Developmental Dysplasia of Hip

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### Definition - **Developmental Dysplasia of the Hip (DDH):** A spectrum of conditions ranging from mild acetabular dysplasia to irreducible dislocation of the femoral head from the acetabulum. - Can be unilateral or bilateral. ### Risk Factors (mnemonic: BREECH) - **B**reech presentation (especially frank breech) - **R**ight hip (3x more common than left for unilateral) - **E**lasticity of ligaments (maternal hormones) - **E**xchange of amniotic fluid (oligohydramnios) - **C**ongenital musculoskeletal anomalies (e.g., torticollis, metatarsus adductus) - **H**istory (family history of DDH) - **F**emale sex (4-6x more common) - **F**irstborn child ### Clinical Presentation #### Neonates & Infants ( 3 months) - **Limited hip abduction:** Key sign. - **Galeazzi sign (Allis sign):** Apparent leg length discrepancy when hips and knees are flexed (dislocated side appears shorter). - **Trendelenburg gait:** Positive sign if unilateral (pelvis drops on unsupported side). - Toe walking, waddling gait (if bilateral). ### Diagnosis #### Imaging - **Ultrasound (US):** Preferred for infants 4-6 months (ossification of femoral head). - **Key X-ray lines:** - **Hilgenreiner's line:** Horizontal line through triradiate cartilages. - **Perkin's line:** Vertical line perpendicular to Hilgenreiner's, passing through lateral margin of acetabulum. - **Shenton's line:** Smooth curvilinear line from medial aspect of femoral neck to inferior border of superior pubic ramus (disrupted in dislocation). - **Acetabular index:** Angle formed by Hilgenreiner's line and a line connecting the acetabular roof (normal ### Treatment #### 18 months - **Open Reduction:** Almost always required. - Often combined with osteotomies (pelvic and/or femoral) to reshape bone and improve hip stability. ### Prognosis - Early diagnosis and treatment lead to excellent outcomes. - Untreated or late-diagnosed DDH can lead to: - Persistent hip instability. - Early onset osteoarthritis. - Pain and functional limitations. - Leg length discrepancy.