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Hospitalization Costs of Total Knee Arthroplasty With a Continuous Femoral Nerve Block Provided Only in the Hospital Versus on an Ambulatory Basis: A Retrospective, Case-Control, Cost-Minimization Analysis
  1. Brian M. Ilfeld, M.D., M.S.,
  2. Edward R. Mariano, M.D.,
  3. Brian A. Williams, M.D., M.B.A.,
  4. Jennifer N. Woodard, B.S. and
  5. Alex Macario, M.D., M.B.A.
  1. Department of Anesthesiology, University of California San Diego, San Diego, CA
  2. Department of Anesthesiology, University of Pittsburgh, Pittsburgh, PA
  3. Department of Anesthesiology, University of Florida, Gainesville, FL
  4. Department of Anesthesiology, Stanford University, Stanford, CA
  5. Department of Health Research and Policy, Stanford University, Stanford, CA.
  1. Reprint requests: Brian M. Ilfeld, M.D., M.S. E-mail: bilfeld{at}


Background and Objectives: After total knee arthroplasty (TKA), hospitalization may be shortened by allowing patients to return home with a continuous femoral nerve block (CFNB). This study quantified the hospitalization costs for 10 TKA patients receiving ambulatory CFNB versus a matched cohort of 10 patients who received CFNB only during hospitalization.

Methods: We examined the medical records (n = 125) of patients who underwent a unilateral, primary, tricompartment TKA with a postoperative CFNB by 1 surgeon at one institution in an 18-month period beginning January 2004. Each of the 10 patients discharged home with an ambulatory CFNB (cases) was matched with a patient with a hospital-only CFNB (controls) for age, gender, body mass index, and health status. Financial data were extracted from the hospital microcosting database.

Results: Nine patients with ambulatory CFNB (cases) were discharged home on postoperative day (POD) 1 and 1 on POD 4. Of the controls, 3 were discharged home on POD 3, 6 on POD 4, and 1 on POD 5. The median (range) costs of hospitalization (excluding implant and professional fees) was $5,292 ($4,326-$7,929) for ambulatory cases compared with $7,974 ($6,931-$9,979) for inpatient controls (difference = $2,682, 34% decrease, P < .001). The total charges for hospitalization, the implant, and professional fees was $33,646 ($31,816-$38,468) for cases compared with $39,100 ($36,096-$44,098) for controls (difference = $5,454, 14% decrease, P < .001).

Conclusions: This study provides evidence that ambulatory CFNB for selected patients undergoing TKA has the potential to reduce hospital length of stay and associated costs and charges. However, the current study has significant inherent limitations based on the study design. Additional research is required to replicate these results in a prospective, randomized, controlled trial and to determine whether any savings exceed additional CFNB costs such as from complications, having caregivers provide care at home, and additional hospital/health care provider visits.

  • Ambulatory continuous peripheral nerve block
  • Ambulatory continuous femoral nerve block
  • Continuous peripheral nerve block
  • Continuous femoral nerve block
  • Ambulatory perineural local anesthetic infusion
  • Health economics

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  • Supported by the University of Florida, Department of Anesthesiology. Dr. Ilfeld is supported by NIH grant GM077026 (Bethesda, MD), and a Mentored Research Training Grant from the Foundation of Anesthesia Education and Research (Rochester, MN). The contents of this article are solely the responsibility of the authors and do not necessarily represent the official views of these entities. Dr. Ilfeld has received research funds and product from companies producing perineural catheters (Arrow International, Reading, PA; B. Braun Medical Inc., Bethlehem, PA) and portable infusion pumps (Smiths Medical, St. Paul, MN; Sorenson Medical, West Jordan, UT; Stryker Instruments, Kalamazoo, MI). Dr. Williams has received honoraria, unrestricted research funds, and/or product from companies producing perineural catheters (Arrow International, Reading, PA; B. Braun Medical Inc., Bethlehem, PA) and portable infusion pumps (I-Flow Corporation, Lake Forest, CA). These companies had no input into any aspect of study conceptualization, initiation, and design; data collection, analysis and interpretation; or manuscript preparation.