Ultrasound of Hip Joints by Graf: Positioning, Standard Section, and Measurement of Angles α and β
Positioning and Physiological Position of the Thigh
The coronal view in the standard plane can be obtained with the thigh in a physiological neutral position (flexion 15–20 degrees) (AIUM, 2024). The transducer is placed in the coronal plane; if necessary, the upper edge of the transducer is rotated 10–15° (usually posteriorly) into an oblique coronal plane to make the iliac bone appear straight (AIUM, 2024).
Standard Section
After adjusting to ensure that the plane passes through the deepest part of the acetabulum (including visualization of the triradiate cartilage and ischium), a coronal view in the standard plane is obtained (AIUM, 2024). The standard plane is defined by identifying:
- the straight iliac line;
- the apex of the acetabular labrum (labrum);
- the transition from the os ilium to the triradiate cartilage (AIUM, 2024).
The ossified acetabulum and proximal femur are hyperechoic with an acoustic shadow, whereas non-ossified structures are visualized differently (Jacobson, 2026).
Baseline and Measurement of Angles α and β
The baseline is the lateral (flat) iliac bone (Jacobson, 2026).
| Angle | Measured Between Which Lines |
|---|---|
| α (bony) | Between the lateral iliac bone (baseline) and the bony roof line of the acetabulum (Jacobson, 2026) |
| β (cartilaginous) | Between the baseline of the lateral iliac bone and the inclination line drawn through the hyperechoic apex of the labrum from the lateral part of the acetabulum (Jacobson, 2026) |
Sign of a Normal/Mature Joint
The coronal view in the neutral position of the thigh is described, and the image is likened to an "egg on a spoon": the line drawn from the flat iliac bone covers at least 50% of the head, and the acetabular angle α exceeds 60 degrees (Jacobson, 2026).
Frequently asked questions
In what position of the thigh is the standard section performed?
In the physiological neutral position with flexion of 15–20 degrees (AIUM, 2024).
What three landmarks define the standard plane?
The straight iliac line, the apex of the acetabular labrum, and the transition from the os ilium to the triradiate cartilage (AIUM, 2024).
What is the baseline for measuring angles?
The lateral (flat) iliac bone (Jacobson, 2026).
How do angles α and β differ?
α is measured between the baseline and the bony roof line, β — between the baseline and the inclination line through the apex of the labrum (Jacobson, 2026).
What values indicate a normal joint?
The line from the flat iliac bone covers ≥50% of the head, and the acetabular angle α >60 degrees (Jacobson, 2026).