Congenital Dislocation of the Hip

What is Congenital Dislocation of the Hip?
Congenital Dislocation of the Hip (CDH) is more properly called Developmental Dysplasia of the Hip (DDH), and is one of the most common problems in newborns and children.
The baby's hip does not develop properly, which can cause a range of problems from mild dysplasia, with perhaps hip pain in adulthood, to severe dislocation as a baby, resulting in delay in walking, limping and shortening of the leg, often ending up with arthritis and a hip replacement as a young adult.

How is it diagnosed?
Screening tests on your baby's hips are done as part of the neonatal examination. The tests are Ortolani test and the Barlow test, which involve gently moving the hips and feeling for clicks and clunks, which, if the examiner is experienced, can detect dislocated and unstable hips. Milder cases, however, cannot be picked up by these tests, and these hips can get worse, going on to dysplasia or dislocation of the hip. To make an early diagnosis ultrasound examination is very helpful.

What is a hip ultrasound?
Hip ultrasound is the same as your obstetrician uses during pregnancy and is completely safe. It is used to take pictures of the hips of babies to look for a dislocated or underdeveloped hip. It can be performed in babies from the newborn period to about 6 months of age. This method has been widely utilized for two decades in the diagnosis and follow-up of developmental dysplasia of the hip due to its ability to visualize the nonossified femoral head and portions of the acetabulum in neonates, dynamic capabilities, accuracy, and lack of ionizing radiation.
The extent of development and maturity of the hip can be assessed by the Alpha and the Beta angles. The Alpha angle measures the bony component and the Beta angle the cartilage component of the socket of the hip joint.

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The hip is classified into 4 types depending on the Alpha angle, the Beta angle and the age of the baby. Type I hips are normal. Type II hips are immature and require monitoring and sometimes treatment, Type III and IV hips are dislocated and require treatment.

When should my baby get a hip ultrasound?
There is still controversy whether ALL baby hips should be screened on a routine basis. A number of medical studies have shown that ultrasound screening reduces dramatically the number of children needing operations[1, 2] (because they can be treated early with a Pavlik harness). In Austria and Germany routine screening was introduced in 1991 and 1996 respectively, and the rate of operation for babies with dislocated hips has been reduced to near zero[3]. Universal screening is now done in many parts of Europe while the USA and UK adopts a selective policy [4]. Hip ultrasound is definitely needed in the following situations: abnormality found through physical examination of a baby's hip like a tight hip or a hip click, a family history of hip dysplasia, and breech presentation, among others

What will happen during the procedure?
The baby will lie on an examining cradle on his or her side. The doctor will place some warm gel (a lotion) on a transducer and place it on the baby's hip and take some pictures. The test usually takes about 10 minutes for each hip.

Limitations of Techniques
US examination is operator dependent and requires training and experience for confident evaluation of the infant hip. Also, because US is highly sensitive in hip imaging, minor abnormalities or normal early laxities may be revealed and these may not be significant clinically.

What kind of treatment is needed?
If the problem is not too severe, and caught early enough, it is often sufficient for your baby simply to wear a splint like a Pavlik harness for a few weeks. This holds his hips comfortably flexed and keeps the hips stable allowing them to develop normally. If the problem is more severe, or your child is over 6 months, he may need a plaster cast or even an operation.

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Recommendation
All newborn hips, especially hips at risks, should have their hips ultrasound screened by a paediatric orthopaedic surgeon or a radiologist who has special training in ultrasound of children's hips, ideally within six weeks of birth.


References
[1] Clegg J, Bache CE, Raut VV. Financial justification for routine ultrasound screening of the neonatal hip. J Bone Joint Surg Br. 1999 Sep;81(5):852-7.
[2] von Kries R, Ihme N, Oberle D, Lorani A, Stark R, Altenhofen L, et al. Effect of ultrasound screening on the rate of first operative procedures for developmental hip dysplasia in Germany. Lancet. 2003 Dec 6;362(9399):1883-7.
[3] Graf R. [The use of ultrasonography in developmental dysplasia of the hip.]. Acta Orthop Traumatol Turc. 2007;41 Suppl 1:6-13.
[4] K. J. Holen, A. Tegnander, T. Bredland, O. J. Johansen, O. D. Sather, S. H. Eik-Nes, T. Terjesen Universal or selective screening of the neonatal hip using ultrasound? J Bone Joint Surg [Br] 2002;84-B:886-90.



About the author
Dr. LI Yun Hoi graduated from the Faculty of Medicine, University of Hong Kong in 1982. He was previously Consultant in-charge of the Paediatric Orthopaedic Department of the Duchess of Kent Children's Hospital and Clinical Associate Professor and Chief of the Division of Paediatric Orthopaedics of the Department of Orthopaedics and Traumatology, University of Hong Kong. Dr. Li was the President of the Hong Kong Orthopaedic Association in 2000-2002 and the Founder President of the Paediatric Orthopaedic Chapter of the Hong Kong Orthopaedic Association 2001-2003.


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