Biomechanical Characterization of Semi-Rigid Constructs and the Potential Effect on Proximal Junctional Kyphosis in the Thoracic Spine
Abstract
Long spinal fusions are the mainstay of treatment in adult spinal deformity; however, proximal junctional kyphosis (PJK) is a common and potentially catastrophic complication that can occur following this procedure. It has been hypothesized that using semi-rigid constructs at the superior aspect of the instrumentation may decrease this complication. The objective of this thesis was to determine if there is a biomechanical advantage between various semi-rigid constructs utilized in long spinal fusions to help decrease the risk of PJK. Nine human cadaveric spines (T1 – T12) instrumented with the standard all-pedicle-screw construct (APS) were compared to various semi-rigid constructs including sublaminar bands (SB), supralaminar hooks (SLH), transverse process hooks (TPH), and short pedicle screws (SS). Results demonstrated that TPH reduced motion at the junction between the instrumented and non-instrumented spine segments and had the most linear change in motion. In comparison, SLH and SS were found to have a high degree of stiffness. No differences were seen between APS and SB. Overall, semi-rigid constructs alter the biomechanics at adjacent levels. TPH provides the most gradual change in motion, which may reduce mechanical stress and decrease the risk of PJK.