13 Adult Hip Dysplasia

Luis F. Pulido-Sierra, Carlos J. Meheux

13 Adult Hip Dysplasia

Introduction

I. Common structural hip disorder ¹ :
1. Acetabular deficiency is the primary component in adult hip dysplasia.
2. Decreased anterior and lateral coverage of the femoral head.
3. Symptoms are related to level of activity and severity of dysplasia.
4. Acetabular rim syndrome ² :
  1. High peak stresses at the superior anterior and lateral rim.
  2. Early failure of the labrum.
  3. Femoral head subluxation.
  4. Early osteoarthritis.
5. Established cause of hip osteoarthritis ³ :
  1. Tönnis grade:
    1. Grade 0: normal.
    2. Grade 1: mild osteoarthritis.
    3. Grade 2: moderate osteoarthritis.
    4. Grade 3: severe osteoarthritis.
  2. End-stage hip osteoarthritis secondary to hip dysplasia ⁴ :
    1. Adult hip dysplasia.
    2. Low-grade dislocation.
    3. High-grade dislocation.
II. Epidemiology of adult hip dysplasia:
1. The prevalence of adult hip dysplasia varies from 2 to 20%.
2. Multifactorial disease with genetic and environmental risk factors.
3. Risk factors for adult hip dysplasia:
  1. Residual congenital hip dysplasia:
    1. Female.
    2. Breech presentation.
    3. Oligohydramnios.
    4. Primiparity.
  2. Family history.
  3. First-degree relatives with developmental dysplasia of the hip (DDH):
    1. Twelvefold increase in risk for DDH.
    2. Twenty-seven-fold increase risk for adult hip dysplasia.
  4. Genetics ⁵ , ⁶ :
    1. Multiple susceptibility genes.
    2. Gene CX3CR1 (variants rs3732378 and rs3732379):
      - i. 2.25-fold increase risk after adjusting for gender.
      - ii. Consistent in different ethnics (Utah and China).
      - iii. Affects chondrocyte maturation and bone formation.
    3. GDF5 (growth differentiation factor 5):
      - i. CDMP1(cartilage-derived morphogenetic protein-1).
    4. ASP (Asporin).
  5. Higher prevalence in certain ethnicities:
    1. Asians:
      - i. Japan.
      - ii. China.
    2. Norway.
    3. Italy.
    4. Native Americans.
III. Common cause of osteoarthrosis:
1. Edge-loading stresses.
2. Acetabular rim syndrome.
3. Multiple studies have shown association of dysplasia and osteoarthrosis.
4. High prevalence (25–50%) of hip dysplasia in patients younger than 50 years who undergo total hip arthroplasty (THA).

Anatomic Considerations

I. Acetabular dysplasia ⁷ – ⁹ :
1. Classic acetabular dysplasia:
  1. Decreased anterior femoral head coverage.
  2. Decreased lateral femoral head coverage.
  3. Steep upsloping acetabular sourcil.
  4. Lateralized femoral head.
  5. Small acetabular volume.
2. Acetabular retroversion:
  1. Different acetabular pathology.
  2. Prevalence of acetabular retroversion is one out of six to one out of three symptomatic hips.
  3. Posterior insufficiency and anterior overcoverage.
  4. Cause of anterior femoroacetabular impingement (FAI):
    1. Anterior labral pathology from impingement.
    2. External rotation of the hemipelvis.
    3. Increased anterior coverage.
    4. Decreased posterior coverage.
II. Femoral abnormalities ¹⁰ – ¹³ :
1. Femoral neck shaft angle:
  1. Increased neck shaft angle:
    1. More common in adult hip dysplasia (44%).
    2. Coxa valga: neck shaft angle greater than 135 degrees:
      - i. Decreased femoral head coverage.
      - ii. Decreased femoral lateral offset.
      - iii. Decreased abductor moment arm.
      - iv. Increased abductor force.
      - v. Increased joint contact forces.
  2. Decreased neck shaft angle:
    1. Less common in adult hip dysplasia (4%).
    2. Coxa vara: neck shaft angle less than 120 degrees:
      - i. Increased femoral head coverage.
      - ii. Increased risk for anterior impingement.
      - iii. Increased femoral lateral offset.
      - iv. Increased abductor moment arm.
      - v. Decreased abductor force.
2. Femoral version:
  1. Normal femoral version: 5 to 20 degrees.
  2. Large variability in adult hip dysplasia:
    1. Ranges from 0 to 80 degrees of anteversion.
  3. Increased femoral anteversion: greater than 20 degrees:
    1. More common in adult hip dysplasia:
      - i. Decreased abductor lever arm.
      - ii. Increased abductor force.
      - iii. Increased joint contact forces.
  4. Decreased femoral anteversion or retroversion: under 5 degrees:
    1. Less common in hip dysplasia.
    2. Increased risk of anterior impingement.
3. Femoral head and neck deformity:
  1. Ten percent to 42% prevalence of cam deformity in hip dysplasia.
  2. Elliptical femoral heads.

