Hip dysplasia

BRECKENRIDGE, COLO. -- Serious consideration should be given to universal ultrasound screening of newborns for signs of developmental dysplasia of the hip, a University of Vermont orthopedic surgeon believes.

"Right now, we're screening selectively [with ultrasound] in most centers in this country.

"I really think we're going to have to wrestle with the question of whether we should be doing this systematically," Dr. David Aronsson said at a meeting on practical pediatrics sponsored by the American Academy of Pediatrics.

Ultrasound detects developmental dysplasia of the hip (DDH) early, limits radiation exposure to infants, and provides a timely warning that conservative therapy is not working, said Dr. Aronsson, professor of orthopaedics and rehabilitation at the University of Vermont in Burlington.

Studies in Spain, Israel, and Germany have determined ultrasound is more accurate than physical examination in diagnosing the condition.

Dr. Aronsson's own research compared ultrasound with sequential physical examinations of breech-presentation babies, those with a questionable hip click, family history of hip dysplasia, or torticollis, from 1991 to 1996. In the years that ultrasound was used, 1994-1996, the condition was detected at an average age of 2.1 months, compared with 6.6 months, when such infants were followed up by careful physical examinations.

Hip dysplasia, once known by the imprecise term congenital dysplasia, can occur in utero or perinatally or as a result of spastic paraplegia associated with cerebral palsy.

A frank breech presentation is associated with a 20%-40% incidence of DDH, a situation in which many experts call for automatic screening.

The condition is seen more frequently in whites, girls, and children with a family history of DDH. Still, it can also occur in babies with no risk factors, and, if it goes untreated, may require open reduction to reinsert the femoral head into the acetabulum.

Missing DDH is a leading reason for liability lawsuits, Dr. Aronsson noted.

"Some dislocations are not detected and some dislocations occur late," he said.

The reasons are many.

The traditional maneuvers used to diagnose DDH--the Barlow provocation test and the Ortolani maneuver--are not fool-proof, particularly with an irritable infant.

The condition also changes over time. Although 1 of 60 infants have a positive Barlow provocation test at birth, indicating instability of the hip joint, 58% stabilize at 1 week, and 88% stabilize at 2 months.

"The majority of these infants are going to do fine if we just leave them alone," Dr. Aronsson said.

Determining which infants will require therapy, such as wearing a Pavlik harness for 2 weeks to promote reduction, is a challenge.

Radiographs are of virtually no use in infants less than 3 months old, since the femoral head and greater trochanter are surrounded in cartilage at this age and are difficult to see on x-ray.

Ultrasound, on the other hand, approaches 100% accuracy in diagnosing and monitoring the progress of DDH in babies at least 2 weeks old.

Ultrasound can determine thickness of the acetabular cartilage, bony rim percentage, and slopes of the osseus acetabulum and cartilaginous labrum--all measures that correlate with the severity of DDH and the likelihood it will require intervention.

Trained technicians and primary care physicians can competently perform these examinations, which do not require a radiologist's interpretation in most cases, Dr. Aronsson said.

"I met with our technicians about a month ago and asked them, 'Do you think in the year 2000 you could miss DDH in an infant?' The answer was no," he said.

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