title: Superolateral hoffa fat-pad edema and patellofemoral maltracking: predictive modeling.
abstract: OBJECTIVE
  Superolateral Hoffa fat-pad edema is a frequent finding with patellar maltracking and may precede clinically significant chondrosis. The purpose of this study was to clarify which patellofemoral measurements are most highly associated and to develop a prediction rule to guide clinical decision making.
  
  
  METHODS
  Twenty-three patellofemoral measurements were performed on 71 knees retrospectively identified as having superolateral Hoffa fat-pad edema at MRI (Hoffa group) and on 45 normal knees (normal group). Univariate analysis was performed to examine the association between these measurements and Hoffa fat-pad edema. Classification and regression tree analysis with 10-fold cross validation was used to generate a prediction model.
  
  
  RESULTS
  For 16 of the 23 patellofemoral measurements, there was a statistically significant difference (p < 0.05) between the Hoffa and normal groups. Classification and regression tree analysis identified a prediction model in which a patient is placed into the Hoffa group if one of three conditions is met: lateral patellar displacement greater than -3.6 mm and Insall-Salvati ratio greater than 0.99; lateral patellar displacement of -3.6 mm or less and Insall-Salvati ratio greater than 1.23; or lateral patellar displacement of -3.6 mm or less, Insall-Salvati ratio of 1.23 or less, and lateral trochlear inclination of 16.5° or less. In fitting of the original sample, this model had 91.6% sensitivity and 88.9% specificity for identifying the Hoffa group. When 10-fold cross validation was applied, the estimated generalizable sensitivity and specificity were 85.9% and 75.6%.
  
  
  CONCLUSIONS
  Superolateral Hoffa fat-pad is strongly associated with a number of measures of patellar maltracking. A prediction model based on these measurements is accurate for differentiating knees with superolateral Hoffa fat-pad edema from normal knees.
authors: 1 Department of Radiology, Keck School of Medicine, University of Southern California, 1500 San Pablo St, 2nd Fl Imaging, Los Angeles, CA 90033.
authors: George R
authors: GR
authors: Matcuk
authors: Steven Yong
authors: SY
authors: Cen
authors: Vadim
authors: V
authors: Keyfes
authors: Dakshesh B
authors: DB
authors: Patel
authors: Christopher J
authors: CJ
authors: Gottsegen
authors: Eric A
authors: EA
authors: White
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D004487:Edema / Q000175:diagnosis* / Q000209:etiology*; D005260:Female; D005269:Femur / Q000473:pathology*; D006801:Humans; D007592:Joint Diseases / Q000175:diagnosis*; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D017847:Patellar Ligament / Q000473:pathology*; D012189:Retrospective Studies
keywords: CART; classification and regression tree; patellar maltracking; patellar tendon–lateral femoral condyle friction syndrome; patellofemoral measurements; superolateral Hoffa fat-pad edema