Facet Joint Implant Anchorage via Transfacet Screw Compression
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Solution Overview
Problem
Existing implant devices for posterior spinal arthrodesis at facet joints tend to experience expulsion due to inadequate anchorage, particularly when using wedge-shaped implants without screws.
Innovation Solution
A system comprising an implant device with a flat or curved element of constant thickness, featuring openings or indentations for bone graft reception and reliefs for anchorage, combined with a transfacet compression screw that passes through the implant openings to secure it in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a wedge-shaped implant device is used without screws, then the device complexity is reduced, but the implant reliability deteriorates due to expulsion risk
Solution Approach 1:
The implant device is divided into multiple functional elements: a constant thickness body portion for structural integrity, reliefs for anchorage, and openings for bone graft reception. This segmentation allows each element to perform its specific function optimally while maintaining overall simplicity
Solution Approach 2:
The compression screw is inserted through the opening in the implant device and threaded into the bone, creating a nested configuration where the screw is contained within the implant structure. This provides secure fixation without requiring additional external fastening components
2Manufacturing precision
If a flat element of constant thickness is used, then the manufacturing precision is improved, but the implant reliability worsens due to potential expulsion
Solution Approach 1:
While the main body of the implant maintains constant thickness for manufacturing simplicity, local variations are introduced through reliefs and openings. The reliefs create interlocking surfaces with the bone, and the openings accommodate bone graft material, providing enhanced anchorage at critical locations without compromising overall geometric precision
Solution Approach 2:
The implant combines the constant thickness flat element with additional structural features (reliefs and openings) that create a composite structure. This composite design integrates both the manufacturing advantages of constant thickness and the retention advantages of varied geometry
3Reliability
If reliefs are added to the implant surfaces, then the implant reliability is improved through better anchorage, but the device complexity increases
Solution Approach 1:
The reliefs are designed as discrete, segmented features on the implant surface rather than continuous complex geometries. This segmentation maintains manufacturing simplicity while providing sufficient anchorage surfaces for bone integration
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
The system effectively prevents implant expulsion by compressing the implant into the facet joint cavity using the transfacet screw, enhancing primary anchorage and promoting bone fusion without the need for screws.
Implementation Method 1
said compression screw being screwed at least into the bone material downstream of said implant... enabling said compression screw to pass into same in order to be screwed at least into the bone material downstream of said implant
Implementation Method 2
The system effectively prevents implant expulsion by compressing the implant into the facet joint cavity using the transfacet screw, enhancing primary anchorage
Data Source
AI summary
The implant device for performing posterior spinal arthrodesis at a facet joint is in the form of a flat element of constant thickness. The element has reliefs on each of its faces so as to form an anchor associated with at least one complementary anchor, such as a screw with a diameter greater than the thickness of the element. The complementary anchor can be screwed into the flat element such that at least some of its threads protrude from the faces. The element has a U-shape with a transverse part from which two branches extend. On the proximal side, the free ends of the branches have retention devices, on the inner side of the U so as to permit the screwing and insertion of the screw between the branches.