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DDH

Solomon Behar, MD and Ann Dietrich, MD
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A review of the risk factors and clinical findings associated with DDH.

Pearls:

  • DDH is the term used to describe the condition in which the femoral head has an abnormal relationship with the acetabulum.  DDH ranges from frank dislocation (luxation) to partial dislocation (subluxation).

  • Established risk factors for DDH prior to 3 months of age include: breech position, female sex, positive family history, first born status, and oligohydramnios.

  • Breech female infants all require an ultrasound of the hips around 6 weeks of age, even if the physical exam is negative.  

 

  • Why was Congenital Dislocation for the Hip changed to DDH?  DDH is now used because many of the findings of DDH may not be present at birth; the term DDH changes that perception.

    • During the immediate newborn period, hip capsule laxity predominates.  If it’s clinically significant, the femoral head may spontaneously dislocate and then relocate.  If the hip relocates and stabilizes within a few days, hip development is normal.

    • If subluxation or dislocation persists, structural anatomic changes may develop.  The position of the femoral head must be a deep concentric position in the acetabulum to have normal development of the hip.

  • What happens when the hip subluxes?  The labrum becomes inverted and flattened, resulting in the acetabulum not growing and becoming shallow; the muscles surrounding the hip, especially the abductors, become contracted, limiting abduction of the hip.

  • What risk factors are associated with later presenting DDH?  Children presenting with DDH after 3 months of age have fewer traditional risk factors.  A high index of suspicion of DDH in older infants and toddlers includes: a swaddling history, a leg length discrepancy, any asymmetry in hip abduction,  a positive Trendelenburg sign (a limp on the affected side), difficulty diapering as reported by the parents, abnormal thigh folds, and/or a positive Galeazzi sign.

    • To perform the Galeazzi maneuver: place the child in the supine position with both hips and knees flexed.  Look at the knees.  Any inequality in the height of the knees is a positive Galeazzi sign; a positive sign usually indicates a hip dislocation or a congenital femoral shortening.  

    • Children with a flexible foot deformity or congenital torticollis require a very careful hip evaluation for DDH.

Mulpuri K, et al.  What risk factors are associated with late-presenting dislocations of the hip in infants? 2016 May;474(5):1131-7. PMID: 26728512

  • What imaging aids in the diagnosis of DDH?  

    • In the first few months of life, ultrasound (US) is an accurate method for imaging because the cartilage can be visualized, the stability of the hip assessed, and the acetabulum evaluated.  

      • Currently, ultrasound is recommended as an adjunct to the clinical evaluation, to assess a high-risk infant, and/or to monitor progress of DDH in a child undergoing treatment.  US of all newborns is not recommended.

        • Accurate US results require training and experience.  US techniques include static and dynamic evaluation of the hip.

        • US during the first few weeks of life, even though it has considerable inter-observer variability, often reveals the presence of minor degrees of instability and acetabular immaturity.  Studies indicate that nearly all of these mild early findings on US which were not apparent on physical exam, will resolve spontaneously without treatment.

          • Newborn screening with US has required a high frequency of reexamination and results in a large number of hips being unnecessarily treated.

    • By 4-6 months of age, radiographs are reliable as the ossification center develops in the femoral head.

    • Between 4 and 6 months of age, US and plain films are equally as good at diagnosing DDH.

Editor’s Note:  When using imaging in premature babies, remember to use their corrected age.  For example, high risk infants in whom US is warranted, should be examined between 6-8 weeks corrected age.

  • What do the current clinical practice guidelines for early detection of DDH say?  All newborns are to be screened by physical exam and the hips should be examined at every well child visit..  The initial exam and the exam at 2 weeks are critical.   

    • If an unequivocal positive Ortolani or Barlow’s sign is found in the newborn exam, the infant should be referred to an orthopedist and no imaging is needed.

      • To perform the Ortolani (attempt to relocate a dislocated hip joint): Place the infant on his/her back, flex the hips and knees to 90 degrees, gently abduct by pushing the knee away from midline.  A positive sign if if you feel a distinctive clunk and then femoral head relocates inferiorly.

      • To perform the Barlow: Place the infant on their back, have his/her knees in your hand, bring the knee toward midline, apply light pressure under the knee which directs the force toward the bed posteriorly.  If the hip is “popped” out of the socket, the test is positive.

Editor’s Note:  The above maneuvers should be performed one hip at a time.  Remember, there are no pathognomonic signs for a dislocated hip.  The whole exam must be taken in clinical context and can often be confusing as we use terms such as clicks and clunks.  For example, as noted in the AAP guidelines, high-pitched clicks are commonly elicited with flexion and extension and are inconsequential.  A dislocatable hip has a distinctive clunk, whereas a subluxable hip feels loose.  Separating true dislocations (clunks) from instability from benign sounds (clicks) takes practice.  The full AAP guidelines can be found here.

    • If the initial exam in the newborn reveals a subtle finding, such as a small click, then one should reevaluate in two weeks.  If still positive, orthopedic referral is required.  

      • If the results of the physical exam are negative at 2 weeks, regular follow up at well child visits is appropriate.

    • The use of triple diapers is not recommended with an abnormal hip exam is detected.

  • What about high-risk infants who have a negative physical exam?  The AAP recommends getting US imaging at 6 weeks or a radiograph at 4 months of age.  For example, a female with a family history of DDH and/or born breech, even with a negative exam, would require imaging.  For males born breech, imaging recommendations are optional.

What are the consequences of missing DDH? Some sequelae include, but are not limited to, chronic pain, degenerative joint disease, osteoarthritis, limping, and/or leg length discrepancies.  

Sara B., MD -

Is it recommended to correct for gestational age when ordering the hip ultrasound at 6 weeks of life?

Solomon B., MD -

Hi Sara-
there is no official AAP recommendation to change the timing of hip US in preterm babies.

Some research (Orak et al. Is prematurity a risk factor for developmental dysplasia of the hip? : a prospective study. Bone Joint J. 2015 May;97-B(5):716-20. doi: 10.1302/0301-620X.97B5.34010) shows that in babies without risk factors for DDH, the incidence of DDH may be lower than in full term babies- thought to possibly be due to less time with pressure on the developing hip.

However, in breech preterm babies, there is an interesting paper that argues perhaps we should correct for gestational age in breech preemies (Lee, J et al. Sonographic screening for developmental dysplasia of the hip in preterm breech infants: do current guidelines address the specific needs of premature infants? J Perinatol. 2016 Feb 25. doi: 10.1038/jp.2016.7. [Epub ahead of print]) because we are screening them too soon if we do not correct for gestational age and potentially missing DDH in this specific set of preemies.
Hope that's useful!

Sol

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Mother Knows Best Full episode audio for MD edition 190:52 min - 90 MB - M4AHippo Peds RAP May 2016 Summary 588 KB - PDF