July/August 2016
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The term developmental dysplasia of the hip (DDH)
indicates a spectrum of pathologies from stable acetabular dysplasia
to frankly dislocated hips. Congruent reduction and stability of the
femoral head are necessary for normal growth and development
of the hip joint. Failure to diagnose DDH and treat in infancy can
result in significant long-term disability.
Natural history studies have shown that untreated subluxation leads
to early degenerative joint disease in the hip, and untreated bilat-
eral dislocations can lead to excessive lumbar lordosis and chronic
low-back symptoms. Early detection and treatment of DDH is crit-
ical for the best chances of obtaining a well-functioning, pain-free
hip joint in adulthood. Early diagnosis can often be accomplished
through thorough physical examination of newborns.
While universal screening is advocated in many countries, in the
United States selective screening by ultrasound is indicated for
those children with risk factors for DDH (family history, breech
presentation, and unstable hip examination at the initial newborn
examination). Ultrasound screening for infants with risk factors for
DDH is recommended at age 6 weeks. Pavlik harness treatment for
children with unstable hips or significant dysplasia on ultrasound
is continued until the hips stabilize and show concentric reduction
on imaging. With time, diagnosis and treatment evolve to accom-
modate the growing child. Infants who fail to respond to nonop-
erative management may require more extensive interventions.
Reconstructive surgeries may be required in adolescents and young
adults, while hip replacement remains the treatment of choice in
adults with advanced arthritis.
It has been estimated that 5 percent to 10 percent of primary
osteoarthritis of the hip is due to dysplasia. Neonatal hip dysplasia
is the most common abnormal finding in newborns, affecting up
to 15 percent of infants based on ultrasound findings, with up to
90 percent of cases resolving spontaneously. The prevalence of
DDH is difficult to determine but approximately 0.5 percent to 2
percent of all newborns are treated for neonatal hip dysplasia. The
overall prevalence of hip dysplasia in the adult population is diffi-
cult to estimate because advanced deterioration of the hip joint
may obscure the primary cause of osteoarthritis. It is estimated that
only 10 percent of adults with residual hip dysplasia were identified
during childhood, making the overall prevalence up to 10 times
that estimated in the neonatal population.
The etiology of DDH remains a debate in the literature. Genetics,
as determined by family history and racial predilection, is a strong
contributor to the development of DDH. Intrauterine mechanical and
hormonal factors also exert significant influence on the development
DDH. Girls’ hips appear to be more sensitive to the ligamentous
laxity induced by the maternal hormone relaxin, which is thought to
contribute to the higher incidence of DDH in female infants. Infants
of multiple gestations, however, are not at an increased risk for DDH,
although twins are reported to have more “positional anomalies,”
such as metatarsus adductus and torticollis, thought to be caused
by increased intrauterine constraint. Perhaps similar to preterm
neonates, babies born from multiple gestations are protected by
their typical preterm birth and low birth weight.
Infant screening
For neonatal hip instability, the results of treatment are directly
related to the severity of the condition and the age at the time of
initial treatment. The best results and longest lasting hips are those
that are treated successfully with nonoperative methods during the
neonatal period.
Despite newborn screening programs, 1 in 5,000 children will have
a dislocated hip detected after 18 months of age. It is important
to appreciate that even with underlying dysplasia, late-presenting
dislocated hips are not always present at birth, and not all hips
dislocated at birth are detectable in the newborn period. In other
countries, particularly in Europe and Australia, universal ultrasound
screening is done to try to capture all cases of DDH in infancy, but
the debate between universal versus selective ultrasound screening
is ongoing. A recent Cochrane review found that neither universal
nor targeted ultrasound screening strategies have been demon-
strated to improve clinical outcomes, including the incidence of
late diagnosed DDH and need for surgery.
Adding further confusion to the debate over the approaches to
optimal DDH screening procedures for DDH is the report by the U.S.
Preventive Services Task Force, which found “insufficient evidence”
to recommend any routine DDH screening, including physical
examination. This recommendation was based on a lack of clear
evidence in the efficacy of infant screening to reduce the incidence
of late-presenting DDH. This view was subsequently rebuked by
both the Pediatric Orthopaedic Society of North America and the
American Academy of Pediatrics.
Recently, the American Academy of Orthopedic Surgeons (AAOS)—
endorsed by the American Academy of Pediatrics, the Pediatric
Society of North America, and the Society for Pediatric Radiology—
published a revised clinical practice guideline to aid in the early
diagnosis and initiation of appropriate intervention of DDH.
1
All
newborns should be screened for DDH by a properly trained health
care provider by physical examination. Risk factors for DDH should
be determined by the treating physician.
The AAOS findings are summarized as follows:
• Universal Ultrasound screening: Moderate evidence
supports not performing universal ultrasound screening of
newborn infants.
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