Multi-axis Spinal Fixation with Square Bolt Segmentation
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Solution Overview
Problem
Existing spinal fixation systems face challenges with the joint geometry between screws and rods/plates due to varying vertebrae angles and sizes, leading to stress-related breakage of rods under conditions like obesity and acute curvatures, which is exacerbated by the need for adjustable structures that compromise bendability.
Innovation Solution
A spondylolisthesis reduction kit featuring extra-long square bolts with a combination of non-threaded and threaded portions, and biocompatible materials like titanium, allowing for secure coupling of stacked vertical plates to horizontal plates, enabling realignment and stabilization without compromising bendability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of vertical plates is increased to prevent breakage under stress, then strength is improved, but bendability deteriorates
Solution Approach 1:
The vertical plate is divided into multiple segments or layers that can bend relative to each other, allowing the overall structure to achieve both strength and flexibility. The plate comprises a stack of individual plate elements that can articulate during bending while maintaining structural integrity under load.
Solution Approach 2:
The vertical plate utilizes composite construction with multiple materials or layered structures that provide both strength and flexibility. The composite design allows different layers to have different mechanical properties, with some layers providing strength and others providing bendability, resolving the contradiction between these two requirements.
2Adaptability or versatility
If adjustable structures are provided to accommodate varying screw head positions, then adaptability is improved, but structural rigidity deteriorates
Solution Approach 1:
The connection system incorporates dynamic elements that allow adjustment during installation or operation to accommodate varying screw positions, while maintaining rigidity when in the fixed position. The adjustable components enable the structure to transition between flexible (during installation) and rigid (during operation) states.
Solution Approach 2:
An intermediary component or mechanism is introduced between the rod and the adjustable structure that maintains structural rigidity while allowing for position accommodation. This intermediary element transfers loads effectively while permitting the necessary adjustments for varying screw head locations.
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3A~3B
AI summary
According to an embodiment, a spinal implant having vertical and horizontal plates with through-holes for receiving a pre-configured square bolt is disclosed. The embodiments of the invention include very long square bolts that can accommodate the height of at least of two vertically stacked plates. When used to reduce spondylolisthesis, a portion of the square bolt can be broken after the desired alignment of the listhetic vertebrae is observed. The square bolts also allow extension of vertical plates above or below an existing fusion by placement of an extension vertical plate on to the previous one without removing it. This makes extension of instrumentation extremely easy.