title: Can bedside patient-reported numbness predict postoperative ambulation ability for total knee arthroplasty patients with nerve block catheters?
abstract: BACKGROUND
  Adductor canal catheters offer advantages over femoral nerve catheters for knee replacement patients because they produce less quadriceps muscle weakness; however, applying adductor canal catheters in bedside clinical practice remains challenging. There is currently no patient-reported outcome that accurately predicts patients' physical function after knee replacement. The present study evaluates the validity of a relatively new patient-reported outcome, i.e., a numbness score obtained using a numeric rating scale, and assesses its predictive value on postoperative ambulation.
  
  
  METHODS
  We conducted a retrospective cohort study pooling data from two previously-published clinical trials using identical research methodologies. Both studies recruited patients undergoing knee replacement; one studied adductor canal catheters while the other studied femoral nerve catheters. Our primary outcome was patient-reported numbness scores on postoperative day 1. We also examined postoperative day 1 ambulation distance and its association with postoperative numbness using linear regression, adjusting for age, body mass index, and physical status.
  
  
  RESULTS
  Data from 94 subjects were included (femoral subjects, n = 46; adductor canal subjects, n = 48). Adductor canal patients reported decreased numbness (median [10(th)-90(th) percentiles]) compared to femoral patients (0 [0-5] vs. 4 [0-10], P = 0.001). Adductor canal patients also ambulated seven times further on postoperative day 1 relative to femoral patients. There was a significant association between postoperative day 1 total ambulation distance and numbness (Beta = -2.6; 95% CI: -4.5, -0.8, P = 0.01) with R(2) = 0.1.
  
  
  CONCLUSIONS
  Adductor canal catheters facilitate improved early ambulation and produce less patient-reported numbness after knee replacement, but the correlation between these two variables is weak.
authors.affiliation: Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, CA, USA.; Anesthesiology and Perioperative Care Service, Veterans Affairs Palo Alto Health Care System, CA, USA.
authors.forename: Seshadri C
authors.initials: SC
authors.lastname: Mudumbai
authors.affiliation: Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, CA, USA.; Anesthesiology and Perioperative Care Service, Veterans Affairs Palo Alto Health Care System, CA, USA.
authors.forename: Toni
authors.initials: T
authors.lastname: Ganaway
authors.affiliation: Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, CA, USA.; Anesthesiology and Perioperative Care Service, Veterans Affairs Palo Alto Health Care System, CA, USA.
authors.forename: T Edward
authors.initials: TE
authors.lastname: Kim
authors.affiliation: Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, CA, USA.; Anesthesiology and Perioperative Care Service, Veterans Affairs Palo Alto Health Care System, CA, USA.
authors.forename: Steven K
authors.initials: SK
authors.lastname: Howard
authors.affiliation: Department of Orthopaedic Surgery, Stanford University School of Medicine, CA, USA.; Surgical Service, Orthopaedic Surgery Section, Veterans Affairs Palo Alto Health Care System, CA, USA.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Giori
authors.affiliation: Anesthesiology and Perioperative Care Service, Veterans Affairs Palo Alto Health Care System, CA, USA.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Shum
authors.affiliation: Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, CA, USA.; Anesthesiology and Perioperative Care Service, Veterans Affairs Palo Alto Health Care System, CA, USA.
authors.forename: Edward R
authors.identifier: 0000-0003-2735-248X
authors.initials: ER
authors.lastname: Mariano
keywords: Adductor canal block; Ambulation; Femoral nerve block; NumbnessPerineural catheter; Total knee arthroplasty