Abstract: The present invention describes a bone anchor having a bone abutment surface adapted for congruent attachment to a bone and methods for the production of said bone anchor. The manufacturing methods generally involve mapping of the form of the bone to which the bone anchor is to be applied, commonly carried out by means of an imaging technique. Manufacturing methods further include any suitable process used to make a three-dimensional object: such process generally include either additive or subtractive manufacturing methods. In particular, said bone anchors are useful for attachment to the spine. The present invention also provides a kit for use in spinal surgery, for correcting spinal deformities and fusing adjacent vertebrae in the spine, using the bone anchors described herein.