Expandable Intervertebral Implant Height Adjustment
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Solution Overview
Problem
Existing spinal implants lack the ability to adjust height post-implantation, which can lead to inadequate support and stability for vertebrae, particularly in cases of degenerative diseases or fractures, where continuous adjustment and repositioning are necessary.
Innovation Solution
A spinal implant with adjustable height, comprising two endplates connected by a frame and an actuator screw, allowing for expansion and retraction within a range, secured by bone screws and a blocking mechanism to prevent migration, and featuring dissimilar materials for enhanced strength and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed-height intervertebral implant is used, then the implant structure is simple and easy to manufacture, but the implant cannot be adjusted post-implantation to accommodate anatomical changes or provide optimal support
Solution Approach 1:
The implant incorporates a dynamic adjustment mechanism allowing the height to be changed post-implantation. The actuator screw, carriage, and ramped surfaces enable the endplates to move relative to each other, transforming the implant from a static to a dynamic structure that can adapt to patient needs while providing continuous height adjustment capability
Solution Approach 2:
The implant is divided into separable components including endplates, frame, actuator screw, and carriage that can move independently. This segmentation allows the height-adjustment function to be integrated without requiring a complete redesign of the entire implant structure, thereby managing complexity while enabling adaptability
2Ease of operation
If an adjustable mechanism is added to the implant, then post-implantation height adjustment is enabled, but the device complexity and number of components increases
Solution Approach 1:
The actuator screw mechanism allows the implant to be adjusted by the patient or practitioner without requiring external tools or complex actuation systems. The screw threads directly with the carriage to produce movement, creating a self-contained adjustment system that is simple to operate while minimizing the number of additional components needed
Solution Approach 2:
The patent replaces complex electronic or hydraulic adjustment systems with a simple mechanical screw mechanism. This substitution maintains ease of operation through direct mechanical engagement while significantly reducing the number of components and overall system complexity compared to alternative actuation methods
3Adaptability or versatility
If the implant allows continuous movement and adjustment, then adaptability to anatomical changes is improved, but the stability and fixation of the implant may be compromised
Solution Approach 1:
The blocking mechanism is designed to prevent unintended movement or backing out of the actuator screw before adjustment is deliberately made. This preliminary protective action ensures that the implant maintains its current height setting and remains stable until intentional adjustment is performed, thereby preserving fixation reliability while allowing adaptability when needed
Solution Approach 2:
The ramped surfaces and carriage interaction provide mechanical feedback that indicates when the endplates are properly engaged and when adjustment limits are reached. This feedback mechanism ensures stable fixation during normal use while enabling controlled adjustment, balancing reliability with adaptability through inherent mechanical cues
Data Source
AI summary
An implant for therapeutically separating bones of a joint has two endplates each having an opening through the endplate, and at least one ramped surface on a side opposite a bone engaging side. A frame is slideably connected to the endplates to enable the endplates to move relative to each other at an angle with respect to the longitudinal axis of the implant, in sliding connection with the frame. An actuator screw is rotatably connected to the frame. A carriage forms an open area aligned with the openings in the endplates. The openings in the endplates pass through the carriage to form an unimpeded passage from bone to bone of the joint. The carriage has ramps which mate with the ramped surfaces of the endplates, wherein when the carriage is moved by rotation of the actuator screw, the endplates move closer or farther apart.