Spinal Fusion Device Locking Mechanism for Screw Retention
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Solution Overview
Problem
Conventional spinal fusion devices face issues with screw disconnection under high stress forces, leading to device mobility or detachment, particularly in anterior or anterolateral approaches, which increases costs, poses safety risks, and requires extensive surgeon training.
Innovation Solution
A spinal fusion device with a cage member and plate member design that uses anchoring and locking fasteners with overlapping head portions to secure the device in place, along with an insertion guide system for precise placement and fixation, allowing for reliable locking and easy detachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional screws are used as fasteners to anchor the device to the vertebrae, then the device can be secured in position, but the screws are subjected to high stress forces that can cause them to become disconnected from the vertebrae, leading to device mobility or detachment
Solution Approach 1:
The fastening function is divided into two distinct fasteners: an anchoring fastener that secures the device to the vertebrae and a locking fastener that prevents disconnection of the anchoring fastener. This segmentation allows each fastener to be optimized for its specific function, with the locking fastener providing additional security against the high stress forces that cause conventional single-fastener systems to fail.
Solution Approach 2:
The anchoring fastener is inserted first to secure the device to the vertebrae, and then the locking fastener is inserted through the plate member and into the cage member to lock the anchoring fastener in position. This preliminary action sequence ensures that the device is firmly anchored before the locking mechanism is engaged, preventing any potential displacement during the locking process.
2Reliability
If conventional spinal fusion devices are implemented for anterior or anterolateral approaches, then spinal fusion can be achieved, but it leads to exorbitant expenses, patient safety issues, supply issues, and the constant need to train and retrain surgeons and staff
Solution Approach 1:
The spinal fusion device is designed with a universal plate member that can be used with different cage members and fasteners, allowing the same basic device architecture to be applied across various spinal approaches and indications. The locking mechanism provides a standardized method of securing the device that can be uniformly implemented regardless of the specific surgical approach, reducing the need for multiple specialized devices and extensive surgeon training.
3Reliability
If a locking mechanism is added to prevent screw disconnection, then device stability is improved, but the device complexity and number of components increases
Solution Approach 1:
The locking fastener is designed to pass through both the plate member and the cage member simultaneously, merging the locking function with the existing structural components. The head portion of the locking fastener engages with the anchoring fastener while the shank portion passes through the cage member, creating an integrated locking system that adds minimal complexity while maximizing retention reliability.
Data Source
AI summary
A spinal fusion device for implantation between spinal vertebrae includes an implant member having an opposed upper and lower surface, an outer sidewall having an aperture having internal threads, and an inner sidewall defining a central opening. A plate member is attached to the implant member such that the plate member is perpendicular relative to the implant member and includes a plurality of angled apertures for receiving anchoring fasteners and a central aperture for receiving a locking fastener. A locking member is attached to the cage member. The locking member includes a tubular shaft having internal threads that is inserted through the aperture of the outer sidewall of the implant member. A locking fastener is inserted through the central aperture of the plate member and into the locking member to thereby lock the spinal fusion device in position.