Case Reports: PDF OnlyL4–5 Degenerative Spondylolisthesis in Monozygous TwinsRyan, Michael D., MS, FRACS, FRCSEdAuthor Information Department of Orthopaedics and Traumatic Surgery, The University of Sydney, The Royal North Shore Hospital of Sydney, St. Leonards, Australia. Spine: April 15, 1994 - Volume 19 - Issue 8 - p 985-986 Buy Abstract Objective The author reports symptomatic spinal canal stenosis due to degenerative spondylolithesis at L4–5 in identical twins. Summary of Background Data The patient reported his brother had a similar condition. Methods Monozygosity was established by phenotyping. Conclusions Spinal morphology and degenerative disease may be genetically determined. © Lippincott-Raven Publishers.