Radiolucent Bone Plate with Self-Threaded Angled Screws
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Solution Overview
Problem
Traditional bone fracture synthesis devices face challenges in securely locking screws due to difficulties in achieving the required inclination, often necessitating auxiliary bushings that increase costs and plate dimensions.
Innovation Solution
A biocompatible and radiolucent plastic plate with through holes and screws featuring a threaded shank and head with a helical thread, allowing for angular selection and self-threading engagement, enabling secure locking with adjustable inclination without increasing hole dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If auxiliary bushings are inserted to permit greater screw inclination, then the screws can assume the required inclination, but the economic cost increases and the plate dimensions must increase to accommodate the hemispherical seat
Solution Approach 1:
The invention extracts the hemispherical seat function from the plate structure and relocates it to the screw head itself. The screw head incorporates a hemispherical articulation that engages with a corresponding seat in the plate, allowing the screw to achieve the required inclination without requiring the plate to have a hemispherical cavity. This eliminates the need for auxiliary bushings and reduces plate dimension requirements.
Solution Approach 2:
The invention introduces a intermediate hemispherical articulation mechanism between the screw and plate that enables angular adjustment. Instead of requiring the plate to have a large hemispherical seat, the articulation is provided at the screw head level, acting as an intermediary that permits inclination adjustment without increasing plate dimensions.
2Strength
If the plate is made from metal, then it provides strong fixation, but radiographic control is difficult and explantation is complex
Solution Approach 1:
The invention uses composite material construction for the plate, combining biocompatible plastic (such as PEEK) with reinforcing elements. This composite approach provides sufficient mechanical strength for fixation while maintaining radiolucency, allowing clear radiographic visualization of the plate and surrounding bone structures without the obscuring effect of metal.
Solution Approach 2:
The invention changes the material parameter of the plate from metal to biocompatible plastic, which fundamentally alters both the radiographic properties (making it radiolucent) and the explantation characteristics (making it easier to remove without threading complications). The plastic material maintains adequate strength while eliminating the drawbacks of metal plates.
3Ease of manufacture
If the screw head diameter is greater than the hole diameter, then self-threading engagement is achieved, but the manufacturing precision requirements increase
Solution Approach 1:
The invention incorporates preliminary threading features in the hole design and corresponding threads on the screw shank that guide the screw into proper alignment before the head engages. The hole is pre-formed with appropriate tolerances and the screw threads are designed to self-align, reducing the precision requirements for the final engagement of the oversized head with the hole.
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 facilitates secure bone fracture reduction with improved radiographic control and easy plate explantation, providing firm anchoring and reducing the risk of plate displacement while maintaining economic viability.
Implementation Method 1
the head is substantially cylindrical and has a helical thread with spiral rings having an external diameter greater than the diameter of the holes so that, when the head is screwed in the holes, the spiral rings engage the hole wall by self-threading so as to lock the screw in the selected angulation
Data Source
Figure 1~2
Figure 3~4
AI summary
Device for synthesis of bone (2) fractures (3), comprising a plate (1) and screws (5) for locking said plate. The plate (1) is entirely made from biocompatible and radiolucent plastic material suitable to permit a radiographic control and an easy explantation of the plate and is provided with through holes (4) for the screws (5) fixing the plate (1) on the bone (2). The screws (5) comprise a threaded shank (7) having an external diameter less than the diameter of said holes (4) and a head (6) having a thread with an external diameter greater than the diameter of said holes (4) so as to permit insertion of the screws (5) according to a plurality of directions and inclination with respect to the axis of the holes (4) in the plate (1), said head (6) being suitable to engage said holes (4) by self-threading.