what is a bilateral pars interarticularis defect
Definitions. Spondylolysis is an interruption of the pars interarticularis, this can either be unilateral or bilateral. Spondylolisthesis: an anterior displacement of a vertebral body in relationship to the segment immediately below, this can occur with or without a defect in the pars interarticularis.efinitions. Spondylolysis is an interruption of the pars interarticularis, this can either be unilateral or bilateral. Spondylolisthesis: an anterior displacement of a vertebral body in relationship to the segment immediately below, this can occur with or without a defect in the pars interarticularis.