Orthopaedic Surgery - Developmental Dysplasia of the Hip

Basics

Developmental dysplasia of the hip (DDH) describes a spectrum of abnormal development and instability of the hip joint, ranging from mild acetabular dysplasia and subluxation to complete dislocation of the femoral head.

The femoral head tends to migrate superolaterally, while the acetabulum becomes progressively shallow and deformed.

Most abnormalities develop in utero, although instability may occasionally evolve during early infancy.

Clinical Presentation Across Age Groups

DDH is usually identified during routine newborn or early-childhood screening.

Occasionally, a mild subluxation or acetabular dysplasia is missed during infancy and first becomes apparent during adolescence or early adulthood because of limping, activity-related discomfort, or hip pain.

Classification by Severity

The condition may be classified according to the degree of hip instability.

A subluxable hip is normally reduced but can be partially displaced from the acetabulum with gentle provocative pressure and spontaneously returns to its reduced position.

A dislocatable hip can be completely displaced from the acetabulum during examination and subsequently reduced.

A dislocated hip remains outside the acetabulum at rest and requires a specific reduction maneuver to relocate the femoral head.

Barlow and Ortolani Findings

The Barlow maneuver assesses whether a located hip can be displaced posteriorly from the acetabulum.

A clearly dislocatable hip represents a positive Barlow test.

The Ortolani maneuver assesses whether an already dislocated hip can be reduced into the acetabulum.

A palpable reduction clunk represents a positive Ortolani sign.

Synonyms

Older terminology includes congenital dislocation of the hip, although developmental dysplasia of the hip is preferred because the disorder includes a much broader spectrum than complete congenital dislocation.

Other terms include hip dysplasia and unstable hip.

General Prevention

There is no reliable method for preventing DDH completely.

The most important strategy is early detection, because treatment becomes more difficult and the risk of complications increases as the child gets older.

Children born to parents with hip dysplasia should be examined particularly carefully.

Epidemiology

Females are affected approximately four times more often than males.

This difference is thought to relate partly to greater ligamentous laxity and hormonal influences.

Incidence

When all degrees of neonatal hip instability are included, DDH occurs in approximately 1 in 200 births.

Complete dislocation is less common, occurring in roughly 1 in 1,000 births.

Risk Factors

Important risk factors include breech presentation, first-born status, female sex, oligohydramnios, and a positive family history.

Connective-tissue disorders associated with ligamentous laxity, such as Ehlers–Danlos syndrome and Marfan syndrome, may also increase risk.

Breech Presentation

Breech positioning is one of the strongest recognized risk factors.

The position increases hamstring tension and alters the mechanical forces acting across the developing hip.

First-Born Status

First-born infants may have less available intrauterine space because of greater uterine and abdominal wall tone, increasing the effect of mechanical constraint.

Oligohydramnios

Reduced amniotic fluid limits fetal movement.

Persistent hip adduction can direct the femoral head toward the edge of the acetabulum and interfere with normal acetabular development.

Genetics

A positive family history substantially increases risk, but DDH does not follow a simple established Mendelian inheritance pattern.

The disorder is generally considered multifactorial, with both genetic susceptibility and mechanical factors contributing.

Etiology

DDH is thought to result from unfavorable mechanical forces acting on a susceptible hip during fetal development.

Persistent adduction or abnormal positioning of the femoral head reduces normal concentric contact between the femoral head and acetabulum.

Because normal acetabular development depends on the femoral head remaining well centered, prolonged displacement leads to increasing dysplasia.

Severity and Timing

The earlier abnormal mechanical forces develop during gestation, the more severe the resulting hip dysplasia may be.

Severe early displacement can result in substantial deformity of both the femoral head and acetabulum.

Ligamentous Laxity

Generalized ligamentous laxity can increase hip instability.

This may partly explain the greater frequency in females and the tendency for DDH to cluster within families.

Postnatal Factors

Postnatal positioning can also influence hip stability.

Persistent adduction, a contralateral abduction contracture, or tight swaddling with the hips extended and adducted may interfere with spontaneous stabilization.

