Developmental Dysplasia of the Hip

X-Ray Image showing hip dysplasia in a baby https://en.wikipedia.org/wiki/Hip_dysplasia

Definition

Abnormal development of the hip, due either to hip joint luxation or subluxation (dislocatability), or a misshaped acetabulum

1. Teratogenic subtype: Occurs in utero and is associated with some syndrome (ex Ehlers Danlos or Down Syndrome) or a neuromuscular disease
2. Typical subtype: Detected postnatally in otherwise normally developed children.

Etiology

1. Multifactorial
2. + family history in 20% - ask about DDH, hip issues, one leg being longer than another, needing hip surgery or a brace as families might not recall DDH as the exact diagnosis
3. incidence of breech 30-50%, thought to be secondary to stretching of the hip capsule. 
4. 15% associated with other intrauterine "packing" issues like congenital muscular torticollis, 1-10% associated with metatarsus adductus
5. Majority of infants have generalized laxity of the ligaments.
6. 9:1 female to male incidence. 
7. Higher incidence in firstborn children
8. Higher incidence in Native Americans
9. Overall incidence approximately 1-2 per 1000
10. Remember that newborns often have some immaturity or mild dysplasia of the hip, but it almost always completely resolves over a matter of weeks and is not considered DDH

Diagnosis

1. Visual inspection
   • Asymmetric skin creases while the child is on their back and the hips are flexed. Exam should include the inguinal, thigh, and gluteal skin creases.
   • Height difference while the infant is on their back and the hips are flexed (Galeazzi sign). Look for asymmetry of the thigh lengths as well.
   • In older children who are walking, look for signs of gait asymmetry- limping, gluteus medius lurch, or positive Trendelenburg sign. The goal, though, is to prevent these signs from manifesting by correcting DDH in early childhood.
2. Physical examination
              
   • Barlow sign- while the knees and hips are flexed, adduct the hips while applying posterior forces and if the hip is dislocatable, you will feel a clunk.
   • Ortolani sign- while abducting the hips, a clunk is felt which represents a reduction of a dislocated hip.
   • Both Ortolani and Barlow signs should be elicited while the infant is supine, while the hip is flexed to 90 degrees and neutrally rotated.
   • A true + Ortolani or Barlow is a “clunk”; do not confuse this with a mild, high pitched “clink”, which is benign (surface tension or tendon snapping)
   • Ortolani and Barlow are most useful only in the first 3 months of life
   • For children aged 3-12 months, Ortalani and Barlow should no longer be used.  For these children, it is important to exam the ROM of each hip, in particular hip abduction. It should be possible to abduct each hip to at least 75 degrees, and adduct to 30 degrees past the midline

Note: If any of the above is abnormal, child should be referred to a pediatric orthopedist for further evaluation. They will either perform radiographic or ultrasound evaluation. The head of the femur doesn't ossify until 3-7 months, therefore xrays may not be useful in young infants.  Whatever the modality used, the key signs are: abnormal position of the femoral head relative to the acetabulum, or delayed ossification of the femoral head.

Normal hip imaging.
https://en.wikipedia.org/wiki/Hip_dysplasia

Imaging in a hip with DDH.
https://en.wikipedia.org/wiki/Hip_dysplasia

Also note, if the exam is normal, but there are significant risk factors (e.g., breech birth, family history) imaging should be obtained.  

Screening guidelines

• Screening based on historical risk factors above should be done.
• Routine ultrasonographic screening is not recommended by the USPSTF due to insufficient evidence.
• The AAP recommends serial physical examination of the hip to detect instability of the joint (as discussed above); this is especially important at birth and 2 weeks but should be continued until the child is walking

Treatment

The goal is to keep the head of the femur in the acetabulum and is dependent on the age of the child.  Treatment earlier is preferable as harnessing or casting may avoid the need for surgery later on.

1. < 6 months. Pavlik Harness which allows the hip to be flexed and abducted. There is enough mobility to prevent avascular necrosis of the head which may develop if extreme abduction is maintained. Infant wears 24 hours/day. The earlier diagnosed, shorter length of time harness needs to be worn
2. >6months. Usually need spica cast to maintain abduction and flexion, some may need surgery. Some recommend traction before placing in cast. There may be delay in motor milestones but usually catch up quickly
3. >18 months. Usually require surgery. 

A happy baby in a Pavlik Harness.
https://en.wikipedia.org/wiki/Hip_dysplasia

Prognosis

1. If diagnosed before 6 months of age, 80-95% have normal development of the hips
2. Later diagnosis and treatment associated with development of avascular necrosis, osteoarthritis, and functional disability in adulthood.

References

1. Ballock, R. Tracy. and Richards, B. Stephens. Hip Dysplasia: Early Diagnosis Makes a Difference. Contemporary Pediatrics. July 1997.
2. Committee on Quality Improvenment and Subcommittee on Developmental Dysplasia of the Hip. Clinical Practice Guideline: Early Detection of Developmental Dysplasia of the Hip. Pediatrics. 2000; 105(4):896-905.
3. Synopsis of AAP Clinical Practice Guidelines : Early Detection of Developmental Hip Dysplasia.  Pediatrics in Review. April 2001
4. Scherl S. Common Lower Extremity Problems in Children. Pediatrics in Review February 2004
5. US Preventive Service Task Force. Screening for Developmental Dysplasia of the Hip.  Recommendation Statements.  Pediatrics March 2006
6. Rosendahl,K. Immediate Treatment versus Sonographic Surveillance for Mild Hip Dysplasia in Newborns.  Pediatrics Jan 2010.