Type | Alpha angle | Beta angle | Bony roof | Ossific rim | Cartilage roof | Interpretation |
I a | >60 | <55 | good | sharp | covers femoral head | mature |
I b | >60 | >55 | good | usually blunt | covers head | mature |
II a | 50-59 | >55 | deficient | rounded | covers head | < 3 months of age (physiological ossification delay) |
II b | 50-59 | >55 | deficient | rounded | covers head | > 3 months of age |
II c | 43-49 | <77 | deficient | rounded/flat | covers head | |
II d | 43-49 | >77 | severely deficient | rounded/flat | compressed | on point of dislocation |
III a | <43 | >77 | poor | flat | displaced up echo poor | dislocated |
III b | <43 | >77 | poor | flat | displaced up reflective | dislocated |
IV | <43 | >77 | poor | flat | interposed | dislocated |