DEVELOPMENTAL DYSPLASIA OF THE HIP


I. Pathophysiology

  1. Traditionally referred to as "congenital hip dislocation," though it is not always congenital and often doesn't involve dislocation-"Includes hips that are unstable, subluxated, dislocated (luxated), and/or have malformed acetabula" (Peds. 2000)
  2. Wide spectrum of abnormalities
    1. Malformation-Any abnormal development of femoral head and/or acetabulum--usually the result rather than the cause of DDH
    2. Instability-Tendency for suluxation or dislocation to occur with externally applied force
    3. Subluxation-Incomplete dislocation with some residual contact between femoral head and acetabulum
    4. Dislocation-Complete displacement of femoral head from acetabulum
      1. "Teratologic" dislocation--refers to hip dislocation in association with other malformation, e.g. chromosomal abnormality or neuromuscular disorders (e.g. arthrogryposis or myelodysplasia); usually occurs early in fetal development (acetabulum and femoral head separate around 11wks)
      2. "Typical" dislocation--refers to hip dislocation in an otherwise healthy infant; can arise in utero or afterward
        1. Risk factors include oligohydramnios and breech presentation (esp. frank breech)
  1. Sequence of events--Subluxation/dislocation in early infancy alters the development of both femoral head & acetabulum so as to promote continued subluxation/dislocation
    1. In utero, hip is flexed and abducted. This results in
      1. Anterolateral orientation of acetabulum
      2. Tight iliopsoas tendon
    2. The tight iliopsoas tendon may push femoral head posteriorly when hip is extended (e.g. with kicking or swaddling), resulting in
    3. Flattening and eversion of labrum and, if subluxation or dislocation persists, then gradually:
      1. Posteromedial surface of femoral head flattens
      2. Femoral anteversion increases
      3. Acetabulum becomes shallow and "dysplastic"--this appears to be a result, rather than a cause, of DDH
      4. Labrum hypertrophies
      5. Hip capsule thickens
      6. Pulvinar (fibrofatty tissue) fills space between acetabulum and femoral head
      7. "Hourglassing" of hip capsule occurs with narrowing (due to pressure from iliopsoas tendon?) between femoral head and acetabulum, rendering the dislocation irreversible w/o surgery
      8. Contraction of the bup adductors limiting hip abduction

II. Clinical and epidemiologic features

  1. Risk increased with positive family history & breech presentation
  2. Whites > blacks
  3. Left > right (3:1; possibly b/c of prevalence of LOA position and thus left hip resting against maternal spine in utero)
  4. Female > male (4:1)
  5. Oligohydramnios
  6. Breech presentation
  7. Associated with other congenital malformations
    1. Congenital torticollis
    2. Metatarsus adductus
    3. Chromosomal abnormalities
    4. Neuromuscular disorders (e.g. arthrogryposis or myelodysplasia)
  1. Postnatal positioning has an impact--hips in flexion & abduction (e.g. parent carrying baby on their hip) reduces risk; hips in extension and adduction (e.g. papoose) increases risk
  2. Natural history is unpredictable--may resolve spontaneously or may progress to complete dislocation
    1. When progresses, can cause limp when starts to walk (often toe-walks on affected side; also intoeing or out-toeing)
    2. Can also cause osteoarthritis later in life

