Implantable Compression Screw With Self-Drilling Flutes
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Solution Overview
Problem
Existing bone screws often fail to provide adequate compression at bone joints or fractures, leading to issues such as nonunion or malunion, and may experience screw toggle and back-out due to bone build-up and lack of secure fixation.
Innovation Solution
The development of self-tapping and self-drilling compression screws with a compression sleeve system that applies compressive force to bone fragments, featuring cutting flutes and slots for enhanced purchase and integration with bone, minimizing screw toggle and allowing for adjustable length without predrilling, and a driver assembly for precise insertion and compression control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional bone screws are used, then the screw can be inserted into the bone, but the screw fails to provide adequate compression at the bone joint or fracture line
Solution Approach 1:
The screw is divided into functionally distinct segments: a compression sleeve that applies compressive force at the fracture site, and a threaded shaft that provides anchorage in the bone. This segmentation allows the compression function to be decoupled from the anchorage function, enabling adequate compression to be applied without compromising screw stability.
Solution Approach 2:
The compression sleeve is designed to be dynamically adjustable relative to the threaded shaft, allowing the compression force to be applied and then maintained at a controlled level. The relative movement between the sleeve and shaft enables the surgeon to apply compression during insertion and then lock it in place, providing both dynamic compression application and static compression maintenance.
2Reliability
If conventional screws are used, then the screw can be inserted, but screw toggle and back-out occur due to lack of secure fixation
Solution Approach 1:
The compression sleeve is nested over the threaded shaft, creating a nested structure where the sleeve provides external compression while the shaft provides internal anchorage. This nested configuration allows the sleeve to apply compression forces while the shaft remains securely anchored in the bone, preventing toggle and back-out motions.
Solution Approach 2:
The screw system combines different material properties and structural characteristics: the compression sleeve provides a smooth, low-friction surface for compression application, while the threaded shaft provides high-friction engagement with the bone. This composite structure optimizes both compression application and fixation security.
3Ease of operation
If self-tapping and self-drilling screws are used, then the screw can be inserted without predrilling, but bone build-up from cutting flutes occurs
Solution Approach 1:
The cutting flutes are positioned only on the threaded shaft portion of the screw, not on the compression sleeve. This extraction of the cutting function to only the necessary location allows the screw to self-drill and self-tap where needed while preventing bone build-up on the compression sleeve surface that would interfere with compression application.
Solution Approach 2:
The screw has different surface qualities at different locations: the threaded shaft has cutting flutes for bone engagement and self-drilling, while the compression sleeve has a smooth, bone-free surface for optimal compression application. This local differentiation of surface quality ensures that cutting occurs only where necessary and compression surfaces remain clean.
4Force
If compression is applied during screw insertion, then bone compression is achieved, but the screw length becomes fixed and cannot be adjusted
Solution Approach 1:
The compression sleeve is designed to be dynamically adjustable during insertion, allowing the surgeon to control the amount of compression applied and the final position of the sleeve relative to the shaft. This dynamic adjustability enables both compression application and length adaptation, as the sleeve can be positioned at different locations along the shaft depending on the required screw length and compression amount.
Solution Approach 2:
The compression sleeve can be advanced partially or fully over the threaded shaft depending on the clinical requirements. This partial action capability allows the surgeon to apply the necessary compression while maintaining the appropriate screw length, avoiding excessive compression or overly short screw insertion that would occur with fixed-length compression mechanisms.
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 effectively applies compression to bone fragments, reducing the incidence of improper healing and preventing screw motion, while allowing for adjustable length and secure fixation without predrilling, enhancing the stability and healing of fractures.
Implementation Method 1
the distal end including a series of bone engaging threads configured to be self-drilling and self-tapping
Implementation Method 2
enhanced purchase and integration with bone, minimizing screw toggle
Implementation Method 3
a series of bone engaging threads configured to be self-drilling and self-tapping
Implementation Method 4
the compression sleeve and bone screw are threadably adjustable relative to one another
Data Source
AI summary
A compression screw for applying compression at a bone joint. The compression screw includes an axial screw body extending from a distal end to a proximal end with the distal end including a series of bone engaging threads configured to be self-drilling and self-tapping and the proximal end including a head which defines a radially extending shoulder. At least one proximal rotary cutting structure is defined proximally of the bone engaging threads. The at least one proximal rotary cutting structure is configured to be self-drilling such that a proximal portion of the axial screw body cuts into and advances within a bone of the bone joint as the axial screw body is advanced. A method of inserting the compression screw is also provided.