Clinical Course
44 year old male with gradual onset of right leg pain. The patient had a known isthmic spondylolisthesis which had been diagnosed years before. He was able to stand only ten minutes before developing leg pain in a sciatic distribution. His physical exam revealed pain in the leg with extension of the spine (bending backwards).

Diagnostic Tests
Lumbar MRI scan showed spondylolisthesis with defects in the pars and foraminal stenosis. There was a degenerative disc at this level. CT discograms did not reproduce his pain above or below the spondylolisthesis.

Decision
The pain in his leg was due to pressure in the foramen from the distortion of the space available for the nerve by loss of disc height, slipping forward of the vertebra stretching the space even more.

Surgical Treatment
An anterior lumbar fusion to distract the disc space and restore its original height would help restore the height of the foramen (exiting channel for the nerve) and a posterior decompression (unroofing the space) and fusion and instrumentation would stabilize the segment which was unstable.

Surgeon's Comment
In the adult with degenerative disc disease and loss of disc height at the level of an isthmic spondylolisthesis (old pars fracture), the restoration of disc space height from anterior distraction (spread the vertebra apart) helps open the nerve foramen at that level. The addition of decompressing the nerve directly from behind (posteriorly) helps assure that the nerve has adequate room. The addition of spinal instrumentation and fusion stabilizes the vertebra involved.