Variable Lordosis Spacer for Low-Distraction Fusion
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Solution Overview
Problem
Conventional fusion devices require significant distraction and often necessitate removal of bone to fit properly, failing to account for lordosis and maintaining intervertebral spacing, leading to installation difficulties and prolonged healing times.
Innovation Solution
An expandable fusion device with endplates and ramps that can transition between collapsed and expanded configurations, allowing insertion at minimal distraction height and maintaining normal disc spacing while accommodating lordosis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fusion devices are used, then intervertebral fusion can be achieved, but significant distraction is required and bone removal is needed to fit properly
Solution Approach 1:
The fusion device incorporates an expandable cage structure that transitions from a compressed insertion state to an expanded functional state. The cage expands along its longitudinal axis after insertion, allowing the device to be inserted at minimal distraction height and then expand to maintain normal disc spacing, eliminating the need for significant pre-distraction or bone removal
Solution Approach 2:
The expandable cage is designed to be inserted in a collapsed or compressed configuration and then expanded to its full functional size within the intervertebral space. This nesting principle allows the device to pass through a smaller insertion pathway and then occupy the appropriate functional volume, avoiding the need for large impaction forces or bone removal
2Reliability
If traditional fusion devices are used, then vertebral bodies can be fused, but lordosis curvature is not adequately accounted for
Solution Approach 1:
The fusion device incorporates asymmetric wedge-shaped elements or variable thickness in its structure to accommodate and correct lordosis curvature. The device can be configured with different angles or geometries on its anterior and posterior aspects, allowing it to match the natural lumbar lordosis and provide proper alignment between adjacent vertebral bodies
Solution Approach 2:
The device features localized structural variations including asymmetric endplate configurations and variable wall thicknesses that are specifically designed to accommodate lordotic curvature. These local quality modifications allow the device to conform to the natural spine curvature while maintaining overall fusion stability
3Reliability
If conventional fusion devices are used, then fusion can be achieved, but procedure time is prolonged due to bone removal
Solution Approach 1:
The expandable cage eliminates the need for bone removal by expanding within the existing intervertebral space after minimal distraction. This dynamic expansion approach preserves more native bone structure and reduces surgical preparation time compared to traditional devices that require bone removal for proper fitting
Solution Approach 2:
The device is pre-configured with expandable structures and lordosis compensation features that are activated after insertion. This preliminary preparation allows the device to adapt to the specific anatomical requirements without requiring time-consuming bone removal or intraoperative customization
4Length of stationary object
If fusion devices are dimensioned larger to maintain height, then disc spacing can be maintained, but installation becomes difficult
Solution Approach 1:
The fusion device transitions from a compressed insertion configuration to an expanded functional configuration. In the compressed state, the device has reduced height allowing easy insertion into the distracted intervertebral space. After insertion, the device expands to achieve the appropriate disc spacing and maintain proper vertebral alignment
Solution Approach 2:
The cage structure is designed to be inserted in a nested or collapsed state and then expanded to its full functional dimensions. This allows the device to pass through a smaller insertion pathway and then occupy the appropriate functional volume to maintain normal disc spacing without requiring large impaction forces
Data Source
AI summary
An expandable fusion device may include a first endplate and a second endplate. The expandable fusion device may also include first and second ramps configured to mate with both the first and second endplates. An inserter instrument includes an outer shaft having a bore extending longitudinally therethrough and an inner shaft extending through the bore in the outer shaft. The outer shaft is configured to engage the first or second opening in the second ramp, and the inner shaft is configured to engage the corresponding first or second opening in the first ramp to control implant height and/or lordotic angle.