Tuberculous vertebral osteomyelitis

  • developing countries, TB endemic areas
  • poverty, malnutrition, overcrowding
  • immunosuppressive states like HIV infection and AIDS
  • spine involvement usually secondary
  • comes from lung or genital tract infection
  • spine TB is 50% of all MSK TB infections
Imaging
  • around thoracolumbar junction
  • infection at anterior end of vertebral bodies
  • spreads under longitudinal ligament to involve contiguous vertebrae
  • skip lesions due to hematogenous spread
  • vertebral body most commonly affected, posterior elements rare (seen in Asians)
  • three patterns of involvement
    • paradiscal lesion: most common form. involvement of subchondral bone adjacent to intervertebral disc with reduction in disc height
    • anterior lesions: spread of infection under periosteum and anterior longitudinal ligament, loss of blood supply to vertebral body, necrosis and infection. abscess formation with stripping of periosteum causes scalloping and multilevel involvement
    • central lesions: centre of vertebral body, with loss of height, result in vertebra plana
  • gibbus deformity: vertebral body collapse, secondary acute angulation of spine
  • paraspinal abscess formation with no inflammation around it, hence called cold abscesses
radiograph
  • normal in acute infection
  • subacute: bone lucency in vertebral bodies. end plate destruction with reduction in intervertebral disc space. cold abscess appears as paraspinal soft tissue
  • chronic: sclerosis of bone and end plates, bone destruction with compression fractures and deformities. gibbus deformity with acute angulation in lateral view. kyphosis and scoliosis
CT
  • guiding biopsy
  • bone changes better seen
  • spinal canal encroachment better seen
  • iv contrast outlines paraspinal abscess
  • helps in abscess drainage guidance and in vertebral or disc biopsy
MRI
  • investigation of choice
  • sag T1, T2 and STIR
  • ax T2
  • well depicts subligamentous spread, multilevel involvement
  • abscess has well defined margins with smooth enhancement and minimal perilesional inflammation
  • STIR depicts the edema in all the involved vertebral bodies
  • posterior element involvement common in thoracic spine. Lamina > pedicles > articular processes.
  • SI joint involvement is rare. Calcification, sequestra and joint destruction favor TB