III. Diagnosis

  1. Will often be clinically undetectable at birth and throughout neonatal period
  2. At the same time, spontaneously-reducing dislocation of hips is common in first few days of life
  3. Screening should be done in first 4d of life and at all well-child visits through 1yo
  4. Note that bilateral DDH does occur and is more difficult to diagnose than unilateral because the asymmetry isn't there as a diagnostic clue
  5. Diagnosis by physical exam-No sign is pathognomonic; pt must be relaxed and on a firm surface
    1. Asymmetry in leg length (apparent shortening of femur on affected side; "Galleazi's sign")
    2. Asymmetry in hip position (less abduction affected side)
    3. Asymmetry of thigh & gluteal folds (observe prone)
    4. Increases prominence of greater trochanter on affected side
    5. Decreased hip ROM
      1. Examine supine with hip in 90' flexion and one hand stabilizing pelvis; should be able to abduct hip 75' and adduct to 30' past midline
    6. Maneuvers to reproduce dislocation or suluxation
      1. Both maneuvers depend on ligamentous and capsular laxity which decreases sharply at 10-12wks of age, so not much use after 12 wks old; rely more on other signs as above
      2. With pt supine, place tips of index & middle fingers over greater trochanters; thumb along medial thigh; have leg in neutral rotation and hips in 90' flexion
      3. Do on one side at a time, using other hand to stabilize pelvis
      4. Ortolani's maneuver: Position pt supine w/hip 90' flexed and neutral rotation; abduct and externally rotate hip while lifting leg anteriorly (with one middle finger over each greater trochanter); feel for "clunk" which is femoral head sliding into acetabulum ("sign of entry")
      5. Barlow's maneuver: After doing Ortolani's, adduct and internally rotate hip while pressing posteriorly; feel for "clunk" which is femoral head sliding out of acetabulum ("sign of exit")
      6. Sometimes will feel "telescoping" of femur with these maneuvers
      7. "High-pitched clicks are commonly elicited with flexion and extension and are inconsequential" (Peds. 2000)-Often due to snapping of iliotibial band
  6. Radiologic studies
    1. AP pelvis x-ray
      1. For use after 4mos old; difficult to interpret earlier because acetabulum and femoral head don't start to ossify until 3-7mos
      2. Analysis uses Hilgenreiner's and Perlin's lines, Shenton's line, etc. (see paper for details)
    2. Ultrasound
      1. For use up to 4mos old; less accurate afterward--"The technique of choice for clarifying a physical finding, assessing a high-risk infant, and monitoring DDH as it is observed or treated" (Peds.2000)
      2. Probably more sensitive than clinical exam but significant false-positive rate, esp. in first 4wks of life; After 4-6wks, acetabular development is such that ultrasound becomes more reliable
      3. Two techniques
        1. "Static technique"--coronal view; angles etc. are analyzed
        2. "Dynamic technique"--visualize anatomy with Ortolani's and Barlow's maneuvers; provides "more useful information" per Peds. 2000

IV. Management recommendations (per Peds article & AAP Guidelines cited below)

  1. Screen all infants with a thorough exam (AAP 2000)
  2. Positive Ortolani's or Barlow's doesn't usually need to be confirmed by ultrasound or x-ray; refer straight to ortho (AAP 2000)
  3. Equivocal physical exam should be repeated in 2wks before referring to ortho
    1. If f/u exam shows positive Ortolani's or Barlow's; refer to Ortho
    2. If exam still equivocal, refer vs. get ultrasound @ 3-4wks of age vs. observe if signs are minimal (AAP 2000)
    3. If exam is normal, f/u per routine well-child visit schedule
  4. If hip Px clearly shows DDH at birth, repeat Px daily and if hip spontaneously reduces, ultrasound at 2 weeks to document reduction and if reduction doesn't occur, consider starting tx at that time
  5. If hip Px is questionable at birth or if risk factors are present, ultrasound at 2-4 weeks and treat if abnormal; if normal and risk factors are present, do x-ray at 4mos
  6. Consider imaging if in any of the following high-risk groups
    1. Consider if Family h/o DDH and Female (u/s at 6wks or AP x-ray of pelvis at 4mos)
    2. RECOMMENDED IF Breech presentation and Female (u/s at 6wks and AP x-ray of pelvis at 4-6mos)
    3. Consider if Breech presentation and Male (u/s at 6wks and AP x-ray of pelvis at 4-6mos)
  7. Treatment modalities--goal of each is to maintain concentric reduction so that bony development occurs normally
    1. "Abduction diapering" (application of 2 or three diapers to keep femoral head in correct anatomic position)-Probably not effective based on available evidence as of 2012
    2. 0-6 mos old: Pavlik device
      1. Tends to guide hips into flexion and abduction but allows some movement
      2. Contraindicated when dislocation is due to paralysis
      3. May worsen the DDH if not adjusted properly
      4. Ultrasound must be done after 1-3wks of tx to confirm reduction
      5. Duration determined by when stability develops-Avg. 3-4mos if started at < 1mo; 9mos if started after 3mo
      6. Success of Pavlik device is much lower (about 50%) after 6mos of age
    3. > 6mo or poor response to Pavlik device-Surgical treatment
      1. Closed reduction with adductor release and casting
      2. Open reduction (severe cases or older children)

(Sources include Pediatrics 94:201, 1994; "Clinical Practice Guideline: Early Detection of Developmental Dysplasia of the Hip" Peds. 105(4) Part 1 of 2, pp. 896-905, 2000; Sources include Core Content Review of Family Medicine, 2012)