hip ultrasound: why, when, and how? dorothy bulas m.d. childrens national medical center washington...

Hip ultrasound: Hip ultrasound: Why, When, and How?Why, When, and How?

Dorothy Bulas M.D.Children’s National Medical Center

Washington D.C.

Disclosure

• I have no relevant financial relationships with the manufacturers of any commercial products and/or provider of commercial services discussed in this CME activity

• I do not intend to discuss an unapproved use of a commercial product/device in my presentation

Objectives

• Review the risk factors for developmental dysplasia of the hip (DDH)

• Understand the appropriate work up and follow up of DDH

Changes in practice

• Use appropriateness criteria to assess for developmental dysplasia.

• Selective screening by ultrasound after 2 weeks of age

Introduction

• Developmental dysplasia of the hip is the preferred term to describe the condition in

which the femoral head has an abnormal relationship to the acetabulum.

• DDH is a spectrum of abnormalities– frank dislocation (luxation)

– partial dislocation (subluxation) – unstable - femoral head comes in & out of socket

– inadequate formation of the acetabulum.

DDH

• Many of these findings may not be present at birth

• SO - the term developmental more accurately reflects the biologic features than the term congenital.

Early Diagnosis

• The earlier a dislocated hip is detected, the simpler and more effective is the treatment.

Late Diagnosis • Late dx in children may lead to increased

surgical intervention and complications.

• Late dx in adults can result in debilitating end-stage degenerative hip joint disease.

Why Screen?

• Screening decreases the incidence of late diagnosis of DDH.

• Despite screening programs, DDH continues to be diagnosed later in infancy /childhood, delaying appropriate therapy

• Substantial number of malpractice claims

Incidence• 1.5 : 1,000 Caucasian Americans

– less frequent African Americans.

• F:M 6:1 (?hormonal)• The reported incidence influenced by FH,

– race, – diagnostic criteria, – experience /training of examiner, – age.

Incidence• Family History

– 6% risk - healthy parents & affected child – 12% risk - affected parent – 36% risk- affected parent & 1 affected child.

• Left hip 3 :1

Embryology• Femoral head / acetabulum develop from the

same block of primitive mesenchymal cells.• A cleft develops at 7- 8 wks' gestation. • By 11 wks' gestation, development complete. • Acetabulum continues to develop.

Fibrocartilaginous labrum surrounds the bony acetabulum deepens the socket.

Embryology• Development of femoral head /acetabulum

related, normal adult hip joints depend on growth of these structures.

Embryology

Hip dysplasia may occur – in utero, – perinatally – during infancy– childhood

Embryology

Dislocations divided into 2 types: teratologic/ typical.

• Teratologic dislocations occur in utero and often associated with neuromuscular disorders - arthrogryposis/myelodysplasia, or syndromes.

• Typical dislocation occurs in otherwise healthy infant - prenatally or postnatally.

Embryology• Newborn period- laxity of hip capsule

– femoral head may spontaneously dislocate and relocate.

• If hip spontaneously relocates /stabilizes, hip development is normal.

• If subluxation/ dislocation persists structural anatomic changes develop.

Embryology• Need deep concentric position of femoral head in

acetabulum. • If not, labrum flattens, acetabulum doesn’t

grow/remodel and becomes shallow. • If dislocates, inferior capsule pulled up over empty

socket. • Adductors contract, limiting hip abduction. • Hip capsule constricts; hip cannot be reduced

manually – operative reduction necessary.

EmbryologyAt risk 4 periods:1) 12th gest week- fetal lower limb rotates medially.

Teratologic. 2) 18th gest week – hip muscles dev.

Myelodysplasia/arthrogryposis lead to Teratologic dislocations

3) Final 4 weeks of gestation Oligohydramnios/breech. Breech 3% of births, DDH up to 23%. Frank breech hip flexion /knee extension at highest risk.

4) Postnatal period -swaddling, combined with ligamentous laxity Typical

Risk Factors

– Family history

– Breech

– Oligohydramnios

– Foot deformities

– Torticollis

Clinical evaluation

• Evolves - clinical exam changes.

• Should be performed at each well-baby visit until 12 months.

• Newborn relaxed, examined on firm surface.

