Expandable Fusion Implant With Deployable Spikes Against Expulsion
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Solution Overview
Problem
Existing expandable fusion devices for spinal fusion procedures face a high risk of anterior expulsion due to increased forces in the axial plane, as the natural barrier provided by the anterior longitudinal ligament is removed during the procedure, necessitating a solution to prevent expulsion.
Innovation Solution
The development of expandable fusion devices with integrated deployable retention spikes that deploy from the implant body to resist expulsion, featuring an actuator assembly and sidecar assembly to adjust height and lordosis, and optionally incorporating electronic components for autonomous operation and communication with robotic/navigation systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the anterior longitudinal ligament is resected to enable cage placement, then direct access to the disc space is achieved, but the natural barrier preventing anterior expulsion is removed
Solution Approach 1:
The patent applies preliminary anti-action by incorporating retention spikes that proactively counteract the harmful expulsive forces before they can cause device displacement. The spikes are designed to engage the anterior longitudinal ligament and vertebral endplate in advance, creating a mechanical barrier that prevents the cage from being pushed anteriorly during compression and expansion procedures.
Solution Approach 2:
The retention spikes are pre-positioned on the cage structure before insertion, ready to engage with the anterior longitudinal ligament as soon as the cage is placed in the disc space. This preliminary positioning ensures that the protective mechanism is already in place before any expulsive forces are applied during the surgical procedure.
2Stability of the object's composition
If a high lordotic profile cage is used to restore segmental lordosis, then sagittal balance is restored, but the risk of anterior expulsion increases due to increased axial forces
Solution Approach 1:
The retention spikes provide preliminary counter-action to the increased axial forces generated by high lordotic profile cages. By engaging the anterior longitudinal ligament and vertebral endplate, the spikes create a mechanical restraint that opposes the expulsive forces generated during cage compression and expansion, allowing the high lordotic profile to be safely utilized.
Solution Approach 2:
The retention spikes are designed with a curved geometry that matches the natural curvature of the vertebral endplate and anterior longitudinal ligament interface. This curved design allows the spikes to conform to the anatomical surfaces, distributing the restraining forces more effectively and preventing anterior expulsion while maintaining the high lordotic profile of the cage.
3Stability of the object's composition
If expandable cages are compressed to increase segmental lordosis, then the desired correction is achieved, but expulsive forces increase causing potential device displacement
Solution Approach 1:
The retention spikes provide preliminary counter-action to the expulsive forces generated during cage compression. As the cage is compressed to increase segmental lordosis, the spikes engage the anterior longitudinal ligament and vertebral endplate, creating a mechanical barrier that prevents the cage from being pushed anteriorly by the compressive forces.
Solution Approach 2:
The retention spikes are designed with a dynamic engagement mechanism that allows them to flex and conform to the vertebral endplate surface during cage compression and expansion. This dynamic design enables the spikes to maintain effective engagement throughout the range of motion, providing continuous protection against anterior expulsion while allowing the necessary lordotic correction.
Data Source
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AI summary
Expandable fusion devices, systems, and methods. The expandable fusion device includes one or more integrated deployable retention spikes configured to resist expulsion of the device when installed in the intervertebral disc space. The implant may include upper and lower main endplates, an actuator assembly configured to cause an expansion in height of the upper and lower main endplates, and a sidecar assembly including a sidecar carrier, an upper carrier endplate engaged with an upper spike, and a lower carrier endplate engaged with a lower spike such that forward translation of the sidecar carrier pushes against the upper and lower carrier endplates, thereby deploying the upper and lower spikes.