title: The Isolated Effect of Adductor Canal Block on Quadriceps Femoris Muscle Strength After Total Knee Arthroplasty: A Triple-Blinded, Randomized, Placebo-Controlled Trial with Individual Patient Analysis.
abstract: BACKGROUND
  Using peripheral nerve block after total knee arthroplasty (TKA), without impeding mobility, is challenging. We hypothesized that the analgesic effect of adductor canal block (ACB) could increase the maximum voluntary isometric contraction (MVIC) of the quadriceps femoris muscle after TKA.
  
  
  METHODS
  We included 64 patients on the first postoperative day. Group A received an ACB with 30 mL ropivacaine 0.75% at t0 and with 30 mL saline 60 minutes later (t60). Group B received the treatment in the opposite order. The primary end point was the difference between groups in MVIC at t60, expressed as a percentage of postoperative preblock values. In this manner, the effect of the ACB could be isolated from the detrimental effect on muscle strength caused by the surgery. Secondary end points were differences between groups in mobility and pain scores. We planned a subgroup analysis dividing patients according to preblock pain scores during knee flexion.
  
  
  RESULTS
  At t60, MVIC was higher in group A, with a median of 170% (95% confidence interval [CI], 147-231) of preblock values compared with 93% (95% CI, 82-98) in group B (P < 0.0001). No statistically significant differences were found in the Timed Up and Go (TUG) test. Three patients lost the ability to perform the TUG test in group A. At t60, differences in visual analog scale pain were in favor of group A; 12 mm (95% CI, 6-18) at rest, 14 mm (95% CI, 5-22) during knee flexion, and 18 mm (95% CI, 10-26) during the TUG test.
  
  
  CONCLUSIONS
  ACB improves quadriceps femoris muscle strength, but whether this translates into enhanced mobility is not clearly supported by this study.
authors.affiliation: From the *Department of Anaesthesia and Intensive Care Medicine, Copenhagen University Hospital, Gentofte Hospital, Hellerup, Denmark; †Department of Anaesthesia, Centre of Head and Orthopaedics, Copenhagen University Hospital, Rigshospitalet, Denmark; and ‡Department of Orthopaedic Surgery, Copenhagen University Hospital, Gentofte Hospital, Hellerup, Denmark.
authors.forename: Johan Kløvgaard
authors.initials: JK
authors.lastname: Sørensen
authors.forename: Pia
authors.initials: P
authors.lastname: Jæger
authors.forename: Jørgen Berg
authors.initials: JB
authors.lastname: Dahl
authors.forename: Bo
authors.initials: B
authors.lastname: Gottschau
authors.forename: Snorre Læssøe
authors.initials: SL
authors.lastname: Stephensen
authors.forename: Ulrik
authors.initials: U
authors.lastname: Grevstad
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000577:Amides / Q000008:administration & dosage / Q000009:adverse effects; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000009:adverse effects; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D053580:Muscle Strength; D009407:Nerve Block / Q000009:adverse effects / Q000379:methods*; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy / Q000517:prevention & control; D011300:Preoperative Care; D052097:Quadriceps Muscle; D000077212:Ropivacaine; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine