Flexible Spinal Implant Screw for Load-Sharing Fixation
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Solution Overview
Problem
Existing spinal implant systems, including screws and rods, often provide rigid fixation that stress-shields bone, leading to a lack of load-sharing and potential instability in spinal stabilization.
Innovation Solution
The development of an implantable screw with a unique design featuring a head portion, a shaft, and a middle portion that includes first and second members extending between the head and the shaft, allowing for elastic deformation under physiological loading to facilitate load-sharing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid fixation is used in spinal implants, then structural strength and stability are improved, but load-sharing capability deteriorates and bone stress-shielding occurs
Solution Approach 1:
The implant is divided into distinct functional segments: a rigid head portion for anchoring, a flexible middle portion for load-sharing through deformation, and a threaded shaft for bone engagement. This segmentation allows each portion to perform its specialized function, resolving the contradiction between overall strength and localized load-sharing capability
Solution Approach 2:
The middle portion is designed to be dynamically flexible, allowing it to deform under physiological loads. This dynamic behavior enables the implant to share loads with the bone rather than providing rigid fixation, improving load-sharing capability while maintaining structural integrity through the rigid head and shaft portions
2Stability of the object's composition
If rigid fixation is used in spinal implants, then immediate stability is improved, but bone stress-shielding and potential instability deteriorate
Solution Approach 1:
Different portions of the implant have different mechanical properties: the head and shaft portions are rigid for stable anchoring, while the middle portion is flexible to allow stress transfer to the bone. This local differentiation of mechanical properties enables immediate stability from rigid portions while preventing bone stress-shielding through the flexible middle portion that permits controlled movement and stress transfer
3Reliability
If flexible design is used to enable load-sharing, then bone stress distribution is improved, but structural strength and stability deteriorate
Solution Approach 1:
The implant is segmented into rigid portions (head and shaft) that provide structural strength and a flexible middle portion that enables load-sharing. This segmentation allows the flexible portion to distribute bone stress while the rigid portions maintain overall structural integrity
Solution Approach 2:
The implant utilizes composite construction with portions made from materials having different mechanical properties. The rigid head and shaft provide strength, while the flexible middle portion (potentially using different material composition or structure) enables load-sharing and bone stress distribution, creating a composite structure that achieves both strength and flexibility
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enables the screws to flex and displace under physiological loads, promoting load-sharing and reducing stress on the bone, thereby enhancing the stability and durability of spinal stabilization systems.
Implementation Method 1
applying a physiological load onto the first implantable screw and the second implantable screw to flex a middle section of each implantable screw and displace a proximal section relative to a distal section of each implantable screw
Data Source
AI summary
The present disclosure includes implantable screws, implants, and systems. The implantable screws including a proximal section, a distal section, and a middle section with two members coupling the proximal section and the distal section. The implantable screws may be used by applying a physiological load onto the first implantable screw and the second implantable screw to flex a middle section of each implantable screw and displace a proximal section relative to a distal section of each implantable screw.