Active Compression Screw Assembly for Orthopaedic Fracture Stabilization
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Solution Overview
Problem
Current fracture treatment devices for long bones, such as femur and tibia, face challenges in providing adequate compression and stability, with non-locking plates offering low shear resistance but risking screw loosening, and locking plates having difficulty in initial screw engagement across the fracture site.
Innovation Solution
The development of an active compression screw assembly with distal and proximal threads for engagement with cancellous and cortical bone, respectively, and a spring mechanism for adjustable compression, which can be integrated into orthopaedic implants like plates and intramedullary nails, allowing for precise fracture reduction and stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If non-locking plates are used, then the screw can compress the bone across the fracture site, but the resistance to shear force is low which can cause screw loosening
Solution Approach 1:
The patent combines the compression capability of non-locking plates with the shear resistance of locking plates by integrating a threaded hole in the plate that receives a screw having both compression and locking functions. The screw threads engage with the plate threads to provide shear resistance while the screw head compresses the bone fragments through the plate.
Solution Approach 2:
The screw assembly serves multiple functions simultaneously: it provides compression across the fracture site through the screw head, engages the bone with distal threads for stability, and locks to the plate through threaded engagement to resist shear forces. This multi-functional design eliminates the need to choose between compression and locking capabilities.
2Reliability
If locking plates are used, then the resistance to shear force is high which reduces screw loosening, but the screw head engages the threaded hole on the locking plate before the screw can compress the plate to bone and/or the bone across the fracture site
Solution Approach 1:
The patent creates a dynamic system where the screw can move freely within the plate aperture during insertion and compression, then transitions to a locked state after compression is achieved. The compression force is applied first while the screw is unthreaded from the plate, allowing direct compression of the bone, and only after compression is the screw threaded into the plate to lock it in place.
Solution Approach 2:
The compression action is performed before the locking action. The screw is inserted through the plate aperture and compresses the bone fragments first, establishing the desired compression force. Only after this preliminary compression is achieved is the screw threaded into the plate's threaded hole to lock the compression in place and provide shear resistance.
3Ease of operation
If a lag screw is inserted through the barrel member, then the fracture can be compressed by adjusting the compression screw, but multiple screws are needed to prevent rotation of the lag screw relative to the compression plate and barrel member
Solution Approach 1:
The patent combines the compression screw and lag screw into a single integrated component. The screw has a head that interfaces with the compression plate for compression adjustment, a smooth portion that slides through the barrel member, and distal threads that engage the bone. This single screw performs all functions previously requiring multiple separate components.
Solution Approach 2:
The multi-functional screw serves as both the compression adjustment mechanism and the lag screw for fracture stabilization. By integrating these functions into one component, the number of screws needed is reduced from multiple to just one, simplifying the overall device while maintaining compression adjustability and rotational stability.
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
This solution enhances fracture healing by providing adjustable and stable compression across the fracture site, reducing the risk of screw loosening and vascular damage, while allowing for effective engagement and stabilization of bone fragments.
Implementation Method 1
a spring mechanism for adjustable compression
Implementation Method 2
The active compression screw includes distal threads for engagement with cancellous bone
Implementation Method 3
The smooth portion of the lag screw is free to slide through the barrel member to permit the adjustment of the compression screw
Data Source
Figure 1~3
Figure 4~6
Figure 7a~10
AI summary
An assembly and method are disclosed. The assembly includes an orthopaedic implant and an active compression member. The implant has a compression screw hole with a step and the active compression member includes an outer tube and an inner slide. The tube and slide allow the proximal end portion and the distal end portion to move relative to one another. The method includes inserting a guide wire, placing a drill over the guide wire and drilling into a femur, tapping the drilled hole, using a compression device to reduce the fracture using the orthopaedic implant step, and inserting one or more active compression members into the tapped hole.