title: Normal anatomical variants of the labrum of the hip at magnetic resonance imaging: a systematic review.
abstract: OBJECTIVE
  To review the literature regarding normal labral variants at MRI.
  
  
  METHODS
  A systematic search was performed in PubMed/MEDLINE and Embase. For each included study, information regarding normal labral variants and findings in asymptomatic subjects was extracted.
  
  
  RESULTS
  There were 24 studies in symptomatic patients, evaluating 822 hips. The presence of a sublabral sulcus was reported by four studies in 41 hips (5 % of all evaluated hips), occurring at all anatomical locations. There were 3 cadaver studies, investigating 32 hips and reporting no normal labral variants. There were 8 studies in asymptomatic subjects, evaluating 1,096 hips. Labral tears were reported in 213 hips (19 %); no sublabral sulci were reported. Labral shape was most commonly triangular (59-89 %), whereas rounded (11-16 %), flattened (13-37 %) and teardrop (41 %) shapes were less frequently seen. Overall methodological quality of included studies was moderate, with median total quality scores of 43 % (symptomatic patients), 71 % (cadavers) and 70 % (asymptomatic subjects).
  
  
  CONCLUSIONS
  At MRI, a sublabral sulcus can be found at any anatomical location. Our results suggest that its prevalence is at least 5 % in symptomatic patients. The most common labral shape is triangular. Rounded, flattened and teardrop shapes are less frequent but are also encountered in asymptomatic subjects.
  
  
  CONCLUSIONS
  • A sublabral sulcus can be detected by MRI at any anatomical site • Its prevalence is estimated to be at least 5 % in symptomatic patients • The most common shape of the hip labrum is triangular • Rounded, flattened and teardrop shapes are less frequent.
authors.affiliation: Department of Radiology, Maastricht University Medical Center, PO Box 5800, 6202 AZ Maastricht, The Netherlands. rmkwee@gmail.com
authors.forename: Robert M
authors.initials: RM
authors.lastname: Kwee
authors.forename: Eoin C
authors.initials: EC
authors.lastname: Kavanagh
authors.forename: Miraude E A P M
authors.initials: ME
authors.lastname: Adriaensen
mesh_terms: D000077:Acetabulum / Q000033:anatomy & histology / Q000473:pathology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D006615:Hip / Q000033:anatomy & histology* / Q000473:pathology; D006621:Hip Joint / Q000033:anatomy & histology / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D055815:Young Adult