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Information

 Bone and Soft-Tissue Disorders

= TRANSIENT BONE MARROW EDEMA

Cause: unknown; ? overactivity of sympathetic nervous system + local hyperemia similar to reflex sympathetic dystrophy syndrome, trauma, synovitis, transient ischemia

Regional Migratory Osteoporosis  !!navigator!!

= rapid onset of self-limiting episodes of severe localized osteoporosis and pain but repetitive occurrence of same symptoms in other regions of same / opposite lower extremity

  • rapid onset of local pain
  • diffuse erythema, swelling, increased heat
  • significant disability ← severe pain on weight bearing

Age: middle-aged males

Location: usually lower extremity (ie, ankle, knee, hip, foot)

  • rapid localized osteoporosis within 4–8 weeks after onset migrating from one joint to another; may affect trabecular / cortical bone
  • linear / wavy periosteal reaction
  • preservation of subchondral cortical bone
  • NO joint space narrowing / bone erosion

MR:

  • affected area has low SI on T1WI, high SI on T2WI (= bone marrow edema)

NUC:

  • increased activity

Prognosis: persists for 6–9 months in one area; cycle of symptoms may last for several years

Rx: variable response to analgesics / corticosteroids

Partial Transient Osteoporosis

= variant of regional migratory osteoporosis with more focal pattern of osteoporosis, which may eventually become more generalized

  1. zonal form = portion of bone involved, ie, one femoral condyle / one quadrant of femoral head
  2. radial form = only one / two rays of hand / foot involved

Transient Osteoporosis of Hip  !!navigator!!

= self-limiting disease of unknown etiology

Age: typically in middle-aged males / in 3rd trimester of pregnancy in females involving left hip; M >F

  • spontaneous onset of hip and groin pain, usually progressive over several weeks
  • painful swelling of joint followed by progressive demineralization
  • rapid development of disability, limp, ↓ range of motion

Site: hip most commonly affected; generally only one joint at a time

  • progressive marked osteoporosis of femoral head, neck, acetabulum (3–8 weeks after onset of illness)
  • virtually PATHOGNOMONIC striking loss of subchondral cortex of femoral head + neck region
  • NO joint space narrowing / subchondral bone collapse

NUC:

  • markedly increased uptake on bone scan without cold spots / inhomogeneities (positive before radiograph)

MR:

  • diffuse bone marrow edema involving femoral head + neck + sometimes intertrochanteric region
  • small joint effusion

Cx: pathologic fracture common

Prognosis: spontaneous recovery within 2–6 months; recurrence in another joint within 2 years possible

DDx:

  1. AVN (cystic + sclerotic changes, early subchondral undermining)
  2. Septic / tuberculous arthritis (joint aspiration!)
  3. Monoarticular rheumatoid arthritis
  4. Metastasis
  5. Reflex sympathetic dystrophy
  6. Disuse atrophy
  7. Synovial chondromatosis
  8. Villonodular synovitis

 Outline