History and Examination ¹⁴

I. Symptoms present in adult hip dysplasia:
1. Pain onset:
  1. Insidious (97%).
  2. Acute (1%).
  3. Traumatic (1%).
2. Pain severity:
  1. Severe (26%).
  2. Moderate (51%).
  3. Mild (23%).
3. Pain location:
  1. Groin (72%).
  2. Lateral hip (66%).
  3. Anterior thigh (29%).
  4. Buttock and groin pain (18%).
  5. Isolated buttock pain (0%).
  6. More than one location (63%).
4. Pain quality:
  1. Activity related (87%).
  2. Dull (ache) (78%).
  3. Sharp (72%).
  4. Intermittent (53%).
  5. Constant (42%).
  6. Night pain (59%).
5. Pain duration:
  1. Common delay in diagnosis.
  2. Average 5 years from onset of symptoms to diagnosis.
6. Associated symptoms:
  1. Snapping/popping (67%).
  2. Locking (23%).
  3. Subluxation (22%).
  4. Limping (85%):
    1. Mild limp (54%).
    2. Moderate limp (25%).
    3. Severe limp (6%).
7. Exacerbating factors:
  1. Walking (81%).
  2. Running (80%).
  3. Standing (70%).
  4. Impact (55%).
  5. Pivoting (45%).
  6. Sitting (44%).
  7. Standing from sitting (31%).
8. Relieving factors:
  1. Rest (75%).
  2. Oral nonsteroidal anti-inflammatory drugs (56%).
  3. Oral narcotics (8%).
II. Physical examination ¹⁴ :
1. Inspection:
  1. Deformity.
  2. Gait:
    1. Limp (85%).
    2. Intoeing.
    3. Negative foot progression angle.
  3. Single leg stance:
    1. Positive Trendelenburg sign (38%).
2. Range of motion:
  1. Unrestricted.
  2. Internal rotation with hip flexion of 90 degrees:
    1. Limited:
      - i. Associated FAI cam morphology.
    2. Excessive:
      - i. Increased femoral anteversion:
        
        evaluate in prone position.
3. Strength:
  1. Abductor weakness and abductor fatigue.
4. Special testing:
  1. Impingement test (flexion, adduction, and internal rotation [FADIR])
  2. Apprehension test (extension, abduction, and external rotation).
  3. Hip adduction and axial load.
  4. Stinchfield’s test (resisted hip flexion during straight leg raise).

Diagnostic Imaging

I. Plain radiographs ¹⁵ :
1. Weight-bearing anteroposterior (AP) pelvis and false profile:
  1. Better acetabular morphology evaluation.
2. Lateral and Dunn views:
  1. Better femoral head and neck morphology evaluation.
3. AP pelvis ( Fig. 13.1 ):
  1. Technique:
    1. Beam at the center of the pelvis.
    2. Bilateral feet in 15 degrees of internal rotation.
    3. Tube perpendicular to the film.
      
      Fig. 13.1 Standing anteroposterior pelvis radiograph showing mild bilateral hip dysplasia.
    4. Tube-to-film distance of 120 cm:
      - i. Standing:
        
        better assessment of the joint space
        
        functional view:
        
        spinopelvic.
      - ii. Supine:
        
        underestimation:
        
        hip joint space
        
        osteoarthritis.
  2. Evaluation:
    1. Joint space.
    2. Degree of osteoarthritis:
      - i. Tönnis classification.
    3. Acetabular inclination:
      - i. Tönnis angle.
    4. Lateral coverage:
      - i. Lateral center edge angle (LCEA) of Wiberg.
    5. Hip congruity.
    6. Cranial subluxation of the femoral head.
      - i. Shenton’s line.
    7. Femoral head lateralization:
      - i. Femoral head relative to lateral teardrop.
      - ii. Distance greater than 10 mm.
    8. Acetabular depth:
      - i. Protrusio acetabuli:
        
        medial femoral head crosses the ilioischial line.
      - ii. Coxa profunda.
    9. Acetabular version:
      - i. Anterior and posterior walls:
        
        acetabular retroversion:
        
        crossover sign (may be prominent subspine rather than focal retroversion),
        
        posterior wall sign,
        
        ischial spine sign.
    10. Femoral head and neck:
      - i. Shape: deformities:
        
        associated cam morphology
        
        head sphericity.
      - ii. Angle:
        
        coxa vara.
        
