Polyaxial Bone Anchoring Device With Low-Profile Locking Ring
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Solution Overview
Problem
Existing polyaxial bone anchoring devices require repeated adjustments of the bone anchoring element and rod relative to the receiving part during spinal surgery, leading to cumbersome handling and increased pressure on vertebrae.
Innovation Solution
A polyaxial bone anchoring device with a locking ring that can be rotated to lock and unlock independently of rod fixation, allowing for reduced profile and lower unlocking force, and featuring extended tabs for convenient manipulation and modular design for versatile implant choices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the locking ring is rotated downward to lock the head, then the head is securely locked, but the profile size increases and additional pressure is exerted on the vertebrae
Solution Approach 1:
The locking mechanism is inverted: instead of rotating the locking ring downward to engage locking features (which would increase profile and exert pressure), the ring is rotated upward to lock the head. This upward rotation causes the locking features to engage while reducing the overall profile size and minimizing pressure on the vertebrae.
2Reliability
If the locking ring uses tapered surfaces for locking, then secure locking is achieved, but significant force is required to unlock
Solution Approach 1:
The locking and unlocking forces are inverted: the locking ring rotates upward to lock (reducing required force) and upward rotation also enables easy unlocking. This inverts the conventional mechanism where downward rotation would be needed for locking, thereby reducing the force required for both locking and unlocking operations.
3Manufacturing precision
If repeated adjustments of bone anchoring element and rod are made during surgery, then proper positioning is achieved, but handling becomes cumbersome and surgery time increases
Solution Approach 1:
The device is segmented into independent adjustable components: the bone anchoring element can be adjusted angularly relative to the receiving part, and the rod can be positioned independently. The locking ring locks these components in place after adjustment. This segmentation allows surgeons to make precise adjustments to each component separately and then lock them, reducing the need for repeated adjustments and improving handling convenience.
4Adaptability or versatility
If multiple inventory items are maintained for different implant configurations, then surgical versatility is achieved, but inventory costs increase
Solution Approach 1:
The receiving part is designed as a universal component that can accommodate different bone anchoring elements and rod configurations. The polyaxial design with adjustable angular positioning and independent locking allows a single receiving part to serve multiple surgical scenarios, replacing the need for multiple specialized implants. This multi-functionality maintains surgical versatility while reducing inventory requirements.
Data Source
AI summary
A bone anchoring device includes a receiving part having a central axis, two legs defining a recess for receiving a rod, and a head receiving portion that is at least partially expandable and having an opening for inserting and pivotably holding a head of a bone anchoring element therein, and a locking ring mountable around the head receiving portion in an axial direction while a rotational orientation of the locking ring relative to the receiving part remains constant. When the locking ring is around the head receiving portion, the locking ring is rotatable around the central axis from a first rotational orientation to a second rotational orientation where a compressive force exerted by the locking ring on the head receiving portion is greater than at the first rotational orientation.