Does spinopelvic alignment affect fixation stability in pelvic ring fractures?: A finite element study.

Area of Science:

• Orthopedic biomechanics
• Spine and pelvic surgery
• Finite element analysis

Background:

• The pelvic ring is crucial for stability during upright posture.
• Lumbopelvic fixation stabilizes pelvic fractures but its mechanics are influenced by spinopelvic alignment.
• The effect of sacral slope on fixation and joint stress is not well understood.

Purpose of the Study:

• To investigate the biomechanical influence of sacral slope on lumbopelvic fixation for pelvic ring fractures.
• To evaluate the impact of spinopelvic alignment on adjacent joint stress and implant performance.
• To assess the role of cross-connectors in enhancing fixation stability.

Main Methods:

• A finite element model of the lumbar spine, pelvis, and femur was developed.
• Simulations analyzed three sacral slope configurations (20°, 26°, 32°) with lumbopelvic fixation, with and without cross-connectors.
• Evaluated fracture displacement, spinal mobility, disc stress, sacroiliac joint motion, and implant stress.

Main Results:

• Steeper sacral slopes increased L5-S1 mobility, disc stress, and sacroiliac joint stress.
• Higher sacral slopes led to increased rod stress and fracture displacement, compromising fixation stability.
• Cross-connectors reduced motion and stress, particularly in steeper sacral slope models.

Conclusions:

• Higher sacral slopes may reduce the biomechanical stability of lumbopelvic fixation for pelvic ring fractures.
• Spinopelvic assessment is important for preoperative planning and implant selection.
• Cross-connectors show potential benefits in high sacral slope cases, warranting further clinical study.