Developmental Dysplasia of the Hip (DDH)

Differential Diagnosis

A candidate must be able to quote the standard hip lines and angles with their normal values — they are routinely shown in the OSCE/ISAWE and underpin the decision to treat residual dysplasia.

Arthrographic signs at examination under anaesthesia

Arthrography (during EUA) shows whether reduction is concentric and what is blocking it: a medial dye pool of more than ~5-7 mm between the femoral head and the acetabular floor indicates a NON-concentric reduction (soft-tissue interposition). The classic obstructive signs are the "rose-thorn" appearance of an inverted labrum (limbus) indenting the contrast, an hourglass / figure-of-eight capsular constriction produced by the iliopsoas tendon crossing the capsule, and pooling from a hypertrophied pulvinar and ligamentum teres. Failure to achieve a concentric reduction (persistent medial pool, rose-thorn limbus) is an indication to convert from closed to open reduction.

Prognostic Factors

Treatment Outcomes by Age

• Diagnosis under 6 weeks: 90-95% success with Pavlik harness alone
• Diagnosis 3-6 months: 70-80% success with Pavlik; may need closed reduction
• Diagnosis 6-12 months: Often requires closed reduction + spica
• Diagnosis 12-18 months: Usually needs open reduction + spica
• Diagnosis over 18 months: Open reduction + pelvic osteotomy + femoral osteotomy

Long-Term Considerations

Children treated for DDH require follow-up until skeletal maturity:

• Acetabular development: Monitor acetabular index; residual dysplasia may need pelvic osteotomy
• Avascular necrosis: May not manifest for 6-12 months post-treatment
• Hip function: Most treated hips function normally if reduction achieved early
• Osteoarthritis risk: Higher with residual dysplasia or AVN; may need THR in adulthood

Avascular Necrosis Risk

AVN is the most feared complication with rates varying by treatment:

• Pavlik harness: 0-5% (with proper technique)
• Closed reduction: 5-15%
• Open reduction: 10-25%
• Risk factors: Excessive abduction, prolonged immobilization, older age at treatment

Prevention of Avascular Necrosis

Avoiding AVN requires adherence to established principles:

• Maintain safe zone of abduction (Ramsey criteria)
• Avoid forced or excessive abduction during treatment
• Consider femoral shortening in older children to reduce reduction pressure
• Monitor closely during treatment for signs of vascular compromise

Global Epidemiology

• Clinical instability at birth: approximately 1-3 per 1000 live births stabilise spontaneously, leaving roughly 1-2 per 1000 with true dysplasia or dislocation requiring treatment.
• Sonographic dysplasia is far more common (immature/dysplastic hips in up to 15-20% of healthy neonates on early ultrasound), which is why universal early ultrasound generates substantial overtreatment.
• Marked geographic variation: very high prevalence in populations that swaddle with the hips extended/adducted (some Indigenous North American, Eastern European and Middle Eastern groups); very low rates where babies are carried abducted/straddled (parts of sub-Saharan Africa and Southeast Asia).
• Risk factors (BFFF): breech presentation, female sex (about 4:1), first-born, positive family history; also oligohydramnios and other packaging deformities (congenital muscular torticollis, metatarsus adductus, talipes).

Screening Strategy - Side by Side

Treatment Guidance - Side by Side

Registry and Surveillance Data

• DDH is tracked through national paediatric surveillance units (e.g. UK and Australian/New Zealand paediatric surveillance units) that monitor late-presenting DDH (diagnosed after the newborn period) as a key quality indicator of screening performance.
• Late-presentation rates of roughly 0.5-1.5 per 1000 persist even in well-resourced programmes, underscoring that no screening strategy eliminates missed cases.
• Unlike arthroplasty, there is no implant registry for paediatric DDH; long-term data come from osteotomy cohort follow-up rather than registries.

High- vs Limited-Resource Practice