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- See:
      - Pathogenesis of DDH
      - Table I

- Discussion:
    - soft-tissue impediments to adequate reduction include:
         - constriction of the joint capsule of hip: most important type of obstruction in older children;
         - contraction of the psoas tendon over acetabular inlet;
         - hypertrophy of the transverse acetabular ligament;
         - pulvinar, or the ligamentum teres;
              - as children reach walking age, hypertrophy of the ligament may preclude hip reduction unless ligament is excised;
         - inverted neolimbus:
              - rare type of obstruction in DDH;
              - formed when dislocated femoral head is above or behind labrum;
              - lip of hypertrophied fibrocartilage may be infolded or everted;
              - may be adherent to hip capsule or supra-acetabular iliac wall;

- Infants Younger than 2 months;
    - when soft-tissue impediments prevent congruent reduction, positioning of hip in safe position (using Pavlik harness) may allow femoral head to overcome soft tissue impediments & become adequately reduced;
           - do not continue w/ this form of treatment for more than 4 weeks, since process of acetabular dysplasia and soft tissue adaptive changes will continue as long as hip remains dislocated;

- Infants Older than 2 months;
    - in children who are older than two months, spica cast may allow femoral head to overcome soft tissue impediments & become adequately reduced;
           - do not continue w/ this form of treatment for more than 4 weeks, since process of acetabular dysplasia and soft tissue adaptive changes will continue as long as hip remains dislocated