Physical Exam

• No signs are pathognomonic for a dislocated hip. – Asymmetrical gluteal folds (best observed prone)

– Apparent limb length discrepancy – Restricted motion

Ortolani Sign- elicits sensation of dislocated hip reducing

• supine, index / middle fingers placed at greater trochanter , thumb along inner thigh.

• The hip is flexed to 90°• Gently abducted while lifting the leg anteriorly. • "clunk" felt as dislocated head reduces into

acetabulum.

Barlow Sign- detects unstable hip dislocating from acetabulum

• Supine hips flexed to 90°.

• Leg adducted while posterior pressure on knee.

• Palpable clunk as head exits acetabulum.

• Forceful /repeated exam can break the seal b/w labrum /femoral head.

Physical Exam after 3 months

• By 8 - 12 weeks, capsule laxity decreases, muscle tightness increases – Barlow /Ortolani maneuvers no longer

positive.

• After 3 mos, limitation of abduction most reliable sign. – Discrepancy of leg lengths.

Physical Exam• False negative exam - Acetabular dysplasia

may have no subluxation/ dislocation. • False Positive exam - <1 mos NORMALLY

increased capsular laxity - subluxation due to maternal estrogens

• Equivocal examination – asymmetric thigh or buttock creases – Apparent or true short leg, – Limited abduction.

Radiographs

• Radiographs readily available, low cost.

• In neonate- femoral heads cartilage, limited– Displacement and instability undetectable

• 4 - 6 months, radiographs more reliable, when ossification center develops.

Developmental Dysplasia of the HipRadiologic Findings

• Acetabular index– slope of acetabular roof

> 30 0

• Line of Hilgenreiner – triradiate cartilage

• Perkins line (vertical)• Femoral epiphysis in

inner lower quadrant• Shenton’s curve

Negative radiograph does not R/O dislocation

Sonographic Evaluation

• No sedation, no radiation• Rapid • Noninvasive• Inexpensive

• Cartilage visualized can assess the stability of the hip and the morphologic features of the acetabulum.

Methods

• Graf method – single coronal plane

• Dynamic or real-time method- Harcke- assesses the hip for stability of femoral head in socket, as well as static anatomy.

• With both techniques, considerable interobserver variability, especially during the first 3 weeks of life.

Sonographic Evaluation

• Assess– Acetabular

depth

– Position of limbus

– Stability of hip

Ac Acetabular cartilage

C Capsule

G Gluteus muscles

GT Greater trochanter

H Cartilaginous femoral head

IL Ilium

Is Ischium

L Labrum

LT/P Ligamentum teres/ pulvinar complex

M Femoral metaphysis

Tr Triradiate cartilage

•Single coronal image emphasizes acetabular development

Graf Technique

– Type 1: normal α angle > 60o

Graf Technique

-Type II : α 44-60o, β 55-88o

IIa < 3 months immature acetabulum (40-59%)

No referral required

IIb,c,d require referral for treatment

Graf Technique

• Type III : α <44o, β>77o

Low displacement

• Type IV : completely dislocated– Immediate therapy

Coronal Harke method

Acetabular Coverage >50%

Acetabular Coverage >50%

40% Coverage

33% Coverage

20% Coverage

Dynamic Sonography-Technique

• Supine or lateral• Coronal view at rest

neutral or flexed– stress view

optional• Transverse flexion

view with stress

Ac Acetabular cartilage

G Gluteus muscles

GT Greater trochanter

H Cartilaginous femoral head

Is Ischium

L Labrum

LT/P Ligamentum teres/pulvinar complex

M Femoral metaphysis

Pu Pubis

Tr Triradiate cartilage

Stress - Stable

Stress - unstable

Dislocated

Dislocated

Calcified femoral epiphysis

Peterlein et al BMC Pediatr. 2010 24;10:98.Reproducibility of different screening

classifications in US of the newborn hip.

• Concordance of 2 classifications of hip morphology and subjective parameters by 3 investigators w/different levels of experience.

• METHODS: 207 newborns: α-angle and β-angle,"femoral head coverage" (FHC) shape of bony roof and position of cartilaginous roof.

• RESULTS: shape of bony roof (0.97) and position of cartilaginous roof (1.0) demonstrated high intra-observer reproducibility.

• Best results were achieved for α-angle, followed by β-angle then FHC.

