USEFULNESS OF ULTRASOUND MONITORING OF HIP INSTABILITY IN NEWBORNS TREATED BY ABDUCTION

Abstract

Purpose of the study: Prenatal screening and search for risk factors has lead to early diagnosis of congenital hip dysplasia. The percent of excentration of the dysplastic hip can be quantified with ultrasonography. The purpose of this study was to evaluate the usefulness of ultrasound monitoring of confirmed hip dysplasia as a method for determining the appropriate time to discontinue treatment.

Material and methods: We collected a series of patients presenting unstable hips one month after birth. Ultrasonographic examinations were performed to quantify the instability. Initial treatment was forced abduction. If the infant’s weight was greater than 5.6 kg, a Pavlik harness was used. Physical examination and control ultrasound examinations were performed at 4, 8 and 12 weeks. Forced abduction and ultrasound surveillance were discontinued when the percent of acetabular cover was greater than 50%. Long-term surveillance consisted in physical examination and plain ap view of the pelvis at four months and at onset of walking.

Results: Ultrasound monitoring was instituted for 71 hips in 51 patients. Mean age at onset of the monitoring scheme was 37.7 days (range 38–74 days). Mean acetabular cover, as evaluated by ultrasound before treatment, was 35.5% (range 20–45%). After four weeks, mean cover for 42 hips was 54.7% (range 50–85%). For the other 29 hips, mean acetabular cover was 41.4% (range 36–47%) at four weeks. At eight weeks, 26 of these 29 hips had a mean cover of 60% (52–85%). Acetabular cover remained below 50% for three hips at twelve weeks. Mean HTE at four months was 20.7° (range 10–26°). At walking, all hips were centered and no irregularities were noted on the x-rays of the femoral nucleus.

Discussion: The majority of infants with unstable hips diagnosed at birth achieve spontaneous cure without treatment. For others, cure can be achieved with forced abduction but with a risk of osteochondritis. In our study, ultrasound monitoring enabled a reliable assessment of the proper moment to interrupt treatment.

Conclusion: Ultrasound examination of the hip joint is a satisfactory method for monitoring hip dysplasia in infants aged less than four months. It appears to be useful for determining the moment to interrupt treatment.