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Pathogenesis of DDH

- See: Impediments to Reduction

- Discussion:
    - dislocated femoral head:
          - femoral head and neck remain anteverted and in the valgus position;
          - is pulled proximally & laterally by hip abductors;
          - becomes misshapen & flattened;
          - has delayed ossification of capital epiphysis;
    - muscles crossing the hip jont (hamstring, hip adductors, & psoas) become shortened and contracted;
           - psoas cross acetabulum, blocking reduction;
                 - arthrogram may show hour glass configuration of joint space;
           - if hip remains dislocated (for weeks), limitation of abduction becomes a more consistent clinical finding;
    - hip joint fills w/ fibrofatty debris known as pulvinar;
    - acetabular labrum
           - becomes enlarged along the superior, posterior, and inferior rim;
           - may infold into joint (inverted limbus);
           - limbus blocks reduction of femoral head;
    - acetabulum
           - becomes flattened (dysplastic) becuase it is not stimulated to develop around the absent femoral head;
    - ligamentum teres becomes lengthened, hypertrophic & redundant;
    - transverse acetabular ligament:
          - is pulled superiorly w/ capsule which blocks lower portion of acetabulum;
    - capsule of hip joint becomes expanded