Spinal Implant Sleeve Locking Mechanism for Rod Stability
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Solution Overview
Problem
Current spinal implant systems for treating musculoskeletal disorders, such as scoliosis and degenerative disc disease, face challenges in providing stable and secure fixation of vertebral rods to vertebrae, often resulting in inadequate alignment and support during healing.
Innovation Solution
A spinal implant system comprising a bone fastener with a U-shaped implant cavity and a tissue-penetrating shaft, along with an extender and sleeve mechanism that allows for axial translation and locking of the fastener to securely engage vertebral rods, providing tension and compression for stable fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple bone fastener is used for spinal implant fixation, then the device complexity is reduced, but the reliability of fixation and stability during healing is insufficient
Solution Approach 1:
The bone fastener is divided into functionally distinct segments: a receiver portion for initial implant engagement, an extender portion for rod attachment, and a sleeve mechanism for locking. This segmentation allows each component to perform its specific function optimally while maintaining overall system reliability without excessive complexity.
Solution Approach 2:
The sleeve is disposed within the extender portion and can translate axially to lock the extender to the receiver. This nested configuration allows the locking mechanism to be integrated within the existing structure rather than adding separate external components, thereby improving reliability without proportionally increasing device complexity.
2Reliability
If a secure locking mechanism is added to prevent rod ejection and rotation, then the fixation reliability is improved, but the device complexity increases
Solution Approach 1:
The locking mechanism merges multiple functions into the sleeve component: it provides axial translation for locking, features arcuate faces for preventing rotation, and includes ejection prevention features. By combining these functions into a single integrated component rather than separate mechanisms, the patent improves engagement security while minimizing the increase in device complexity.
Solution Approach 2:
Instead of using a mechanism that actively secures the rod through complex fastening elements, the patent uses a passive locking approach where the sleeve's geometry and friction inherently prevent ejection and rotation. This inverted approach simplifies the mechanism while maintaining high reliability.
3Ease of operation
If the extender allows axial translation for engagement, then the ease of operation is improved, but the stability during translation may be compromised
Solution Approach 1:
The sleeve acts as an intermediary mechanism that controls the axial translation of the extender. It provides guided movement through its internal geometry and friction characteristics, ensuring smooth engagement while maintaining alignment stability throughout the translation process. The arcuate faces on the sleeve further stabilize the connection by preventing rotation during translation.
Data Source
AI summary
A spinal implant system includes a first member comprising walls that include a first end surface defining a first locking cavity, a second end surface and an outer surface extending therebetween. A second member includes a first arm having an inner surface that defines a first cavity and a second arm having an inner surface that defines a second cavity. The inner surface of the first arm includes a first projection disposable in the first cavity and the inner surface of the second arm includes a second projection disposable in the second cavity. A third member includes a first extension having an inner surface that defines a first cavity and a second extension having an inner surface that defines a second cavity. The third member is configured for axial translation relative to the second member between a first orientation and a second orientation. Methods of use are disclosed.