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Developmental Dysplasia of the Hip

Introduction

  • Developmental dysplasia of the hip (DDH) is an umbrella term that encompasses a wide range of congenital problems of alignment of the head of the femur and the acetabulum
  • These may be teratogenic or sporadic

Pathogenesis

  • The pathophysiology of DDH is poorly understood, especially non-teratogenic forms
  • Pre-natal factors : mostly play a mechanical role
    • Constrained uterine environment, particularly in the last trimester
    • Excess birth weight
    • Oligohydramnios
    • Breech presentation
  • Post-natal factors : perhaps account for the geographic and ethnic differences in DDH
    • Swaddling techniques

Aetiology              

  • Malalignment of the developing hip and femur prevents correct development either in the intrauterine or extra-uterine environment
    • Correct alignment is essential for proper development of the acetabulum
    • Without proper intervention, the resultant joint space will be malformed and will lead to greater disability and dysfunction as the child develops
  • I think that theories about swaddling techniques are very interesting, but I imagine that intrauterine factors (especially space-limiting conditions that would directly affect limb rotation and alignment) are the most compelling factors in disease development

Nutritional factors         

  • Maternal nutrition may play a role in allowing a child a proper intrauterine growth environment
  • In particular, gestational diabetes can lead to extreme increases in fetal size, which would restrict intrauterine space and may play a role in preventing proper limb rotation during the 3rd trimester

Risk factors        

  • Breech position
  • Positive family history
  • Female sex
  • Firstborn
  • Oligohydramnios

Natural History

  • DDH prevalence in unscreened populations is estimated to be 1.3 per 1000 live births
  • There is much geographic variation in prevalence
    • Lowest 1.7/1000 in Sweden
    • Highest 188.5/1000 in one region of Manitoba, Canada
  • Post-natal risk factors, e.g. swaddling techniques, may account for such a wide variation

Clinical Presentation

  • Children with DDH may present with
    • Asymmetric thigh folds
    • Excessive hip motility or flexibility
    • Asymmetric leg length
  • Hip instability or true dislocation may be evoked by the Barlow or the Ortolani manoeuvres
    • The Barlow manoeuvre adducts the flexed hip and pushes the thigh posteriorly to attempt to dislocate the hip joint
    • The Ortolani test is the reverse; the examiner tries to reduce a dislocated hip

Late presentation

  • Children whose hips escape examination or in whom DDH is not detected, may present with
    • Limping
    • Obvious leg-length discrepancy
    • Waddling gait
    • Excessive lordosis, to accommodate the leg length difference
  • These children have far more difficult disease to treat, due to the obvious deformities in the femur and acetabulum
  • They require more invasive treatment in order to correct the problem

Psychosocial impact of disease                

  • No parent wants to have a child with a disease or malformation
  • Treatments for DDH usually involve serial casting, braces or corrective surgeries, all of which may traumatize or stigmatize children and their parents
  • Untreated disease can result in serious orthopaedic deformities and limping, both of which can be very stigmatizing

Imaging and Diagnostic Studies

  • There can be some degree of perceived hip instability in newborns in up to 1 in 100 live births
  • Because DDH encompasses a wide variety of hip defects, their common presentation is one of perceived hip instability either through the Ortolani or Barlow maneuver
  • Many centers (especially those in Europe) now routinely ultrasound infants' hips to elucidate true DDH from normal variation of mobility and stability

X-ray

  • Best reserved for children over 6 months of age, to allow ossification of the bones to happen
  • Less operator dependent than US, though they do expose children to radiation
  • Assess the alignment of the hip and its position within the joint according to landmarks
    • Hilgenreiner's line
    • Perkin's line
    • Shenton's line

Ultrasonography

  • In children under 6 months the best imaging modality is ultrasound, as the joints are primarily carilagenous and are not visible on X-Ray
  • On ultrasound, a truly dislocated hip will appear outside of the acetabular fossa
  • Ultrasonographic screening may be the best method of routinely assessing newborns for DDH
  • This is routinely done in most of continental Europe
  • Ultrasound, being relatively inexpensive and non-invasive, may prevent future expensive and invasive interventions and therefore represents a beneficial intervention to do on most infants

Laboratory evidence     

  • Teratogenic hip dislocation may have other associated lab abnormalities, however the vast majority of DDH children are otherwise healthy

Treatment

  • Cases detected early are usually treated with braces to properly align the hip and avoid future surgical intervention

Outcome

  • Braces work!
  • A significant portion of people requiring total-hip-replacements under 60 years of age suffer from long term consequences of DDH
    • 4.8% for congenital hip disorders
    • 24.0% for DDH

Complications

  • The risks of serial splinting and braces are mostly minor
    • Skin irritation
    • Muscular irritation or contraction
    • Disuse weakness
  • Castings tend to be short-term (weeks rather than months) and, at least here in the US, most children with DDH do well in the short- and intermediate-term
  • Surgical risk include osteonecrosis, especially in the older child

Related Topics

Native American and Eastern European cultures routinely swaddle their infants in positions that bring the hips into extension, putting tension on the developing joint and possibly explaining these two population's high prevalence of DDH

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