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