title: Is the lateral extension of the acromion related to the outcome of shoulder injections?
abstract: OBJECTIVE
  To assess patients' outcomes after subacromial or glenohumeral injections based on the degree of lateral extension of the acromion.
  
  
  METHODS
  307 patients were prospectively included after therapeutic fluoroscopy-guided subacromial (n = 148) or glenohumeral (n = 159) injections with anaesthetic and long-acting corticosteroids. Pre- and post-injection outcomes at 1 week and 1 month were obtained using the 11-point numerical rating scale (NRS) for pain. Lateral extension of the acromion was quantified and categorized by the critical shoulder angle (CSA) and the acromion index (AI) on anteroposterior conventional radiographs.
  
  
  RESULTS
  Patients' outcomes at 1 week and 1 month were significantly improved (p < 0.001) compared to baseline for subacromial and glenohumeral injection patients. Patients with a CSA <35° showed significantly higher pain reduction 1 month after subacromial injection compared to patients with a CSA >35° (4.2 ± 2.6 vs. 3.2 ± 3.0, p = 0.04). A significant difference in the 1-month NRS change in pain scores is noted for smaller AIs after subacromial injection (4.3 ± 2.8 vs. 2.6 ± 2.9; p = 0.01). No significant association was noted between clinical outcome and the lateral extension of the acromion after glenohumeral joint injections.
  
  
  CONCLUSIONS
  A short lateral extension of the acromion was associated with better clinical outcomes in subacromial injection patients but not in glenohumeral injection patients.
  
  
  CONCLUSIONS
  • Patients' outcomes at 1 month improved significantly compared to baseline for subacromial injections. • Patients' outcomes at 1 month improved significantly compared to baseline for glenohumeral injections. • Short acromial lateralization was associated with better clinical outcome after subacromial injection. • The acromial lateralization was not associated with clinical outcome after glenohumeral injection.
authors.affiliation: Orthopedic University Hospital Balgrist, University of Zurich, Faculty of Medicine, Forchstrasse 340, 8008, Zurich, Switzerland, tobiasjdietrich@gmail.com.
authors.forename: Tobias Johannes
authors.initials: TJ
authors.lastname: Dietrich
authors.forename: Beat K
authors.initials: BK
authors.lastname: Moor
authors.forename: Gabor J
authors.initials: GJ
authors.lastname: Puskas
authors.forename: Christian W A
authors.initials: CW
authors.lastname: Pfirrmann
authors.forename: Juerg
authors.initials: J
authors.lastname: Hodler
authors.forename: Cynthia K
authors.initials: CK
authors.lastname: Peterson
mesh_terms: D000174:Acromion / Q000000981:diagnostic imaging*; D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D005938:Glucocorticoids / Q000008:administration & dosage; D006801:Humans; D007270:Injections, Intra-Articular; D008297:Male; D011446:Prospective Studies; D012372:ROC Curve; D011859:Radiography; D019534:Shoulder Impingement Syndrome / Q000000981:diagnostic imaging / Q000188:drug therapy*; D012785:Shoulder Joint; D016896:Treatment Outcome; D014221:Triamcinolone / Q000008:administration & dosage*
chemical_list: D005938:Glucocorticoids; D014221:Triamcinolone