Destroyed Femoral Heads

Christopher G. Anton, MD

DIFFERENTIAL DIAGNOSIS

Less Common

Legg-Calvé-Perthes (LCP) Disease
Avascular Necrosis
Septic Arthritis
Juvenile Idiopathic Arthritis (JIA)
Slipped Capital Femoral Epiphysis (SCFE)

Rare but Important

Meyer Dysplasia
Idiopathic Chondrolysis
Epiphyseal Bone Tumors
Epiphyseal Dysplasias

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Age and clinical presentation
Need to exclude infection in child with hip pain and femoral head destruction

Helpful Clues for Less Common Diagnoses

Legg-Calvé-Perthes (LCP) Disease
- Avascular necrosis of femoral head of unknown etiology
- Age: 3-12 years old, peak 6-8 years old
- Bilateral (10-20%)
Radiographs
- Normal
- Flattening, sclerosis, fragmentation of femoral head ± subchondral fracture (best seen on frog leg lateral view)
- Bone scintigraphy: Earlier diagnosis than radiographs with decreased or absent perfusion
- MR: Earlier diagnosis than radiographs with decreased perfusion; loss of fatty marrow signal T1WI within femoral head
- 3 stages (initial fragmentation reparative)
  - Initial: Necrosis, vascular invasion, cartilage hypertrophy, overgrowth
  - Fragmentation: Necrotic/dead bone is resorbed, ± metaphyseal cysts (cartilage) and cartilage hypertrophy
  - Reparative: Healing and replacement of necrotic/dead bone
- Key: Prognosis heavily depends on containment of femoral head
  - Femoral head grows laterally (extrusion of femoral head) with widening of medial joint space
  - Incongruency between femoral head and acetabulum
  - Point of maximum weight bearing shifts laterally and leads to labral degeneration osteoarthritis 3rd or 4th decade of life
Avascular Necrosis
- Most commonly located: Anterolateral weight bearing portion of femoral head but can occur anywhere within femoral head
- Important to detect and treat prior to subchondral fracture subchondral collapse
- T2WI: “Double line” sign
- Many causes, including sickle cell disease, trauma, steroids, vasculitis, Gaucher disease, hemophilia
- Children with acute lymphoblastic leukemia (ALL) and those treated with steroids particularly at risk
Septic Arthritis
- Staphylococcus aureus most common
- May extend into joint from femoral epiphysis, metaphysis, joint capsule, or acetabulum
- Key: Early diagnosis and treatment
  - Ultrasound: Detect joint effusion (cannot distinguish infected vs. aseptic fluid)
  - Complications: Cartilage destruction (joint space narrowing), erosions, periosteal reaction, osteonecrosis, and soft tissue abscesses
Juvenile Idiopathic Arthritis (JIA)
- a.k.a. juvenile rheumatoid arthritis (JRA)
- < 16 years old and symptoms > 6 weeks in duration
- Joint space narrowing is a late finding
Slipped Capital Femoral Epiphysis (SCFE)
- Femoral head or joint destruction as complication in treatment
- Acute or chronic presentations
- Salter-Harris 1 femoral physeal fracture
- More common in boys
- Bilateral in up to 36%
  - When bilateral, contralateral SCFE usually occurs within 18 months
- Age
  - Girls: 8-15 years old
  - Boys: 10-17 years old
- Predisposition
  - Obesity (most significant)
  - Growth spurt, endocrine deficiencies, Down syndrome, and renal rickets
- Complications
  - Chondrolysis (10%)
  - Avascular necrosis (1%), increase in open reduction with fixation or pins across superolateral quadrant of femoral head ossification center
  - Pin penetration

Helpful Clues for Rare Diagnoses

Meyer Dysplasia
- Age: 2-4 years old
- Mostly boys
- Bilateral (60%)
- Asymptomatic
- When clinical sign or symptoms present, consider early LCP disease
Idiopathic Chondrolysis
- Destruction of articular cartilage of femoral head and acetabulum
- Stiffness, limp, and pain around hip
- Radiographs: Concentrically joint space narrowing, < 3 mm with osteopenia, pelvic tilt
- MR: Rectangular hypointense T1 and hyperintense T2 signal abnormality of center 1/3 of femoral head, ± ill defined within acetabulum
Epiphyseal Bone Tumors
- Chondroblastoma
  - 1% of primary bone tumors
  - 2nd decade of life, > 90% are seen in patients < 30 years old
  - M:F = 2:1
  - Well-defined, eccentric, lucent, sclerotic borders
  - Calcified matrix (50%)
- Giant cell tumor
  - 4-5% of primary bone tumors
  - Considered benign, but malignant in up to 10% (can metastasize to lungs)
  - Slight female predominance
  - After growth plate closure
Epiphyseal Dysplasias
- Diastrophic dysplasia
  - Characteristic: “Hitchhiker thumb”
  - Cervical platyspondyly and kyphosis, clubfoot
- Multiple epiphyseal dysplasia
  - Ribbing (milder form) or Fairbank forms
  - Should differentiate from LCP
  - Bilateral and symmetric changes, short limbs
- Spondyloepiphyseal dysplasia
  - Congenita: Evident at birth; short trunk, mildly short limbs, pear-shaped vertebral body, atlantoaxial instability
  - Tarda: Presents at age 5-10; short trunks, disc spaces widened anteriorly and narrowed posteriorly, flattening vertebral bodies, dysplastic epiphyses