title: Does patellofemoral congruence following total knee arthroplasty correlate with pain or function? Intraoperative arthroscopic assessment of 30 cases.
abstract: BACKGROUND
  Anterior knee pain (AKP) is observed in total knee arthroplasty (TKA) both with and without patellar resurfacing, and neither patellar denervation nor secondary resurfacing are effective for treating the symptoms. The exact causes for pain remain unclear, though abnormal patellofemoral forces due to patellar malalignment or inadequate implant design can play an important role. The purpose of this study was to arthroscopically evaluate patellofemoral congruence after wound closure following TKA without patellar resurfacing and correlate it to patellar morphology and postoperative pain and function.
  
  
  METHODS
  The authors prospectively studied 30 patients that received uncemented mobile-bearing TKA. Patellofemoral congruence was assessed arthroscopically after wound closure by estimating the contact area between the native patella and the prosthetic trochlea (> two-thirds, > one-third, < one-third). The findings were correlated to preoperative assessments of patellar geometry (Wiberg classification using X-rays) and clinical outcomes [Knee Society Score (KSS), AKP on Visual Analogic Scale (VAS), and patient satisfaction].
  
  
  RESULTS
  Knees of 22 women and 8 men aged 69.8 years (range, 61-84 years) were analyzed at 16 months (range, 12-23 months). Preoperative patellar geometry was Wiberg type A in 11, type B in 12 and type C in 7 knees. Postoperative KSS was 79.1 (range, 50.0-94) and the VAS for AKP was 1.6±1.3 (median, 1; range, 0-5). Patellar congruence was correlated with patellar morphology (P<0.001) but not correlated with any clinical outcomes (KSS, VAS or satisfaction). There were also no statistical correlations between patellar morphology or patellofemoral congruence and patient characteristics.
  
  
  CONCLUSIONS
  While patellar morphology and patellofemoral congruence are strongly related, they are not associated with clinical outcomes or patient demographics. Considering that numerous incongruent patellofemoral joints were pain-free, and conversely, many perfectly congruent patellofemoral joints had anterior pain, the authors suppose that pain is probably caused by mechanisms other than patellofemoral pressures.
authors: Department of Orthopaedic Surgery, Ramsay Générale de Santé, Hôpital Privé de l'Estuaire, Le Havre, France; ; Department of Orthopaedic Surgery, Rouen University Hospital, Rouen, France;
authors: Antoine
authors: A
authors: Senioris
authors: Department of Medical Research, Alliance Scientifique SAS, Lyon, France; ; Department of Medical Technology, Accelerate Innovation Management SA, Geneva, Switzerland.
authors: Mo
authors: M
authors: Saffarini
authors: Department of Orthopaedic Surgery, Ramsay Générale de Santé, Hôpital Privé de l'Estuaire, Le Havre, France; ; Department of Orthopaedic Surgery, Rouen University Hospital, Rouen, France;
authors: Said
authors: S
authors: Rahali
authors: Department of Orthopaedic Surgery, Ramsay Générale de Santé, Hôpital Privé de l'Estuaire, Le Havre, France; ; Department of Orthopaedic Surgery, Rouen University Hospital, Rouen, France;
authors: Louis
authors: L
authors: Malekpour
authors: Department of Orthopaedic Surgery, Rouen University Hospital, Rouen, France ;
authors: Franck
authors: F
authors: Dujardin
authors: Department of Orthopaedic Surgery, Ramsay Générale de Santé, Hôpital Privé de l'Estuaire, Le Havre, France ;
authors: Olivier
authors: O
authors: Courage
keywords: Total knee arthroplasty (TKA); Wiberg type; anterior knee pain (AKP); patellar morphology; patellofemoral congruence