Normal Hilgenreiner's Epiphyseal Angle Size on Radiography
Hilgenreiner's epiphyseal angle (HEA) is a radiographic measurement describing the inclination of the proximal femoral epiphyseal plate relative to Hilgenreiner's line (the horizontal line drawn through both triradiate cartilages) on an anteroposterior pelvis radiograph. It serves as a quantitative marker of femoral head alignment and acetabular development in the growing child. Accurate measurement of the HEA is particularly important in the early detection and monitoring of developmental dysplasia of the hip (DDH).
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Anteroposterior | <60¡ |
Clinical Significance
A normal Hilgenreiner's epiphyseal angle is less than 60°. Values at or exceeding this threshold suggest abnormal inclination of the proximal femoral physis, which may indicate dysplasia, subluxation, or dislocation of the hip. The HEA is most useful in infants and young children before the femoral head epiphysis has fully ossified, a period when other standard measurements such as the acetabular index may be less reliable in isolation.
An elevated HEA is associated with lateral and superior displacement of the femoral head relative to the acetabulum. Serial measurements can help gauge the response to treatment, such as Pavlik harness application or closed reduction. Clinicians should be cautious about patient positioning, as pelvic tilt or rotation can artificially alter the angle and lead to misinterpretation.
- Developmental dysplasia of the hip (DDH)
- Hip subluxation or dislocation
- Neuromuscular hip dysplasia (e.g., cerebral palsy)
- Coxa valga with associated acetabular insufficiency
- Post-treatment assessment following reduction
Reference: Tachdjian MO. Clinical pediatric orthopedics, the art of diagnosis and principles of management. McGraw-Hill/Appleton & Lange. (1997).
Imaging Notes
The HEA is measured on a standard anteroposterior (AP) pelvis radiograph. To obtain the angle, first draw Hilgenreiner's line through both triradiate cartilages, then draw a second line along the plane of the proximal femoral epiphyseal plate. The angle formed between these two lines represents the HEA. Accurate positioning is essential: the pelvis must be neutral without rotation or tilt, and the hips should be in the neutral position with the legs slightly internally rotated to profile the femoral necks adequately.
Because the measurement depends on clear visualization of the physis, image quality and patient cooperation are critical. In very young infants where ossification is minimal, correlation with ultrasound (Graf method) may complement radiographic findings. Bilateral comparison is recommended, as asymmetry can be an early indicator of unilateral hip pathology.