title: Inter- and intra-rater reliability of patellofemoral kinematic and contact area quantification by fast spin echo MRI and correlation with cartilage health by quantitative T1ρ MRI.
abstract: BACKGROUND
  Patellar maltracking is a leading cause of patellofemoral pain syndrome (PFPS). The aim of this study was to determine the inter- and intra-rater reliability of a semi-automated program for magnetic resonance imaging (MRI) based patellofemoral kinematics.
  
  
  METHODS
  Sixteen subjects (10 with PFPS [mean age 32.3; SD 5.2; eight females] and six controls without PFPS 19 [mean age 28.6; SD 2.8; three females]) participated in the study. One set of T2-weighted, fat-saturated fast spin-echo (FSE) MRIs were acquired from each subject in full extension and 30° of knee flexion. MRI including axial T1ρ relaxation time mapping sequences was also performed on each knee. Following image acquisitions, regions of interest for kinematic MRI, and patellar and trochlear cartilage were segmented and quantified with in-house designed spline- based MATLAB semi-automated software.
  
  
  RESULTS
  Intraclass Correlations Coefficients (ICC) of calculated kinematic parameters were good to excellent, ICC > 0.8 in patellar flexion, rotation, tilt, and translation (anterior -posterior, medial -lateral, and superior -inferior), and contact area translation. Only patellar tilt in the flexed position and motion from extended to flexed state was significantly different between PFPS and control patients (p=0.002 and p=0.006, respectively). No significant correlations were identified between patellofemoral kinematics and contact area with T1ρ relaxation times.
  
  
  CONCLUSIONS
  A semi-automated, spline-based kinematic MRI technique for patellofemoral kinematic and contact area quantification is highly reproducible with the potential to help better understand the role of patellofemoral maltracking in PFPS and other knee disorders.
  
  
  METHODS
  Level IV.
authors.affiliation: UCSF Department of Orthopaedic Surgery, United States. Electronic address: laub@orthosurg.ucsf.edu.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Lau
authors.affiliation: UCSF Department of Orthopaedic Surgery, United States.
authors.forename: Daniel U
authors.initials: DU
authors.lastname: Thuillier
authors.affiliation: UCSF Department of Radiology and Biomedical Imaging, United States.
authors.forename: Valentina
authors.initials: V
authors.lastname: Pedoia
authors.affiliation: UCSF Department of Radiology and Biomedical Imaging, United States.
authors.forename: Ellison Y
authors.initials: EY
authors.lastname: Chen
authors.affiliation: UCSF Department of Radiology and Biomedical Imaging, United States.
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: UCSF Department of Orthopaedic Surgery, United States.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Feeley
authors.affiliation: UCSF Department of Physical Therapy and Rehabilitation Science, United States.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Souza
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D002356:Cartilage / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D057071:Patellofemoral Joint / Q000473:pathology / Q000503:physiopathology*; D046788:Patellofemoral Pain Syndrome / Q000175:diagnosis* / Q000503:physiopathology; D012372:ROC Curve; D016059:Range of Motion, Articular / Q000502:physiology*; D015203:Reproducibility of Results; D055815:Young Adult
keywords: MRI; Patellofemoral kinematics; Reliability; T1ρ