Polyaxial Bone Anchor Locking Element for Wide-Angle Low-Profile Fixation
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Solution Overview
Problem
Existing bone plate assemblies for polyaxial bone anchors lack a sufficient range of angular motion and have a high profile, which limits their versatility and safety in clinical applications, particularly in areas with minimal soft tissue coverage.
Innovation Solution
A bone plate assembly with a locking element that allows up to 35° pivot angle relative to the vertical position, providing a wide range of angular motion while maintaining stability, and featuring a low profile design with minimal parts for economical manufacturing, along with offset holes and locking plugs for versatility and adaptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a polyaxial bone anchor assembly uses a conventional locking mechanism, then the angular stability is improved, but the range of angular motion is limited and the profile height increases
Solution Approach 1:
The locking element is nested within the bone anchor head, with the spherical locking surface positioned inside the hollow interior of the head. This allows the locking mechanism to be contained within the existing bone anchor structure without adding external height, achieving a low profile while maintaining polyaxial capability
Solution Approach 2:
The locking mechanism operates in a radial direction rather than axially. The locking element engages the bone anchor head through radial compression forces applied to the spherical surface, allowing stabilization without increasing the axial profile height of the assembly
2Stability of the object's composition
If a polyaxial bone anchor assembly uses a conventional locking mechanism, then the angular stability is improved, but the range of angular motion is limited to less than 35 degrees
Solution Approach 1:
The locking mechanism is designed to allow dynamic adjustment within a wide angular range (up to 35 degrees pivot angle or 60 degree motion cone) before final engagement. The spherical locking surface and compression mechanism enable the bone anchor to pivot freely within this range, then lock stably at the desired position
Solution Approach 2:
The design changes the locking parameter from fixed angular positions to a continuous range of motion. By using a spherical locking surface with radial compression, the system allows continuous angular adjustment within the 35-degree pivot range, providing versatility while maintaining stability at any position within the cone
3Reliability
If a polyaxial bone anchor assembly uses multiple locking components, then the safety is improved, but the device complexity increases
Solution Approach 1:
The locking element combines multiple functions into a single component: it provides angular stabilization through spherical surface engagement, prevents pull-out through radial compression, and allows wide range of motion through its geometric design. This single integrated element replaces what would traditionally require multiple separate components
Solution Approach 2:
The locking element serves multiple purposes simultaneously: it acts as both the locking mechanism and the angular adjustment mechanism, provides both stabilization and pull-out prevention, and enables both wide range of motion and final position fixation. This multi-functionality reduces the overall number of parts needed in the assembly
Data Source
AI summary
A locking element is configured to be used with a polyaxial bone anchor. The locking element including a central axis, a bottom side, a top side opposite to the bottom side, and a peripheral surface portion that extending completely around the locking element that has an external thread. The bottom side defines a first recess facing toward the bottom side for accommodating and applying a force in a direction toward the bottom side to at least the portion of the head of the polyaxial bone anchor. The top side defines a second recess having a non-circular cross-section in a plane perpendicular to the central axis for torqueable engagement with a driver.