FIG 1. Trephine set for biopsy of the thoracic spine. 1 = fine needle (external diameter, 1.5 mm); 2 = rigid guidewire (length, 32 cm); 3 = graduated external sheath (external diameter, 2.8 mm); 4 = hollow intermediate piece with handle; 5 = serrated cannula (internal diameter, 1.6 mm; external diameter, 2.2 mm); 6 = obturator. In the set for biopsy of the lumbar spine, the rigid guidewire is 40 cm long. The graduated external sheath has an external diameter of 4 mm, and the serrated cannula, an internal diameter of 2.2 mm