title: A modified mid-femoral approach to the sciatic nerve block: a correlation between evoked motor response and sensory block.
abstract: BACKGROUND
  The lateral sciatic mid-femoral block (LSMF), proved to be reliable, safe, and effective on both branches of the sciatic nerve with a single injection. However, we do not know which component of the sciatic nerve (the tibial [T] or the common peroneal [CP]) produces a better success rate when performing a LSMF with a single injection technique. In this prospective study we compared the success rate of the T motor response with the CP motor response.
  
  
  METHODS
  Ninety-five patients undergoing ankle or foot surgery were enrolled. Thirty milliliters of 0.475% ropivacaine was injected at the first evoked motor response, either T or CP, with a minimal intensity between 0.3 and 0.5 mA.
  
  
  RESULTS
  Seventy-two patients were included in group T and 23 in group CP. The block was considered a success when a complete sensory block of the sciatic nerve was obtained. The success rate was 90% (65) for the T response and 70% (16) for the CP response (P < 0.05). Time to perform the block (CP: 4.5 +/- 3 min vs T: 4.5 +/- 4 min; P = NS) as well as sensory and motor onset times were not significantly different between groups. No complications were observed in either group.
  
  
  CONCLUSIONS
  We conclude that the evoked motor response of the T branch is associated with a higher success rate than a CP response using the modified LSMF block.
authors.affiliation: Department of Anesthesiology and Intensive Care, University Hospital of Toulouse, University Paul Sabatier, Toulouse, France. a.pianezza@wanadoo.fr
authors.forename: Antoine
authors.initials: A
authors.lastname: Pianezza
authors.forename: Marie-Luce
authors.initials: ML
authors.lastname: Gilbert
authors.forename: Vincent
authors.initials: V
authors.lastname: Minville
authors.forename: Daren
authors.initials: D
authors.lastname: Filsinger
authors.forename: Quentin
authors.initials: Q
authors.lastname: Gobert
authors.forename: Alain
authors.initials: A
authors.lastname: Guérot
authors.forename: Régis
authors.initials: R
authors.lastname: Fuzier
authors.forename: Olivier
authors.initials: O
authors.lastname: Fourcade
mesh_terms: D000328:Adult; D000368:Aged; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D005267:Femoral Nerve / Q000502:physiology*; D005528:Foot / Q000502:physiology / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D011446:Prospective Studies; D012584:Sciatic Nerve / Q000502:physiology*