        coxa valga.
4. False profile ( Fig. 13.2 ):
  1. Technique:
    1. Standing.
    2. Affected hip against the film.
    3. Pelvis rotated 65 degrees.
    4. Tube-to-film distance of 102 cm.
  2. Evaluation:
    1. Anterior coverage:
      - i. Anterior center edge angle (of Lequesne).
    2. Anterior joint space.
      
      Fig. 13.2 Standing false-profile radiograph illustrating anterior hip dysplasia and mildly incongruent hip joint.
    3. Degree of osteoarthritis.
    4. Anterior inferior iliac spine.
    5. Hip congruity.
5. Cross-table lateral:
  1. Technique:
    1. Supine.
    2. Neutral extension of the affected hip and 15-degree internal rotation.
    3. Contralateral hip flexion of 90 degrees.
    4. X-ray beam at 45-degree angle to the affected hip.
  2. Evaluation:
    1. Posterior hip joint space.
    2. Degree of osteoarthritis.
    3. Anterior cam.
6. Frog leg lateral:
  1. Technique:
    1. Supine.
    2. Affected hip abducted 45 degrees and flexed 30 to 40 degrees.
    3. The heel rests on the contralateral medial knee.
    4. Beam at the center of the pelvis.
    5. Tube-to-film distance of 102 cm.
  2. Evaluation:
    1. Femoral head and neck.
    2. Hip reduction with abduction.
7. Dunn 45 degrees:
  1. Technique:
    1. Supine.
    2. Affected hip abducted 20 degrees, flexed 45 degrees, and neutral rotation.
    3. Beam at the center of the pelvis.
    4. Tube-to-film distance of 102 cm.
  2. Evaluation:
    1. Femoral head and neck.
    2. Sensitive for anterolateral cam detection.
8. Dunn 90 degrees:
  1. Technique:
    1. As Dunn 45 degrees, but with the hip flexed at 90 degrees.
  2. Evaluation:
    1. Femoral head and neck.
II. Radiographs interpretation:
1. Degree of osteoarthritis:
  1. Tönnis classification:
    1. Grade 0: normal.
    2. Grade 1: mild:
      - i. Increased sclerosis.
      - ii. Slight joint space narrowing.
    3. Grade 2: moderate:
      - i. Small cysts.
      - ii. Moderate joint space narrowing.
      - iii. Moderate loss of femoral head sphericity.
    4. Grade 3: severe:
      - i. Large cysts.
      - ii. Severe joint space narrowing.
      - iii. Joint space obliteration.
      - iv. Severe deformity of the femoral head.
2. Evaluation of acetabular dysplasia ¹⁵ :
  1. Tönnis angle ( Fig. 13.3 ):
    1. Acetabular roof angle of Tönnis.
    2. Evaluation of acetabular inclination.
    3. Measurement of the angle of Tönnis:
      - i. AP pelvis radiograph.
        
        Fig. 13.3 Anteroposterior pelvis radiograph illustration on how to measure the acetabular inclination using the acetabular roof angle of Tönnis. Draw a horizontal inter teardrop line (line 1) to correct the pelvic obliquity. Bring line 1 at the level of the inferior sourcil (IS). Identify the lateral margin of the sclerotic sourcil (LS) and draw line 2 connecting the inferior sourcil with the lateral sourcil. The Tönnis angle (TA) is formed by the intersection of lines 1 and 2.
      - ii. Line 1:
        
        horizontal inter-teardrop line,
        
        raise line 1 to the inferior sourcil,
        
        corrects pelvic obliquity.
      - iii. Line 2:
        
        inferior point of the sclerotic sourcil;
        
        lateral point of acetabular sourcil:
        
        lateral margin of the sclerotic sourcil;
        
        connect the lateral and inferior sourcil.
      - iv. Angle is formed by the intersection of lines 1 and 2.
    4. Normal angle is 0 to 10 degrees.
    5. Hip dysplasia if angle is greater than 10 degrees.
  2. LCEA ( Fig. 13.4 ):
    1. Evaluation of the femoral head lateral coverage.
    2. LCEA of Wiberg.
    3. Measurement:
      - i. AP pelvis.
      - ii. Mark the center of the femoral head.
      - iii. Line 1:
        
        horizontal inter-teardrop line.
        