Associated Conditions

DDH may occur with other so-called packaging disorders caused by limited intrauterine space.

These include muscular torticollis and metatarsus adductus.

Syndromic Associations

Hip dysplasia may also be seen in genetic disorders, particularly connective-tissue diseases and skeletal dysplasias.

The presence of associated congenital abnormalities should increase clinical suspicion.

Diagnosis

Signs and Symptoms in Infancy

Infants with DDH are usually asymptomatic.

The diagnosis during the first months of life depends primarily on careful physical examination and, when indicated, imaging.

Hip Instability

The most important early finding is a palpable clunk as the femoral head moves out of or back into the acetabulum during the Barlow or Ortolani maneuver.

This should be distinguished from a benign soft-tissue click.

Hip Position

The affected hip may rest in slight adduction.

A deeper proximal thigh crease can sometimes be present, although skin-crease asymmetry alone is neither sensitive nor specific.

Limited Abduction

Reduced hip abduction is an important finding.

The affected hip may abduct less than approximately 50–60°, depending on age and examination technique.

Parents may first notice this limitation while changing diapers.

Hip Click

An isolated hip click without a true clunk is usually nonspecific.

Clicks may arise from the fascia lata, synovial folds, or even structures around the knee and may occur in completely normal infants.

Loss of Instability Clunk With Age

By approximately 6 months of age, the classic Barlow and Ortolani signs may disappear because a chronic dislocation becomes more fixed.

At this stage, limited abduction becomes increasingly important diagnostically.

Walking Development

A child with DDH may begin walking at the expected age or only slightly later.

Therefore, normal timing of walking does not exclude hip dysplasia.

Findings After Walking Age

Once walking begins, asymmetry may become more obvious.

The affected thigh may appear smaller, proximal thigh creases may become more pronounced, and leg-length discrepancy may be evident.

Toe Walking

A child with unilateral dislocation may appear to toe walk on the affected side as compensation for limb shortening.

Trendelenburg Gait

Weakness of the hip abductor mechanism can produce a Trendelenburg limp.

When the child stands on the affected side, the pelvis drops on the opposite side because the displaced hip provides a poor mechanical lever arm for the abductors.

Bilateral DDH

When both hips are dislocated, limb-length asymmetry may be less obvious.

The child may instead develop a waddling gait and increased lumbar lordosis.

Pain

Pain is generally absent during childhood.

Symptoms usually appear only after secondary cartilage degeneration and osteoarthritis develop, potentially beginning in late adolescence but often much later.

Physical Examination

Hip Abduction

Hip abduction should be assessed carefully in every infant.

Asymmetric or restricted abduction is one of the most useful clinical signs of DDH across age groups.

Barlow Test

The infant should be warm, calm, and relaxed.

With one hip examined at a time, the hip is flexed and gently adducted while posteriorly directed pressure is applied through the knee or thigh.

A positive test occurs when the femoral head can be partially or completely displaced from the acetabulum.

Ortolani Test

After the Barlow maneuver, the hip is gently abducted while the examiner lifts the greater trochanter anteriorly.

A palpable clunk as the femoral head reduces into the acetabulum indicates a positive Ortolani sign.

Examination Technique

The examination should be gentle.

Forceful manipulation should be avoided because aggressive testing can cause discomfort and makes the infant less relaxed, reducing examination reliability.

Galeazzi or Allis Sign

With the infant supine, hips and knees are flexed and the feet placed symmetrically.

A difference in knee height indicates apparent femoral shortening and suggests unilateral hip dislocation.

This is known as the Galeazzi or Allis sign.

Gait Examination

Walking children should be observed for limping, Trendelenburg gait, toe walking, waddling, and excessive lumbar lordosis.

Imaging

Ultrasound

Ultrasound is the preferred imaging modality during the first several months of life, before sufficient ossification of the femoral head makes radiographs more informative.

It is particularly indicated when the physical examination is abnormal or important risk factors are present.

Timing of Ultrasound

Ultrasound is most useful during the first approximately 6 months of life.

Interpretation requires experience because neonatal hip anatomy is largely cartilaginous.

Plain Radiographs

Plain radiographs become increasingly useful after approximately 4–6 months, as the femoral head and acetabulum become more readily evaluated radiographically.

Radiographic Assessment

Radiographs should assess both the shape of the acetabulum and the position of the proximal femur relative to it.

Acetabular shallowness, lateral migration, and proximal displacement may all be present.

Shenton Line

The Shenton line is a curved line formed by the medial femoral neck and the superior pubic ramus.

In a normally located hip it forms a smooth continuous arc.

Disruption suggests displacement of the proximal femur.

Femoral Head Position

The proximal femoral epiphysis should lie medial to the outer margin of the acetabulum.

Lateral or superior displacement supports the diagnosis of subluxation or dislocation.

Arthrography

Arthrography can be used during reduction procedures to define the cartilaginous femoral head, acetabulum, and structures that may block reduction.

A small residual space between the femoral head and acetabulum following reduction suggests a better-quality reduction.

CT and MRI

CT and MRI have limited roles in routine screening and diagnosis.

They may be useful in selected cases, particularly after reduction when clarification of hip position is necessary or when complex anatomy must be assessed.

Pathological Findings

Acetabular Changes

The acetabulum becomes shallow and flattened, particularly posterosuperiorly, when the femoral head is not concentrically reduced.

Femoral Head Changes

The femoral head may become flattened anteriorly, and femoral anteversion may increase.

These abnormalities become more pronounced with longstanding displacement.

Degenerative Changes

Chronic dysplasia causes abnormal joint loading.

Cartilage degeneration and secondary osteoarthritis can develop beginning in the second decade of life or later.

Differential Diagnosis

Benign Soft-Tissue Click

A simple hip or knee click caused by fascia or synovial tissue should not be confused with a true instability clunk.

Neuromuscular Hip Dysplasia

Children with cerebral palsy or spina bifida may develop hip subluxation or dislocation because of abnormal muscle forces.

This is a different mechanism from classic developmental dysplasia.

Congenital Femoral Abnormalities

Congenital femoral shortening and coxa vara can produce limb-length discrepancy or altered gait while the femoral head remains located within the acetabulum.

Treatment

General Principles

The goal of treatment is to obtain and maintain a concentrically reduced hip early enough to permit normal development of the acetabulum and proximal femur.

Earlier treatment is generally easier, safer, and more successful.

Early Reduction

When a true dislocation is identified in early infancy, reduction should be achieved promptly, ideally within the first several weeks of life.

Delay allows soft tissues to contract and acetabular deformity to progress.

Treatment by Age

Management varies substantially according to the child’s age and the severity and stability of the hip.

Newborn Management

Mild Instability

A newborn with a mild click or transient subluxability may initially undergo serial examinations, because some unstable neonatal hips stabilize spontaneously during the first days or weeks of life.

A true dislocation or persistent instability requires treatment.

Birth to 6 Months

Pavlik Harness

Persistent instability or a dislocated hip in a young infant is commonly treated with a Pavlik harness or similar dynamic abduction brace.

The harness holds the hips flexed and abducted while allowing controlled movement.

Hip Position

Hip flexion is usually maintained beyond approximately 90°, while excessive forced abduction is avoided.

The goal is to guide the femoral head gently into the acetabulum without compromising its blood supply.

Specialist Supervision

Pavlik harness treatment should be supervised by an orthopaedic surgeon experienced in pediatric hip disorders.

Improper positioning can cause complications.

Confirmation of Reduction

The hip should become reduced within the first few weeks of harness treatment.

Reduction is confirmed using ultrasound or appropriate radiographic imaging.

If the hip remains unreduced, prolonged ineffective harness treatment should be avoided.

Duration of Bracing

The brace is typically worn full-time until the hip becomes clinically and radiographically stable.

It may then be used part-time until acetabular development has normalized sufficiently.

