Prevalence and morphological features of acetabular dysplasia with coexisting femoroacetabular impingement-related findings in a Japanese population: a computed tomography-based cross-sectional study

Figures

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  Fig. 1.. Measurement of CE angle, Sharp angle and AI. These angles were measured on a slice of femoral head center in the coronal plane. θ1, θ2, and θ3 is CE angle, Sharp angle and AI, respectively. CE angle was measured as the angle between the line joining the lateral aspect of the acetabulum and the femoral head center, and the line perpendicular to the line parallel to the transverse axis of the pelvis. Sharp angle was measured as the angle between the line joining the lateral aspect of the weight bearing zone and the inferior point of teardrop, and the line parallel to the transverse axis of the pelvis. AI was measured as the angle between the line joining the medial and lateral aspects of the weight bearing zone, and the line parallel to the transverse axis of the pelvis.

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  Fig. 2.. Measurement of the acetabular version angle in four axial slices. (A) Reference plane for measuring the acetabular version angle. Each line represents one of the four slices; a slice at the level of the superior margin of the femoral head (slice A1), a slice 5 mm below the superior margin of the femoral head (slice A2), a slice 10 mm below the superior margin of the femoral head (slice A3) and a slice 15 mm below the superior margin of the femoral head (slice A4). (B) Axial slice of A1. Angle ø is the acetabular version angle.

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  Fig. 3.. Measurement of the α-angle and HNOR in multiple radial slices (clockwise system). (A) Reference plane for measuring the α-angle and HNOR. The dotted line is the axis through the center of the femoral neck. It is adjusted to be parallel to the femoral neck–shaft angle. The solid line is the reference plane for radial angle reconstruction. (B) The reconstructed three-dimensional image demonstrates superimposed radial reference lines at 15° intervals. R1 (3:00 o’clock) is the oblique axial slice (dotted line in A). R2 (2:30 o’clock) is a plane rotated 15° from R1. R3 (2:00 o’clock) is a plane rotated 30° from R1. R4 (1:30 o’clock) is a plane rotated 45° from R1. R5 (1:00 o’clock) is a plane rotated 60° from R1. R6 (12:30 o’clock) is a plane rotated 75° from R1. (C) Angle ø is the α-angle. The α-angle is the angle between the line joining the center of the femoral head and the center of the femoral neck, and the line from the center of the femoral head to the point where the spherical image of the femoral head is lost. The HNOR was calculated by dividing the anterior offset (asterisk) by the maximum diameter of the femoral head of each slice. The anterior offset is the thickness of…

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  Fig. 4.. We defined an HP as a cystic-like lesion underneath the anterior cortex at the anterosuperior femoral head–neck junction with clear demarcation and a diameter of >3 mm. A HP (arrow) was evaluated in multiradial six slices.

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  Fig. 5.. The presence of a PGD was subjectively judged on reconstructed three-dimensional reconstructed computed tomography images. This case was judged to be PGD-positive bilaterally (arrow).

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  Fig. 6.. The representative case of the hip of AD with coexisting FAI-related findings. This case was 50 years old women, left hip was defined as a hip of borderline AD with coexisting cam deformity. (A) CE angle, Sharp angle and AI was 21°, 44° and 20°, respectively. (B) The acetabular version angle was 7° at a slice at the level of the superior margin of the femoral head (slice A1). (C) The α-angle and HNOR at a slice of R4 (1:30 o’clock) was 57° and 0.125, respectively. HP was also positive. (D) PGD was negative. According to the CE and Sharp angle, this hip was defined as a borderline AD. On the other hand, this hip was also defined as a cam deformity due to α-angle > 55°, HNOR < 0.13 and HP positive. However, this hip did not coexist with a pincer deformity, because the AI was over 0° and acetabular version angle was not negative.