A 3-month-old girl born to non-consanguineous parents is screened for hip dysplasia. On examination, she has a positive Barlow test but a negative Ortolani test. Her mother asks what distinguishes developmental dysplasia of the hip (DDH) from hip dislocation. Which clinical finding is the best discriminator between a dislocatable hip and a truly dislocated hip?

Explanation

## Distinguishing Dislocatable from Dislocated Hip ### Clinical Examination Maneuvers **Key Point:** The Ortolani test (reduction maneuver) is the gold standard for detecting a *dislocated* hip that can be reduced, whereas the Barlow test (provocation maneuver) detects a *dislocatable* but currently located hip. | Feature | Dislocatable Hip | Dislocated Hip | |---------|------------------|----------------| | **Ortolani Test** | Negative (hip already in socket) | **Positive — clunk on abduction** | | **Barlow Test** | **Positive — clunk on adduction** | May be positive or negative | | **Abduction Limit** | Usually normal (>60°) | Restricted (<60°) | | **Skin Fold Asymmetry** | May be present in both | Non-specific finding | ### Mechanism of the Ortolani Test 1. Hip is flexed to 90° and adducted (starting position: dislocated) 2. Examiner abducts the hip while applying gentle anterior pressure 3. **Positive result:** Palpable clunk as femoral head reduces into acetabulum 4. This clunk indicates the hip was *out* and is now *in* — diagnostic of dislocation **High-Yield:** A positive Ortolani test = **dislocated hip that is reducible**. This is the most specific finding for true dislocation in the neonatal period. ### Clinical Pearl In this case, the infant has a **positive Barlow** (dislocatable) but **negative Ortolani** (not currently dislocated). This represents DDH with hip instability but no frank dislocation — the hip remains in the socket at rest. **Mnemonic:** **OBOE** — **O**rtolani = **O**ut-then-in (reduction); **B**arlow = **B**ad (provokes dislocation). [cite:Tuli's Orthopedics 6e Ch 8]