Expandable Corpectomy Spacer with Automatic Locking Mechanism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional vertebral body replacement implants face challenges such as proximity to the dura and spinal cord due to natural lordosis/kyphosis, cumbersome screw installation, and limited space for bone graft material delivery, especially in expandable cages with limited expansion ranges.
Innovation Solution
An expandable corpectomy spacer with a locking mechanism and threaded actuator system that allows for greater expansion and secure attachment to vertebrae, featuring a gear system and spring clips for rotational stability, enabling bone graft delivery and automatic locking to prevent implant movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional corpectomy cages are used with natural lordosis/kyphosis, then the implant can be inserted to replace the vertebral body, but the center segment of the cage settles into a position very close to the patient's dura and spinal cord causing pain, discomfort or further damage
Solution Approach 1:
The cage is designed to be expandable from an initial compressed state to a final expanded state, allowing dynamic adjustment of the implant height and position. This dynamic capability enables the surgeon to insert the cage in a compressed state and then expand it in situ to achieve optimal positioning away from the dura and spinal cord, resolving the safety issue of fixed-height cages.
Solution Approach 2:
The cage is pre-configured in a compressed state for easy insertion, and the expansion mechanism is prepared in advance to allow controlled expansion after insertion. This preliminary preparation enables the cage to be inserted safely close to sensitive structures and then expanded to create the necessary clearance, preventing harm to the dura and spinal cord.
2Strength
If endplates are secured to the cage with screws, then the implant can be firmly attached to the vertebrae, but the screws are cumbersome to install and make it more difficult to safely remove and replace components
Solution Approach 1:
The attachment system is segmented into modular components including the cage body, endplates, and a separate actuator mechanism. This segmentation allows each component to be independently manipulated, inserted, and secured, simplifying the installation process and enabling safe removal and replacement of components without affecting the entire construct.
Solution Approach 2:
An actuator mechanism serves as an intermediary between the surgeon's tools and the cage expansion/locking system. This intermediary device enables controlled expansion of the cage and engagement of the locking mechanism without requiring direct manipulation of screws or complex fastening operations, significantly improving ease of operation while maintaining secure attachment.
3Strength
If expandable VBR cages have limited expansion range (e.g., 3-4mm for a 15mm cage), then the implant maintains structural integrity, but there is limited space for packing bone graft materials and limited ability to deliver bone graft material into the implant after expansion
Solution Approach 1:
The cage employs a dynamic expansion mechanism that allows progressive expansion from a compressed insertion state to a fully expanded functional state. This dynamic capability maximizes the volume available for bone graft material while maintaining structural integrity throughout the expansion process, enabling both adequate graft capacity and strong structural support.
Solution Approach 2:
The cage is inserted in a compressed state with pre-prepared channels or spaces for bone graft material. After insertion and expansion to the desired height, bone graft material can be delivered through these pre-established pathways. This preliminary preparation ensures adequate graft capacity is achieved without compromising structural integrity during the expansion process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively positions the implant away from sensitive structures, facilitates easy installation and removal, and allows for increased bone graft material delivery, enhancing surgical outcomes by providing greater expansion and secure fixation without the need for manual locking screws.
Implementation Method 1
a threaded actuator disposed inside the outer ring and having a gear
Implementation Method 2
a threaded actuator disposed inside the outer ring and having a gear
Data Source
Figure 1
Figure 2~5
Figure 6~7
AI summary
An implant assembly including an expandable vertebral body replacement implant. The implant assembly includes a right hand end and a left hand end configured to attach to a threaded actuator. An outer ring is configured to surround each of the right and left hand ends and the threaded actuator. The implant assembly may include removable endplates configured to engage vertebral bodies as interbody spacer or through a corpectomy. The implant assembly includes a locking mechanism to prevent collapse or movement the implant assembly after implantation. The locking mechanism automatically engage after removal of an inserter instrument from the implant assembly.