A 46-year-old, known alcoholic, presented with pain in the dorsal spine. On examination there is tendrness at the dorso-lumbar junction. Radiograph shows destruction of the 12thdorsal vertebra with loss of disc space between D12- L1 vertebrae. The most probable diagnosis is -

Characteristic radiological feature of pott's spine is obliteration of disc space with destruction (wedge compression) of one or two adjacent vertebrae. This feature differentiate Koch's spine from other diseases causing vertebral destruction (like metastasis, multiple myeloma), in which disc space is preserved.