Developmental Dysplasia of the Hip

Developmental dysplasia of the hip is a spectrum of abnormal hip joint development, from mild acetabular dysplasia to frank hip dislocation. It results from abnormal development of the acetabulum, femoral head, or both, with associated capsular and ligamentous laxity.

It is an important, common cause of long-term hip dysfunction if not identified and treated during the critical early period of infancy and childhood. During this period the hip joint retains substantial capacity for normal remodelling in response to treatment.

Universal or selective screening (according to national or regional protocols) is an essential component of routine newborn and infant care. It uses structured clinical examination, supported by targeted ultrasound in higher-risk infants. The aim is early detection and treatment before remodelling capacity diminishes with age.

Pathophysiology and risk factors

• Normal hip development depends on adequate, concentric reduction of the femoral head within a well-formed acetabulum during fetal and early postnatal development. Developmental dysplasia of the hip is a disruption of this process.
• Severity ranges from mild acetabular dysplasia, through subluxation (partial displacement of the femoral head), to frank dislocation in the most severe cases. In mild acetabular dysplasia the acetabulum is shallow and underdeveloped, and the femoral head is still located but imperfectly contained.
• Well established risk factors are breech presentation (particularly, though not exclusively, at delivery), a positive family history, female sex, first-born status, and oligohydramnios.
• Female sex reflects a recognised, though incompletely understood, relative hormonal ligamentous laxity in female infants.
• These risk factors inform the selective screening approach used in many healthcare settings, which targets more intensive ultrasound-based screening toward infants with one or more of them.
• The hip joint retains substantial capacity for remodelling and adaptation in response to treatment during infancy. This potential progressively diminishes with age.
• Early detection and treatment are therefore essential. Delayed diagnosis and treatment bring substantially less favourable outcomes and an increasing likelihood of more invasive, surgical treatment.

• The newborn screening examination is the essential, standard component of routine newborn hip examination. It comprises two tests.
  • Barlow test: attempting to gently dislocate a located, but potentially dislocatable, hip through adduction and posterior pressure.
  • Ortolani test: attempting to reduce a dislocated hip through abduction and anterior pressure. A palpable "clunk" reflecting successful reduction is a positive finding.
• A palpable clunk on either manoeuvre is a positive finding warranting prompt investigation and referral.
• Further findings are particularly relevant where the condition was not identified by earlier newborn screening:
  • asymmetric skin creases (thigh or gluteal folds)
  • leg length discrepancy, with the affected leg typically appearing relatively shortened, assessed through the Galeazzi sign (comparing relative knee height with the hips and knees flexed)
  • in an older infant who has begun weight-bearing, a characteristic limp (or, with bilateral involvement, a waddling gait) or delayed walking
• The Barlow and Ortolani tests become progressively less reliable and less likely to be positive as the infant ages beyond the early newborn period. Periarticular soft tissues stiffen and, where relevant, a more fixed, established dislocation develops.
• Perform these standard screening manoeuvres at the earliest possible newborn assessment, while they remain most sensitive and reliable.
• Limited hip abduction is a further useful clinical finding. It is often the most reliable examination sign in an older infant beyond the early newborn period, when the Barlow and Ortolani manoeuvres have become less reliable.

• Clinical examination, incorporating the Barlow and Ortolani manoeuvres, is the essential, standard initial screening approach, performed as a routine component of newborn examination. Any positive finding warrants prompt evaluation and referral to a specialist paediatric orthopaedic service.
• Hip ultrasound is the imaging investigation of choice in infants under approximately four to six months of age. The infant hip is predominantly cartilaginous at this age, which limits the value of plain radiography. Ultrasound gives detailed assessment of acetabular morphology and femoral head position and coverage.
• Structured, selective ultrasound screening is standard practice in many healthcare settings. It targets infants with one or more risk factors, or with an equivocal or positive clinical examination finding. Some settings use a more universal ultrasound approach.
• Plain radiography becomes the preferred imaging investigation from approximately four to six months of age. Ossification of the femoral head and surrounding structures has progressed enough to allow reliable radiographic assessment, and radiography supersedes ultrasound as the primary modality.
• Ongoing clinical surveillance throughout infancy supports identification of cases not apparent on the initial newborn examination. Repeat clinical hip examination at routine infant health surveillance visits. A proportion of cases only become clinically apparent somewhat later in infancy.

• The Pavlik harness is the standard, first-line treatment for confirmed developmental dysplasia of the hip identified in early infancy (generally up to around six months of age). It is a dynamic splinting device that holds the hips in flexion and abduction while permitting some active movement.
• It aims to maintain stable, concentric reduction of the femoral head within the acetabulum. The hip's substantial remodelling capacity at this age then progressively normalises the acetabular and femoral head morphology.
• Monitor the treatment course regularly with clinical examination and ultrasound or radiographs, to confirm satisfactory reduction and progress.
• Closed reduction under general anaesthesia, followed by hip spica cast immobilisation, is the standard approach for dislocated hips not successfully treated with a Pavlik harness. It is also used for hips presenting somewhat later in infancy, beyond the optimal window for harness treatment alone. Individualise the technique and the duration of immobilisation to the clinical circumstances.
• Open surgical reduction is required for hips not successfully treated with less invasive approaches. It is also required for later presentations (generally beyond approximately eighteen months to two years), when the potential for successful closed treatment has substantially diminished with the progressive loss of natural remodelling capacity.
• Add acetabular or femoral osteotomy procedures where indicated by the degree and pattern of associated dysplasia.
• Long-term orthopaedic follow up extends through childhood and, in some cases, into adolescence. Late residual dysplasia or secondary complications (including early osteoarthritis) can develop even after apparently successful initial treatment.
• Prognosis is substantially more favourable with earlier diagnosis and treatment. This reinforces the essential importance of structured newborn and infant screening programmes in achieving optimal long-term outcomes.