Developmental dysplasia of the hipz
Definition
- Represents the gamut of disorders including: dysplasia, subluxation, & dislocation
- spectrum of abnormalities from dysplasia to subluxation to dislocation
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characterised by altered femoral and/or acetabular structure
- child with subluxable, reducible or unreducible hip where femoral head does not have normal relationship with acetabulum
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may not be present at birth (- not DDH)
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i.e. refers to the full spectrum of alterations of hip growth & stability that occurs in the intra-uterine, newborn & neonatal stages
- Instability
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Ability to dislocate or reduce femoral head into or out of acetabulum
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Dislocated
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complete loss of contact between femoral head & acetabulum
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Subluxation
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partial contact
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Femoral head is not articulating with most medial portion of acetabulum
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Irreducible
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Dysplasia
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AbN acetabulum where it is both shallower than N & its inclination is more vertical than N
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Late presentation
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Acetabular dysplasia
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acetabular cavity is shallower than normal & acetabular inclination is more vertical
- Coverage
- usu defined as centre edge angle
- greater the centre edge angle implies greater coverage & the larger surface area over which wt is distributed & hence less tendency to Osteoarthritis
- Congruence
- measure of the roundness of the femoral head & acetabulum
- Congruent incongruency
- matching of head & acetabulum in one position, but the head is not spherical
- Shenton’s line
- when broken there is loss of congruency
- Containment
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