A Possible Cause of Degenerative Spondylolisthesis

Study Design. A case-control study. Objective. To measure the orientation of the facet joints at both cephalad and caudad portions and to compare them between patients with degenerative spondylolisthesis (DS) and patients with lumbar spinal stenosis (LSS, controls). Summary of Background Data. Several radiologic studies have indicated a correlation between DS and an increased sagittal orientation of the facet joints. However, the orientation of the facet joints have only been measured on 1 axial cut of computed tomography scans and magnetic resonance imaging. Methods. Thirty-two patients with DS only at the L4 –L5 level were assigned to group-1, and 28 patients with LSS without DS were assigned to group-2. Two computed tomography scans for the cephalad and caudad portions of the facet joint were made for L3–L4 and L4 –L5 levels, respectively. Delta facet angle was defined as facet angle (cephalad)–facet angle (caudad). Results. Facet angles of the cephalad portion were more sagittally oriented (P 0.001) than those of the caudad portion in group-1. The mean facet angle of the cephalad portion was 72° and that of the caudad portion was 57° at L4 –L5. The mean facet angle of the cephalad portion at L4 –L5 was greater (P 0.001) in group-1 (72°) than in group-2 (62°). Delta facet angles were significantly greater in group-1 than in group-2. Mean delta facet angle was 15° in group-1 and 2° in group-2 at L4 –L5 (P 0.001), and 4° and 0°, respectively, at L3–L4 (P 0.046). Conclusion. In this study, we confirmed that the cephalad portion of the facet joints were more sagittally oriented and that the caudad portion of the facet joints were more coronally oriented in patients with DS. These findings were observed not only at L4 –L5 but also at the uninvolved L3–L4 level in patients with DS at the L4 –L5 level.