title: A comparison of ultrasound-guided and landmark-based approaches to saphenous nerve blockade: a prospective, controlled, blinded, crossover trial.
abstract: BACKGROUND
  Blockade of the saphenous nerve is often used for surgeries below the knee. Depending on the approach, success rates vary widely ranging from 33% to 88%. In this prospective volunteer study, we compared 2 ultrasound-guided techniques, the modified vastus medialis and perifemoral saphenous nerve block with a below the knee field block.
  
  
  METHODS
  Twenty volunteer adults, in a single-blinded, crossover, prospective trial underwent 3 different saphenous nerve blocks. The primary end point of block success was loss of sensation in the distal two-thirds distribution of the saphenous nerve. Secondary variables included time to perform the block, time to sensory loss, pain during block, and motor weakness.
  
  
  RESULTS
  Compared with the below the knee field block success rate (30%), both the modified vastus medialis and perifemoral techniques had significantly higher success rates (80%, difference 50% with confidence interval [CI], 23%-77%, P = 0.009, and 100%, difference 70% with CI, 41%-91%, P < 0.001, respectively). However, the difference when comparing the perifemoral ultrasound technique against the modified vastus medialis ultrasound technique did not show significance (difference 20% with CI, -7% to 49%, P = 0.125). Also, no statistical differences were found with the other variables measured, except the perifemoral technique showed faster block performance times than below the knee field block (P = 0.007).
  
  
  CONCLUSIONS
  In our prospective study, we have demonstrated that ultrasound-guided above the knee saphenous nerve blocks have higher success rates than a below the knee field block and are easily performed in a short amount of time.
authors: Department of Anesthesiology, Naval Medical Center San Diego, 34800 Bob Wilson Dr San Diego, CA 92134, USA.
authors: Michael L
authors: ML
authors: Kent
authors: Robert J
authors: RJ
authors: Hackworth
authors: Robert H
authors: RH
authors: Riffenburgh
authors: Julie L
authors: JL
authors: Kaesberg
authors: David C
authors: DC
authors: Asseff
authors: Eugenio
authors: E
authors: Lujan
authors: John M
authors: JM
authors: Corey
mesh_terms: D000328:Adult; D001340:Autonomic Nerve Block / Q000379:methods* / Q000592:standards; D018592:Cross-Over Studies; D006801:Humans; D008297:Male; D010525:Peripheral Nerves / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D016037:Single-Blind Method; D018084:Ultrasonography, Interventional / Q000379:methods* / Q000592:standards