title: Effectiveness of MR imaging in selection of patients for arthroscopy of the knee.
abstract: OBJECTIVE
  To determine the effectiveness of magnetic resonance (MR) imaging in the appropriate identification of those patients with a high clinical suspicion of internal derangements of the knee who require arthroscopic therapy.
  
  
  METHODS
  In a prospective multicenter study, MR imaging was performed at 0.5 T in 430 consecutive patients. The sensitivity and specificity of MR imaging in the patients who underwent arthroscopy and the corrected sensitivity and specificity of MR in all the study patients were calculated. For this correction, patients with negative MR and arthroscopic results were considered representative of the patients with negative MR results who were conservatively treated, and the number of the former was doubled. The standard errors of the corrected values were adjusted with the delta method.
  
  
  RESULTS
  At MR imaging, arthroscopy was indicated in 221 patients, 200 of whom underwent arthroscopy. Two hundred nine patients with negative MR imaging results were randomized for arthroscopic (105 patients) or for conservative treatment (104 patients). Of the 105 patients randomized for arthroscopy, 93 actually underwent arthroscopy. Arthroscopic treatment was necessary in 13 of 93 patients with a negative diagnosis at MR imaging. Arthroscopic treatment was necessary in 179 of 200 patients with a positive diagnosis at MR (sensitivity, 93.2%; specificity, 79.2%). Sensitivity and specificity corrected for randomization were 87.3% and 88.4%. Sensitivity and specificity corrected for randomization, respectively, were 84.1% and 94.2% for the diagnosis of medial meniscal tears and 69.5% and 94.5% for the diagnosis of lateral meniscal tears at MR.
  
  
  CONCLUSIONS
  MR imaging is an effective tool in the selection of patients for arthroscopy from among a general population.
authors.affiliation: Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands. p.w.j.vincken@lumc.nl
authors.forename: Patrice W J
authors.initials: PW
authors.lastname: Vincken
authors.forename: Bert P M
authors.initials: BP
authors.lastname: ter Braak
authors.forename: Arian R
authors.initials: AR
authors.lastname: van Erkell
authors.forename: Theo P W
authors.initials: TP
authors.lastname: de Rooy
authors.forename: Walter M C
authors.initials: WM
authors.lastname: Mallens
authors.forename: Wendy
authors.initials: W
authors.lastname: Post
authors.forename: Johan L
authors.initials: JL
authors.lastname: Bloem
mesh_terms: D000293:Adolescent; D000328:Adult; D019645:Arthroplasty, Replacement, Knee; D001182:Arthroscopy; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000175:diagnosis* / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity