Computed Tomography: Role in Femoroacetabular Impingement

Abstract

Femoroacetabular impingement (FAI) physiopathology is still unclear; however, there is a consensus that a pathological mechanical contact between the femoral neck-head junction and the acetabulum leads to pain and cartilage damage. Computed tomography (CT) is useful in FAI diagnosis and surgical planning. In the present chapter, we will analyze the role of CT in FAI, with special emphasis on alignment and comparison of measurements related to epidemiological variables. We analyzed 101 CT of patients that consulted in our institution for a non-joint-or-bone-related reason. Prior to the measurement of acetabular variables, CT image must be corrected in three planes. Acetabular version is a gender-and age-related measurement. As age increased, acetabular version increased, and the same impact age has on Wiberg angle. Femoral FAI-related measurement is not related to epidemiological variables. CT has a very important role for a beter understanding of hip anatomy, and further research using CT images should be encouraged.

Parafoveal chondral lesion of the femoral head in patients with femoroacetabular impingement

“…The femoral head-neck offset was defined as the distance between the anterior margin of the femoral head-neck junction and the anterior margin of the femoral head. It was categorized as pathological if it was < 8 mm ( 8 - 10 ) .…”

“…A line was drawn from the center of the femoral head to the outer margin of the acetabulum, intersecting with a vertical line drawn from the center of the femoral head, perpendicular to the horizontal line that passes between the ischial tuberosities. An acetabular angle ≥ 40° was considered indicative of coxa profunda or excessive total acetabular coverage ( 8 - 10 ) .…”

“…It was considered normal when in anteversion. When in retroversion (< 15°), it was considered suggestive of the pincer type of impingement ( 8 - 10 ) .…”

“…• The alpha angle was measured in the axial oblique plane by using sectional methods. The alpha angle is defined as the intersection between a line drawn along the axis of the femoral neck and another extending from the center of the femoral head to the point where the circumference of the head is intercepted by the border of the femoral neck (8) . An alpha angle ≥ 55° was categorized as pathological, in accordance with most of the data in the literature (9)(10)(11)(12) .…”