroplasty, Replacement, Knee; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000187:drug effects / Q000294:innervation; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D010147:Pain Measurement / Q000379:methods; D010149:Postoperative Pain / Q000188:drug therapy*; D016059:Range of Motion, Articular / Q000187:drug effects; D000077212:Ropivacaine; D012720:Severity of Illness Index; D012965:Sodium Chloride / Q000008:administration & dosage
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D012965:Sodium Chloride; D000077212:Ropivacaine
keywords: acute pain; arthroplasty, replacement, knee; nerve block; pain, postoperative