Unilateral External Fixator With Universal Joints for 3D Correction
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Solution Overview
Problem
Existing external fixators are cumbersome, difficult to use in multiple planes, and challenging for surgeons to visualize and manage during complex bone deformity corrections, particularly in three dimensions, leading to discomfort for patients and inefficiency in daily life.
Innovation Solution
A unilateral external fixator (UEF) with universal joints and adjustable screws for precise control of bone position and orientation, combined with a computer-assisted method for planning and adjusting fixator positions using x-ray images and software algorithms to achieve desired bone alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a circular fixator with two rings and six struts is used, then some problems of unilateral fixator are solved, but the hardware becomes complex and surgeons have difficulty seeing the surgical area
Solution Approach 1:
The fixator is divided into modular components: a central body with universal joints connecting to base structures, each with independent adjustment mechanisms. This segmentation allows complex correction capabilities while maintaining manageable hardware complexity through standardized modules.
Solution Approach 2:
The universal joints enable the fixator to function in multiple planes (frontal, sagittal, and axial) with a single unified structure. The same central body and base configuration provide correction capability across different planes, eliminating the need for separate adjustment mechanisms for each plane.
2Adaptability or versatility
If a circular fixator with struts around the patient's extremity is used, then correction in multiple planes is achieved, but patients have difficulty carrying such a bulky device on their extremity
Solution Approach 1:
The fixator uses a compact segmented design with a central body and separate base structures connected by universal joints. This segmentation allows the device to achieve multi-plane correction while minimizing overall volume and bulk compared to traditional circular fixators with extensive struts.
3Adaptability or versatility
If a circular fixator with multiple struts is used, then correction capability is improved, but adjusting strut lengths every day is not easy because at least three struts are outside of the patient's view
Solution Approach 1:
The adjustment mechanisms are segmented and integrated into accessible portions of the device. The angulation adjustment screw assemblies and axial adjustment screws are positioned on the base structures that remain visible and accessible to patients and caregivers, enabling daily adjustments without requiring removal of the entire device.
Solution Approach 2:
The adjustment mechanisms are designed to be easily manipulated by patients or caregivers without requiring complex procedures. The screw assemblies provide self-contained adjustment capability that can be performed daily at home, eliminating the need for frequent clinic visits for adjustment.
4Device complexity
If a unilateral fixator is used, then the apparatus is simpler, but it is difficult for complex deformities in three dimensions and surgeons have difficulty foreseeing the bone position in a plane other than that being corrected
Solution Approach 1:
The universal joints provide multi-functionality by enabling the fixator to correct deformities in multiple planes (frontal, sagittal, and axial) while maintaining a relatively simple unilateral structure. The same basic mechanism provides correction capability across different planes, eliminating the need for separate adjustment mechanisms for each plane.
Solution Approach 2:
The universal joints provide dynamic adaptability, allowing the fixator to adjust and accommodate deformities in three dimensions. The joints enable the device to adapt to complex spatial relationships between bone segments, providing versatile correction capability while maintaining structural simplicity.
Data Source
AI summary
A unilateral external fixator (“UEF”) and method of controlling the UEF. Apparatus comprises a central body connected to a first base and a second base via joints. Two angular adjustment screw assemblies control position between the central body and the first base. Two additional angular adjustment screw assemblies control position between the central body and the second base. A first axial adjustment screw assembly in the first base adjusts axial position of a first bone attachment base. A second axial adjustment screw in the second base adjusts axial position of a second bone attachment base. Method comprises uploading a first set of x-rays to a computer program, characterizing geometry of a bone deformity with the program, recommending frame geometry for correcting the deformity, then after surgery uploading a second set of x-rays with fixator attached, characterizing geometry again, calculating fixator adjustments necessary to align bones, and providing proposed fixator positions.