U-Shaped Fork Head with Deflectable Legs for Spinal Osteosynthesis
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Solution Overview
Problem
Existing osteosynthesis devices face challenges with complex and costly multi-piece constructions, mechanical instability, and assembly issues due to tight tolerances, particularly when using pedicle screws with bone anchors of larger diameters, which can lead to premature implant failure and increased manufacturing complexity.
Innovation Solution
A U-shaped fork head with internal threads and deflectable legs that securely clamp bone anchors via compressive and tensile stresses, allowing for easy assembly and disassembly, accommodating different rod diameters, and enabling temporary clamping for conversion between polyaxial and monoaxial screws, utilizing additive manufacturing for a one-piece construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a multi-piece construction of fork head with clamping cage or collet chuck is used, then assembly flexibility is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the fork head and clamping mechanism into a single integrated component. The fork head includes integrated deflectable legs with pressing elements that directly contact the bone anchor head, eliminating the need for separate clamping cages or collet chucks. This integration reduces the number of components while maintaining the ability to securely clamp the bone anchor.
2Manufacturing precision
If tight tolerances are adhered to in multi-piece construction, then assembly precision is improved, but manufacturing complexity and cost increase
Solution Approach 1:
By combining multiple components into a single fork head structure with integrated deflectable legs, the patent eliminates the need for tight tolerances between separate parts. The monolithic construction ensures precise positioning of the pressing elements relative to the bone anchor contact surfaces without requiring complex tolerance stacking or multiple precision measurements during assembly.
3Strength
If bone anchor outer diameter is larger than fork head opening diameter, then load capacity is improved, but assembly becomes problematic
Solution Approach 1:
The patent employs deflectable legs that can dynamically change their configuration during assembly. The legs are designed to be flexible enough to deflect outward to accommodate insertion of bone anchors with diameters larger than the nominal opening, then return to their clamping position to secure the anchor. This dynamic behavior allows assembly of larger bone anchors without compromising the structural integrity or load capacity.
4Adaptability or versatility
If temporary clamping capacity is implemented, then application spectrum is enhanced, but technological complexity and manufacturing cost increase
Solution Approach 1:
The patent implements temporary clamping through the inherent elastic properties of the deflectable legs. The legs can be manually deflected to open the clamping path, allow bone anchor insertion, and then automatically return to their clamping position through elastic recovery. This self-service mechanism provides temporary clamping and positioning capabilities without requiring additional actuators, motors, or complex control systems.
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
The solution provides a modular, cost-effective, and mechanically stable osteosynthesis device that can handle larger bone anchors, reduces component complexity, and maintains clamping force under stress, preventing premature loosening and allowing for precise manipulation of vertebrae during surgery.
Implementation Method 1
a compressive stress arises in the outer wall and a tensile stress arises in the inner wall, whereby the at least one deflectable leg is forced against the outer circumference of the spherical head
Implementation Method 2
a compressive stress arises in the outer wall and a tensile stress arises in the inner wall
Implementation Method 3
the at least one leg has an outer wall and an inner wall, which are interconnected at at least one point in such a way that upon tightening the grub screw, a pressing against one another of the outer wall and the inner wall from the proximal to the distal direction is generated
Data Source
AI summary
An osteosynthesis device for the treatment of the spine is disclosed having a fork head which is U-shaped in a side view, and which fork head, in the proximal direction, has two fork legs with an internal thread and in which a connecting rod can be received, and a grub screw is passed through the internal thread, and the fork head is detachably connected to a bone anchor. The bone anchor is pivotably mounted in the ball seat of the fork head, wherein the fork head in the ball seat area has slots open towards the distal side and thereby at least one deflectable leg is formed.