Composite Pedicle Screw Construct for Clear Imaging and Fixation
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Solution Overview
Problem
Metallic pedicle screw systems in spinal surgeries face challenges such as interference with imaging, radiation therapy, stress shielding, biocompatibility issues, and lower fatigue resistance, necessitating the development of composite material alternatives that minimize these drawbacks.
Innovation Solution
A pedicle screw implant construct kit using composite materials with reinforcing filaments embedded in a polymer matrix, featuring a pedicle screw, embracing structure, upper and lower fasteners, and locking rings to provide secure fixation without metal interference, allowing for improved imaging and radiation therapy compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic pedicle screw systems are used for spinal fixation, then adequate bending and torsion strength is provided, but interference with imaging (fluoroscopy, CT, MR) and radiation therapy occurs
Solution Approach 1:
The patent applies composite materials consisting of carbon fiber reinforcement embedded in a PEEK (polyether ether ketone) polymer matrix. This composite construction provides adequate mechanical strength for spinal fixation while being radiolucent, allowing clear imaging with fluoroscopy, CT, and MR without the interference artifacts produced by metallic implants. The carbon fiber reinforcement specifically contributes to the bending and torsion strength requirements.
2Strength
If metallic implants are used for spinal stabilization, then fixation and immobilization is achieved, but stress shielding phenomena occurs due to different elasticity compared to bone
Solution Approach 1:
The patent changes the elastic modulus parameter of the implant material by using PEEK polymer with carbon fiber reinforcement. This composite material has an elasticity more closely matched to human bone compared to metallic materials, allowing for physiological load transfer and minimizing stress shielding phenomena while maintaining adequate fixation strength for spinal stabilization.
3Strength
If metal construction is used for pedicle screws, then adequate mechanical strength is provided, but fatigue resistance is poorer compared to some composite materials
Solution Approach 1:
The patent employs carbon fiber reinforced PEEK composite material which demonstrates superior fatigue resistance compared to traditional metallic implants. The carbon fiber reinforcement within the polymer matrix creates a structure that better withstands cyclic loading conditions, enhancing the reliability and longevity of the spinal fixation device while maintaining the necessary mechanical strength.
4Strength
If metallic implants such as stainless steel are used, then structural integrity is maintained, but biocompatibility problems occur due to corrosion and sensitization reactions
Solution Approach 1:
The patent changes the material composition from metal to carbon fiber reinforced PEEK polymer. This material substitution eliminates the corrosion and sensitization reactions associated with metallic implants like stainless steel, while the carbon fiber reinforcement ensures that structural integrity and mechanical strength are maintained for spinal fixation applications.
Data Source
AI summary
Some embodiments relate to a pedicle screw implant construct kit, comprising: at least one pedicle screw including a head; an embracing structure shaped and sized for embracing at least a portion of the screw head; an upper fastener for mounting onto the embracing structure, the upper fastener having a polygonal profile at least on a face of the upper fastener facing a direction opposite the screw.