Angulated Locking Plate Screw Interface
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Solution Overview
Problem
Current bone fracture repair methods face challenges in securely affixing fixation plates to bones, particularly when screws need to be inserted at angles other than perpendicular, as existing technologies do not effectively accommodate angled insertion while preventing screw backout.
Innovation Solution
A locking fixation plate with threaded screw holes featuring a double helix thread configuration and countersinks, combined with screws having a conical head and single thread that interferes with the plate's threading for secure engagement at angles, allowing for angled insertion and locking without dictating the insertion angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a locking screw is inserted at an angle other than perpendicular to the threaded screw hole, then the screw can be anchored into more solid bony mass away from the fracture line, but the locking threads may not properly engage with the plate's threading
Solution Approach 1:
The threaded portion of the screw hole is divided into two distinct segments: an upper countersink portion and a lower threaded portion. The upper countersink portion accommodates the angled insertion of the screw head without requiring threading engagement, while the lower threaded portion provides secure locking engagement. This segmentation allows the screw to be inserted at various angles while maintaining reliable locking through the threaded portion.
Solution Approach 2:
The invention introduces a vertical dimension to the screw hole structure by creating a countersink that extends above the plane of the plate surface. This additional dimensional space allows the screw head to approach from angled directions while the threaded portion below maintains proper orientation for locking engagement, effectively adding a depth dimension to accommodate angular variability.
2Reliability
If the threaded portion of the screw hole is made deeper to ensure proper thread engagement, then locking reliability improves, but the screw cannot be inserted at angled positions
Solution Approach 1:
The screw hole threading is segmented into an upper countersink region and a lower threaded region. The upper region provides angular access without requiring thread engagement, while the lower region ensures deep, reliable thread engagement. This segmentation resolves the contradiction by separating the functions of angular accommodation and secure locking into distinct spatial zones.
Solution Approach 2:
The upper countersink portion performs the preliminary action of receiving and orienting the screw head at the required angle before the threaded portion engages. This preliminary angular positioning allows the screw to be inserted at various angles while ensuring that the threaded engagement occurs at the correct orientation for reliable locking.
3Adaptability or versatility
If the screw head is made larger to provide better bearing surface, then the insertion angle flexibility improves, but the screw hole requires more space and complicates the plate structure
Solution Approach 1:
The screw hole is segmented into an upper countersink portion that accommodates the screw head and a lower threaded portion that provides locking engagement. This segmentation allows the screw head to have adequate bearing surface for angular insertion while keeping the threaded portion compact and simple, thereby reducing overall structural complexity.
Solution Approach 2:
The countersink creates a conical space above the plate surface, utilizing the vertical dimension to accommodate the screw head's bearing surface requirements. This dimensional approach allows adequate head size for angular flexibility without increasing the lateral footprint or complicating the plate's overall structure.
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
Enables screws to engage the plate in half as many turns and secure at angles other than parallel, providing a stable connection and accommodating both locking and non-locking screws, enhancing the stability and versatility of bone fracture repair.
Implementation Method 1
the portion of the thread disposed on the generally conical head may be configured to interfere with the pair of threads disposed on the inner surface of the screw hole to lock the screw into the screw hole
Implementation Method 2
the thread height of a portion of the thread disposed on the head may be shallow enough to enable the portion of the root disposed on the head to contact the pair of threads disposed on the inner surface of the screw hole when the screw is screwed into the screw hole
Data Source
AI summary
A system for lockably engaging bone screws into a fixation plate may include a locking fixation plate including a threaded screw hole defined by an inner surface surrounding the threaded screw hole, the inner surface comprising an upper countersink and a threaded portion, the threaded portion comprising a pair of threads arranged in a double helix configuration, and a screw comprising a generally conical head tapering into a generally cylindrical shaft that ends at a tip and a single thread beginning near the tip and extending along the generally cylindrical shaft and onto the generally conical head, a thread height of the single thread being constant over a majority of the generally cylindrical shaft and tapering as the thread extends onto the head.