Contents
Introduction
Developmental dysplasia of the hip (DDH, formerly known as congenital dislocation of the hip) describes any abnormality found in the neonatal hip joint. The degree of abnormality varies considerably. The problem may arise from structural defects in the head of the femur, the acetabulum or surrounding structures. Approximately 1 in 100 births are affected and it is more common in the left hip.
It is not always detectable at birth.
Most cases can be treated conservatively with braces (usually a Pavlik Harness) or in some cases, casting. It is associated with an increased risk of need for hip replacement in adulthood.
Epidemiology and Aetiology
- Affects 1-3% of newborns
- 80% of cases are in females – probably due to hormonal effects on ligament laxity
- 20% of cases are bilateral
- Left hip predominance is thought to be due to the left occiput anterior position in utero, which is more common than the right lie
- Breech position with vaginal delivery increases the risk 17x !
- Breech with caesarian increases the risk 7x
- Swaddling babes tightly, with legs straight (seen in some cultures) increases the risk
- These babies often present later (typically around age 3 months)
- Genetic factors
- Sibling with DDH increases risk by 5%
Many risk factors are indicated in DDH. Previously, all babies with any risk factor were screened in the UK. However, only babies who are breech presentation or those who have a positive family history are now screened as these have been identified as the most significant risk factors. Other risk factors include oligohydramnios (reduced amniotic fluid volume), firstborn babies, race (high in Native Americans) and gender (80% of cases are female).
Diagnosis is suggested during newborn checks that all babies receive before leaving the hospital. It can only be confirmed on ultrasound.
Screening
Screening is part of the newborn examination and the 6-8 week “baby check”.
- Screening consists of examination of the hips, typically with the Barlow and Ortolani tests
- Ultrasound screening is not routinely recommended for all children. However in those with the following risk factors, USS is recommended:
- FHx of DDH, or FHx hip problems in early life
- Breech presentation
Examination of the hips in a newborn
- Inspection: Look for difference in leg length by flexing knees fully and comparing knee height (Galeazzi’s sign). Look for defined skin creases (not very sensitive).
- Ortolani’s test: With knees flexed and in the midline the hip is abducted until flat on the bed. The examiners fingers should be on the greater trochanter.
- Barlow’s test: With hips in the position post-Ortolani’s test hips are adducted back to the midline with pressure applied posteriorly along shaft of femur.
During a positive Ortolani’s test a ‘clunk’ will felt by the examiner as the femoral head is reduced from a posterior position into the acetabulum. During Barlow’s the femoral head is returning to its dislocated position.
- At >3 months of age, Barlow’s and Ortolani’s tests are unreliable, and ultrasound IS recommended as the investigation of choice in children of this age with suspected DDH
- Signs suggestive of DDH in children this age include:
- Restricted hip abduction
- Leg length discrepancy
- Asymmetrical thigh and gluteal skin folds
- Not a very reliable sign
- Seen in 25% of normal infants
- May not be asymmetrical in bilateral DDH
- Ultrasound is only recommended until 4.5 months old. After this age, X-ray is more sensitive
- CT and MRI are occasionally used, but require sedation
- USS will report:
- Femoral head coverage – this describes the amount of the femoral head that sites in the acetabulum. Normal >50%
- Alpha angle – Normal >60 degrees
- In older children
- Abnormal gait
- Affected hip externally rotated
- Toe-Walking on affected side
- Waddling gait, increased lumbar lordosis may be suggestive of bilateral DDH
- Abnormal gait
Management
Most hips the are unstable at birth will stabilise by 6 weeks of age. Any hip instability after this age requires definitive management. Hip dislocation at birth requires immediate management.
The most common treatment for DDH is the use of a Pavlik harness.
The Pavlik harness holds the child’s legs in an abducted position with the hip flexed (much like Ortolani’s). The child is able to further flex or abduct the hip but adduction and hip extension are limited. The harness must be worn continuously for at least 6 weeks.
In children over 6 months of age the harness is not indicated and surgical reduction may be required. If DDH is left untreated there is a high risk of early onset osteoarthritis.
- Assess all children during use of a Pavlik harness to ensure adherence to the treatment, and to assess for femoral nerve palsy (loss of knee extension)
- If treatment is started by the age of 3 months, only 6% of children will need any further management
- It is more effective, the earlier it is started
- Pavlik harness is contraindicated in children greater than 4.5 months of age with an irreducible hip
Mild DDH
- Defined as femoral head acetabular coverage of 40-50% OR an alpha angle of 50-60 degrees on USS
- Can be safely monitored in general practice without use of a harness
- Advise parents about safe swaddling and wrapping
- Repeat USS at 6 weeks
Moderate and severe DDH
Defined as:
- Obviously dislocating hip on examination, OR
- USS findings of <40% bony coverage or alpha angle of <50 degrees
Treat with:
- Pavlik Harness
- After 6 weeks in Pavlik Harness, repeat USS
- If remains abnormal – Pavlik harness for another 6 weeks, and repeat USS again
- If remains abnormal at 12 weeks, refer to orthopaedics for consideration for surgery
- Surgery typically includes an adductor or poses tenotomy, which reduces hip adduction, followed by 3-4 months of plaster cast – with the legs held in a similar position to Pavlik Harness
- Surgery after the age of 18 months is typically more difficult and less successful
- Surgery after 3 years is generally not recommended, and may have a better outcomes if the hip is left alone. By this age, there may not be sufficient remodelling of the hip after surgery and there is increased risk of osteonecrosis
References
- DDH – patient.info
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
- Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
- Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy