Biomechanical evaluation and comparison of polyetheretherketone rod system to traditional titanium rod fixation

BACKGROUND CONTEXT: Polyetheretherketone (PEEK) has been increasingly used as a biomaterial for spinal implants. PEEK lumbar fusion rods have recently become available for use in posterior lumbar fusion procedures. PURPOSE: To compare Polyetheretherketone Rod System to traditional titanium rod fixation in a cadaveric model and provide mechanical test data for the PEEK system. STUDY DESIGN: Biomechanical testing. METHODS: Cadaveric biomechanical testing was conducted to compare Expedium 5.5 min PEEK rods to titanium rods of equivalent diameter. Biomaterials testing was performed to determine static and dynamic performance of Expedium 5.5 mm PEEK rods with 6% BaSo4 in compressive bending and torsion. RESULTS: Cadaveric testing demonstrated that PEEK rods can significantly reduce the range of motion of a destabilized segment. The testing showed no significant difference in the stability provided by PEEK and titanium rods in posterolateral fusion (PLF) or posterior lumbar interbody fusion (PLIF) constructs. PEEK static compressive bending tests showed 67 degrees displacement without fracture of the rod. Torsion testing showed 30 degrees of rotation without yield or plastic deformation. Dynamic compression testing revealed two fatigue runouts at 23 degrees. CONCLUSIONS: PEEK rods provide comparable stability to titanium rods of equivalent diameter in cadaveric testing. Mechanical testing suggests PEEK rods can withstand far beyond the angular displacements suggested by cadaveric testing and that of normal physiologic range of motion. Potential advantages to PEEK rods include better anterior column load sharing, reduced stress at bone-to-screw interface, and reduced computed tomography and magnetic resonance imaging scatter and artifact. (C) 2009 Elsevier Inc. All rights reserved.