title: A randomized comparison of proximal and distal ultrasound-guided adductor canal catheter insertion sites for knee arthroplasty.
abstract: OBJECTIVE
  Proximal and distal (mid-thigh) ultrasound-guided continuous adductor canal block techniques have been described but not yet compared, and infusion benefits or side effects may be determined by catheter location. We hypothesized that proximal placement will result in faster onset of saphenous nerve anesthesia, without additional motor block, compared to a distal technique.
  
  
  METHODS
  Preoperatively, patients receiving an ultrasound-guided nonstimulating adductor canal catheter for knee arthroplasty were randomly assigned to either proximal or distal insertion. A local anesthetic bolus was administered via the catheter after successful placement. The primary outcome was the time to achieve complete sensory anesthesia in the saphenous nerve distribution. Secondary outcomes included procedural time, procedure-related pain and complications, postoperative pain, opioid consumption, and motor weakness.
  
  
  RESULTS
  Proximal insertion (n = 23) took a median (10th-90th percentiles) of 12.0 (3.0-21.0) minutes versus 6.0 (3.0-21.0) minutes for distal insertion (n = 21; P= .106) to anesthetize the medial calf. Only 10 of 25 (40%) and 10 of 24 (42%) patients in the proximal and distal groups, respectively, developed anesthesia at both the medial calf and top of the patella (P= .978). Bolus-induced motor weakness occurred in 19 of 25 (76%) and 16 of 24 (67%) patients in the proximal and distal groups (P = .529). Ten of 24 patients (42%) in the distal group required intravenous morphine postoperatively, compared to 2 of 24 (8%) in the proximal group (P = .008), but there were no differences in other secondary outcomes.
  
  
  CONCLUSIONS
  Continuous adductor canal blocks can be performed reliably at both proximal and distal locations. The proximal approach may offer minor analgesic and logistic advantages without an increase in motor block.
authors.affiliation: Departments of Anesthesiology, Perioperative and Pain Medicine (E.R.M., T.E.K., M.J.W., N.F., T.K.H., T.W., T.G., S.K.H.) and Orthopedic Surgery (N.G., S.W.), VA Palo Alto Health Care System, Palo Alto, California USA; and Stanford University School of Medicine, Stanford, California USA. emariano@stanford.edu.
authors.forename: Edward R
authors.initials: ER
authors.lastname: Mariano
authors.affiliation: Departments of Anesthesiology, Perioperative and Pain Medicine (E.R.M., T.E.K., M.J.W., N.F., T.K.H., T.W., T.G., S.K.H.) and Orthopedic Surgery (N.G., S.W.), VA Palo Alto Health Care System, Palo Alto, California USA; and Stanford University School of Medicine, Stanford, California USA.
authors.forename: T Edward
authors.initials: TE
authors.lastname: Kim
authors.affiliation: Departments of Anesthesiology, Perioperative and Pain Medicine (E.R.M., T.E.K., M.J.W., N.F., T.K.H., T.W., T.G., S.K.H.) and Orthopedic Surgery (N.G., S.W.), VA Palo Alto Health Care System, Palo Alto, California USA; and Stanford University School of Medicine, Stanford, California USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wagner
authors.affiliation: Departments of Anesthesiology, Perioperative and Pain Medicine (E.R.M., T.E.K., M.J.W., N.F., T.K.H., T.W., T.G., S.K.H.) and Orthopedic Surgery (N.G., S.W.), VA Palo Alto Health Care System, Palo Alto, California USA; and Stanford University School of Medicine, Stanford, California USA.
authors.forename: Natasha
authors.initials: N
authors.lastname: Funck
authors.affiliation: Departments of Anesthesiology, Perioperative and Pain Medicine (E.R.M., T.E.K., M.J.W., N.F., T.K.H., T.W., T.G., S.K.H.) and Orthopedic Surgery (N.G., S.W.), VA Palo Alto Health Care System, Palo Alto, California USA; and Stanford University School of Medicine, Stanford, California USA.
authors.forename: T Kyle
authors.initials: TK
authors.lastname: Harrison
authors.affiliation: Departments of Anesthesiology, Perioperative and Pain Medicine (E.R.M., T.E.K., M.J.W., N.F., T.K.H., T.W., T.G., S.K.H.) and Orthopedic Surgery (N.G., S.W.), VA Palo Alto Health Care System, Palo Alto, California USA; and Stanford University School of Medicine, Stanford, California USA.
authors.forename: Tessa
authors.initials: T
authors.lastname: Walters
authors.affiliation: Departments of Anesthesiology, Perioperative and Pain Medicine (E.R.M., T.E.K., M.J.W., N.F., T.K.H., T.W., T.G., S.K.H.) and Orthopedic Surgery (N.G., S.W.), VA Palo Alto Health Care System, Palo Alto, California USA; and Stanford University School of Medicine, Stanford, California USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Giori
authors.affiliation: Departments of Anesthesiology, Perioperative and Pain Medicine (E.R.M., T.E.K., M.J.W., N.F., T.K.H., T.W., T.G., S.K.H.) and Orthopedic Surgery (N.G., S.W.), VA Palo Alto Health Care System, Palo Alto, California USA; and Stanford University School of Medicine, Stanford, California USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Woolson
authors.affiliation: Departments of Anesthesiology, Perioperative and Pain Medicine (E.R.M., T.E.K., M.J.W., N.F., T.K.H., T.W., T.G., S.K.H.) and Orthopedic Surgery (N.G., S.W.), VA Palo Alto Health Care System, Palo Alto, California USA; and Stanford University School of Medicine, Stanford, California USA.
authors.forename: Toni
authors.initials: T
authors.lastname: Ganaway
authors.affiliation: Departments of Anesthesiology, Perioperative and Pain Medicine (E.R.M., T.E.K., M.J.W., N.F., T.K.H., T.W., T.G., S.K.H.) and Orthopedic Surgery (N.G., S.W.), VA Palo Alto Health Care System, Palo Alto, California USA; and Stanford University School of Medicine, Stanford, California USA.
authors.forename: Steven K
authors.initials: SK
authors.lastname: Howard
mesh_terms: D000368:Aged; D000779:Anesthetics, Local / Q000008:administration & dosage*; D019645:Arthroplasty, Replacement, Knee; D004837:Epinephrine / Q000008:administration & dosage; D005260:Female; D005267:Femoral Nerve / Q000187:drug effects; D006801:Humans; D008297:Male; D008619:Mepivacaine / Q000008:administration & dosage; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D011446:Prospective Studies; D013848:Thigh / Q000294:innervation; D013997:Time Factors; D018084:Ultrasonography, Interventional
chemical_list: D000779:Anesthetics, Local; D008619:Mepivacaine; D004837:Epinephrine
keywords: continuous adductor canal block; knee arthroplasty; musculoskeletal ultrasound; perineural catheter; ultrasound-guided regional anesthesia