External Fixator with Lockable Universal Joints for Fracture Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional external fixators for fracture fixation are invasive, risk infection, restrict joint movement, and are difficult to align with joints, especially when spanning joints like the wrist or ankle, leading to misalignment and poor healing.
Innovation Solution
A non-invasive external fixator with proximal and distal portions and an articulation member featuring selectively lockable universal joints, allowing three-dimensional movement at the joint and fracture site, and adjustable cuffs for secure limb mounting, enabling movement without disturbing fracture alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional external fixator with a steel rod is used to fix a fracture, then the fracture fragments are held together, but the risk of infection and surgical complications increases
Solution Approach 1:
The invention extracts the pins that penetrate the skin and bone in conventional fixators, replacing them with a non-invasive cuff system that contacts only soft tissue. This removes the source of infection while maintaining the fixator's ability to stabilize the fracture through external rigid rods and articulation mechanisms.
Solution Approach 2:
The invention introduces an intermediary cuff system that interfaces between the external fixator and the patient's limb. The cuff acts as a mediator that transfers mechanical forces without requiring skin penetration, thereby eliminating infection risk while maintaining secure attachment and fracture stabilization.
2Reliability
If a conventional external fixator spans a joint, then fracture fixation is achieved, but joint movement is restricted
Solution Approach 1:
The fixator is segmented into separate components: rigid rods for fracture stabilization and an articulation mechanism with universal joints for joint movement. This segmentation allows the fracture fixation function and joint mobility function to operate independently, resolving the contradiction between maintaining alignment and enabling movement.
Solution Approach 2:
The invention replaces the static, rigid rod spanning the joint with a dynamic articulation mechanism featuring universal joints that can lock and unlock. This dynamic system allows the fixator to adapt between providing rigid stabilization when needed and permitting full joint movement when appropriate, eliminating the trade-off between alignment and mobility.
3Ease of operation
If an articulated fixator is used to allow joint movement, then mobility is improved, but alignment with the joint plane becomes difficult
Solution Approach 1:
The universal joint provides multi-directional movement capability in all three planes, making the articulation inherently adaptable to any joint orientation without requiring precise pre-alignment. This universal movement capacity eliminates the manufacturing precision issue while maintaining full joint mobility.
Solution Approach 2:
The invention uses selectively lockable universal joints that can change their movement parameters dynamically. The joints can be unlocked to permit movement in multiple planes for positioning, then locked to maintain the desired alignment, allowing easy adjustment without requiring precise manufacturing tolerances.
4Ease of operation
If known articulated fixators allow multidirectional movement including rotation, then joint mobility is enabled, but fracture position stability is compromised
Solution Approach 1:
The articulation mechanism features selectively lockable universal joints that can dynamically switch between locked and unlocked states. When locked, the joints provide stable fracture fixation; when unlocked, they permit joint movement. This dynamic control resolves the contradiction between mobility and stability.
Solution Approach 2:
The invention applies different functional qualities to different parts of the system: the universal joints near the joint line remain unlocked to permit movement, while the articulation near the fracture site is locked to maintain stability. This localized differentiation allows simultaneous joint mobility and fracture stability.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention relates to a non-invasive external fixator (10) particularly suitable for fracture fixation. In particular, the fixator of the invention comprises proximal (16) and distal (18) portions for mounting on a limb (12) either side of a fracture (14), each of the proximal and distal portions including a rigid member (32, 34); and an articulation member (40, 42) connecting the proximal and distal portions, the articulation member comprising a universal joint for allowing relative movement between the proximal and distal portions, wherein the articulation member connects the rigid members.