title: Patellar Height After Total Knee Arthroplasty: Comparison of 3 Methods.
abstract: Total knee arthroplasty (TKA) is the gold standard procedure for knee osteoarthritis. However, there have been conflicting reports concerning whether TKA is associated with modifications in patellar height. This controversy might be partially explained by the diversity of methods used to measure patellar height. Therefore, we aimed at assessing the reproducibility of 3 radiological indices commonly used to evaluate patellar height-Insall-Salvati (IS), Blackburne-Peel (BP), and Caton-Deschamps (CD) ratios. Additionally, we aimed at evaluating the short-term differences between preoperative and postoperative patellar heights as measured by those 3 methods.
  
  
  
  Patellar heights were blindly measured by 2 researchers using IS, BP, and CD ratios in 203 knees. Interobserver agreement was evaluated by determination of intraclass correlation coefficients (ICC) and Bland-Altman plots. Preoperative and postoperative patellar heights were compared with Wilcoxon test. The association between postoperative pain and modifications in patellar height was assessed using Mann-Whitney U test.
  
  
  
  High interobserver agreement was found for IS (preoperative and postoperative ICC = 0.93), BP (preoperative ICC = 0.89; postoperative ICC = 0.91), and CD (preoperative ICC = 0.89; postoperative ICC = 0.90) ratios. Preoperative and postoperative patellar heights were not significantly different whatever the method used. Postoperative pain was reported after 23% procedures and was significantly associated with wider patellar height variations as measured by the BP ratio (P = .018).
  
  
  
  The methods evaluated appear to be reproducible. Although patellar height tended to be lower when measured postoperatively, this difference was not significant for any of the methods studied.
authors.affiliation: Center for Health Technology and Services Research (CINTESIS), Faculty of Medicine, University of Porto, Porto, Portugal.
authors.forename: Filipe
authors.initials: F
authors.lastname: Cabral
authors.affiliation: Center for Health Technology and Services Research (CINTESIS), Faculty of Medicine, University of Porto, Porto, Portugal; Department of Health Information and Decision Sciences (CIDES), Faculty of Medicine, University of Porto, Porto, Portugal.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Sousa-Pinto
authors.affiliation: Orthopaedics and Traumatology Department, Centro Hospitalar de São João, E.P.E., Porto, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Pinto
authors.affiliation: Orthopaedics and Traumatology Department, Centro Hospitalar de São João, E.P.E., Porto, Portugal; Faculty of Medicine, University of Porto, Porto, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Torres
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D010149:Postoperative Pain; D010329:Patella / Q000000981:diagnostic imaging*; D011184:Postoperative Period; D011859:Radiography / Q000379:methods*; D015203:Reproducibility of Results
keywords: Blackburne-Peel; Caton-Deschamps; Insall-Salvati; patellar height; total knee arthroplasty