title: Sublabral sulcus at the posteroinferior acetabulum: a potential pitfall in MR arthrography diagnosis of acetabular labral tears.
abstract: OBJECTIVE
  Our study correlated findings on hip MRI and MR arthrography with hip arthroscopy to assess the location, prevalence, and potential pitfall of a normal acetabular sublabral sulcus.
  
  
  METHODS
  We retrospectively collected 58 hip MRI studies along with surgical reports in 58 patients who underwent hip arthroscopy over a 5-year period. Intraoperative photography (n = 23), radiography (n = 56), unenhanced MRI (n = 13), and MR arthrography (n = 54) studies were available for review. Two radiologists described hip anatomy on radiology studies with agreement by consensus.
  
  
  RESULTS
  A normal posteroinferior sublabral groove was confirmed on available arthroscopy photographs in four (17.4%) of 23 hips. In each of these four patients, the anatomic sublabral groove correlated with apparent partial labral detachment on MR arthrography. On review of all studies, 13 hips (22.4%) without a posterior labral tear at surgery had imaging findings of a sublabral sulcus. The sulcus was not associated with acetabular dysplasia, which was radiographically noted in 12 cases (21.4%). Preoperatively, the sulcus was misdiagnosed as a tear in two cases. Labral tears were anterior or anterosuperior in 51 patients.
  
  
  CONCLUSIONS
  A posteroinferior sublabral groove is a relatively common normal anatomic hip variation. If not recognized as normal, the sulcus may serve as a diagnostic pitfall on MR arthrography. Its location is distinct from most labral tears. We did not discover a sublabral sulcus at the anterior or anterosuperior acetabulum, the most common sites of labral injury.
authors.affiliation: Department of Radiology, Walter Reed Army Medical Center, 6900 Georgia Ave., NW, Washington, DC 20307-5001, USA. phil.dinauer@us.army.mil
authors.forename: Philip A
authors.initials: PA
authors.lastname: Dinauer
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Murphy
authors.forename: John F
authors.initials: JF
authors.lastname: Carroll
mesh_terms: D000077:Acetabulum / Q000293:injuries* / Q000473:pathology; D000293:Adolescent; D000328:Adult; D001182:Arthroscopy; D002358:Cartilage, Articular / Q000293:injuries* / Q000473:pathology; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D025981:Hip Injuries / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA