Variable-Length Compression Screw for Controlled Fracture Compression
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Solution Overview
Problem
Existing bone screws lack effective mechanisms for providing compression at the bone joint or fracture line to prevent nonunion and malunion, and often require additional instrumentation for countersinking, which can cause soft-tissue irritation and increase surgical complexity.
Innovation Solution
A variable length headless compression screw system comprising a bone screw and a compression sleeve, driven by a driver assembly, which allows for self-tapping and self-drilling, minimizes screw toggle and back-out, and facilitates controlled compression and countersinking through adjustable length and threading configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional bone screw is used for internal fixation, then the fracture can be stabilized, but compression at the bone joint or fracture line is insufficient leading to nonunion or malunion
Solution Approach 1:
The screw is divided into two functional segments: a bone screw portion with threading for bone engagement and a compression sleeve portion that can rotate independently. This segmentation allows the compression sleeve to apply axial compression force to the bone fragments while the bone screw provides anchorage, simultaneously achieving both fracture stabilization and compression.
Solution Approach 2:
The invention merges the functions of fracture fixation and compression into a single integrated device. The compression sleeve is coupled to the bone screw such that one component performs both anchorage and compression functions, eliminating the need for separate fixation and compression devices.
2Force
If additional instrumentation is added to provide compression, then compression force can be applied, but device complexity and surgical procedure complexity increase
Solution Approach 1:
The compression sleeve serves multiple functions: it provides compression force to the bone fragments, acts as a driver engagement interface for applying torque, and serves as a protective collar for the bone screw. This multi-functionality eliminates the need for separate compression devices while maintaining relatively simple device structure.
Solution Approach 2:
The compression sleeve is designed to fit over the bone screw in a nested configuration, with the bone screw inserted through the compression sleeve. This nesting arrangement allows both components to work together in a compact integrated structure without requiring complex assembly mechanisms.
3Manufacturing precision
If additional instrumentation is added for countersinking, then precise implantation can be achieved, but soft-tissue irritation and surgical complexity increase
Solution Approach 1:
The countersinking function is merged with the compression application process. The compression sleeve itself serves as the countersinking tool, allowing the bone screw to be countersunk into the bone surface while applying compression, eliminating the need for separate countersinking instrumentation that would increase soft-tissue irritation.
Solution Approach 2:
The compression sleeve performs the countersinking function as part of its own operation. When the compression sleeve is rotated to apply compression, it simultaneously countersinks the bone screw into the bone, allowing the device to perform multiple functions without requiring additional external instrumentation.
4Adaptability or versatility
If the screw length is fixed, then manufacturing is simplified, but adaptability to different bone sizes and fracture locations is reduced
Solution Approach 1:
The screw system transitions from a fixed length configuration to a variable length configuration. The compression sleeve can be rotated relative to the bone screw to adjust the overall length of the implanted device, allowing adaptation to different bone sizes and fracture locations while maintaining relatively simple manufacturing of individual components.
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 system provides controlled compression and countersinking, reducing the risk of nonunion and malunion while minimizing surgical complexity and soft-tissue irritation, and allows for precise adjustment of screw length and compression force.
Implementation Method 1
are self-tapping and/or self-drilling
Implementation Method 2
provide compression upon a bone into which the screw is implanted
Implementation Method 3
The bone screw includes a proximal end having an external threading threadably received in the compression sleeve
Data Source
AI summary
A variable length headless compression screw insertion system includes a compression screw and a driver assembly for driving the compression screw into a bone. The compression screw has a bone screw and a compression sleeve coupled to the bone screw. The bone screw includes a proximal end having an external threading threadably received in the compression sleeve, and the compression sleeve includes a proximal end having a predefined drive feature and an external threading. The driver assembly includes a sleeve coupler adapted to threadably receive the external threading of the compression sleeve. A ram driver is coupled to the sleeve coupler and has a predetermined length such that its distal end is shaped to contact the proximal end of the bone screw to prevent translation of the bone screw relative to the compression sleeve.