title: Is there a link between the neutrophil-to-lymphocyte ratio and venous thromboembolic events after knee arthroplasty? A pilot study.
abstract: BACKGROUND
  This study aimed to identify (1) if the postoperative increase in the neutrophil-to-lymphocyte ratio (NLR) is different between contrasting knee arthroplasty procedures, and (2) if the NLR predicts venous thromboembolism (VTE) after total knee arthroplasty (TKA).
  
  
  METHODS
  To address the first objective, we retrospectively studied patients who underwent primary unilateral TKA (n = 111) or unicompartmental knee arthroplasty (UKA; n = 74) between 2009 and 2012. Patients who required a blood transfusion, underwent autologous blood salvage, experienced any postoperative complication (such as VTE), or were re-admitted >90 days were excluded from analysis. For the second objective, we retrospectively identified patients (cases, n = 10) who underwent primary unilateral TKA between 2010 and 2012 and developed postoperative VTE (deep venous thrombosis, pulmonary embolism, or both) during inpatient care (postoperative day 1 or day 2). Cases were matched to surgeon, gender, body mass index, age, and date of surgery controls (n = 20) who underwent primary unilateral TKA without developing VTE before patient discharge. The NLR was calculated from the neutrophil and lymphocyte counts extracted from pre- and postoperative (day 1 and day 2) blood chemistry records.
  
  
  RESULTS
  On postoperative day 1, the NLR increase was exacerbated (p = 0.02) following TKA compared to UKA and predicted (p = 0.02) the occurrence of VTE in TKA patients prior to hospital discharge.
  
  
  CONCLUSIONS
  We conclude that the NLR increase is greater following TKA compared to UKA and could serve as a matrix to predict or identify a patient susceptible of sustaining VTE after TKA.
  
  
  METHODS
  3.
authors.affiliation: The Orthopedic Specialty Hospital, 5848 S. Fashion Blvd., Murray, UT, 84107, USA. tyler.barker@imail.org.
authors.forename: Tyler
authors.initials: T
authors.lastname: Barker
authors.affiliation: The Orthopedic Specialty Hospital, 5848 S. Fashion Blvd., Murray, UT, 84107, USA.
authors.forename: Victoria E
authors.initials: VE
authors.lastname: Rogers
authors.affiliation: The Orthopedic Specialty Hospital, 5848 S. Fashion Blvd., Murray, UT, 84107, USA.
authors.forename: Vanessa T
authors.initials: VT
authors.lastname: Henriksen
authors.affiliation: The Orthopedic Specialty Hospital, 5848 S. Fashion Blvd., Murray, UT, 84107, USA.
authors.forename: Kimberly B
authors.initials: KB
authors.lastname: Brown
authors.affiliation: The Orthopedic Specialty Clinic, 5848 S. Fashion Blvd, Murray, UT, 84107, USA.
authors.forename: Roy H
authors.initials: RH
authors.lastname: Trawick
authors.affiliation: The Orthopedic Specialty Clinic, 5848 S. Fashion Blvd, Murray, UT, 84107, USA.
authors.forename: Nathan G
authors.initials: NG
authors.lastname: Momberger
authors.affiliation: The Orthopedic Specialty Clinic, 5848 S. Fashion Blvd, Murray, UT, 84107, USA.
authors.forename: G
authors.initials: G
authors.lastname: Lynn Rasmussen
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008214:Lymphocytes; D008297:Male; D008875:Middle Aged; D009504:Neutrophils; D010865:Pilot Projects; D011183:Postoperative Complications / Q000097:blood*; D011237:Predictive Value of Tests; D011655:Pulmonary Embolism / Q000097:blood*; D012189:Retrospective Studies; D054556:Venous Thromboembolism / Q000097:blood*
keywords: Lymphocyte; Neutrophil; Total knee arthroplasty; Unicompartmental knee arthroplasty; Venous thromboembolic event