ULTRASOUND SCREENING FOR HIPS AT RISK IN DEVELOPMENTAL DYSPLASIA. RESULTS OF A TEN YEAR PROSPECTIVE STUDY

Abstract

Introduction: The results of a 10 year prospective hip ultrasound surveillance programme of ‘at risk’ or clinically unstable hips are analysed.

Method: Between June 1992 and may 2002, there were 34723 births in the Blackburn area. Over this period 2,578 infants with unstable hips and or risk factors for developmental dysplasia of the hip were assessed with bilateral hip ultrasound scans. Clinically unstable hips were imaged within two weeks post natally and those with ‘at risk’ groups within eight weeks. All results were collected prospectively by the senior author. The degree of Dysplasia was classified using Graf’s alpha angle. Dynamic instability or irreductable dislocation was recorded.

Results: Early dislocation was present in 77 patients of which 53 (68.8%) were referred as being Ortolani-positive or unstable, only 24 were identified from the screening programme alone. The dislocation rate was 2.6 per 1000 live births. There were 21 irreducible dislocations in 19 infants, a rate of 0.54 per 1000 live births.

Only 31.2 % of the dislocated hips belonged to the major ‘at risk’ group. In infants referred for possible clinical instability one dislocation was detected for every 8.5 infants screened, whereas in the ‘at risk’ group this number rose to 1 in 88. From the ‘at risk’ groups those with breech and a positive family history were most likely to reveal a dislocation. There was a 1:45 chance of instability/irreducibility in family history, compared with a 1:70 chance in breech presentation or 1:71 chance in foot abnormality. No patients with oligohydramnios alone had evidence of hip instability or dislocation. If type III dysplasia is assessed there is a 1:22 chance in family history, a 1:43 chance in breech presentation and a 1:61 chance in foot deformity.

Discussion: Screening groups with possible risk factors such as oligohydramnios or Caesarian section cannot be justified. Selective ultrasound screening of the clinical instability, family history, breech presentation and foot abnormality groups looking for dislocation or type III dysplasia may be justified on a National basis.