Expandable Corpectomy Spacer with Threaded Actuator and Locking Mechanism
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Solution Overview
Problem
Conventional vertebral body replacement implants face challenges such as limited space for bone graft material delivery, restricted expansion, and cumbersome screw-based attachment systems, which can lead to complications like subsidence and difficulty in component removal and replacement during spinal procedures.
Innovation Solution
An expandable corpectomy spacer with a threaded actuator and locking mechanism, allowing for greater expansion and facilitating bone graft delivery, and eliminating the need for screws by using a snap-fit endplate attachment system and automatic locking mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional corpectomy cages are used, then the implant can be inserted into the vertebral column, but the center segment will settle close to the dura and spinal cord causing pain and potential damage
Solution Approach 1:
The corpectomy cage is designed to be expandable from a compressed insertion state to an expanded deployed state. This dynamic transformation allows the implant to be inserted in a compact form and then expanded to achieve the desired lordotic angle that positions it away from the spinal cord, eliminating the settlement problem of conventional static cages
Solution Approach 2:
The implant changes its geometric parameters through expansion - the height and angle are adjusted from the compressed to expanded state. This parameter change enables the cage to achieve the optimal lordotic positioning that prevents contact with the dura and spinal cord
2Adaptability or versatility
If expandable VBR cages are used, then expansion capability is provided, but the space for bone graft material delivery is limited
Solution Approach 1:
The cage is divided into multiple expandable segments or struts that can be expanded independently or collectively. This segmentation allows the implant to expand to a larger final volume, creating sufficient space for bone graft material delivery while maintaining the expandable capability
Solution Approach 2:
The cage components are nested in a compressed configuration during insertion, similar to nested dolls. Upon expansion, these nested components unfold to create a larger volume structure that provides adequate space for bone graft material
3Strength
If screws are used to secure endplates to the cage, then attachment is achieved, but the system becomes cumbersome and difficult to remove or replace
Solution Approach 1:
The screw fastening system is extracted and replaced with a snap-fit attachment mechanism. This removal of the screw system eliminates the complexity of installation and removal operations while maintaining adequate attachment strength through the snap-fit design
Solution Approach 2:
The mechanical screw-fastening system is substituted with a snap-fit mechanical engagement system. This substitution simplifies the attachment mechanism, making it easier to install and remove while providing sufficient structural strength
4Reliability
If screws are used for attachment, then secure fastening is achieved, but there is inherent risk of screw loss during procedure
Solution Approach 1:
The loose screw components are extracted from the system and replaced with an integrated snap-fit attachment mechanism. This eliminates the risk of screw loss during the surgical procedure while maintaining reliable fastening through the snap-fit design
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 solution provides increased space for bone graft delivery, minimizes subsidence by maintaining the implant away from the dura and spinal cord, and simplifies the surgical process by eliminating screw-related complications and manual locking steps.
Implementation Method 1
a threaded actuator disposed inside the outer ring and having a gear
Implementation Method 2
a locking mechanism disposed in the outer ring and configured to removably engage with the gear
Data Source
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.