Motion implants to improve spinal kinematics

A surgical method for creating a desired lordosis or kyphosis between a first upper vertebrae and a second lower vertebrae, comprising:

• removing at least a portion of a natural intervertebral disc from between the upper and lower vertebrae to create a disc space;
• resecting at least a first portion of a natural endplate and at least a first portion of a first natural pedicle of the lower vertebrae to create a first resected lower vertebral surface which exposes a cancellous bone interior of the lower vertebra and which extends outside of the disc space;
• inserting a lower portion of a first arthroplasty device at least partially into the disc space, the first arthroplasty device including a first lower bone contacting surface having a keel extending outwardly therefrom, the first lower bone contacting surface which substantially matches the first resected lower vertebral surface and extends at least partially outside of the disc space, at least a portion of the first lower surface being in direct contact with the cancellous bone interior of the lower vertebra;
• and
• attaching the first arthroplasty device to the lower vertebrae with a first bone fastener;
• and
• resecting at least a second portion of the natural endplate and at least a second portion of a second natural pedicle of the lower vertebrae to create a second resected lower vertebral surface which extends outside of the disc space;
• inserting a lower portion of a second arthroplasty device at least partially into the disc space, the second arthroplasty device including a second lower surface that substantially matches the second resected lower vertebral surface and extends at least partially outside of the disc space;
• and
• attaching the second arthroplasty device to the lower vertebrae with a second bone fastener, wherein the first resected lower vertebral surface is nonparallel to the second resected lower vertebral surface.