Fracture Fixation Plate with Expandable Bearings
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Solution Overview
Problem
Existing fracture fixation systems face challenges in securely positioning and stabilizing bone screws or posts at variable angles without excessive plate thickness, limited torque resistance, and cumbersome surgical procedures due to reliance on fixed tines, set screws, or narrow frictional contacts.
Innovation Solution
A fracture fixation system that employs an intermediate bearing between the screw and the plate hole, allowing adjustable angulation through threaded expansion, distributing torque resistance across multiple contact zones and preventing spinning, with slots for radial expansion and optional features like microtexturing or tabs to enhance stability and prevent rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed tines are used in the plate, then the plate structure is simple, but the tines are located at fixed positions which may not be optimally positioned and may enter a fracture site or protrude into the joint
Solution Approach 1:
The device is segmented into a plate component and a separate post component with tine. This allows the post to be independently positioned and angled relative to the plate, enabling optimal placement away from fracture sites and joints while keeping the plate structure relatively simple.
Solution Approach 2:
The post is designed to be adjustable in angle relative to the plate through a bearing mechanism. This dynamic positioning capability allows the surgeon to optimize the tine position for each specific fracture geometry, preventing entry into fracture sites or joints while maintaining a simple plate structure.
2Strength
If threaded holes in the plate are used to secure posts, then the post can be secured firmly, but the plate must have sufficient thickness to allow adequate number of threads for fixation
Solution Approach 1:
A bearing mechanism is introduced as an intermediary between the post and the plate. The bearing contains the threading and fixation mechanism, allowing strong fixation without requiring the plate itself to be thick. The bearing acts as a mediator that provides the necessary thread engagement length while keeping the plate thin.
3Adaptability or versatility
If a set screw is used to secure the post head in the plate hole, then the post can be fixed at variable angles, but the set screw only compresses the head over a small surface area resulting in small frictional forces and risk of inadequate fixation
Solution Approach 1:
The bearing serves as an intermediary that provides a large surface area for frictional contact between the post head and the bearing interior. This replaces the inadequate set screw compression mechanism, distributing the compressive forces over a much larger area and generating sufficient frictional forces to reliably prevent post migration while maintaining angular flexibility.
4Adaptability or versatility
If a slotted head post is used, then the post can be placed at variable angles, but the slotted area creates considerable weakness where the shaft connects to the head making it prone to breakage
Solution Approach 1:
The bearing acts as an intermediary that receives the post head and provides frictional locking without requiring slots in the post head. The bearing's internal frictional forces secure the post at variable angles, eliminating the need for a slotted head design and thereby preventing the creation of weak points in the post structure.
5Strength
If a narrow bushing is used to expand and frictionally lock the screw, then the screw can be secured, but the contact area between the bushing and the hole surface is limited to a narrow zone resulting in limited torque resistance
Solution Approach 1:
The bearing is introduced as an intermediary between the post and the plate hole, providing a large contact area for frictional locking. Unlike the narrow bushing, the bearing's spherical geometry and interaction with the post head distribute the contact forces over a much larger surface area, significantly increasing torque resistance while maintaining secure locking.
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 reliable and simple screw or post fixation with improved torque resistance and reduced risk of breakage, allowing for precise angulation control and secure bone fragment stabilization without excessive plate thickness or cumbersome set screws.
Implementation Method 1
the frictional forces generated are relatively small whereby there is a risk of inadequate fixation of the post or screw
Implementation Method 2
allowing adjustable angulation through threaded expansion
Implementation Method 3
distributing torque resistance across multiple contact zones and preventing spinning
Implementation Method 4
with slots for radial expansion
Data Source
AI summary
A fracture fixation system in which a plate is secured to stable bone and posts are inserted at varying angles into an unstable bone fragment by engaging in rotatable bearings which are fixedly secured in the plate when the posts are fully engaged in the bone fragment. The bearings are formed as truncated spherical members having a number of longitudinal slots extending partway along the length of the bearing to form petals which are expanded outwardly when the posts are advanced in the bearing to produce non-uniform distribution of forces between the bearing and the plate which generate force couples to resist angulation of the posts and loss of fracture fixation. Various other ways of producing non-uniform force distribution are described.