Cannulated Compression Screw with Proximal Lip for Small Bone Fixation
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Solution Overview
Problem
In orthopedic surgery for small bones, existing compression screws face challenges in maximizing compression and ease of insertion, particularly due to limited bone and muscle tissue, requiring implants that minimize volume and avoid additional drilling steps.
Innovation Solution
A compression screw design featuring a tapered proximal portion with cutting flutes that act as a stop, a threadless constant diameter intermediate segment, and a self-tapping, threaded distal insertion tip, allowing for self-drilling and compression without self-countersinking, optimized for small bones by maximizing longitudinal compression and ease of insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional compression screw is designed with self-tapping and self-countersinking features, then ease of insertion is improved, but the ability to generate maximum compression is reduced due to the need for countersinking
Solution Approach 1:
The patent inverts the traditional headless compression screw design by creating a proximal lip that acts as a stop before the cutting flutes. This inversion allows the screw to generate maximum compression by impacting the cortical bone with the lip, rather than relying on countersinking. The lip is positioned proximal to the cutting flutes, reversing the typical sequence and enabling the screw to achieve both ease of insertion and maximum compression force.
Solution Approach 2:
The screw is segmented into distinct functional zones: a proximal portion with cutting flutes that form a stop lip, a threadless intermediate segment, and a threaded distal insertion tip. This segmentation allows each portion to perform its specific function optimally - the proximal lip for compression generation, the intermediate segment for structural transition, and the distal tip for self-tapping and insertion.
2Productivity
If the screw is designed to be self-tapping and self-drilling, then additional drilling steps are eliminated, but the compression generated may be reduced without a proper stop portion
Solution Approach 1:
The proximal lip is formed in advance as part of the screw structure before insertion. This preliminary stop portion is positioned to engage the cortical bone during insertion, automatically generating compression without requiring additional drilling or countersinking steps. The lip is pre-formed to the correct position and geometry to provide the necessary stop and compression function.
3Ease of operation
If the cutting flutes extend through to the proximal terminal surface, then self-countersinking is achieved, but the longitudinal compression is reduced
Solution Approach 1:
The patent extracts the countersinking function from the cutting flutes by positioning them to terminate before the proximal terminal surface. The cutting flutes are shortened to form a stop lip, removing the traditional countersinking capability while preserving the self-tapping function. This extraction allows the screw to maintain longitudinal compression by preventing the flutes from extending through the proximal end.
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 screw effectively generates optimal compression by engaging the cortical bone, reducing tissue irritation and the need for additional drilling, while maintaining a flush surface, thus enhancing fixation and repair in delicate bone areas like the scaphoid or correcting conditions like flat feet.
Implementation Method 1
The proximal compression taper is self-drilling to the bone cortex, but will act to generate compression when the distal side of the lip engages the cortical bone that forms the top of the screw hole
Implementation Method 2
This design helps to provide optimal compression by causing the screw to impact the hard cortical portion of the bone and to thus drive the bone toward the distal end of the screw
Implementation Method 3
The present invention has a threaded distal end, which is preferably self-tapping
Implementation Method 4
The proximal compression taper is self-drilling to the bone cortex
Data Source
AI summary
A cannulated compression screw is used as an orthopedic implant and has a threaded distal end with an insertion tip that includes at least one and preferably two, three or four flutes to allow the screw to be self-tapping. Optionally, the screw also includes one or more reverse cutting flutes proximal to the insertion tip. The distal threads are cancellous threads having a generally constant minor diameter and a generally constant major diameter and a generally constant thread pitch. An intermediate portion of the screw is non-threaded and the proximal end includes a compression wedge or taper that has at least one, and preferably two to five flutes that terminate before the top of the screw. The proximal end further includes a radiused bevel to the terminal surface that includes a hexagonal torque driving recess. The diameter of the non-threaded shaft section is constant distal from the compression wedge to the distal tip where it defines the minor diameter of the threaded portion. The screw optionally includes a tapered insertion tip.