Spinal Fixing System with Spherical Head for Multi-Axial Alignment
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Solution Overview
Problem
Conventional spinal fixings face challenges in accurately aligning bone screws with rods, especially in small animals, due to confined spaces and soft bone structures, leading to instability and loosening of joints, particularly at the lumbo-sacral region where perpendicular placement is often not possible.
Innovation Solution
A spinal fixing system featuring a partially spherical head and elongate extension with a washer for enhanced contact and load distribution, allowing multi-axial positioning and stabilization, along with a compression member for locking, which prevents pivotal movement and ensures a rigid joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional rod anchoring methods are used in small animals, then the fixation can be achieved, but the alignment of bone screw with rod cannot be adequately matched due to confined spaces
Solution Approach 1:
The fixing part is designed with dynamic adjustability, allowing the bone screw to be positioned at multiple angles relative to the rod. The spherical head interface enables rotational movement and angular adjustment, permitting precise alignment adaptation to various anatomical configurations in confined spaces while maintaining stable fixation.
2Strength
If perpendicular placement of bone screw is attempted in lumbo-sacral region, then direct fixation can be achieved, but the soft bone structure cannot support perpendicular placement
Solution Approach 1:
The fixing part allows multi-axial adjustment of the bone screw angle relative to the rod, enabling optimization of the insertion angle according to the specific bone anatomy. This dynamic positioning capability permits adaptation to soft lumbo-sacral bone structures by selecting angles that maximize purchase in available bone while maintaining fixation strength.
Solution Approach 2:
The spherical head interface enables continuous variation of the bone screw angle parameter, allowing optimization of the insertion trajectory to match the specific anatomical constraints of the lumbo-sacral region. This parameter adjustment capability transforms the fixed perpendicular requirement into a flexible angular parameter that can be optimized for each patient's anatomy.
3Reliability
If conventional fixing devices are used, then initial fixation can be achieved, but they loosen over time providing unstable joint
Solution Approach 1:
The spherical head interface is designed with appropriate clearance and conforming surfaces that distribute loads and reduce stress concentrations. This beforehand cushioning effect prevents premature wear and loosening by accommodating minor misalignments and reducing peak stresses at the bone-screw-rod interface, thereby maintaining joint stability over time.
4Ease of operation
If bone screw is forced to become loose, then initial placement can be achieved, but forces on the fixing device cause loosening
Solution Approach 1:
The spherical head interface provides dynamic adjustment capability that allows easy initial placement and positioning of the bone screw at the optimal angle. The same dynamic mechanism that facilitates ease of placement also maintains reliability over time by allowing continuous adaptation to loading conditions, preventing the fixation from loosening under physiological forces.
Data Source
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AI summary
A spinal implant comprising an elongate body insertable between adjacent vertebrae, the elongate body comprising first and second portions, the first and second portions each having an internal surface, the internal surface of the first portion facing the internal surface of the second portion in use, at least part of each internal surface of the first and second portions being threaded, the spinal implant further comprising a bolt, at least part of the bolt being externally tapered and externally threaded, the external threads of the bolt corresponding with the threads of the internal surfaces of the first and second portions, wherein the bolt is insertable between the first and second portions of the elongate body such that the external threads of the bolt engage with the internal threads of the elongate body, whereby rotation of the bolt in the threaded internal surfaces of the first and second portions causes relative movement of first and second portions away from one another.