Expandable Corpectomy Spacer Locking for Safer Vertebral Replacement
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Solution Overview
Problem
Conventional vertebral body replacement implants face issues such as proximity to the dura and spinal cord due to lordosis/kyphosis, cumbersome screw installation, difficulty in safely removing and replacing components, and limited space for bone graft material delivery in expandable cages.
Innovation Solution
An implant assembly with a threaded actuator, gear, and locking mechanism that allows for expandable vertebral body replacement, featuring a single component locking mechanism that removably engages with the gear to splay open or disengage, enabling easy expansion and contraction, and includes an insertion instrument for unlocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional corpectomy cages are used, then the implant can replace the vertebral body, but the center segment settles close to the dura and spinal cord causing pain and potential damage
Solution Approach 1:
The corpectomy cage is designed with expandable features that allow dynamic adjustment of its height and configuration after implantation. This dynamic capability enables the cage to adapt to the natural lordosis/kyphosis of the patient's spine while maintaining optimal distance from the dura and spinal cord, thereby preventing pain and potential damage.
2Strength
If endplates are secured with screws, then the components are firmly attached, but the screws are cumbersome to install and difficult to remove or replace safely
Solution Approach 1:
The attachment system is segmented into modular components including the endplate, cage, and separate fixation elements. This segmentation allows the endplate to be securely attached to the cage through simplified mechanisms that are easier to install and remove compared to traditional screw systems, while maintaining firm attachment strength.
3Adaptability or versatility
If expandable VBR cages are used, then the implant can be adjusted in size, but the space for packing bone graft materials is limited
Solution Approach 1:
The expandable VBR cage incorporates a nested structure where bone graft material can be packed within the cage body and also delivered through channels or compartments that are nested within the expandable mechanism. This nested design allows for significant bone graft material capacity while maintaining the expandable feature for size adjustment.
4Adaptability or versatility
If expandable VBR cages with limited expansion range are used, then the implant can provide some adjustment, but the expansion capacity is insufficient for adequate bone graft delivery
Solution Approach 1:
The expandable VBR cage employs a dynamic expansion mechanism with enhanced range that allows the implant to expand sufficiently to create adequate space for bone graft material delivery. The dynamic system enables the cage to transition from a compact insertion state to a fully expanded state with sufficient volume for adequate bone graft packing.
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 implant assembly effectively positions the vertebral body replacement away from the dura and spinal cord, facilitates easy component removal and replacement, and allows for greater bone graft material delivery, enhancing surgical safety and efficacy.
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
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.