Zeitschrift für Wirbelsäule

Implications of Decompressive Surgical Procedures for Lumbar Spine Stenosis on the Biomechanics of the Adjacent Segment: A Finite Element Analysis

Abstract

Francesco Travascio, Shihab Asfour, Joseph Gjolaj, Loren L. Latta, Shady Elmasry and Frank Eismont

Surgeries for Lumbar Spinal Stenosis (LSS) aim at decompressing spinal nerves and relieving symptoms of radiculopathy or myelopathy. Frequently after surgery, stenosis may progress in adjacent spinal segments, but the etiology of adjacent segment degeneration is still unclear. It is hypothesized that surgical approaches for LSS may alter the normal biomechanics of adjacent segments, eventually contributing to the development of stenosis. This study investigated implications of established decompressive surgical approaches on adjacent segments biomechanics. A realistic finite element model of a L1-L5 human lumbar spine was used for assessing changes in spine segments’ biomechanics due to laminotomy and laminectomy surgeries. First, the model was validated by comparing its predictions to previously reported spine kinematic data obtained after multi-level laminotomy and laminectomy. Subsequently, using a hybrid loading protocol, segments’ kinematics, intradiscal pressure, and stress in flexionextension were investigated simulating single level (L4-L5) laminotomy and laminectomy procedures. Alterations of spine segments biomechanics due to laminotomy were minimal. In contrast, after laminectomy, the L3-L4 range of motion, intradiscal pressure, and stress increased up to 50%, 20%, and 120%, respectively. These results suggest that laminotomy represents a better approach than laminectomy for reducing risks of spine instability or mechanically-accelerated disc degeneration in adjacent segments.