Lumbar Fusion Leads to Increases in Angular Motion and Stress Across Sacroiliac Joint
Alexander A. Ivanov, M.D. et al., Spine 2009; 34, No. 5: E162-169
SI Joint Key Points:
- A finite element model of the lumbar spine-pelvis was used to simulate the posterior fusion at L4-L5, L4-S1, and L5-S1 levels, and assess motion at the SI joint.
- Prevalence of SI joint involvement in postfusion low back pain ranges from 29% to 40%
- The results of the study indicate that posterior fusion of the lumbar spine leads to increase of motions at the SI joint and increase of stresses across SI joint articular surfaces.
Study Design: The assessment of sacrum angular motions and stress across sacroiliac joint articular surfaces using finite element lumbar spine-pelvis model and simulated posterior fusion surgical procedures.
Objectives: To quantify the increase in sacrum angular motions and stress across SI joint as a function of fused lumbar spine using nite element lumbar spine-pelvis model.
Background Data: A review of literature suggests that for 20% to 30% of spine surgery patients, failed back surgery syndrome as a possible complication.
Methods: A fi nite element model of the lumbar spine-pelvis was used to simulate the posterior fusion at L4-L5, L4-S1, and L5-S1 levels. The magnitude of the sacrum angular motion and average of stresses across SI joint articular surfaces were compared with intact model.
Results: The computed sacrum angular motions in intact spine, after L4-L5, L5-S1, and L4-S1 fusion gradually increased with maximum value in L4-S1 fusion model. Also, the average stress on SI joint articular surfaces progressively increased from minimum in L4-L5 to maximum in L4-S1 fusion models.
Conclusion: The fusion at the lumbar spine level increased motion and stresses at the SI joint. This could be a probably reason for low back pain in patients after lumbar spine fusion procedures.
