Purpose: Femoroacetabular impingement (FAI) which restricts range of hip motion is regarded as an important cause leading to early development of degenerative arthritis. Although three-dimensional imaging such as CT and MRI are regarded as precise imaging modalities for three dimensional morphology of FAI, the modalities have several limitations for screening tool in out-patient clinic. The paucity of morphologic data of FAI in Korean makes it difficult to choose which method of radiograph is the most useful to screen out general orthopedic problems. We postulated the distribution of cam deformity have individual variation in Korean population. Thus we investigated the distribution of cam deformity in asymptomatic Korean population.
Materials and Methods: From Jan 2011 to Dec 2015, hip CT images of 120 subjects without any history around hip joint were evaluated. A computer program which reconstructs three dimensional model from CT scan was used to provide sectional images which cross the central axis of femoral head and neck. Alpha angle was measured in each sectional images. Alpha angle above 55 degrees were regarded as cam deformity.
Results: Mean alpha angle was 43.5°(34.7-56.1°) in 3 o’clock, 51.24°(39.5-58.8°) in 2 o’clock, 52.45° (43.3-65.5°) in 1 o’clock, 44.09°(36.8-49.8°) in 12 o’clock, 40.71°(33.5-45.8°) in 11 o’clock, 39.21°(34.1-44.6°) in 10 o’clock. Alpha angle in 1 and 2 o’clock was significantly larger than any locations (P<0.01). The prevalence of cam deformity was 15% and 15.8% in 1 and 2 o’clock, respectively.
Conclusion: Cam deformity of FAI was observed on 25.8% of asymptomatic hip. The most common region of cam deformity was antero-superior area of femoral head-neck junction (1 and 2 o’clock). The present study first reported the prevalence and the distribution of cam deformity in asymptomatic Korean population. The results would provide anatomical comprehension of cam deformity for diagnosis and surgical treatments.
