Transforaminal Intersomatic Cage with Tangential End Hole
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Solution Overview
Problem
Existing intersomatic cages for intervertebral fusion are either made from bone and prone to illness due to imperfect sterilization, or have large dimensions and complex shapes that make them difficult to implant through the transforaminal approach without damaging articular processes, and require long times for arthrodesis.
Innovation Solution
A transforaminal intersomatic cage with a body defining an arc, featuring a lateral concave and convex surface, a tangentially oriented end hole for instrument insertion, and an incurvate return part with a return hole, designed for secure gripping and easy implantation through the transforaminal approach, along with an instrument comprising a rod and spatula for optimal alignment and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cages are made from bone material, then they can fuse with the graft inserted into the disc space, but they are capable of causing illness in the event of imperfect sterilisation
Solution Approach 1:
The invention changes the material parameter from organic bone to inorganic PEEK polymer, eliminating the sterilization-related illness risk while maintaining the structural function of the cage. The PEEK material provides the necessary mechanical properties and radiopacity without the biological contamination risks associated with bone material.
2Reliability
If cages have large dimensions and complex shapes to maintain disc space, then they can effectively replace the intervertebral disc, but they require relatively long time before achieving arthrodesis and have difficulty being implanted through transforaminal approach
Solution Approach 1:
The invention optimizes the geometric parameters of the cage, transitioning from large complex shapes to compact arc-shaped designs with controlled dimensions. This allows effective disc space maintenance while enabling transforaminal implantation and reducing arthrodesis time through improved graft contact surfaces and optimized structural configuration.
3Ease of operation
If cages are designed with holes oriented toward the centre for instrument insertion, then instruments can be inserted to hold the cage during implantation, but the cage becomes more fragile and the hole orientation does not conform to the general curvature of the cage
Solution Approach 1:
The invention repositions the insertion hole from a central location to the peripheral edge of the cage, and changes its orientation to be substantially tangential to the arc defined by the cage body. This dimensional repositioning and angular reorientation allows instrument access while maintaining cage structural integrity and conforming to the cage's curved geometry.
4Ease of operation
If the axis defined by the insertion hole forms a large angle with the tangent axis of the cage curvature, then the hole can accommodate the instrument, but the cage is in danger of breaking when pressure has to be applied at an angle that is too large
Solution Approach 1:
The invention changes the angular parameter of the insertion hole orientation, reducing the angle between the hole axis and the tangent to the cage arc from a large angle to substantially zero (tangential alignment). This parameter optimization allows instrument accommodation while minimizing stress concentration and preventing cage fracture under implantation pressure.
Data Source
AI summary
This disclosure presents various embodiments of a transforaminal intersomatic cage for an intervertebral fusion graft, and an instrument and method for implanting the cage, an embodiment of the cage having a body in the shape of a circular arc and comprising a lateral concave surface, a lateral convex surface, a straight upper surface, a straight lower surface and an end wall having at least one hole, called the end hole, designed to receive a rod of an instrument for implanting the cage between the vertebrae, wherein: the end hole has an orientation that is more or less tangential to the circular arc described by the body; the extremity opposite to the end wall of the body includes a return part extending the body toward the center of the circle on which the circular arc described by the body lies.