title: Reinterpretation of O'Brien test in posterior labral tears of the shoulder.
abstract: BACKGROUND
  Injuries to the posterior labrum are less common and more difficult to diagnose compared to anterior labral pathology. This may be in part due to difficulties in preoperative diagnosis. Posterior labral injuries cause abnormal loading of the rotator cuff with subsequent weakness. Examination using the O'Briens test tightens the posterior capsule and posteriorly translates the humeral head, stressing the labrum resulting in pain and weakness.
  
  
  METHODS
  A retrospective study.
  
  
  RESULTS
  Of 74 patients diagnosed with a posterior labral tear at arthroscopy 55 had subjective weakness on performing a O'Briens test, a sensitivity of 83% and a positive predictive value (PPV) of 90%.
  
  
  CONCLUSIONS
  Multiple tests have been described for posterior labral pathology and none of these, on their own, have a high sensitivity rate. Posterior labral injuries can often be missed on magnetic resonance imaging scanning and also at surgery if not specifically looked for. Using a sign of clinically demonstrated weakness when performing the O'Briens test, and hence reinterpretation of the test, is sensitive, with a high PPV for posterior labral pathology and can help guide further treatment.
authors.affiliation: University of Manchester Medical School, Bridgewater Hospital, Manchester, MA15 5AT, UK.
authors.forename: J Matthew
authors.initials: JM
authors.lastname: Owen
authors.affiliation: The University of Manchester, School of Medicine, Manchester M13 9PT, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Boulter
authors.affiliation: University of Manchester Medical School, Bridgewater Hospital, Manchester, MA15 5AT, UK.
authors.forename: Mike
authors.initials: M
authors.lastname: Walton
authors.affiliation: University of Manchester Medical School, Bridgewater Hospital, Manchester, MA15 5AT, UK.
authors.forename: Lennard
authors.initials: L
authors.lastname: Funk
authors.affiliation: University of Manchester Medical School, Bridgewater Hospital, Manchester, MA15 5AT, UK.
authors.forename: Tanya Anne
authors.initials: TA
authors.lastname: Mackenzie
keywords: O'Briens test; posterior instability; posterior labral injury