Bone Screw Assembly with Acute-Angle Through Hole for Fixation Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bone screws, pins, or nails used in bone fixation devices can become dislodged during patient movement, leading to instability in bone fixation.
Innovation Solution
A system comprising a bone screw with a through hole and an aiming guide that allows for precise insertion of a second screw at an acute angle, enhancing stability by using a conical internal thread and a polyaxial pivot bearing for guided alignment and secure anchoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single bone screw is used for fixation, then the device complexity is low, but the stability and reliability of bone fixation deteriorates due to dislodgment risk
Solution Approach 1:
The patent implements a nested screw configuration where a second screw is inserted through the head of the first bone screw into the bone. The second screw passes through the longitudinal axis of the first screw's head and engages with the bone at an acute angle relative to the first screw's longitudinal axis. This nesting arrangement allows the second screw to lock the first screw in place, preventing dislodgment while maintaining a relatively compact overall structure.
Solution Approach 2:
The patent introduces a second screw that operates in a different spatial dimension and orientation compared to the first screw. The second screw is inserted at an acute angle (e.g., 30-60 degrees) relative to the longitudinal axis of the first screw, creating a multi-dimensional fixation system. This angular arrangement provides enhanced stability by distributing fixation forces across different vectors, preventing the bone-screw assembly from dislodging in any single direction.
2Reliability
If a second screw is added through the bone screw head, then the bone fixation stability improves, but the ease of operation deteriorates due to complex insertion procedures
Solution Approach 1:
The patent incorporates a pre-formed through-hole in the head of the first bone screw along its longitudinal axis. This through-hole is prepared in advance during manufacturing, eliminating the need to drill a separate hole through the screw head during surgery. The second screw can be directly inserted through this pre-existing through-hole, significantly simplifying the surgical procedure. Additionally, the head geometry is designed to naturally guide the second screw at the correct acute angle relative to the first screw's axis.
Solution Approach 2:
The through-hole in the first screw's head serves as an intermediary structure that facilitates the insertion of the second screw. This intermediate feature provides a predetermined pathway and angular guidance, acting as a mediator between the first screw and the second screw. The through-hole ensures proper alignment and positioning of the second screw without requiring complex alignment tools or procedures during surgery.
3Reliability
If screws are inserted at acute angles, then the bone fixation reliability improves by preventing dislodgment, but the manufacturing precision requirements worsen for angled through-holes
Solution Approach 1:
The patent employs asymmetric geometry in the design of the first screw's head, with the through-hole positioned and angled specifically to receive the second screw at a predetermined acute angle (e.g., 30-60 degrees) relative to the first screw's longitudinal axis. This asymmetric through-hole configuration is optimized for the specific function of guiding the second screw, allowing for reliable angular positioning while simplifying manufacturing compared to requiring precise angular alignment during assembly. The asymmetric design embeds the angular relationship directly into the geometry of the first screw's head.
Data Source
AI summary
A bone screw includes a screw shaft extending longitudinally along a screw axis and a screw head extending from a proximal end of the screw shaft and configured to be releasably coupled to a surgical tool. The bone screw also includes a through hole defining a through hole axis and extending through the screw head, the through hole axis intersecting the screw axis at an acute angle a, the through hole being adapted to receive therein a second screw and tapering from a first end at a proximal end of the screw head to a second end opening to an outer surface of the screw head.