During a newborn screening program in Delhi, two infants with developmental dysplasia of the hip are identified. Infant A has a positive Ortolani test with a palpable clunk and a normal abduction angle. Infant B has a negative Ortolani test but restricted abduction (<50°) and a positive Barlow test. Which clinical finding best distinguishes Infant A (acute/recent dislocation) from Infant B (chronic/neglected dislocation)?

Explanation

## Acute vs. Chronic DDH: Clinical Discrimination ### Pathophysiological Progression **Key Point:** The natural history of untreated DDH progresses from a *reducible* dislocated hip (acute) to a *fixed* dislocated hip (chronic) as soft tissue contractures develop over weeks to months. | Stage | Ortolani Test | Abduction Limit | Barlow Test | Pathology | |-------|---------------|-----------------|-------------|----------| | **Acute Dislocation** | **Positive (clunk)** | Normal (>60°) | May be positive | Femoral head dislocated; no contracture | | **Chronic/Neglected** | **Negative** | **Severely restricted (<50°)** | May be positive | Fixed dislocation; capsular & muscle contracture | ### Why Abduction Restriction Develops 1. **Weeks 1–2:** Hip remains dislocated; soft tissues begin to shorten 2. **Weeks 2–4:** Adductor muscles, hip capsule, and ligamentum teres contract 3. **Weeks 4+:** Fibrosis and muscle contracture become fixed; Ortolani maneuver can no longer reduce the hip 4. **Result:** Progressive loss of abduction; Ortolani becomes negative (hip cannot be reduced) **High-Yield:** **Degree of abduction restriction is the most sensitive indicator of chronicity.** A hip with <50° abduction indicates chronic dislocation with established contractures; a hip with >60° abduction indicates acute/recent dislocation that is still reducible. ### Clinical Pearl Infant A (normal abduction, positive Ortolani) = **acute dislocation** — the hip is out but can still be reduced because soft tissues have not yet contracted. Infant B (restricted abduction <50°, negative Ortolani) = **chronic/neglected dislocation** — the hip is fixed out due to muscle and capsular contracture; reduction is no longer possible by clinical maneuver alone. **Mnemonic:** **CAR** — **C**hronic = **A**bduction **R**estricted (contracture); Acute = Abduction Adequate. [cite:Tuli's Orthopedics 6e Ch 8]