Spondylolytic spondylolisthesis: various imaging features and natural courses.

The purpose of this paper is to review typical and atypical imaging features of spondylolytic spondyolisthesis and natural courses. Imaging features of the typical pars defect in early phase include bone marrow edema of the isthmus on MR imaging with progression of bone defect on plain radiography or CT. There are various defect types (pedicular cleft, retroisthmic cleft) and locations (upper lumbar spine and unilateral lesions). Natural courses also vary, with different patterns of progression and stabilization. Clinical correlation of the imaging and clinical features is often difficult.