Prevalence of Imaging Features on CT Thought to Be Associated With Femoroacetabular Impingement: A Retrospective Analysis of 473 Asymptomatic Adult Hip Joints

Abstract

Imaging features on CT that are known to be associated with FAI are common in asymptomatic adult hip joints, especially in men, with a high degree of coexistence among the findings.

What is the Prevalence of Radiographic Hip Findings Associated With Femoroacetabular Impingement in Asymptomatic Asian Volunteers?

“…The prevalence of hip osteoarthritis is lower in Asian than in white populations [19,34], and some authors have reported that the low prevalence of FAI-related morphologic features in Asian populations might explain this phenomenon [11,21,44]. However, recent studies, including ours, show the opposite [25,30,31]. Our findings cannot explain the discordance between the high rate of FAI-related morphologic features and low rate of hip osteoarthritis in Asian populations [6].…”

“…Establishment of the prevalence of FAI-related morphologic features may be the first step to elucidating its natural history. A high prevalence of asymptomatic FAIrelated features has been reported in Western populations [5,10,17,22,23,26,27], but no clear consensus has been reached in Asian populations [12,21,25,30,31,44]. Previous studies of Western populations [5,10,17,22,23,26,27] reported a prevalence of 14% to 66%, with the prevalence varying according to the imaging method, population (such as an unselected population or a population consisting of athletes), sex of those analyzed, and morphologic features of interest (cam, pincer, or all types).…”

“…Mimura et al [30] investigated CT scans of 103 hips and found that 56.3% of hips had radiologic evidence of FAI-related morphologic features (51.5% had an alpha angle greater than 50°and 16.5% had negative acetabular anteversion). Kim et al [25] retrospectively reviewed CT scans of 473 hips and concluded that 40% of the patients had at least one feature suggesting cam or pincer-type FAI (18% had an alpha angle [ 55°and 27% had an LCE angle [ 40°). Both CT-based studies were performed with patients who had CT for conditions unrelated to hip disorders, however, it is unknown whether study participants were truly asymptomatic.…”

“…A second line was drawn between the center of the femoral head and the point where the cortex of the femoral head exited the imaginary circle, and the angle between the two lines was measured. An alpha angle greater than 55°was chosen as the reference value and considered to be the camtype pathologic feature [25,43].…”

“…The prevalence of asymptomatic FAI-related features in Asian populations is less-well studied, and previous studies report conflicting results, with prevalence ranging from 0.6% to 50% [12,21,25,30,44]. Moreover, some of these studies involve data from tests that were performed owing to problems unrelated to the hip, and it is unknown whether study participants were truly asymptomatic [25,30]. Studies regarding the prevalence of FAI in a proven asymptomatic cohort of Asian populations are lacking.…”