Classification of Adult Isthmic Spondylolisthesis: Based on the Morphologic Changes of Spinal Canal and Neural Contents by Myelography and CT Scan / 대한척추외과학회지

ABSTRACT

STUDY DESIGN: We classified adult isthmic spondylolisthesis based on the findings of postmyelographic CT scanning. OBJECTIVES: To propose a new classification that could be used as a useful guideline when evaluating the patient with adult isthmic spondylolisthesis. SUMMARY OF LITERATURE REVIEW Morphologic changes of the spinal canal and its neural contents in the adult patient with isthmic spondylolisthesis and their relations to radiological variables have not been well described in literature. MATERIALS AND METHODS: 32 adult patients with one level isthmic spondylolisthesis underwent myelography followed by CT scanning. Based on these findings, we classified each patient with four morphologic criteria; 1. dural station I or ll by the location of dural sac, 2. non-compression or compression type by the existence of lateral compression of dural sac. 3. root station I or ll by the location of nerve root, 4. hook or smooth type by the shape of spinal canal. Subsequent statistical analyses to assess the relationships between our newly developed classification and clinical variables were tested by SPSS software. RESULTS: Dural station correlated positively with percent slip(rpb=0.39; p=0.026). Patient age was closely related to the lateral compression(rpb=0.54, p<0.01) which consequently decreased transverse diameter of dural sac(rpb=-0.68, p<0.01). Both dural station and lateral compression were important in the prediction of the extent of the dural involvement. Root station of the smooth type correlated positively with percent slip(reb=0.47 p=0.038), while that of the hook type did not. Consequently, nerve root of the hook type entered neural foramen under the pedicle, whereas that of the smooth type entered at various locations depending on the degrees of percent slip. Depth of lateral recess was significantly less in the hook type than in the smooth type(p<0.01). Stretching of the nerve root, produced by posterior migration of the nerve root, was observed only in the smooth type. CONCLUSIONS: We strongly recommend the use of our classification because it is easy to apply and has a high correlation with radiological variables.