Objective: To determine the prevalence of cam-type femoroacetabular impingement (FAI) in the hip joints of asymptomatic Thai individuals using increased alpha angle of more than 55° on computed tomography (CT) images.

Materials and Methods: The prospective study was conducted between 2019 and 2021. CT images of the 226 hip joints with no history of hip pain within three months prior to CT, no history of congenital dysplasia, Perthes disease, slipped capital femoral epiphysis, hip fracture, hip surgery, and inflammatory arthropathy, negative anterior impingement test, and no CT findings of osteoarthritis were evaluated. Alpha angles were measured in the axial oblique and radial planes at 12 o’clock, 1 o’clock, 1:30 o’clock, 2 o’clock, and 3 o’clock. Alpha angles of more than 55° were considered cam-type FAI morphology.

Results: The prevalence rates of cam-type FAI morphology using increased alpha angles of more than 55° measured on axial oblique and radial plane images at 12 o’clock, 1 o’clock, 1:30 o’clock, 2 o’clock, and 3 o’clock were 0.4%, 0%, 4.9%, 8.4%, 8.0%, and 1.8% respectively. Cam-type morphology was common in the anterosuperior aspect of the femoral head-neck junction. The prevalence of cam-type morphology was significantly higher in men than in women.

Conclusion: The range of prevalence rates of cam-type FAI morphology are between 0 to 8.4%. The prevalence is different in each image plane and location of the femoral head-neck junction. The prevalence of cam-type morphology in the present study differed from those in the previous studies conducted in other countries, which may be caused from variations in race and ethnicity.

Keywords: Prevalence; Cam-type Femoroacetabular Impingement (FAI); Alpha angle; Computed tomography (CT)

DOI: 10.35755/jmedassocthai.2022.07.13351

Received 22 November 2021 | Revised 18 May 2022 | Accepted 27 May 2022