Spondylolysis and spondylolisthesis after five-level lumbosacral laminectomy for selective posterior rhizotomy in cerebral palsy.

Of 163 children who have undergone five-level lumbosacral laminectomies for selective posterior rhizotomy, 20% of those re-X-rayed post-operatively (19/99) have developed incidental isthmic spondylolysis or grade I spondylolisthesis. The majority of patients were ambulatory, active, spastic diplegics. There were five children with isthmic defects at L3-4, three at L4-5 and 11 at L5-S1. Six of the 19 children had grade I spondylolisthesis, but none were symptomatic nor has there been any evidence of further slipping to date. It is postulated that the laminectomy, associated lordosis and increased mobility after rhizotomy may be factors in the causation.