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Bone and Soft-Tissue Disorders

= NEUROTROPHIC JOINT = CHARCOT JOINT= “OSTEOARTHRITIS WITH A VENGEANCE”

[Jean-Martin Charcot (1825–1893), first professor of neurology at the Salpêtrière hospital in Paris]

= progressive degenerative + destructive joint disorder in patients with abnormal pain sensation + proprioception

Cause:

  1. Congenital
    1. Myelomeningocele
    2. Congenital indifference to pain = asymbolia
    3. Familial dysautonomia (Riley-Day syndrome)
    4. Hereditary sensory and motor neuropathy (Charcot-Marie-Tooth disease)
  2. Acquired
    1. central neuropathy
      1. Injury to brain / spinal cord
      2. Syringomyelia (in ⅓ of patients): shoulder, elbow
      3. Neurosyphilis = tabes dorsalis (in 15–20% of patients): hip, knee, ankle, tarsals
      4. Spinal cord tumors / infection
      5. Extrinsic compression of spinal cord
      6. Multiple sclerosis
      7. Alcoholism
    2. peripheral neuropathy
      1. Diabetes mellitus (most common cause, although incidence low): midfoot, tarsometatarsal joints (middle cuneiform + base of 2nd metatarsal bone first affected), intertarsal joints, subtalar joints, metatarsophalangeal joints, ankle
      2. Peripheral nerve injury
      3. Peripheral nerve tumor
      4. Leprosy (Hansen disease)
      5. Poliomyelitis
    3. others
      1. Scleroderma, Raynaud disease, Ehlers-Danlos syndrome
      2. Rheumatoid arthritis, psoriasis
      3. Amyloid infiltration of nerves, adrenal hypercorticism
      4. Uremia
      5. Pernicious anemia
  3. Iatrogenic
    1. Prolonged use of pain-relieving drugs
    2. Intraarticular / systemic steroid injections

mnemonic: DS6

  • Diabetes
  • Syphilis
  • Steroids
  • Spinal cord injury
  • Spina bifida
  • Syringomyelia
  • Scleroderma

Pathophysiology:

loss of proprioception with sensory deficits arising in the spinal cord / peripheral nerves

  1. Neurotraumatic theory
    = repetitive trauma with absence of normal protective sensory feedback
  2. Neurovascular theory
    = absence of neural stimuli → loss of sympathetic tone resulting in vasodilatation and hyperemia, which promotes bone resorption + weakening of subchondral bone

Pathology:

  1. atrophic pattern (most common):
    • joint destruction, resorption of fragments (osteoclasts + macrophages remove bone + cartilage debris), dissolution / “amputation” of periarticular bones, joint effusion
      • notable absence of osteosclerosis + osteophyte formation
    • Associated with: syringomyelia, peripheral nerve lesion, also in diabetes
    • Location: non-weight-bearing joints of upper extremity
    • DDx: surgical amputation, septic arthritis
  2. hypertrophic pattern (only sensory nerves affected):
    joint destruction, fragmentation of bone, periarticular bony debris
    • osteosclerosis + osteophyte formation (early, attaining enormous size)

    DDx: severe osteoarthritis
  3. mixed pattern
  4. common to both: joint disorganization, large persistent bloody joint effusion
  • no history of trauma
  • swollen + warm joint with normal WBC count + ESR (infection may coexist)
  • usually painless joint; pain at presentation (in ⅓) with decreased response to deep pain + proprioception
  • joint changes frequently precede neurologic deficit
  • synovial fluid: frequently xanthochromic / bloody, lipid crystals (from bone marrow)
  • persistent joint effusion (first sign)
  • narrowing of joint space
  • speckled calcification in soft tissue (= calcification of synovial membrane)
  • fragmentation of eburnated subchondral bone
  • NO juxtaarticular osteoporosis (unless infected)
  • “bag-of-bones” appearance in late stage (= marked deformities around joint)
    mnemonic: 6 Ds
    • Dense subchondral bone (= sclerosis)
    • Degeneration (= attempted repair by osteophytes)
    • Destruction of articular cortex (with sharp margins resembling those of surgical amputation)
    • Deformity (“pencil point” deformity of metatarsal heads)
    • Debris (loose bodies)
    • Dislocation (nontraumatic)
  • subluxation of joints (laxity of periarticular soft tissues)
  • progressive rapid bone resorption
  • joint distension (by fluid, hypertrophic synovitis, osteophytes, subluxation)
  • fracture: healing with exuberant bizarre callus formation

MR:

  • decreased SI in bone marrow on T1WI + T2WI ← osteosclerotic changes
  • Shoulder
    Cause: syringomyelia, cord trauma with paraplegia
    • shoulder mass (due to fluid distension)
    • amputated appearance of proximal humerus
    • dislocation
    • large joint effusion
    • fragmented osseous debris in joint capsule + subacromial-subdeltoid bursa

    DDx: chondrosarcoma
  • Neuropathic spine = Charcot spine (involved in 6–21%)
    Cause: diabetes mellitus >traumatic spinal cord injury, syringomyelia, inadequately treated syphilis, amyloidosis, congenital insensitivity to pain
    Site: lower thoracic spine, lumbar spine >cervical spine, upper thoracic spine, sacrum
    • mild pain and spinal deformity
    • intervertebral disk space narrowing
    • disk vacuum phenomenon
    • osteolysis / sclerosis of vertebrae:
      • extensive osseous fragmentation extending beyond confines of vertebral body margins into paraspinous musculature + into spinal canal
    • large hypertrophic beaking endplate osteophytes
    • paraspinous soft-tissue calcification:
      • mineralized paraspinal fluid collections containing osseous debris
    • facet joint erosion + subluxation (early findings) → spondylolisthesis
    • scoliosis + abrupt curvature
    • rimlike enhancement of disk + signal intensity changes of bone marrow

    DDx: infectious spondylitis (NO involvement of facet joints, diffuse enhancement of disk + endplates), metastasis, granulomatous infection, severe degenerative disk disease
  • Hands + feet
    Cause: leprosy (due to trauma + secondary bacterial infection)
    • claw hand / claw toes
    • “licked candy cane” appearance of metatarsal bone / tapered phalanx ← concentric bone atrophy with decrease in bone length + width

    DDx: diabetes mellitus, frostbite, pernicious anemia, scleroderma, syringomyelia, tabes dorsalis, familial sensory neuropathy
  • Foot + ankle
    Cause: long-term poorly controlled diabetes mellitus, syphilis
    • soft-tissue swelling, warmth, erythema

    Site: often begins in midfoot
    • vascular calcifications
    • subluxation (starting at 2nd tarsometatarsal joint)