• CONCLUSIONS: Higher measurement differences in objective scorings. Variations by every investigator irrespective of level of experience

Follow up

• Can perform exam in Pavlik Harness

• Perform out of harness only if requested and/or hip appears stable

• Once femoral head ossifies difficult to assess position.

Treatment

• Dislocated – treat

• Stable – don’t treat

• Unstable (lax not displaced) – ? Early treatment or observation??– 80% normalize

DDH - 35%

One month later

Follow Up

Should we Screen?

• There is no consensus on imaging screening for DDH.

• Screening balanced between the benefits of early detection of DDH and the increased treatment and cost factors.

Who?• Universal Newborn Screening

– pro- treat early– con-over treat minor abnormalities that

resolve• Considerable resources• Late cases missed• Higher rate of therapy? • Higher rate of avscular necrosis?

Universal Screening

• Randomized trials evaluating primary US screening did not find significant decrease in late diagnosis of DDH.

• This practice is yet to be validated by clinical trial.

Who?

Selective screening

• AAP US recommended as adjunct to clinical evaluation. technique of choice to clarify physical finding, assess high-risk infant, and monitor DDH as is observed or treated.

• Can guide treatment and may prevent overtreatment

Who?

• In the United States, hip US is selectively performed – Club foot– Torticollis– Females in breech position– Optional males in breech position– Optional females with positive FH– Inconclusive PE

Studies – Selective Screening• British 10 yr prospective of 34,723

– 2,578 clinical instability or risk factor– 77 unstable - 31% risk factor

• Irish 52,893 infants – US – 5,484 with FH, breech, click. – 18 dislocatable,153 (2.73%) dysplastic

3.2/1000 required Rx

• 33 center United Kingdom Hip Trial – found reduces splinting, and no increase in

surgical Rx

Preterm infants

• DDH may be unrecognized.• When the infant has cardiorespiratory problems,

the diagnosis and management are focused on providing appropriate ventilatory and cardiovascular support, careful examination may be deferred until a later date.

• The most complete examination the infant receives may occur at the time of discharge from the hospital, and this single exam may not detect subluxation or dislocation.

• critical to examine the entire child.

When?• PRO - US can detect abnormal position,

instability, and dysplasia not evident on clinical examination.

• CON - during the first month minor degrees of instability and acetabular immaturity.– nearly all mild early findings not be apparent on PE,

resolve spontaneously without treatment.

• Newborn screening - high frequency of reexamination and hips being unnecessarily treated.

• screening with higher false-pos results yields increased prevention of late cases.

When?• Screen those at risk at 4-6 wks (9%)

–pro• less expense,simpler process

• fewer false positives

–con• miss late cases

Hip Evaluation

S TO P

N o ris k fac to rs

U S 4 w ks

R isk fac to rs

N orm a l E xam

U S 4 w ks

S tab le C lic k

U s 1 -2 w ks

U n s tab le C lic k

A b n orm a l E xam

C lin ica l E xam

What are the AAP recommendations?1. All newborns screened by PE by a properly

trained health care provider (Evidence strong.)

2. US of all newborns is not recommended. (Evidence fair; consensus is strong.)

• Although indirect evidence supports US screening of all newborns, not advocated – • operator-dependent,

• availability is questionable,

• increases treatment,

• interobserver variability is high,

• increased costs.

 3. If positive Ortolani or Barlow sign found in the newborn, refer to an orthopaedist.

4. If results of the PE at birth are "equivocally" positive (ie, soft click, mild asymmetry,), FU hip exam by the pediatrician in 2 weeks is recommended. (Evidence is good; consensus is strong.)

• The hips must be examined at every well-baby visit – (2–4 days for newborns discharged in less

than 48 hours after delivery, 1 mos, 2 mos, 4 mos, 6 mos, 9 mos, 12 mos).

• If DDH is suspected confirmation made by a focused PE, by consultation with another pediatrician, orthopaedist, by US if the infant is < 5 months of age, or by radiography if the infant > 4 months of age.

Conclusions

• US has become the standard of care in the evaluation of the neonate with possible developmental dysplasia of the hip.

• Availability widespread, however, accurate results require training and experience.

Changes in practice

• Use appropriateness criteria to assess for developmental dysplasia.

• Selective screening by ultrasound after 2 weeks of age

AAP Clinical Practice Guideline: Early Detection of DDH

• Committee on Quality Improvement, Subcommittee on Developmental Dysplasia of the Hip