After 6 Months

Closed or Open Reduction

After approximately 6 months of age, treatment frequently requires closed reduction under anesthesia, with open reduction performed when a stable concentric reduction cannot be achieved.

Spica Casting

Following successful reduction, the hip is usually maintained in a hip spica cast for a period of several months.

Age 6–24 Months

Traction

Some surgeons historically use a period of skin traction before reduction to gradually stretch contracted soft tissues.

Its use varies by treatment protocol.

Reduction

Closed reduction is attempted when feasible.

If soft-tissue structures prevent stable reduction, an open procedure is required.

Post-Reduction Immobilization

After reduction, the hip may be maintained in a spica cast for approximately 3–6 months, with cast changes and imaging as required.

Older Than 24 Months

Open Reduction

Older children more commonly require open reduction because the capsule, muscles, and intra-articular structures have become contracted and dysplastic.

Femoral Osteotomy

A femoral osteotomy may be performed to shorten, derotate, or realign the proximal femur.

Shortening can decrease excessive pressure on the reduced femoral head and may reduce the risk of avascular necrosis.

Pelvic Osteotomy

An iliac or other pelvic osteotomy may be needed to improve acetabular coverage of the femoral head.

The choice depends on age and the specific acetabular deformity.

Adductor Tenotomy

An adductor tenotomy may be performed when tight adductor muscles limit the safe range of hip abduction after reduction.

The goal is to enlarge the stable zone in which the hip remains reduced without excessive pressure.

Age and Surgical Outcome

The results of surgical reduction generally become less predictable as the child gets older.

Nevertheless, reduction may still provide worthwhile functional improvement in selected children up to approximately 6–8 years of age.

Physical Therapy

Routine physical therapy is usually limited.

Young children generally regain strength and hip motion naturally after reduction and immobilization.

Therapy may be used selectively when stiffness, weakness, or gait abnormalities persist.

Follow-Up

Long-Term Surveillance

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

Even after successful reduction, acetabular and femoral development may remain abnormal.

Residual Dysplasia

Approximately 10–25% of successfully reduced hips may fail to remodel completely.

Persistent acetabular or proximal femoral dysplasia may eventually require an osteotomy.

Prognosis

Early Treatment

When DDH is identified and treated successfully during infancy, the hip may develop nearly normally and long-term function can be excellent.

Untreated Complete Dislocation

Untreated complete dislocation results in abnormal hip mechanics and usually produces a permanent waddling or Trendelenburg gait.

Pain and degenerative change frequently develop by approximately 30–50 years of age, sometimes earlier.

Subluxated Hip

A persistently subluxated hip may develop symptomatic osteoarthritis earlier than a completely dislocated hip because the remaining articular surface is exposed to highly concentrated abnormal loading.

Complications

Femoral Nerve Palsy

Excessive hip flexion in a Pavlik harness can produce transient femoral nerve palsy.

Historically, this has been reported in approximately 2.5% of treated infants.

Redislocation

Redislocation may occur after reduction, with reported rates around 5%.

Stable maintenance of reduction and careful follow-up are therefore important.

Residual Dysplasia

Residual acetabular dysplasia may persist despite successful reduction.

Historical rates have been reported around 25%, depending on age and treatment method.

Avascular Necrosis

Avascular necrosis of the proximal femoral epiphysis is one of the most serious complications of treatment.

It may occur if blood supply to the femoral head is compromised by excessive positioning, forceful reduction, or other treatment-related factors.

Historical rates have been approximately 10%, although incidence varies substantially by technique and severity.

Consequences of Avascular Necrosis

Growth disturbance following AVN can produce femoral head deformity, shortening, altered neck-shaft relationship, joint incongruity, and later degenerative arthritis.

Once established, these changes may not be fully reversible.

Patient Monitoring

Patients require regular examination and imaging after treatment to ensure that the hip remains reduced and the acetabulum continues to develop normally.

Monitoring should include hip range of motion, limb length, gait, acetabular development, femoral head growth, and signs of avascular necrosis or recurrent instability.

Because incomplete remodeling may not become apparent until later childhood, surveillance should continue through skeletal maturity.