J Korean Soc Radiol.  2015 Jun;72(6):385-392. 10.3348/jksr.2015.72.6.385.

Hip Morphometry of Femoroacetabular Impingement Pattern in Patients with Ankylosing Spondylitis

• Lee JY
• Lee E
• Choi JA

• KMID: 2098017
• DOI: http://doi.org/10.3348/jksr.2015.72.6.385

Abstract

PURPOSE
To analyze hip morphometry of femoroacetabular impingement (FAI) pattern in patients with ankylosing spondylitis (AS) and correlate them with sacroiliitis grades.
MATERIALS AND METHODS
384 patients with AS were analyzed regarding demographics, radiologic signs of FAI for hip involvement, and sacroiliitis grades. FAI was classified into 3 types according to alpha angle, lateral center-edge angle and pistol grip deformity. Sacroiliitis was graded according to the New York criteria. Prevalence of FAI morphometry types was determined and evaluated for association with sacroiliitis grades. Statistical analysis regarding numerical variables, including age, sacroiliitis score using t-test, sacroiliitis score in three groups using Kruskal-Wallis test and Mann-Whitney U-test, corrected by Bonferroni methods for post hoc analysis was done.
RESULTS
Among 384 patients, 141 (36.7%) had FAI morphometry. Male predominance was found in group with FAI pattern involvement (87.2%) (p = 0.000). Pincer type (20.6%) was the most common. Hip involvement group also showed greater sacroiliitis score (2.49 vs. 1.75, p = 0.000). Combined-type had greater sacroiliitis score compared with others (p = 0.002, 0.003).
CONCLUSION
FAI morphometry was frequent in hips of AS patients (36.7%), especially pincer type, more frequent in male, and associated with significantly greater grade of sacroiliitis; combined type FAI pattern had greater sacroiliitis score.

MeSH Terms

Congenital Abnormalities
Demography
Femoracetabular Impingement*
Hand Strength
Hip*
Humans
Male
Prevalence
Sacroiliitis
Spondylitis, Ankylosing*

Figure

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  Fig. 1 Radiographic presentations of alpha angle on translateral radiograph by drawing a circle along the femur head circumference, drawing a line between the center of the circle and the point of head-neck offset, according to the method described by Nötzli et al. (6).

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  Fig. 2 Radiographic presentations of lateral center-edge angle on anteroposterior radiographs. The lateral center edge angle is the angle formed by a vertical line and a line connecting the femoral head center with the lateral edge of the acetabulum.

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  Fig. 3 Radiographic presentations of flattening of the head-neck junction (so called pistol grip deformity) on anteroposterior radiographs.

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  Fig. 4 Pelvic radiograph of 33-year-old man with ankylosing spondylitis. A. Pincer type femoroacetabular impingement pattern showing lateral center-edge angle estimated to be 52.3°. B. Demonstrating bilateral sacroiliitis grade 3, showing subchondral sclerosis and irregularities of the joint surface, including erosions.

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  Fig. 5 Pelvic radiograph of in 26-year-old man with ankylosing spondylitis. A. Cam type femoroacetabular impingement pattern showing alpha angle estimated to be 62.4°. B. Demonstrating bilateral sacroiliitis grade 2, showing equivocal subchondral sclerosis.

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  Fig. 6 Pelvic radiograph of 31-year-old man with ankylosing spondylitis. A. Combined type femoroacetabular impingement pattern showing lateral center-edge angle estimated to be 45.0° and positive pistol grip deformity. B. Demonstrating bilateral sacroiliitis grade 4, showing complete ankylosis.

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