gms | German Medical Science

Objectives: Lumbar stenosis is a pathology that consists in the narrowing of the spinal canal or the intervertebral foramina, that may cause nerve roots compression. It can be related to the hypertrophy of the flavum ligament, osteoarthrosis, osteophyte formation, disc protrusion and degenerative spondylolisthesis [1]. Surgical treatment to relieve pain can be performed by removing osteophytes, laminae and ligaments either partially or entirely, thus leading to a risk of iatrogenic instability. The aim of this work was to determine the alteration to the kinematics of the lumbar spine due to degenerative stenosis and to quantify the risk of instability when performing laminotomy and laminectomy for decompression.

Methods: A numerical model of the intact lumbar spine (L3-L5) complete of all the osteo-ligamentous structures was built and validated in terms of RoM (Range of Motion) with data available in literature. The stenosis was simulated modifying the intact model, to represent different degrees of narrowing of the spinal canal. Finally, laminotomy and laminectomy were simulated and the results compared with the intact and stenotic models. Pure moments up to 10 Nm, in flexion-extension, lateral bending and axial rotation were imposed in each case and the stiffness of the motion segments and the intradiscal pressure were calculated.

Results and Conclusion: The RoM of each functional unit is in good agreement with literature data. The stenosis causes an increased stiffness of the motion segment, proportional to the degree of canal narrowing. The removal of the flaval ligament in association with the reduction of the laminae (laminotomy) increased the RoM in all directions, especially in lateral bending and axial rotation. The laminectomy produces the greatest variation in the stiffness and flexibility of the motion segment.

The bilateral laminectomy is the technique that mostly affects the stiffness of the motion segment, increasing the RoM. Despite the comparative approach of the present computational study, in order to better improve it further experimental tests will be lead on human L3-L5 spine segments.

Acknowledgments: Funding by the Italian Ministry of Health (project GR-2011-02351464) is gratefully acknowledged.