Vertebra bodies in the human spine are stabilized through the use of minimally invasive surgery for the implantation of an elongate implant plate assembly having spaced first and second screw receiving socket elements which are configured for respective attachment to first and second spaced vertebra with the aid of bone fixation screws and these elements are slidably received with respect to each other for adjustably changing the distance between the screw receiving socket elements. A lock assembly is also provided for selectively locking the first and second screw receiving elements from further relative sliding. An elongate insertion tool is releaseably secured to the plate assembly, and the insertion tool is configured for manipulating the plate assembly as a whole and for remotely manipulating the screw receiving socket elements for adjusting the distance therebetween.