Diagnosis of DDH - Alistair Jepson 31/10/2000

Introduction:

DDH: generic term encompassing the many variations of congenital hip dysplasia, subluxation, and dislocation

o Klisic [1] (1989) introduced this term to replace CDH in order to encompass more accurately other abnormalities around the hip  

o This term is preferred to CDH as many cases have normal examination at birth

Diagnosis :

o Early diagnosis & treatment important as the deformity in the biologically plastic infant skeleton is readily corrected by re-positioning of the femoral head in the acetabulum

o Success of treatment directly related to age that diagnosis is made

o Diagnosis can be v. difficult

1. Clinical suspicion

i. Breech (loose hip capsule stretched by intra-uterine position i.e. acutely flexed hips with knees extended during development à ¢€" deforms labrum)

ii. Female (4-8x greater risk - ?because more susceptible to the placental passage of maternal oestrogens that cause pelvic relaxation during delivery)

iii. First born

iv. Ethnic factors ( ­ increased incidence in North American Indians, Japanese, Central & Southern Europeans)

v. Family Hx of DDH (~10x greater risk of dysplasia if first degree relative affected) [2]

vi. Metatarsus varus

vii. Clubfoot

viii. Torticollis ( £ 15% association with idiopathic muscular torticollis)

ix. Other congenital abnormalities (cardiac, renal)

x. Any congenital syndrome

2. Physical examination

Neonate

• Ortalani test [3]
  • In 1937 Marino Ortalani, Italian paediatrician, documented the association of a type of hip movement with the radiographic findings of DDH & popularised screening of neonates
  • Test is of reducibility: dislocated hip is reduced with abduction & gentle forward pressure - a clunk/click/shift/jerk of entry is felt
• Barlow test
  • Test of hip dislocatability (adduction & posterior force being applied)
  • Moore in 1989 [4] reported that the Barlow test might be more harmful than good (i.e. increase risk of instability)

• Normally repetitive combination of the two, starting with Barlow & then Ortalani components
  • As recommended in the SMAC guidelines (Standing Medical Advisory Committee) handbook, "Screening for the Detection of Congenital dislocation of the hip", published in 1986 by the DHSS

• Screening presently recommended by the DoH:
  • Within 24 hrs of birth
  • On discharge from hospital
  • 6 weeks
  • between 6 and 9 months
  • between 15 and 21 months

Older Infant (>1/12):

- By 2-3/12 hip become fixed in dislocated position due to soft tissue contractures

- Restricted abduction is a very impt finding (even 10 °), asymmetrical thigh skin folds & apparent femoral shortening, due to proximal as well as lateral migration - Galeazzi sign (Toddlers: Trenelenburg gait once start to walk due to gluteal muscle shortening. Duck-like waddle if bilateral with increased lumbar lordosis

- Adolescence: fatigue & pain on exercise

3. Radiology

Ultrasound:

• First choice of investigation before age of 4-5 months as secondary ossific centre for femoral head has not yet appeared
• Reinhard Graf [5]
  • Austrian paediatric orthopaedic surgeon who clarified the value of US in detecting and staging DDH (noted that ultrasound does pass through cartilage)
  • Static examination looking at a & b measured angles
• Harcke [6] [7]
  • American radiologist from the duPont Institute in Wlimington, Delaware
  • Developed a dynamic method of US study that actually stresses the hip, similar to an Ortalani & Barlow

Xray:

• AP XR with both legs extended & neutral abduction
• Reference grid constructed on the XR
  • Shenton's line
    • Described in 1902 specifically in relation to the diagnosis of DDH
  • Perkin's line [8]
    • Dropped perpendicular to the lateral margin of the boney acetabulum
  • Hilgenreiner's Line [9] (Y line, c.f. 'Y' cartilages)
    • Transverse line through the triradiate cartilage bilaterally
    • Also described a line on the inclined acetabulum - its intersection with the original line is the acetabular index, a measure of acetabular depth
    • <30 ° is normal (depends on age)
  • Centre-Edge angle of Wiberg [10]
    • Used in older children

CT:

Helpful after age of 6/12

Has the advantage that, unlike US, it can be performed while patient in cast to check reduction (only a few selected slices required)

MRI: