Hip Pelvis.  2018 Mar;30(1):5-11. 10.5371/hp.2018.30.1.5.

Prevalence of Cam Deformity with Associated Femoroacetabular Impingement Syndrome in Hip Joint Computed Tomography of Asymptomatic Adults

• Han J
• Won SH
• Kim JT
• Hahn MH
• Won YY

• KMID: 2408179
• DOI: http://doi.org/10.5371/hp.2018.30.1.5

Abstract

PURPOSE
Femoroacetabular impingement (FAI) is considered an important cause of early degenerative arthritis development. Although three-dimensional (3D) imaging such as computed tomography (CT) and magnetic resonance imaging are considered precise imaging modalities for 3D morphology of FAI, they are associated with several limitations when used in out-patient clinics. The paucity of FAI morphologic data in Koreans makes it difficult to select the most effective radiographical method when screening for general orthopedic problems. We postulate that there might be an individual variation in the distribution of cam deformity in the asymptomatic Korean population.
MATERIALS AND METHODS
From January 2011 to December 2015, CT images of the hips of 100 subjects without any history of hip joint ailments were evaluated. A computer program which generates 3D models from CT scans was used to provide sectional images which cross the central axis of the femoral head and neck. Alpha angles were measured in each sectional images. Alpha angles above 55° were regarded as cam deformity.
RESULTS
The mean alpha angle was 43.5°, range 34.7-56.1°(3 o'clock); 51.24°, range 39.5-58.8°(2 o'clock); 52.45°, range 43.3-65.5°(1 o'clock); 44.09°, range 36.8-49.8°(12 o'clock); 40.71, range 33.5-45.8°(11 o'clock); and 39.21°, range 34.1-44.6°(10 o'clock). Alpha angle in 1 and 2 o'clock was significantly larger than other locations (P < 0.01). The prevalence of cam deformity was 18.0% and 19.0% in 1 and 2 o'clock, respectively.
CONCLUSION
Cam deformity of FAI was observed in 31% of asymptomatic hips. The most common region of cam deformity was antero-superior area of femoral head-neck junction (1 and 2 o'clock).

Keyword

Hip; Femur; Deformity; Femoroacetabular impingement; Three dimensional imaging

MeSH Terms

Adult*
Congenital Abnormalities*
Femoracetabular Impingement*
Femur
Head
Hip Joint*
Hip*
Humans
Magnetic Resonance Imaging
Mass Screening
Methods
Neck
Orthopedics
Osteoarthritis
Outpatients
Prevalence*
Tomography, X-Ray Computed

Figure

• 

  Fig. 1 (A) The 12 o'clock position was defined as the superior aspect of the proximal femur in a standing position. (B) The alpha angle was assessed from the line drawn between the center of the femoral neck at its narrowest point and the center of the femoral head at clock-face positions at 30°intervals using three-dimensional reconstruction of computed tomography imaging of the femur.

• 

  Fig. 2 Point A is the center of the femoral head and the line drawn from A to B is the long axis line connecting the centers between the femur head and neck. The line drawn from A to C is the line extending from the center of the femoral head to the point the femoral head extrudes a circle drawn around the femoral head. The angle formed between these two lines is defined as alpha. The alpha angle is described as the angle formed by the femoral neck axial line and the line from the center of the femoral head to a point where the femoral head extends outside the circle around the femoral head.

• 

  Fig. 3 Mean alpha angles of different clock-face positions.

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