Polyaxial Bottom-Loading Screw Rod Assembly
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Solution Overview
Problem
Current spinal fixation systems require complex procedures for mounting spinal rods, which can limit visibility and access for surgeons during implantation, and often necessitate pre-assembling components that can be cumbersome and prone to errors.
Innovation Solution
The anchor assembly includes a bone anchor with an enlarged head, a collet, and a body portion with an integral rod, allowing for in-situ assembly where the bone anchor is secured to the vertebra before being received within the body portion, enabling the surgeon to maximize visibility and access, and the collet and body portion can 'pop-on' to the bone anchor, facilitating simpler and more efficient rod insertion into a second bone fixation element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spinal rods are mounted using traditional pedicle screws with rod receiving channels, then spinal fixation is achieved, but the procedure becomes complex and visibility/access for surgeons is limited
Solution Approach 1:
The device is divided into separate components: a bone anchor that is implanted first, and a body portion with an integral rod that is attached afterward. This segmentation allows the bone anchor to be implanted through a simple procedure while the rod attachment is performed separately, reducing overall procedural complexity while maintaining fixation reliability
Solution Approach 2:
The body portion with the integral rod is designed to snap onto the implanted bone anchor, creating a nested configuration where the rod-receiving channel in the body portion receives the bone anchor. This nesting approach simplifies the assembly process compared to traditional methods requiring separate rod insertion into screw channels
2Ease of operation
If components are pre-assembled for spinal fixation, then assembly is simplified, but errors increase and visibility/access during implantation is reduced
Solution Approach 1:
The bone anchor is implanted into the vertebra first as a preliminary action, establishing a secure foundation. Then the body portion with the integral rod is attached in a second step. This preliminary action approach allows each component to be optimally positioned and secured separately, improving assembly accuracy while maintaining simplicity
Solution Approach 2:
The body portion is designed with a snap-on feature that self-aligns with and secures to the bone anchor through complementary geometric features. This self-service mechanism eliminates the need for complex alignment tools or multiple fastening steps, improving both assembly simplicity and accuracy
3Reliability
If traditional pedicle screws with separate rod insertion are used, then spinal fixation is achieved, but rod insertion complexity increases
Solution Approach 1:
The body portion is designed with an integral rod that is combined with the rod-receiving channel into a single unified component. This merging eliminates the need for separate rod insertion steps required by traditional pedicle screws, thereby improving surgical efficiency while maintaining reliable spinal fixation through the integrated structure
Data Source
AI summary
An anchor assembly for use in spinal fixation to interconnect a longitudinal spinal rod, which is integrally formed with a body of the anchor assembly. The anchor assembly includes a bone anchor, a collet, a body portion, a rod portion, and a locking cap. The anchor assembly is preferably configured so that in use, the bone anchor may be secured to the patient's vertebra prior to being received within the body portion. The anchor assembly enables a surgeon to implant the bone anchor without the body portion to maximize visibility and access around the anchoring site. Once the bone anchor has been secured to the patient's vertebra, the rod portion may be inserted into the rod-receiving channel of a second bone fixation element having a rod-receiving channel implanted at a second site and the body portion can be snapped-onto the bone anchor.