Reduction of intradiscal pressure by the use of polycarbonate-urethane rods as compared to titanium rods in posterior thoracolumbar spinal fixation

• Published in: Journal of materials science. Materials in medicine Vol. 28; no. 10; p. 148
• Main Authors: Jacobs, Eva, Roth, Alex K., Arts, Jacobus J., van Rhijn, Lodewijk W., Willems, Paul C.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.10.2017; Springer Nature B.V
• Subjects: Animals; Biocompatibility; Biocompatible Materials; Biomaterials; Biomechanical Phenomena; Biomedical Engineering and Bioengineering; Biomedical materials; Ceramics; Chemistry and Materials Science; Clinical Applications of Biomaterials; Composites; Compression; Compression tests; Control equipment; Deformation mechanisms; Deformities; Ethyl carbamate; Fixation; Force distribution; Glass; Incidence; Instrumentation; Instruments; Internal Fixators; Load distribution; Load distribution (forces); Load transfer; Lumbar Vertebrae; Materials Science; Materials Testing; Mechanical properties; Natural Materials; Osteoporosis; Pain; Polycarbonate; Polycarboxylate Cement; Polymer Sciences; Pressure; Range of Motion, Articular; Regenerative Medicine/Tissue Engineering; Rods; Salvage; Segments; Spinal Fusion - instrumentation; Spine; Stiffness; Stress concentration; Stress, Mechanical; Surfaces and Interfaces; Surgery; Swine; Thin Films; Titanium; Urethane; Thoracolumbar hyperkyphosis; Intradiscal pressure; Axial stiffness; Spinal fixation; Polycarbonate-urethane
• ISSN: 0957-4530; 1573-4838
• DOI: 10.1007/s10856-017-5953-0

Loss of sagittal alignment and balance in adult spinal deformity can cause severe pain, disability and progressive neurological deficit. When conservative treatment has failed, spinal fusion using rigid instrumentation is currently the salvage treatment to stop further curve progression. However, fusion surgery is associated with high revision rates due to instrumentation failure and proximal junctional failure, especially if patients also suffer from osteoporosis. To address these drawbacks, a less rigid rod construct is proposed, which is hypothesized to provide a more gradual transition of force and load distribution over spinal segments in comparison to stiff titanium rods. In this study, the effect of variation in rod stiffness on the intradiscal pressure (IDP) of fixed spinal segments during flexion-compression loading was assessed. An ex vivo multisegment (porcine) flexion-compression spine test comparing rigid titanium rods with more flexible polycarbonate-urethane (PCU) rods was used. An increase in peak IDP was found for both the titanium and PCU instrumentation groups as compared to the uninstrumented controls. The peak IDP for the spines instrumented with the PCU rods was significantly lower in comparison to the titanium instrumentation group. These results demonstrated the differences in mechanical load transfer characteristics between PCU and titanium rod constructs when subjected to flexion-compression loading. The concept of stabilization with a less rigid rod may be an alternative to fusion with rigid instrumentation, with the aim of decreasing mechanical stress on the instrumented segments and the possible benefit of a decrease in the incidence of screw pullout. Graphical abstract