Abstract
Aims
We aimed to examine the true incidence of DDH in our area, and to investigate both known and unknown risk factors for the condition.
Methods
Data were prospectively recorded on all live births in the Exeter area from January 1998 to December 2008. The data included the baby's gestational age, sex, demographic details of parents, maternal age and parity, geographic and socioeconomic data, mode of presentation and delivery, and family history of DDH. Data were also collected prospectively on all treated cases of DDH (Graf 2c and above) for the same period. Using the population live birth data as controls, odds ratios (OR) and confidence intervals were calculated.
Results
The incidence of DDH in our area was 4.9 per 1000 live births. Although this might have been influenced by selective ultrasound screening, our records show that 74% of our cases had a Graf 3 or Graf 4 hip or presented late, and thus they would arguably have presented with or without screening. The remaining 26% had significant dysplasia (Graf 2c) with or without instability. Female sex (OR 7.3, 4.5-10.1), primiparity (OR 3.6, 2.3-5.6), positive family history (OR 12.6, 8.9-17.8) and breech presentation (OR 8.6, 6.1-12.1) were confirmed as risk factors for DDH. Caesarian section was protective in both cephalic (reduction in OR 0.5) and breech (reduction in OR 2.3) presentations. Postmaturity increased the chance of DDH (OR 2.7, 1.9-3.9). Certain postcodes also had significantly higher incidences (up to 11 per 1000 births), and these areas scored higher on an index of social deprivation. Birth weight, head circumference, and maternal blood group had no significant effects.
Conclusions
Incidence in our area was higher than is usually quoted. Our data suggest that there are geographical variations in the condition's incidence. We identified novel risk factors that warrant further investigation.
