A precision depth guided instrument, such as a Jamshidi needle, is provided for use in various surgeries related to the vertebrae. The instrument includes an outer cannula, an inner cannula and a stylet. After the cortical bone of a vertebra is penetrated by the outer cannula of the instrument, the depth of penetration of the inner cannula is adjusted by rotation of the inner cannula. The inner cannula is then moved further into the vertebrae, and a stop mounted on the outer cannula controls the depth of penetration of the inner cannula. The correct depth of penetration is determined by radiography prior to the procedure.