Correlation Between Sacral Slope and Pedicle Morphology of the Fourth Lumbar Vertebra in Degenerative Lumbar Spondylolisthesis.

Study Design: Retrospective Radiographic Review. Objectives: The purpose of this study was to investigate the correlation between the sacral slope (SS) and pedicle morphological parameters of the fourth lumbar vertebra in degenerative lumbar spondylolisthesis (DLS). Methods: Our study included 134 patients with L4-5 DLS. We used preoperative multi-slice spiral computed tomography to measure a range of pedicle morphological parameters, and the SS and percentage of slip distance (SDP) of the L4 vertebra were measured on preoperative standing neutral lumbar radiography. Patients were divided into three groups based on their degree of SS: the low sacral slope (LSS) group with SS values of <35 degrees, the mean sacral slope (MSS) group with SS of 35 degrees-45 degrees, and the high sacral slope (HSS) group with SS > 45 degrees. Results: As the SS increased across groups, the pedicles of L4 became longer and thinner and the pedicle camber angle was smaller. The SDP, pedicle length parameters were positively correlated with the SS, while pedicle width, height, and camber angle were negatively correlated with the SS in the three groups. Conclusions: SS had an impact on the degree of spondylolisthesis and on pedicle morphological parameters in patients with DLS, with greater slope resulting in greater impact. The progression of DLS occurred due to the increasing forward shear force of the vertebra being greater than the reverse resistance. The pedicle at the slip level adaptively remodeled, becoming slenderer and tilting inward due to the long-term traction of the two opposing forces.