Korean J Radiol.  2015 Dec;16(6):1319-1325. 10.3348/kjr.2015.16.6.1319.

Associations between Alpha Angle and Herniation Pit on MRI Revisited in 185 Asymptomatic Hip Joints

Affiliations
  • 1Department of Radiology, Seoul National University Bundang Hospital, Seongnam 13620, Korea. jachoi88@gmail.com
  • 2Department of Radiology, Hallym University Dongtan Sacred Heart Hospital, Hwaseong 18450, Korea.

Abstract


OBJECTIVE
To evaluate the association between alpha angle and herniation pit on MRI in asymptomatic hip joints and their associations with demographic variables.
MATERIALS AND METHODS
Hip MRI of 185 asymptomatic hip joints of 105 adults (age 18 to 80 years) from September 2011 through December 2012 were retrospectively studied. Alpha angles were measured on oblique axial MR images by 2 observers. Herniation pit was determined by 1 observer. Size measures, prevalence, and statistical analyses were conducted regarding its association with age, gender, laterality (right or left hip). Intra- and inter-observer agreements were determined by intra-class correlation coefficient.
RESULTS
The prevalence of herniation pit in asymptomatic hips was 21.6%. The range of alpha angle was 27.6-65.0 degrees. Seventeen and 16 out of 185 (9.1% and 8.6%) hip joints showed alpha angle of ≥ 55 degrees in first and second measurement sessions, respectively. There was no association between alpha angle ≥ 55 and presence of herniation pit. There was no association between alpha angle ≥ 55 and the size of herniation pit. Inter-observer agreement of alpha angle was 0.485 between first measurements of first vs. second observer, respectively. Intra-observer agreement of alpha angle was 0.654, respectively. Forty (21.6%) of 185 hip joints (35 of 105 patients, 33.3%) had herniation pit, with no difference according to age, gender, or laterality of hip joint.
CONCLUSION
There is no association between alpha angle ≥ 55 degrees and presence of herniation pit or demographic variables.

Keyword

Hip; MRI; Herniation pit; Alpha angle

MeSH Terms

Adolescent
Adult
Aged
Aged, 80 and over
Asymptomatic Diseases
Female
Femur Neck/anatomy & histology/radiography
Hip Joint/anatomy & histology/*radiography
Humans
*Magnetic Resonance Imaging
Male
Middle Aged
Prevalence
Retrospective Studies
Young Adult

Figure

  • Fig. 1 Alpha angle was measured on oblique axial MR images parallel to axis of femoral neck.Subsequently, prevalence of alpha angle ≥ 55° and herniation pit was calculated and statistical analysis was done regarding their association with age, gender, laterality of hip (right or left).

  • Fig. 2 Presence of herniation pit was determined on MRI.It was shown as focal fibrocystic lesion with low signal intensity (arrow) on T1-weighted image (A) and intermediate to high signal intensity (arrow) on T2-weighted image (B) in location of femur head and neck junction.


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