title: MRI features of the acromioclavicular joint that predict pain relief from intraarticular injection.
abstract: OBJECTIVE
  Our objective was to evaluate the predictive value of various MRI findings in the acromioclavicular joint for pain relief after intraarticular injection.
  
  
  METHODS
  The acromioclavicular joint of 50 patients (20 women, 30 men; mean age, 51 years; range, 25-75 years) was evaluated on MRIs of the shoulder. Osteophytes, subchondral cysts and irregularities, bone marrow edema, joint effusion, and joint capsule hypertrophy were assessed by two musculoskeletal radiologists in consensus. Local anesthetics were injected into the acromioclavicular joint with fluoroscopic guidance. Patients graded pain relief on a visual analogue scale (0-100%) after 15 min. The relationship between pain relief and MRI findings was assessed with the Mann-Whitney U test. Pain relief equal to or greater than 70% was rated as a positive response to the injection. This cutoff value was used to calculate sensitivity, specificity, accuracy, and predictive values of the various MRI findings in determining which acromioclavicular joints were responsive to joint injections.
  
  
  RESULTS
  Mean pain relief after injection was 38%. Pain relief was significantly related to capsular hypertrophy (p = 0.007) and was equal to or greater than 70% in 11 patients. The sensitivity in diagnosing a successful injection (range, 9-82%) was highest for caudal osteophytes (82%) and capsular hypertrophy (73%). The specificity (range, 51-97%) was highest for subchondral cysts (97%), subchondral bone marrow edema (95%), and joint effusion (92%).
  
  
  CONCLUSIONS
  Pain relief after intraarticular injection is significantly related to capsular hypertrophy diagnosed on MRI. MRI findings have a reasonable sensitivity and a high specificity in predicting relevant short-term pain relief after intraarticular injection.
authors.affiliation: Department of Radiology, Orthopedic University Hospital, Balgrist, Forchstr. 340, Zurich CH-8008, Switzerland. klaustro@bluewin.ch
authors.forename: Klaus
authors.initials: K
authors.lastname: Strobel
authors.forename: Christian W A
authors.initials: CW
authors.lastname: Pfirrmann
authors.forename: Marco
authors.initials: M
authors.lastname: Zanetti
authors.forename: Ladislav
authors.initials: L
authors.lastname: Nagy
authors.forename: Juerg
authors.initials: J
authors.lastname: Hodler
mesh_terms: D000173:Acromioclavicular Joint / Q000187:drug effects* / Q000473:pathology*; D000328:Adult; D000368:Aged; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage* / Q000627:therapeutic use*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007269:Injections, Intra-Arterial; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000150:complications / Q000188:drug therapy* / Q000473:pathology*; D010146:Pain / Q000188:drug therapy* / Q000209:etiology / Q000473:pathology*; D010147:Pain Measurement; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors; D016896:Treatment Outcome; D014222:Triamcinolone Acetonide / Q000008:administration & dosage* / Q000627:therapeutic use*
chemical_list: D000893:Anti-Inflammatory Agents; D014222:Triamcinolone Acetonide