Spring Washer Bone Fixation for Sustained Fracture Compression
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Solution Overview
Problem
Current medical devices for bone fixation fail to sustain optimal compression across bone discontinuities, leading to hardware loosening, prolonged healing times, and increased risk of complications such as bone and muscle atrophy, infection, and delayed union or non-union of fractures.
Innovation Solution
The development of a spring washer system with specific load versus deflection characteristics, integrated into bone screws and plates, which sustains compression across bone discontinuities, allowing for early weight-bearing and reduced healing time by maintaining optimal bone stress levels between 18 MPa and 30 MPa, promoting direct lamellar bone growth and minimizing callus formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional internal fixation hardware is used to stabilize bone fragments, then bone stabilization is achieved, but hardware loosening occurs over time due to bone gaps created by osteoclastic resorption
Solution Approach 1:
The patent employs a dynamic spring element integrated into the bone screw that allows controlled micromotion and maintains continuous compression force across the fracture site. The spring accommodates bone gap changes during healing while sustaining optimal compressive stress, preventing hardware loosening that occurs with rigid fixed-angle plates. This dynamic mechanism enables the hardware to adapt to changing bone geometry during the healing process.
Solution Approach 2:
The invention changes the mechanical parameter of compression force maintenance from static (conventional hardware) to dynamically adjustable through spring deflection. The spring element continuously adjusts compression parameters based on bone gap size, ensuring optimal stress levels (20-30 MPa) are maintained throughout healing. This parameter adjustment prevents the bone gaps that lead to osteoclastic resorption and subsequent hardware loosening.
2Stability of the object's composition
If conventional fixed-angle plates are used for bone fixation, then structural stability is provided, but bone and muscle atrophy occurs due to lack of physiological loading
Solution Approach 1:
The spring-loaded bone screw provides dynamic stability that allows controlled micromotion and physiological loading during healing. Unlike rigid fixed-angle plates that completely immobilize the fracture site, the spring mechanism permits controlled movement that stimulates bone and muscle maintenance through stress application. This dynamic stability prevents atrophy while maintaining adequate fracture stability.
Solution Approach 2:
The spring element creates periodic loading cycles through its elastic deformation and recovery, subjecting the bone and surrounding muscles to rhythmic stress that mimics physiological loading conditions. This periodic mechanical stimulation prevents disuse atrophy of bone and muscle tissues while still providing adequate fracture stability during the healing process.
3Productivity
If high compression force is applied to bone fragments to promote fusion, then bone growth is stimulated, but excessive stress causes osteoclastic resorption when sustained above 60 MPa
Solution Approach 1:
The spring element is designed with specific elastic properties that automatically regulate compression force parameters, maintaining stress within the optimal therapeutic window of 20-30 MPa. The spring's force-deflection characteristics ensure that compression never exceeds the 60 MPa threshold that triggers osteoclastic resorption, while still providing sufficient stress to stimulate bone growth and accelerate fusion.
4Strength
If rigid bone fixation hardware is used, then initial stability is achieved, but healing time is prolonged due to hardware loosening and need for protective measures
Solution Approach 1:
The spring mechanism provides initial rigidity for stable fixation while enabling progressive adaptation during healing. As bone consolidation progresses, the spring gradually deflects to accommodate reducing bone gap sizes, maintaining compression without requiring hardware replacement or protective casting. This dynamic adaptation eliminates the prolonged non-weight bearing period required with conventional rigid hardware that loosens over time.
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 spring washer system effectively sustains compression, reducing healing time by up to 50%, minimizing complications, and enabling early return to activity while reducing the risk of morbidities like bone atrophy and infection.
Implementation Method 1
a spring washer with specific load versus deflection characteristics achieved by specific design, material, and fabrication
Implementation Method 2
The development of a spring washer system with specific load versus deflection characteristics, integrated into bone screws and plates
Data Source
AI summary
Bone compression systems for internal fixation of bone portions include one or more spring washers having ultra high load capacity and ultra low displacement to close diminution gaps that develop in a discontinuity between the bone portions after fixation. The spring washers may be included in implant systems with bone screws and/or bone plates.