Intervertebral Prosthesis Ribs with Asymmetric Angles
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Solution Overview
Problem
Intervertebral prostheses face challenges in securing fixation with minimal vertebral body distraction, especially in the cervical spine, where traditional self-tapping projections can cause excessive damage or fail to penetrate due to anatomical irregularities.
Innovation Solution
The design features obliquely extending ribs with a steep ventral side face for resistance and a gently inclined dorsal side face for easy insertion, allowing secure penetration into the bone surface under natural loading, minimizing damage and ensuring stability with minimal initial distraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-tapping fixing projections are used to penetrate the bone surface, then fixation reliability is improved, but excessive damage to the vertebral body cover plate occurs when distraction is insufficient
Solution Approach 1:
The rib structure implements local quality by differentiating the inclination angles of its two side faces. The ventral side face has a steep inclination (approximately perpendicular to the base surface) to provide resistance against forward movement, while the dorsal side face has a gentle inclination to minimize damage during insertion. This localized differentiation of geometric properties allows the single rib structure to simultaneously achieve secure fixation and reduced bone damage.
2Reliability
If traditional self-tapping projections are used, then fixation is achieved, but considerable distraction is required which is not tolerable in the cervical spine
Solution Approach 1:
The rib structure employs asymmetry by extending obliquely with respect to the implantation direction rather than perpendicular to it. This asymmetric orientation, combined with the differentiated side face inclinations, allows the prosthesis to be inserted with minimal distraction while the oblique geometry enables the ribs to penetrate the bone surface under natural loading conditions without requiring excessive separation of the vertebral bodies.
3Ease of operation
If the fixing projections are made sharp to penetrate bone easily, then insertion ease is improved, but excessive damage to the bone surface occurs
Solution Approach 1:
The rib structure applies local quality by creating a localized sharp edge at the anterior end where the two side faces meet, while the dorsal side face maintains a gentle inclination. This localized sharpness at the insertion point enables easy penetration into the bone surface, while the gently inclined dorsal face minimizes damage as the rib slides along the bone surface during insertion.
Data Source
AI summary
An intervertebral prosthesis, in particular for the cervical spine, has two attachment plates connected in an articulated manner. The attachment surfaces of the attachment plates, which are configured for attachment to adjacent vertebral bodies have a base surface configured to bear on the surface of the vertebral bodies, and self-tapping fixing projections rising from the base surface. These fixing projections are formed by at least one pair of ribs which extend in opposite directions obliquely with respect to a predetermined implantation direction and whose side faces oriented more away from the implantation direction are steeper than their side faces oriented more in the implantation direction. The ribs can be toothed.