Case study 76 - pars defects Spondylolysis is a term used to describe a defect that can develop in a bony portion of the spine. The defect is actually a stress fracture that occurs in a portion of the spine called the “pars”. Another term for spondylolysis is “pars fracture” or “pars defect”. This defect can lead to low back pain and in some cases, to instability of the bones. Spondylolysis can cause the bone with the stress fracture to slip forward on top of the bone below. When this slip occur