FORMATION OF PROXIMAL ADJACENT SEGMENT STENOSIS FOLLOWING LUMBAR TRANSPEDICULAR FIXATION: CLINICAL AND BIOMECHANICAL ANALYSIS, RISK FACTORS, AND SURGICAL STRATEGY

Proximal adjacent segment stenosis is one of the most important late complications of lumbar transpedicular fixation and is considered as a clinical expression of adjacent segment disease. Rigid stabilization causes increased mechanical loading and intradiscal pressure at the adjacent levels and can change the biomechanical environment of the spine and accelerate the process of intervertebral disk degeneration, hypertrophy of the facet joints and liga­mentum flavum, and development of the spinal canal stenosis. We retrospectively reviewed patients with degenerative spinal pathology undergoing transpedicular fixation, assessing clinical results, Oswestry Disability Index (ODI), spinopelvic parameters and MRI findings. The factors signif­icantly associated with development of clinically significant adjacent segment stenosis were age >60 years, pre-exist­ing degeneration of the superior adjacent intervertebral disk, PI-LL >10°, postoperative hypolordosis, and fixation of two or more segments. Our results confirm the important function of sagittal alignment abnormalities in the devel­opment of degenerative changes at adjacent levels and highlight the necessity of individualized preoperative plan­ning to reduce the risk of revision surgery.