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Developmental Dysplasia of the Hip

Developmental dysplasia of the hip (DDH) is a term used to describe abnormal development of the joint where the head of the femur fits into the pelvic acetabulum, a ball-and-socket joint. It is an inclusive term incorporating several conditions: hip dysplasia, in which the acetabulum is too shallow for the head of the femur to fit tightly; subluxation, in which the head fits incorrectly into the acetabulum causing hip instability with the femur sliding in and out of the acetabulum; or complete hip dislocation, with the head of the femur residing outside the pelvic socket. It may be present at birth, and thus was once known as congenital hip dislocation. Hip dysplasia may also develop during infancy or childhood. The left hip alone is involved in 60% of cases, the right hip in 20%, and both hips in 20%. Causation is multifactorial, and it is more common in females, breech positioned babies, those with a family history of DDH, and in infants with other lower limb deformities; it is not specifically related to prematurity.

If untreated, DDH may result in permanent dislocation of the femur, a shorter leg and limited hip mobility, and degenerative arthritis. Prevention of disability depends upon diagnosing DDH as early as possible, limiting joint deformity, and careful effective therapy to prevent avascular necrosis of the femoral head or persistent dysplasia.

DDH is a condition that often results in malpractice litigation against a clinician (it may perhaps be the most frequent cause of successful litigation in pediatric cases). Therefore, as you perform well child exams, always check for DDH until the child is walking, or one year of age, whichever comes last, and consider the possibility of DDH when an older child demonstrates limited hip abduction and/or an abnormal gait. Secondly, it is prudent to announce clearly to the caregiver that you are checking the child's hips so that there is never any question in the caregiver's mind that you may have forgotten to do so. Thirdly, always chart current hip findings as they could subsequently change. Chart more than just the negative hip "click" or "clunk" attributed to the Ortolani maneuver; additionally mention the child's gait, leg length comparison, and the other observations of hip integrity you have made.

There are at least six tests that can help you identify DDH. The tests should be used cumulatively whenever possible to decrease any possible chance of a missed diagnosis.

For infants, the clinician should observe for:

  1. The Galeazzi (or Allis) sign - With the child lying supine on a firm flat table or surface, flex the hips and knees and place the feet flat on the table near the buttocks. With the knees together, check the height of the knees, which should be even. If the knee height is uneven, the shorter knee will indicate the leg with hip dysplasia.
  2. Hip abduction - with the child lying supine and hips and knees slightly flexed, allow the legs to fall naturally so that the knees move laterally toward the table. They should abduct equally. If they do not, the hip that is unable to fully abduct is the hip with dysplasia.
  3. Barlow maneuver - With your long fingers on the greater trochanters of each femur, use your thumbs to hold the knees together with the hips and knees flexed. Apply gentle vertical pressure to the knees, one at a time. The pressure applied downward toward the table will cause an affected hip to dislocate and the head of the femur will subluxate, riding upward out of the acetabulum. Try to feel with your long finger the stability of the hip. Does it stay in the socket or move out of it?
  4. Ortolani maneuver - Again, with your long finger on the greater trochanter of the femur, your thumb resting on the superior aspect of the infant's knee, abduct the hip gently, one leg at a time. If the hip is dislocated, this maneuver reduces the dislocation and you will feel the hip slip back into the pelvic socket (acetabulum). This sensation has been called a "jerk" or a "click" or a "clunk"; however, it is rarely audible and is rather a feeling of having a ball slip into a matched round hole. Alternatively, an audible brief "click" typically represents simple ligamentous laxity induced by maternal hormones and is not a positive sign. Of all the hip stability tests, the Ortolani maneuver is probably the most reliable confirmation of hip dysplasia, particularly in cases where one clearly feels and visualizes a "clunk," which represents a somewhat dramatic reduction of the dislocation. This maneuver is most reliable when implemented during the first four to six months of life, and is most diagnostic when used in the first 1 to 2 months after birth.
  5. Leg lengths - With the infant still supine, flex the hips and keep the knees straight (extended). Are the heels and soles even? If not, the shorter leg is affected by hip dysplasia. You may also extend the hips with the knees straight, keeping the legs together, allowing the legs to gently come down to rest on the table. The child will appear to be lying in the anatomically neutral position. Compare leg lengths. Note that such hip extension pulls the affected hip out of the socket. The shorter leg here is indicative of dysplasia. Leg length comparison is an important finding to chart, especially at six months and beyond when the Ortolani reduction can no longer be detected.
  6. Asymmetric thigh folds - While checking leg lengths, also look to see if thigh folds match. This is not a singularly reliable test because many infants have asymmetric folds that do not represent hip dysplasia. However, if thigh folds do not match, one should repeat tests 1-4 above to verify previous results.
  7. Asymmetric buttock creases - Roll the child over into a prone position and observe to see if the buttock creases are symmetric. Again, this is not the most reliable test because many children have asymmetric creases; however, if creases do not match, one should repeat tests 1-4 to reconfirm negative findings.

Important Points of Observation for the Ambulatory Child Include:

  1. Trendelenburg sign - have the child stand and raise one leg off the floor. If the pelvis drops on the side of the raised leg, this is a positive Trendelenburg sign and represents weakness of hip abductor muscles on the weight-bearing leg. The hip opposite the raised leg is the one affected.
  2. Leg length discrepancy with asymmetric toe-walking - demonstrated by toe-walking on the affected side. Watch the child's gait with shoes off.
  3. Marked lordosis - a suggestive sign, often found in unaffected children as well.
  4. Painless limping or waddling gait - another suggestive, less definitive sign. A wide-based limp could represent bilaterally dislocated hips.

Any infant positioned breech, whether delivered vaginally or by cesarean section, warrants an ultrasound of the hips. This is best performed at six weeks of age. Reliable radiographic assessment of hip dysplasia is not possible until around four months of age, when previously radiolucent cartilage in the hip area is replaced by bony landmarks. Although DDH is not a preventable condition, early identification is an important responsibility of the health care provider. Early detection allows timely treatment, which is imperative to promote optimum function and prevent further clinical deterioration. Again, analysis of hip abduction, leg lengths, and thigh folds - as well as performance of the Galeazzi, Barlow, and Ortolani maneuvers - should be done at each well-baby exam.

References

Burns, C. E., Dunn, A. M., Brady, M. A., Starr, N. B., & Blosser, C. G. (2004). Pediatric primary care: A handbook for nurse practitioners (3rd ed.). St. Louis: Saunders.

Green, M., Haggerty, R. J., & Weitzman, M. (1999). Ambulatory pediatrics (5th ed.). Philadelphia: W. B. Saunders Co.