Plantar flexion seems more reliable than dorsiflexion with Labat's sciatic nerve block: a prospective, randomized comparison

Anesth Analg. 2005 Jan;100(1):250-4. doi: 10.1213/01.ANE.0000143338.69202.76.


Labat's classic approach to the sciatic nerve has not been able to show which motor response of the foot provides a more frequent rate of complete sensory and motor block. In this prospective, randomized, double-blind study, we compared plantar flexion with dorsiflexion with regard to onset time and efficacy of sciatic nerve block using the classic posterior approach. A total of 80 patients undergoing hallux valgus repair were randomly allocated to receive sciatic nerve block after evoked plantar flexion (n=40) or dorsiflexion (n=40). Twenty milliliters of 0.75% ropivacaine was injected after the motor response was elicited at <0.5 mA. Success rate was defined as complete sensory and motor block in all sciatic nerve distributions associated with a pain-free surgery. Time required for onset of sensory and motor block of the foot was recorded. Success was more frequent after elicited plantar flexion (87.5%) than dorsiflexion (55%; P <0.05). Onset of complete sensory and motor block of the foot was faster after elicited plantar flexion (10 +/- 10 min and 13 +/- 10 min, respectively) compared with dorsiflexion (20 +/- 11 min and 24 +/- 12 min; P <0.05). We conclude that plantar flexion of the foot predicts a shorter onset time and a more frequent success rate than dorsiflexion with Labat's classic posterior sciatic nerve block.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Anesthesia
  • Blood Pressure / drug effects
  • Double-Blind Method
  • Electrocardiography / drug effects
  • Evoked Potentials, Motor / drug effects
  • Female
  • Foot*
  • Hemodynamics / drug effects
  • Humans
  • Male
  • Middle Aged
  • Movement / drug effects*
  • Nerve Block*
  • Oximetry
  • Prospective Studies
  • Sciatic Nerve*