Polyaxial Insert for Orthopedic Bone Plate Screw Alignment
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Solution Overview
Problem
Traditional orthopaedic bone plates lack flexibility in aligning locking screws with bone fragments of variable orientations, leading to inadequate fixation and potential damage from high tensile stresses, as they are limited by pre-defined threaded holes and require the screw to pass through the plate, constraining its orientation.
Innovation Solution
A bone plate insert with a set screw that creates a pivotal axis, allowing 360° rotation and enabling the locking screw to be inserted at various angles through the insert, which is not confined by the bone plate's geometry, using a self-tapping locking screw with a threaded head to secure into the insert at different angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional bone plates with pre-defined threaded holes are used, then the bone plate structure is simple and rigid, but the locking screw orientation is constrained and cannot align with bone fragments of variable orientations
Solution Approach 1:
The bone plate is segmented into two functional components: a rigid bone plate body providing structural support and a separate polyaxial insert providing orientation flexibility. The insert contains the threaded hole and can rotate independently within the bone plate, allowing the locking screw to be inserted at various angles while the bone plate maintains its simple rigid structure.
Solution Approach 2:
The polyaxial insert acts as an intermediary component between the rigid bone plate and the locking screw. It mediates the orientation mismatch by allowing rotational movement within the insert, enabling the locking screw to align with bone fragments of variable orientations while the bone plate itself remains structurally simple and rigid.
2Adaptability or versatility
If the locking screw is required to pass through the bone plate, then the bone plate maintains structural integrity, but the screw orientation is limited to perpendicular alignment with the plate
Solution Approach 1:
The polyaxial insert introduces dynamic rotational capability into the otherwise static bone plate structure. The insert can rotate dynamically to accommodate different locking screw angles, allowing reliable fixation of bone fragments regardless of their orientation, while the locking screw still passes through the bone plate structure maintaining structural integrity.
3Adaptability or versatility
If additional flexibility components are added to the bone plate, then screw orientation flexibility improves, but the risk of component loosening and movement increases
Solution Approach 1:
The polyaxial insert provides localized flexibility only where needed for screw orientation, while the rest of the bone plate maintains its rigid stable structure. The insert is precisely fitted within a dedicated cavity in the bone plate, providing orientation adjustment capability without compromising the overall structural stability and preventing unwanted movement or loosening.
Data Source
AI summary
An improved insert for assembly with a bone plate is described. The insert has a first opening adapted to receive a set screw and a second opening adapted to receive a bone screw. The insert is connectable to the bone plate using a set screw. The insert in conjunction with the set screw provides an improved range of relative motion for placing the bone screw at outboard locations with respect to the bone plate. That way, bone fragments that are not necessarily reachable using the bone plate without the insert can be secured together for improved healing.