Developmental Dysplasia of the Hip in Children

Epidemiology and predisposing factors

The population prevalence of the pathology ranges from 0.1–20%, with true congenital dislocation detected in 0.1–0.4% of newborns.

Key risk factors are formed intrauterinely and genetically:

• Breech presentation of the fetus and birth as a firstborn.
• Female sex: estrogens produced by the fetus itself cause additional relaxation of the ligamentous apparatus of the joint.
• Hereditary predisposition (burdened family history), as well as racial characteristics.

Cultural infant care habits are of immense importance. For example, the traditions of Southeast Asian peoples of carrying children on their backs with their legs widely abducted protect the joint from decentration, so the incidence of the pathology is minimal there. Conversely, the practice of tight swaddling among the indigenous population of North America leads to a sharp increase in morbidity. Within the Russian Federation, high rates are recorded in the Nenets Autonomous Okrug (up to 8.7–10.9%) and the North Caucasus (3.4%).

Normal ultrasound anatomy of the joint

Sonography serves as the primary imaging method for the developing joint, avoiding radiation exposure to the infant.

The normal ultrasound picture includes the following parameters:

• Centered position of the femoral head within the acetabulum.
• Sufficient degree of coverage of the bony head by the anatomical roof of the acetabulum.
• Correct shape of the bony contours of the acetabulum and intact cartilaginous labrum (cartilaginous labrum).
• Initial markers of ossification of the femoral head epiphysis.
• Compliance of Graf angles with normative values: the alpha angle (alpha) and beta angle (beta) lie within normal limits (normally, the alpha angle is at least 60°, for example, 63°).

Radiological landmarks and Putti's triad

To objectively assess anatomical relationships on a pelvic overview radiograph, a grid of reference lines is constructed:

• Hilgenreiner's line (Hilgenreiner's line) is the baseline horizontal connecting the inferior points of the Y-shaped (triradiate) cartilages.
• Perkin's line (Perkin's line) is the vertical dropped perpendicular to the baseline horizontal from the outermost edge of the bony acetabular roof.
• Shenton's line (Shenton's line) is an arch smoothly running along the inner surface of the femoral neck to the lower border of the superior pubic ramus; displacement of the femur makes this arch discontinuous.
• Medial gap (medial gap) is the interval between the acetabular floor and the adjacent edge of the femur, which increases in pathology.

To confirm severe dysplasia and dislocation, Putti's triad is evaluated:

1. Increase in the acetabular angle — obliquity of the acetabular roof relative to Hilgenreiner's horizontal line.
2. Delayed ossification of the femoral head nucleus — hypoplasia or delayed appearance of the epiphyseal center of ossification.
3. Superolateral displacement of the proximal femur — the landmarks exit lateral to Perkin's vertical and superior to Hilgenreiner's horizontal.

Surgical management and radiation control

Severe degrees of displacement require surgical intervention — open reduction of the femoral head (open reduction) combined with internal fixation (internal fixation). To consolidate the joint in the postoperative period, immobilization using a hip spica cast (spica cast) is used.

Standards for radiological support and interdisciplinary examination:

• Three-dimensional CT reconstruction (in maximum intensity projection mode, MIP) is used after surgery to confirm congruence and correct reduction of the head.
• Multidisciplinary team: primary examination by a pediatrician and an anesthesiologist-resuscitator is mandatory; in case of signs of vascular thrombosis, a vascular surgeon is involved, and for paresis or altered consciousness, a neurologist.
• If concomitant bone trauma of the proximal femur is suspected, direct radiography of the damaged and contralateral healthy joint, as well as an additional axial projection, must be performed.

Class and exam questions

What else to study on this topic

• T2 mapping of articular cartilage under load on MRI in dysplasia
• High-resolution CT arthrography for detecting labral defects
• Differential diagnosis of dysplasia, transient synovitis, and Legg-Calvé-Perthes disease
• Pathogenesis of the transformation of infant dysplasia into secondary coxarthrosis in adults
• Epidemiology of proximal femoral fractures in elderly patients

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.