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Children's Orthopaedics

WHY DOES SELECTIVE ULTRASOUND SCREENING FOR DDH FAIL?

Warwick, England, 22 January 2010



Abstract

Purpose of study

Results clinically & statistically of a 10 year prospective observational longitudinal study of the effects of sonographic screening for ‘risk’ factors in DDH.

Methods & Results

From 1997 to 2006 the project analysed the results of a sonographic screening programme for clinical instability & ‘risk factors’ in Blackburn (modified Graf system). ‘Risk factors’ included: breech presentation, strong family history, foot deformities & oligohydramnios. Statistically 95% confidence intervals, relative risk, sensitivity, specificity PPV & NPV were calculated. The outcome measure was irreducible dislocation of the hip joint. There was a birth population of 37,510, of which 2693 were ‘at risk’ & 132 clinically unstable.

Three subsections:

1. Clinically unstable hips (birth) 2 irreducible dislocations
2. ‘At risk’ 6 irreducible dislocations
3. Secondary referral (GP screening) 11 irreducible dislocations

The overall irreducible dislocation rate was 0.51 per 1000 live births.

‘Risk factors’: mGraf Type III/IV/ Irreducible:

CTCV: 1: 13.8 RR = 26.5
Family history: 1:18.5 RR = 23.3
Breech: 1:35 RR = 14.8
Oligohydramnios 1:99.5
TEV (postural) 1:202
CTEV (fixed) 0.0

Narrow 95% CI for Breech, CTCV & CTEV

Wide 95% CI for Family history, oligohydramnios & TEV (postural)

95% CI (RR) for Oligohydramnios & TEV not significant.

RR for clinical hip instability was 983.6

Percentage female

18/19 irreducible hips 94.74%
64/92 Type IV hips 69.56%
26/30 Type III hips 86.66%

34.15% of clinically unstable hip joints had a ‘risk factor’

Conclusion

Only 13 from 2693 ‘at risk’, had Type IV or Irreducible hips. Only 7 were treatable by splintage. Clinically & statistically screening for at ‘risk hips’ alone has a poor return. Female gender & clinical instability appear more important.