Spinal Distractor Post With Expandable Socket
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Solution Overview
Problem
Current spinal surgery methods face challenges in effectively separating and maintaining apart adjacent vertebrae during the removal of intervertebral disc tissue and insertion of implants, as existing distractor devices lack efficient mechanisms for polyaxial pivotability and secure coupling to bone fixation elements.
Innovation Solution
A spreader system comprising elongate posts with expandable members and sockets that securely couple to bone fixation elements, allowing polyaxial pivotability and relative movement between posts, enabling effective separation and stabilization of vertebrae for surgical access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a distractor device uses a spring clamp coupling mechanism to hold distractor pins, then the device can be assembled, but the coupling reliability and secure attachment to bone fixation elements is insufficient
Solution Approach 1:
The device is divided into separate components: a receiver that attaches to the bone fixation element and a post that connects to the receiver. This segmentation allows each component to be optimized independently for its specific function, improving overall coupling reliability while maintaining manageable complexity.
Solution Approach 2:
The post is inserted into the receiver, creating a nested structure where the post body engages with the receiver's internal features. This nesting provides secure mechanical coupling through interference fit and geometric interlocking, enhancing attachment reliability.
2Adaptability or versatility
If bone fixation elements are rigidly fixed to vertebrae, then stable attachment is achieved, but polyaxial pivotability and adjustment capability are lost
Solution Approach 1:
The connection between the post and receiver transitions from rigid to dynamic, allowing polyaxial rotation and adjustment. The post can pivot within the receiver before being locked in place, providing adaptability for different anatomical configurations while maintaining stability when locked.
Solution Approach 2:
The system allows changes in orientation parameters (polyaxial rotation) and positional parameters during assembly and adjustment. The post can be rotated and positioned at various angles relative to the receiver, enabling adaptation to different surgical requirements while maintaining secure attachment.
3Strength
If distractor devices use simple pin insertion, then device complexity is reduced, but the ability to securely retain and maintain separation of vertebrae is compromised
Solution Approach 1:
The system combines different mechanical features: a threaded distal portion for bone engagement, a smooth post body for insertion, and a receiver with internal retention features. This composite structure integrates multiple functions (anchoring, retention, and adjustment) into a single system, providing strong vertebrae separation while maintaining manageable complexity.
Solution Approach 2:
The post combines multiple functions: it serves as both the distractor element that separates vertebrae and the connector that attaches to the bone fixation element. The receiver merges the functions of attachment and retention, creating an integrated system that provides both separation and secure retention.
4Reliability
If the socket is designed to tightly receive the bone fixation element head, then secure coupling is achieved, but the expandable member cannot expand to permit insertion
Solution Approach 1:
The socket's internal dimensions are dynamic rather than static. The expandable member allows the socket to transition from a larger diameter (permitting easy insertion) to a smaller diameter (providing secure retention). This dynamic adjustment resolves the contradiction between insertion ease and coupling security.
Solution Approach 2:
The expandable member undergoes a phase transition from an expanded state during insertion to a contracted state during retention. This transition allows the socket to accommodate the bone fixation element head during insertion, then securely retain it after insertion is complete.
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 system provides secure coupling and polyaxial pivotability, facilitating efficient separation and stabilization of vertebrae, thereby enhancing surgical access and implant placement in spinal surgery.
Implementation Method 1
a coil spring that is disposed within the socket such that when the socket receives the head of the bone fixation element the coil spring couples the post body to the bone fixation element
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
A post that is configured to be coupled to a head of a bone fixation element that is attached to a bone part can include a post body that is elongate along a first direction and defines a proximal end and a distal end that is spaced from the proximal end along the first direction. The post body can include an internal surface that defines a socket at the distal end. The socket can be configured to receive the head of the bone fixation element. The post can further include a locking member that is disposed within the socket such that when the socket receives the head of the bone fixation element the locking member couples the post body to the bone fixation element. The post body is polyaxially pivotable relative to the head when the post body is coupled to the bone fixation element.