        Fig. 13.4 Anteroposterior pelvis illustration on how to measure the acetabular lateral center edge angle (LCEA) of Wiberg. Identify and mark the center of the femoral head. Draw a horizontal inter-teardrop line (line 1) to correct the pelvic obliquity. Draw a vertical line (line 2) perpendicular to the inter-teardrop line and through the center of the femoral head. Draw a line from the center of the femoral head to the lateral margin of the sclerotic sourcil (line 3). The lateral center angle of Wiberg is formed by the intersection of lines 2 and 3.
      - iv. Line 2:
        
        vertical line through the center of the femoral head
        
        perpendicular to line 1 inter-teardrop (90 degrees).
      - v. Line 3:
        
        center femoral head.
        
        lateral margin of the sclerotic sourcil.
      - vi. Angle formed by the intersection of lines 2 and 3.
    4. Normal angle is between 25 and 45 degrees.
    5. Hip dysplasia if angle is less than 25 degrees:
      - i. Twenty to 25 degrees = borderline dysplasia.
      - ii. Less than 20 degrees = dysplasia:
        
        mild—15 to 20 degrees.
        
        moderate—5 to 15 degrees.
        
        severe: less than 5 degrees.
    6. Overcoverage if angle is greater than 40 degrees (pincer morphology).
  3. Hip joint congruity:
    1. Relationship of the femoral head contour to the acetabulum.
    2. Hip congruity:
      - i. The femoral head matches the arc of the acetabulum.
    3. Hip incongruity:
      - i. The femoral head does not match the arc of the acetabulum:
        
        shape of the femoral head,
        
        shape of the acetabulum,
        
        severity of acetabular dysplasia,
        
        prognostic factor in surgical treatment,
        
        skeletally immature:
        
        salvage or shelf osteotomy.
  4. Anterior center edge angle ( Fig. 13.5 ):
    1. Evaluation of the femoral head anterior coverage.
    2. Anterior center edge angle of Lequesne and de Seze.
    3. Affected by the spinopelvic position.
    4. Measurement:
      - i. False-profile view.
      - ii. Mark the center of the femoral head.
      - iii. Line 1:
        
        vertical line through the center of the head.
      - iv. Line 2:
        
        anterior margin of the sclerotic sourcil.
      - v. Angle formed by the intersection of lines 1 and 2.
        
        Fig. 13.5 False-profile illustration on how to measure the acetabular anterior center edge angle (ACEA) of Lequesne. Identify and mark the center of the femoral head. Draw a vertical line through the center of the femoral head (line 1). Draw a line from the center of the femoral head to the anterior margin of the sclerotic sourcil (line 2). The ACEA of Lequesne is formed by the intersection of lines 1 and 2.
    5. Normal angle is ≥20 degrees.
    6. Anterior instability or dysplasia if angle is less than 20 degrees.
III. Computed tomography (CT):
1. Supplementary diagnostic test:
  1. Not routinely performed.
2. Useful in the evaluation of:
  1. Femoral torsional deformity.
  2. Mild hip dysplasia.
3. Pelvis with distal femur acquisition:
  1. Femoral version.
  2. Acetabular version.
4. Three-dimensional reconstructions.
IV. Magnetic resonance imaging (MRI):
1. Supplementary diagnostic test:
  1. Not routinely performed.
2. Useful in the evaluation of:
  1. Mechanical hip symptoms.
  2. Associated cam morphology.
3. Hip at 3.0 T.
4. MRI arthrogram:
  1. Better labral evaluation.
5. Biochemical MRI ¹⁶ :
  1. Delayed gadolinium-enhanced MRI of the cartilage (DGEMRIC).
  2. Limited access:
    1. Not routinely used in clinical practice.
  3. Measures the glycosaminoglycan content of the cartilage.
  4. Low biochemical index may precede structural cartilage damage.