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Information

Bone and Soft-Tissue Disorders

Frequency: 1–3–5% of tuberculous patients

Age: any; rare in 1st year of life; M÷F = 1÷1

Location: spinal column, pelvis, hip, knee, wrist, elbow

Pathogenesis:

  1. Hematogenous spread from
    1. primary infection of lung (particularly in children)
    2. quiescent primary pulmonary site / extraosseous focus
    3. lymphatic focus in synovium
  2. Direct spread from adjacent focus of osteomyelitis (rare)
  3. Reactivation: especially in hip

Average delay in Dx: 16–19 months

Tuberculous Arthritis!!navigator!!

= joint involvement usually ← direct spread from adjacent osteomyelitis / hematogenous dissemination

Prevalence: 84% of skeletal tuberculosis (about 50% as tuberculous spondylitis)

Pathophysiology: synovitis with pannus formation leads to chondronecrosis

Age: middle-aged / elderly

  • chronic pain, weakness, muscle wasting
  • soft-tissue swelling, draining sinus
  • joint fluid: high WBC count, low glucose level, poor mucin clot formation (similar to rheumatoid arthritis)

Location: hip, knee (large weight-bearing joints) >>elbow, wrist, sacroiliac joint, glenohumeral, articulation of hand + foot

  • TYPICALLY monoarticular!

Nonspecific imaging findings similar to other arthritides:

  • osteopenia
  • synovitis + other soft-tissue swelling
  • marginal erosions
  • varying degrees of cartilage destruction
  • Phemister triad:
    1. Gradual narrowing of joint space ← slow cartilage destruction (DDx: much quicker cartilage destruction in pyogenic arthritis)
      Associated with: hyperemia + epiphyseal overgrowth in young patients
    2. Peripherally located (= marginal) bone erosions
    3. Juxtaarticular osteoporosis
      (DDx: fungal disease, rheumatoid arthritis)

Imaging findings favoring tuberculous arthritis:

  • insidious onset
  • minimal sclerosis
  • relative absence of periosteal reaction + bone proliferation
  • relative preservation of joint space in early stages

Early radiographs:

  • joint effusion (hip in 0%, knee in 60%, ankle in 80%)
  • extensive periarticular osteopenia (deossification) adjacent to primarily weight-bearing joints
  • soft tissues usually normal

Late radiographs:

  • small cystlike marginal erosions in non–weight-bearing line opposing one another
    DDx: pyogenic arthritis (erodes articular cartilage)
  • NO joint space narrowing for months (CLASSIC!) ← preservation of articular cartilage until late in disease
  • articular cortical bone destruction earlier in joints with little unopposed surfaces (hip, shoulder)
  • “kissing sequestra” = wedge-shaped areas of necrosis on both sides of the joint ← infection of subchondral bone
  • increased density with extensive soft-tissue calcifications in healing phase
  • rice bodies
  • sinus formation

Cx: fibrous (rarely osseous) ankylosis; leg shortening

Dx: joint aspiration (microscopic analysis), synovial biopsy (in 90% positive), culture of synovial fluid (in 80% positive)

DDx: pyogenic / fungal arthritis (central erosion of articular cartilage, early joint space narrowing, bony ankylosis)

Tuberculous Osteomyelitis!!navigator!!

◊Isolated tuberculous osteomyelitis in the absence of tuberculous arthritis is RARE!

Frequency: 16% of skeletal tuberculosis

Age: children <5 years (0.5–14%); rare in adults

Predisposed: HIV-infected individuals

  • painless swelling of hand / foot

Location: femur, tibia, small bones of hand + foot (most common); any bone may be involved

Site:

  1. metaphysis (TYPICALLY) with transphyseal spread (in child) (DDx: pyogenic infections usually do not extend across physis)
  2. epiphysis with spread to joint / spread from adjacent affected joint
  3. diaphysis (<1%)
  • initially round / oval poorly defined lytic lesion with minimal / no surrounding sclerosis
  • varying amounts of eburnation + periostitis:
  • NO periosteal reaction (in adult)
  • advanced epiphyseal maturity / overgrowth ← hyperemia
  • ± limb shortening from premature physeal fusion
  • cystic tuberculosis = well-marginated round / oval radiolucent lesions with variable amount of sclerosis
    1. in children (frequent): in peripheral skeleton, ± symmetric distribution, no sclerosis
    2. in adults (rare): in skull / shoulder / pelvis / spine, with sclerosis
      (DDx: eosinophilic granuloma, sarcoidosis, cystic angiomatosis, plasma cell myeloma, chordoma, fungal infection, metastasis)
  • tuberculous dactylitis = digit with exuberant lamellated / solid periosteal new-bone formation and fusiform soft-tissue swelling (children >>adults):
    • spina ventosa (“wind-filled sail”) = ballooning dactylitis forming an enlarging cystlike cavity with erosion of endosteal cortex (end-stage disease)
  • formation of sinus tracts

DDx:

  1. Pyogenic osteomyelitis (no transphyseal spread)
  2. Syphilitic dactylitis (bilateral symmetric involvement, less soft-tissue swelling and sequestration)
  3. Sarcoidosis, hemoglobinopathies, hyperparathyroidism, leukemia

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