DDH: Screening, Diagnosis, and Treatment Guidelines

Developmental Dysplasia of the Hip (DDH) is the most common orthopaedic disorder in newborns. It is not a static condition but a spectrum—from a shallow acetabulum (dysplasia) to a subluxatable hip, to a frankly dislocated teratologic hip.

The goal of screening and treatment is simple: a concentric, stable reduction to stimulate normal acetabular development. Failure to achieve this leads to early osteoarthritis and lifelong disability.

Visual Element: An infographic of the "DDH Spectrum": Normal Hip -> Dysplastic (Shallow) -> Subluxated (Head riding on rim) -> Dislocated (Head outside acetabulum).

The Etiology: Risk Factors (The 4 F's)

While many cases are idiopathic, the classic risk factors remain:

1. Female (6:1 ratio vs males. Estrogen sensitivity leads to ligament laxity).
2. First Born (Tight uterus -> mechanical constraint).
3. Feet First (Breech presentation. The most significant mechanical risk factor).
4. Family History (Genetics play a strong role). Also: Oligohydramnios and packaging disorders (torticollis, metatarsus adductus).

Screening Guidelines: The Global Debate

Clinical Screening (Universal)

Every newborn must be examined.

• Barlow Test: "Bad" test. Adduct and push posterior. Attempts to dislocate a stable hip. (Provocative).
• Ortolani Test: "Out to In". Abduct and lift anterior. Attempts to reduce a dislocated hip. The "Clunk" is the feeling of the head reducing. (Therapeutic).
• Galeazzi Sign: Knee height discrepancy. Only valid in unilateral cases.
• Limitations: Clinical exam misses up to 50% of dysplastic (but stable) hips.

Ultrasound Screening (Selective vs Universal)

• Universal Ultrasound (Austria/Germany): Screen every baby. High cost, high rate of "over-treatment" of physiologic immaturity (Graf 2a).
• Selective Ultrasound (UK/USA/Australia): Screen only "High Risk" babies (Breech, Family Hx, or Abnormal Exam).
• Timing: Perform at 6 weeks. Before 6 weeks, maternal hormones cause physiologic laxity that usually resolves spontaneously. Ultrasound too early leads to unnecessary stress and treatment.

The Graf Classification (Ultrasound)

Professor Reinhard Graf revolutionized DDH with hip sonography. You must speak this language.

Visual Element: A schematic of the Standard Coronal Plane ultrasound. Labeling: Ilium (Straight line), Labrum, Bony Roof (Alpha angle), Cartilage Roof (Beta angle).

Clinical Pearl: The Alpha angle measures the bony roof (acetabular depth). The Beta angle measures the cartilaginous roof (labrum). As the bone gets worse (Alpha drops), the labrum works harder to hold the hip in (Beta rises) until it fails (Type D).

Treatment: The Pavlik Harness

The Pavlik harness is a dynamic flexion-abduction orthosis. It works by the "Principle of Reciprocal Action"—when the baby kicks (extends), the posterior straps pull the hip into flexion. When the baby adducts, the anterior straps check the motion.

Application Technique

• Chest Strap: Nipple line. Two fingers breadth space (to allow breathing).
• Anterior Straps: Flexion straps. Hold hip at 90-100° flexion.
• Posterior Straps: Abduction straps. Prevent adduction.

The "Safe Zone" of Ramsey

This is the range of abduction where the hip is reduced but safe.

• Limit of Adduction: The angle where the hip pops out (redislocates).
• Limit of Abduction: The angle where the hip is forced against the acetabulum. Danger: Excessive abduction causes AVN (Avascular Necrosis) by pinching the circumflex vessels.
• The Goal: The harness keeps the hip in the middle of this zone.

Pavlik Disease

If the hip is not reducible (e.g., inverted labrum), and you leave it in a harness, the femoral head grinds against the posterior acetabular rim. This causes erosion of the posterior wall (Pavlik disease), making future reduction harder.

• Rule: If not reduced in 3 weeks by ultrasound -> ABANDON HARNESS. Move to rigid abduction brace (Ilfeld) or closed reduction.

Treatment of the Late Presenter (> 6 months)

Once the ossific nucleus appears (4-6 months), ultrasound is useless. We rely on X-rays.

Radiographic Lines

• Hilgenreiner’s Line: Horizontal through triradiate cartilages.
• Perkin’s Line: Vertical from lateral acetabular edge.
• Shenton’s Line: Arc along femoral neck and obturator foramen. (Broken in dislocation).
• Acetabular Index (AI): Angle of the roof. Normal is <25° at 1 year. >30° is dysplastic.

Management Steps

1. Closed Reduction: Examination Under Anaesthesia (EUA) + Arthrogram. If stable -> Spica Cast.
2. Open Reduction: If closed reduction fails (adductor tight, psoas constriction, inverted limbus). Usually medial or anterior approach.
3. Osteotomy:
   • Femoral: Varus Derotation Osteotomy (VDRO) if excessive valgus/anteversion.
   • Pelvic: Salter / Dega / Pemberton osteotomy to cover the head if acetabulum is shallow.

Conclusion

DDH is a time-sensitive diagnosis. A hip diagnosed at 2 weeks is cured with a strap. A hip diagnosed at 2 years needs major surgery. A hip diagnosed at 20 years needs a joint replacement.

Vigilance, selective screening, and safe harness use are the pillars of success.

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