Developmental Hip Dysplasia
KEY FACTS
Imaging
- • Shallow acetabulum ± subluxation of femoral head
- • US useful before 6 months of age
- • Normal hip
- • Subluxation: < 50% bony coverage at rest
- • Dislocation: Femoral head lies completely outside of bony acetabulum at rest
- • Modified Graf staging
Type Ia = mature hip, angular bony promontory, α > 60°, β < 55°
Type Ib = mature hip, roundish bony promontory, α > 60°, β < 55°
Type IIa = physiologic immaturity < 3 months, α = 50-60°, β = 55-77°
Type IIb = immaturity > 3 months, α = 50-60°, β = 55-77°
Type IIc = critical hip, subluxation, α = 43-49°, β > 77°
Type III = dislocated hip, α < 43°
Type IV = dislocated hip, inverted labrum, α < 43°
- • Roundish anterior acetabular rim can be physiological and often seen in immature hips
- • Obtain single image showing deepest part of acetabulum, triradiate cartilage, center of femoral head, straight iliac contour
, cartilaginous acetabular roof 
, acetabular labrum 
, triradiate cartilage 
, ischium 
, and ossified femoral metaphysis 
.
, acetabular labrum 
, femoral metaphysis 
, and gluteal muscle are shown.
, acetabular roof 
, between the acetabular promontory and the tip of acetabular labrum 
, and the α and β angles formed by the intersection of these lines.
.IMAGING
General Features
Ultrasonographic Findings
- • Both morphology (coronal and transverse views) and dynamic evaluation
- • Morphology: Graf technique
Coronal (“egg in spoon”) view
- – Most important image
- – Obtained from lateral approach with hip and knee in slight (~ 20°) flexion; infant in decubitus (or supine) position
- – Align transducer 10-15° obliquely (usually posteriorly) from coronal plane to obtain straight iliac line
- – Obtain single image showing deepest part of acetabulum, triradiate cartilage, center of femoral head, straight iliac contour
- – Normal hip
Transverse (“ice cream cone”) view
3 lines drawn on coronal view to assess acetabular morphology
- – Line along straight contour of ilium (iliac line)
- – Line along osseous acetabular roof
- – α angle measured at intersection between iliac line and line along osseous acetabular roof
- – Line from promontory to tip of labrum
- – β angle measured at intersection between iliac line and line from acetabular promontory to tip of labrum
Modified Graf staging
- – Type Ia = mature hip, angular bony promontory, α > 60°, β < 55°
- – Type Ib = mature hip, roundish bony promontory, α > 60°, β < 55°
- – Type IIa = physiologic immaturity < 3 months, α = 50-60°, β = 55-77°
- – Type IIb = delayed ossification = immaturity > 3 months, α = 50-60°, β = 55-77°
- – Type IIc = very deficient acetabulum = subluxation, α = 43-49°, β > 77°
- – Type III = dislocated hip, α < 43°
- – Type IV = severe dysplasia = dislocated hip, inverted labrum, α < 43°
- • Dynamic testing: Apply Barlow maneuver (i.e., posterior force on adducted and flexed hip)
Attempt to displace femoral head from acetabulum during real-time imaging
Lack of relaxation by infant can limit acquisition of optimal stress view and can produce false-negative examination
Acetabular bony coverage
- – Portion of femoral head contained within bony acetabulum
- – Center of femoral head relative to iliac straight line
- – Capsular laxity: > 50% bony coverage femoral head at rest, < 50% bone coverage on stress examination or active movement
- – Subluxation: < 50% bony coverage at rest
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