title: The effects of ultrasound-guided adductor canal block versus femoral nerve block on quadriceps strength and fall risk: a blinded, randomized trial of volunteers.
abstract: OBJECTIVE
  Adductor canal block (ACB) has been suggested as an analgesic alternative to femoral nerve block (FNB) for procedures on the knee, but its effect on quadriceps motor function is unclear. We performed a randomized, blinded study to compare quadriceps strength following adductor canal versus FNB in volunteers. Our hypothesis was that quadriceps strength would be preserved following ACB, but not FNB. Secondary outcomes included relative preservation of hip adduction and degree of balance impairment.
  
  
  METHODS
  The ACB was performed in one leg and the FNB in the contralateral leg in 16 volunteers using a randomized block sequence. For all blocks, 15 mL of 3% chloroprocaine was injected under ultrasonographic guidance. Maximal voluntary isometric contraction of knee extension and hip adduction was measured at baseline and at 30 and 60 minutes after block. After 60-minute assessments were complete, the second block was placed. A test of balance (Berg Balance Scale) was performed 30 minutes after the first block only.
  
  
  RESULTS
  Quadriceps strength and balance scores were similar to baseline following ACB. Following FNB, there was a significant reduction in quadriceps strength (95.1% ± 17.1% vs 11.1% ± 14.0%; P < 0.0001) and balance scores (56 ± 0 vs 37 ± 17.2; P = 0.02) compared with baseline. There was no difference in hip adductor strength (97.0% ± 10.8% vs 91.8% ± 9.6%; P = 0.17).
  
  
  CONCLUSIONS
  Compared with FNB, ACB results in significant quadriceps motor sparing and significantly preserved balance.
authors.affiliation: Department of Anesthesiology of St Luke’s–Roosevelt Hospital Center, New York, NY, USA.
authors.forename: M Kwesi
authors.initials: MK
authors.lastname: Kwofie
authors.forename: Uma D
authors.initials: UD
authors.lastname: Shastri
authors.forename: Jeff C
authors.initials: JC
authors.lastname: Gadsden
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Sinha
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Abrams
authors.forename: Daquan
authors.initials: D
authors.lastname: Xu
authors.forename: Emine A
authors.initials: EA
authors.lastname: Salviz
mesh_terms: D000058:Accidental Falls / Q000517:prevention & control*; D000293:Adolescent; D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000009:adverse effects; D001696:Biomechanical Phenomena; D005267:Femoral Nerve; D006621:Hip Joint / Q000187:drug effects; D006801:Humans; D007537:Isometric Contraction / Q000187:drug effects; D007719:Knee Joint / Q000187:drug effects; D008875:Middle Aged; D053580:Muscle Strength / Q000187:drug effects*; D009407:Nerve Block / Q000009:adverse effects / Q000379:methods*; D009519:New York City; D004856:Postural Balance / Q000187:drug effects; D011343:Procaine / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives*; D052097:Quadriceps Muscle / Q000187:drug effects* / Q000294:innervation; D016059:Range of Motion, Articular; D013997:Time Factors; D018084:Ultrasonography, Interventional; D055815:Young Adult
chemical_list: D000779:Anesthetics, Local; D011343:Procaine; C004616:chloroprocaine