Kinematic effects of a pedicle-lengthening osteotomy for the treatment of lumbar spinal stenosis

Abstract

Object Lumbar spinal stenosis (LSS) may lead to disabling neurogenic symptoms and has traditionally been treated using open laminectomy. A new technique for correcting LSS involves lengthening the lumbar pedicles through bilateral percutaneous pedicle osteotomies. In this paper, the authors' goal was to evaluate the changes in spinal canal dimensions and kinematic behavior after pedicle-lengthening osteotomies. Methods The kinematic behavior of 8 cadaveric lumbar segments was evaluated intact and after bilateral pedicle-lengthening osteotomies at the L-4, L-5, and L-4 and L-5 levels. Testing was conducted with and without a compressive preload using a custom kinematic apparatus that allowed for 3D tracking of each vertebra during flexion-extension, right-left bending, and right-left rotation. A validated finite element (FE) spine model was used to measure the changes in the cross-sectional area of the spinal canal and neural foramen after 2-, 3-, and 4.5-mm simulated pedicle-lengthening osteotomy procedures. Results The overall and segmental kinematics were not significantly altered after the pedicle-lengthening osteotomy procedure at the L-4 and/or L-5 pedicles. The kinematic signatures of the intact and lengthened states were similar for all motion pairs. The FE spine model yielded kinematics predictions within or close to the 95% confidence interval for the cadaveric data. The FE spine demonstrated substantial, pedicle length–dependent enlargement of the cross-sectional areas of the spinal canal and neural foramen after simulated pedicle lengthening. Conclusions Bilateral pedicle-lengthening osteotomies produced substantial increases in the cross-sectional areas of the spinal canal and neural foramen without significantly altering normal spinal kinematics. This technique deserves further study as a less invasive treatment option for LSS.