EARLY RADIOLOGICAL OUTCOME OF ULTRASOUND CONTROLLED TREATMENT IN DEVELOPMENTAL DYSPLASIA OF THE HIP

Abstract

Reduction therapy in developmental dysplasia of the hip (DDH) is initialized in the newborn period. Harness treatment is continued until normal ultrasound-values are reached. Above the age of one year the assessment of DDH relies mainly on interpretation of plain radiographs of the pelvis. In order to rule out residual dysplasia after ultrasound controlled treatment radiological control is advised to the time children start walking. The purpose of this study is to evaluate the early radiological outcome after ultrasound controlled treatment of DDH and to examine whether there is a correlation between the initial severitiy of DDH, measured by ultrasound, and the severity of residual DDH on the radiograph at the time of the first follow-up.

A. p. pelvic radiographs of 90 children (72 girls, 18 boys, 180 hips) with DDH (29 unilateral, 61 bilateral) were reviewed retrospectively. To the beginning of the ultrasound surveilled therapy (mean age 7,2 weeks) the morphologic findings were staged according to the Graf classification. Ultrasound surveilled abduction treatment was continued until normal ultrasound findings were reached. To the time children started walking (mean age 14,8 months) an a. p. radiograph of the pelvis was performed. The acetabular index (AI) was measured and classified according to the normal values of the hip joint described by Tönnis. The initial ultrasound findings expressed by the Graf classification were compared with the AI in the radiographic follow-up and Tönnis’ normal values.

To simplify matters the 180 Graf-classified hips were distributed into 4 categories: Graf Ia/b=category 1, Graf IIa-D=category 2, Graf IIIa/b=category 3, Graf IV=category 4. The initially normal contralateral hips in ultrasound (n=29, category 1) presented in 37,9% a normal AI, in 41,4% with a mild dysplasia (between 1SD and 2SD) and in 20,7% with a severe dysplasia (beyond 2SD). The Graf type IIa-D hips (n=81, category 2) presented in 37% a normal AI, 32,1% showed a mild dysplasia and 30,9% a severe dysplasia. The Graf type III a/b hips (n=60, category 3) showed 35%, 30% and 35%, Graf type IV hips (n=10, category 4) 60%, 30% and 10%, respectively.

The mean AI in all four categories differed only marginally.

In our setting of patients different conclusions can be drawn:

• Even after successful ultrasound guided therapy with a sonographically normal hip at the time bracing is finished there is a risk for residual dysplasia. Therefore radiological follow-up of every once treated hip is necessary.

• To reduce the number of radiographs the time for the first radiographic follow up may be delayed to the age of two. We only see a minimal risk to miss a dislocated hip in time. In very rare cases the indication for an acetabuloplasty is generally seen before the age of two, in our patient population we saw no immediate indication for surgery.