members 16 to effect spinal fixation each single axis pedicle screw assembly 12 of the present invention includes a screw member 20 having a shaft 22 and a housing 24 as well as a locking screw 26 the shaft 22 and housing 24 are integrally formed as a unitary article such that the shaft 22 and housing 24 are in fixed relation hence the term u201c single axis u201d to describe this type of pedicle screw assembly 12 according to the present invention the shaft 22 includes a thread 28 suitable for introduction into and purchase within bone each housing 24 includes first and second branches 30 32 which collectively form a generally u201c u u201d shaped area dimensioned to receive at least one of a ball portion 34 and or a rod portion 36 forming either end of the rod member 16 according to a further aspect of the present invention and thereafter the locking screw 26 in a preferred aspect each component of the fixed angle pedicle screw assembly 12 is cannulated i e it is equipped with a longitudinal lumen extends through the locking screw 26 and screw member 20 such that a k wire may be used to guide the fixed angle pedicle screw assembly 12 into the patient each poly axial pedicle screw assembly 14 of the present invention includes a screw member 40 a housing 44 and a locking screw 46 the screw member 40 includes a shaft 42 the screw member 40 and housing 44 are separate articles such that the angle of the housing 44 relative to the screw member 40 may be varied in any number of fashions prior to locking them together hence the term u201c poly axial u201d to.