Developmental Hip Dysplasia (DDH)
NUTSHELL DEVELOPMENTAL HIP DYSPLASIA © 2025 D.Magid, MD, M.Ed
No Longer called “congenital DH’ since many, esp. CP, born normal but become increasingly dysplastic with on-going modified weight bearing and muscle imbalances.
1 to 1.5/1000 live births, Left>Right (fetal lie across sacrum), 80% female
EMBRYOLOGY: pre-cartilaginous anlage cleaves 7-11 wks, forming joint
Head grows faster than acetabulum, free ROM induces sphericity
Laxity and uncovered head maximizes ROM for safe delivery; acetabular growth spurt first few weeks
Action of head against acetabulum INDUCES spherical ‘ball’ in spherical ‘socket’
Neonatal pelvis mostly cartilage; residual fetal hip flexion XR measurements and landmarks very ‘soft’
ETIOLOGIES:
Some genetic/ethnic influence/tendancy (Native American, Lapp, etc)
Limited intrauterine space: first pregnancy, multiple fetuses, disproportionate paternal size, oligohydramnios
Breech birth (25-40% of DDH?), over-swaddling
Prenatal conditions: arthrogryposis, neurologic disease, Down and certain syndromes
CP or neurologic imbalances: Wollfe’s law
CAPITAL EPIPHYSIS (femoral head ossification center) does not ossify until 6-9 months
Successful treatment only with early/immediate diagnosis—clinical suspicion/experience primary to diagnosis
Many neonatal hips indeterminate or subluxable but rapidly ‘tighten’; physical exam highly operator-dependent
US best first few months (operator-dependent)
XR: meticulous positioning; less useful until heads ossifying
RADIOGRAPHIC LANDMARKS AND SIGNS
Asymmetry of capital epiphysis ossification, size, shape, and/or radiodensity
HILGENREINER’S LINE: baseline across the superior bony margin of triradiate cartilage lucency
PERKIN’S LINE: from superior lateral ossified acetabulum dropping perpendicularly to Hilgenreiner’s line
Ossification center should be in medial inferior quadrant formed by 2 lines’ junction
ACETABULAR ANGLE: line from most inferior to most superior ossified acetabular landmarks.
Normal~28 degres and symmetric;then decreases with age as acetabulum deepens/ossifies
DDH: increased bec acetabular growth/induction delayed
SHENTON’S LINE: reflects subluxation rather than dysplasia
Smooth arc or curve from inferior margin superior pubic ramus to medial femoral neck.
Elongation, asymmetry, =s subluxed proximal femur
CT: only if low-mAs,and VERY limited number of slices, in precisely positioned infant; 3D NOT INDICATED!
Most useful for post-op in abduction spica cast: confirms head remains reduced into acetabulum and symmetric
MR: evaluates cartilage, labrum, ligamentum teres, and AVN (more often 2dary to treatment than 1ary)
BUT usually needs sedation; expensive