Expandable Spinal Interbody Spacer with Ratchet Locking
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Solution Overview
Problem
Conventional spinal implants face challenges in maintaining desired lordosis, allowing bone growth between vertebrae, resisting dislocation, and securely positioning between adjacent vertebrae post-discectomy.
Innovation Solution
A spinal implant comprising an upper body, a lower body, a ratchet mechanism, and bone screws, designed to be pivotably affixed and capable of movement relative to each other, with obliquely angled screw holes for secure attachment to vertebral bodies and a ratchet mechanism for locking the implant in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional prosthetic implant is inserted between adjacent vertebrae, then the implant can maintain disc spacing, but the implant may be dislodged or moved from its desired implantation location due to patient movement before sufficient bone growth occurs
Solution Approach 1:
The implant transitions from a static structure to a dynamic system with movable bodies connected by a hinge. The upper and lower bodies can move relative to each other during insertion, then are locked in place by the ratchet mechanism to provide stability during bone growth while maintaining the ability to be positioned accurately during implantation
Solution Approach 2:
The ratchet mechanism acts as an intermediary between the upper and lower bodies, allowing controlled movement during insertion while preventing dislodgement afterward. The ratchet teeth engage with corresponding slots to lock the relative position of the bodies, providing stability without compromising the ability to position the implant correctly during surgery
2Adaptability or versatility
If a conventional prosthetic implant is designed to allow bone growth between adjacent vertebrae, then bone fusion can occur, but the implant cannot be adjusted to achieve the desired lordosis after implantation
Solution Approach 1:
The hinge connection between upper and lower bodies provides dynamic adjustability for lordosis during the bone growth period. Once bone fusion is achieved, the ratchet mechanism locks the bodies in their final position, maintaining the desired lordosis while allowing bone growth through the porous surfaces and screw pathways
Solution Approach 2:
The desired lordosis is established during implantation by positioning the upper and lower bodies at the appropriate angle before locking with the ratchet mechanism. This preliminary positioning ensures the correct spinal curvature is achieved, and the locked structure maintains this position throughout the bone growth and fusion process
3Strength
If screw holes are oriented at an oblique angle towards adjacent vertebral bodies, then secure attachment to bone is achieved, but the structural complexity of the implant increases
Solution Approach 1:
The implant is divided into upper and lower bodies with separate screw holes in each body oriented at oblique angles towards the respective adjacent vertebral bodies. This segmentation allows each body to be optimized for its specific attachment requirements while maintaining overall structural integrity and enabling secure bone attachment without excessive complexity
Data Source
AI summary
An expandable spinal implant configured for positioning within a space between adjacent vertebral bodies includes an upper body, a lower body, a ratchet mechanism, and a plurality of bone screws. The upper body and lower body are pivotably affixed at a first end and are capable of movement relative to each other. The ratchet mechanism is slidably disposed on one of the upper and lower body and is capable of engaging the opposite one of the upper and lower body thereby permitting movement of the upper and lower body relative to each other in a first direction, but not in a second direction. An insertion instrument capable of being attached to the expandable spinal instrument and a method of performing spinal surgery is also disclosed.