title: The reliability and validity of radiological assessment for patellar instability. A systematic review and meta-analysis.
abstract: OBJECTIVE
  To determine the discriminative validity and reliability of the evidence base using meta-analysis.
  
  
  METHODS
  A review of published sources using the databases AMED, CINHAL, EMBASE, MEDLINE, Scopus and the Cochrane Library, and for unpublished material was conducted. All studies assessing the reliability, validity, sensitivity or specificity of magnetic resonance imaging (MRI), computed tomography (CT) or ultrasound (US) of the patellofemoral joint of patients following patellar dislocation, subluxation or instability, were included. A meta-analysis was performed to assess the difference in radiological measurements between healthy controls and subjects with patellar instability in order to assess discrimination validity. A narrative assessment was used to evaluate the inter- and intra-observer reliability as well as the sensitivity and specificity of specific radiological measurements.
  
  
  RESULTS
  A total of 27 studies were reviewed. The findings indicated that there was acceptable inter-observer and intra-observer reliability and validity for different methods of assessing patellar height and the sulcus angle with X-ray, MRI and CT methods, and the tibial tubercle-trochlear groove (TT-TG) assessed using CT. There was poor reliability or validity for the assessment of severity of trochlear dysplasia and the sulcus angle using US.
  
  
  CONCLUSIONS
  There is insufficient evidence to determine the reliability, validity, sensitivity or specificity of tests such as the congruence angle, lateral patellar displacement, lateral patellar tilt, trochlear depth, boss height, the crossing sign or Wiberg patellar classification. A critical appraisal of the literature identified a number of recurrent methodological limitations. Further study is recommended to evaluate the reliability and validity of these radiological outcomes using well-designed radiological trials.
authors.affiliation: Faculty of Health, University of East Anglia, Queens' Building, Norwich, NR4 7TJ, UK. toby.smith@uea.ac.uk
authors.forename: Toby O
authors.initials: TO
authors.lastname: Smith
authors.forename: Leigh
authors.initials: L
authors.lastname: Davies
authors.forename: Andoni P
authors.initials: AP
authors.lastname: Toms
authors.forename: Caroline B
authors.initials: CB
authors.lastname: Hing
authors.forename: Simon T
authors.initials: ST
authors.lastname: Donell
mesh_terms: D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging*; D031222:Patellar Dislocation / Q000000981:diagnostic imaging; D057071:Patellofemoral Joint / Q000000981:diagnostic imaging*; D011859:Radiography; D015203:Reproducibility of Results; D015599:Trauma Severity Indices