- refers to the full spectrum of alterations of hip growth & stability that occurs in the intra-uterine, newborn & neonatal stages
- spectrum of abnormalities from dysplasia to subluxation to dislocation
- characterised by altered femoral and/or acetabular structure
Definitions and Terminology
- Instability
- Ability to dislocate or reduce femoral head into or out of acetabulum
- Dislocated
- complete loss of contact between femoral head & acetabulum
- Subluxation
- partial contact
- Femoral head is not articulating with most medial portion of acetabulum
- Irreducible
- unable to be reduced
- Dysplasia
- AbN acetabulum where it is both shallower than N & its inclination is more vertical than N
- Late presentation
- after 6 months
- Acetabular dysplasia
- 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
- measure of subluxation