DDH - Imaging - OrthoNet AI

Modern Study Review (AI-Generated)

High-Yield Summary

Developmental Dysplasia of the Hip (DDH) is a spectrum of hip joint abnormalities ranging from mild acetabular dysplasia to frank dislocation. Early and accurate imaging is critical for diagnosis and guiding treatment to prevent long-term morbidity such as gait abnormalities and early osteoarthritis. Ultrasound is the preferred modality in infants under 4-6 months, while radiographs become more reliable after ossification begins. Understanding key imaging landmarks and classification systems is essential for timely intervention.

Key Diagnostic Findings

Anatomy

Hilgenreiner’s Line: Horizontal line through the triradiate cartilages of the pelvis.
Perkins’ Line: Vertical line perpendicular to Hilgenreiner’s line at the lateral edge of the acetabulum.
Shenton’s Line: Smooth curvilinear line along the inferior border of the superior pubic ramus and medial border of the femoral neck; disruption suggests subluxation or dislocation.
Teardrop Figure: Radiographic landmark formed by the acetabular notch and adjacent structures; in DDH, it is often wide and underdeveloped due to lack of femoral head stimulus.

Clinical Presentation

Limited hip abduction in infants.
Asymmetric thigh or gluteal folds.
Positive Ortolani or Barlow maneuvers in neonates.

Imaging

Modality	Key Features	Age Applicability
Ultrasound	Graf method: measures alpha (acetabular roof slope) and beta (labral inclination) angles. Alpha >60° normal; higher alpha indicates better coverage. Beta angle increases with labral displacement.	Best <4-6 months (before ossification)
X-ray	Use after 4-6 months when ossification centers appear. Assess acetabular index (normal decreases with age), Shenton’s line, and femoral head position relative to Perkins and Hilgenreiner lines.	>4-6 months

Classification Systems

System	Description	Notes
Tönnis Classification	Grades hip displacement on AP pelvis radiograph based on femoral head position relative to quadrants formed by Perkins and Hilgenreiner lines.	Grade 1: Located; Grade 4: Complete dislocation
Graf Classification	Ultrasound-based system categorizing hips by alpha and beta angles and morphology into types I (normal) to IV (dislocated).	Widely used for early diagnosis

Current Gold Standard Treatment

Non-operative

Pavlik Harness: First-line for infants <6 months with reducible hips; maintains hip in flexion and abduction to promote concentric reduction and acetabular development.
Close Monitoring: Serial ultrasounds or radiographs to ensure reduction and acetabular development.
Indications: Stable or reducible hips without fixed dislocation.

Operative

Indications: Failure of harness treatment, irreducible dislocation, or late presentation (>6 months).
Procedures:
Closed reduction with spica casting (usually under 6-18 months).
Open reduction +/- pelvic osteotomy (e.g., Salter, Pemberton) for acetabular dysplasia or older children.
Femoral osteotomy may be added for femoral head/neck alignment.

Modern Complications & Outcomes

Complications

Complication	Description
Avascular Necrosis (AVN)	Most feared complication; risk increased with forceful reduction or prolonged immobilization.
Residual Dysplasia	Persistent acetabular insufficiency requiring late osteotomy.
Re-dislocation	Failure of reduction, often due to inadequate immobilization or soft tissue interposition.
Nerve Injury	Rare, but possible with surgical intervention.

Outcomes

Early diagnosis and treatment correlate with excellent functional outcomes and normal hip development.
Delayed diagnosis increases risk of AVN, residual dysplasia, and early osteoarthritis.
Long-term follow-up into adolescence is recommended to monitor acetabular development and hip function.

Classic Clinical Notes

DDH – Imaging

Developmental Dysplasia of the Hip – Imaging

X-rays

Perkins (Vertical) and Hilgenreiner’s (Horizontal) Line

Shenton’s line

Teardrop is not ossified and is WIDE (does not have the femoral head to push against it and stimulate development)

Tonnis grades of dislocation: a located hip lies in inferomedial quadrant of Perkins/Hilgenreiners

Acetabular Index

25-35 in the newborn

should decrease to no more than 25 in the 25 month old

should follow it to make sure that it continues to go in the right direction

Ultrasound

better than x-ray for the first 3 months

Graf technique – reliable at about 2-4 weeks of age (enough ossification to make it valid)

alpha angle represents slope of the acetabulum – the shallower the acetabulum, the smaller this angle becomes – therefore want lots of alpha! (normal > 60)

beta angle represents slope of cartilaginous labrum – as the hip dislocates, the labrum gets pushed up and away from vertical, increasing the angle – hence, you want less beta (normal)

Last Updated on January 25, 2026 by orthonet