Effects of Sacral Slope Changes on the Intervertebral Disc and Hip Joint: A Finite Element Analysis

-OBJECTIVE: Spinopelvic parameters are vital compo-nents that must be considered when treating patients with spinal disease. Several finite element (FE) studies have explored spinopelvic parameters such as sacral slope (SS) and the impact on the lumbar spine, although no study has examined the effect on the hip and sacroiliac joint (SIJ) on varying SS angles. Therefore, it is necessary to have a biomechanical understanding of the impact on the spino-pelvic complex.-METHODS: An FE lumbar, pelvis, and femur model was created from computed tomography scans of a 55-year-old female patient with no abnormalities. Three models were created: a normal model (SS = 26 & DEG;), a model with high SS (SS = 30 & DEG;), and a model with low SS (SS = 20 & DEG;). These models underwent loading for flexion, extension, lateral bending, and axial rotation. Range of motion (ROM), intra-discal pressures, hip joint, and SIJ contact stresses were analyzed. -RESULTS: The high SS model (SS = 30 & DEG;) indicated the highest ROM in the L5-S1 (slip angle) level and the highest intradiscal pressures. The highest average hip and SIJ contact stresses were present in this model, although the low SS model (SS = 20 & DEG;) in extension had the largest stresses for the hip and SIJ.-CONCLUSIONS: The results provide evidence that pa-tients with higher SS may be more prone to increased ROM at the slip angle (L5-S1). In addition, patients with higher SS were shown to have higher contact stresses on the hip joint and SIJ, potentially leading to SIJ dysfunction. Clini-cally, correcting lumbar lordosis including SS is important; however, a high SS may have a negative impact on the intervertebral disc, SIJ, and hip joint.