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 a stop mounted to the outer 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.