Split Spinal Disc Prosthesis for Posterior Insertion
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Solution Overview
Problem
Conventional intervertebral disc prostheses lack effective motion restraint, particularly torsional motion restraint, when implanted posteriorly, leading to increased risk of damage to adjacent motion segments due to lack of natural motion restraint and obstruction by the spinal cord during insertion.
Innovation Solution
An articulating intervertebral disc prosthesis is designed with longitudinally split bodies to allow lateral separation, featuring motion restraint means that mimic the natural facet joint, reducing bearing pressure and enabling posterior insertion by avoiding the spinal cord, with bearing surfaces shaped to approximate spheroidal joints for optimal motion coupling and wear reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional intervertebral disc prostheses are implanted posteriorly, then insertion is simplified, but motion restraint is insufficient leading to damage risk to adjacent motion segments
Solution Approach 1:
The prosthesis is divided into two separate bodies (first body and second body) that can be inserted independently through separate access points. This segmentation allows posterior insertion while maintaining proper positioning and providing effective motion restraint through the distributed structure with bearing surfaces that articulate with adjacent vertebrae.
2Device complexity
If a single prosthesis body is used, then structure is simpler, but it obstructs spinal cord during posterior insertion
Solution Approach 1:
The prosthesis is divided into two separate bodies that can be inserted through separate access points lateral to the spinal cord, avoiding obstruction. The first body includes a first bearing surface that articulates with a first vertebra, and the second body includes a second bearing surface that articulates with a second vertebra, allowing independent insertion paths.
3Ease of manufacture
If bearing surfaces are flat, then manufacturing is easier, but bearing pressure is high causing wear
Solution Approach 1:
The bearing surfaces are designed with spheroidal curvature instead of flat surfaces. The first bearing surface and second bearing surface are shaped to approximate spherical segments, which distributes bearing pressure more evenly across the articulation interface, reducing contact stress and wear while maintaining manufacturing feasibility through standard machining processes.
Data Source
AI summary
Described is an articulating intervertebral disc prosthesis including a first member having a vertebra engaging portion and a bearing surface; a second member having a vertebra engaging portion and a bearing surface, which in use abuts the first member bearing surface to form a first bearing joint, —and motion restraint means adapted to provide ax-ticulation restraint of the bearing joints at predetermined limits of articulation similar to the natural motion restraint of a facet joint; wherein the prosthesis is longitudinally—split into two bodies so that the two bodies can be laterally separated, each body having an articulating bearing joint. Preferably, the second member bearing surface is shaped to include at least a portion of a first substantially circular curve when viewed in a first section, and at least a portion of a second substantially circular curve when viewed in a second section, said first and second curves being of respectively different sizes of circle. Further described is a chisel and a chisel guide for preparing the disc space for implantation.