Risk Factors for Developmental Dysplasia of the Hip (DDH)
The most important risk factors for developmental dysplasia of the hip (DDH) are female gender (2.5x risk), breech positioning in utero (3.8x risk), and positive family history (1.4x risk). 1, 2
Primary Risk Factors
Female sex: Females have 2.5 times higher risk than males 1, with some studies showing 4-8 times higher incidence 2. Recent research indicates an even higher odds ratio of 5.36 (95% CI, 4.63-6.20) 3
Breech positioning: Carries a 3.8 times increased risk 1
- Breech position causes extreme hip flexion with knee extension
- Leads to shortening and contracture of the iliopsoas muscle
- Promotes femoral head dislocation 1
Family history: Increases risk by 1.4 times 1
- Studies show increased prevalence among monozygotic twins compared to dizygotic twins
- Genetic predisposition is supported by chromosomal analysis in familial DDH 1
Left hip: Three times more frequently affected (relative risk 1.5) 1
- Theorized to result from left occiput anterior in utero position
- This positioning places the left hip against the mother's spine and limits abduction 1
Additional Risk Factors
Infant swaddling: Particularly when legs are extended and adducted 1, 2
Skeletal pathologies: Associated with 2.04 times increased risk (95% CI, 1.21-3.42) 3
Oligohydramnios: Associated with 1.75 times increased risk (95% CI, 1.44-2.13) 3
- Can restrict in utero hip mobility 1
Factors Not Proven to Increase DDH Risk
Firstborn status: Despite previous beliefs, not consistently proven as a risk factor 1
Torticollis: Not proven to increase DDH risk 1
Foot abnormalities: Not proven to increase DDH risk 1
Preterm infants: Not at increased risk for DDH 1
Multiparity: Lack of consensus on association with DDH 1
Risk Factors for Late Diagnosis
Interestingly, risk factors for late diagnosis (after 3 months of age) differ from those for early diagnosis:
- Female sex
- Vertex presentation
- Normal delivery
- Rural birth
- Early discharge from hospital (less than 4 days after birth) 4
Clinical Implications
- Unrecognized and untreated DDH can lead to early degenerative joint disease
- DDH causes up to one-third of all total hip arthroplasties in patients under 60 years 1, 2
- Early detection and treatment significantly improve outcomes 5
- Selective screening is recommended for infants with risk factors 1, 2
Screening Recommendations
- All infants should undergo clinical examination at every well-baby visit until 12 months of age 2
- Ultrasound screening is recommended for high-risk infants between 4 weeks and 4 months of age 2
- Radiography is preferred for infants older than 4 months 2
Understanding these risk factors is crucial for early identification and intervention, as late presentation significantly worsens prognosis and increases the likelihood of requiring complex treatment and surgical intervention 1.