Compliant Hip Fixation System for Femoral Head Cut-Out Prevention
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Solution Overview
Problem
Current plate-based fixation devices for the hip joint often result in femoral head cut-out due to the screw's migration, leading to inadequate fixation and potential damage to the articular surface.
Innovation Solution
A compliant hip fixation system featuring a plate member with a barrel portion and a compliant member that allows the fixation element to change its angular orientation in response to load, reducing peak loads and preventing micro-crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the screw is permitted to slide parallel to its long axis in the barrel, then dynamic compression of the fracture is achieved which encourages and improves fracture healing, but the femoral head may be damaged by cut-out where migration of the femoral head relative to the screw causes the screw to project through the articular surface
Solution Approach 1:
The invention employs a dynamic compression mechanism where the screw is permitted to slide parallel to its long axis within the barrel, enabling dynamic compression of the fracture to encourage healing. This dynamic capability allows the system to adapt to the healing process while maintaining control over screw migration through the designed sliding mechanism rather than unrestricted movement.
Solution Approach 2:
The barrel structure serves as an intermediary mechanism between the screw and the femoral head. It controls and mediates the screw's movement, allowing controlled sliding for compression while preventing uncontrolled migration that would cause cut-out. The barrel acts as a mediator that translates the compression force into beneficial fracture compression while limiting the screw's path to prevent articular surface damage.
2Strength
If the screw is inserted obliquely into the proximal femur at an angle of about 135 degrees, then the screw can bridge at least one fracture and provide fixation, but the screw may project through the articular surface causing cut-out and damage
Solution Approach 1:
The barrel functions as an intermediary protective structure that houses the screw during insertion and fixation. It mediates the oblique insertion at approximately 135 degrees by controlling the screw's trajectory and position, preventing the screw from projecting through the articular surface while still allowing it to bridge fractures and provide adequate fixation strength.
3Stability of the object's composition
If the fixation device is made rigid to provide stable fixation, then the screw remains firmly anchored, but the peak loads at the implant-bone interface increase causing micro-crack formation
Solution Approach 1:
The invention changes the mechanical parameters of the fixation system by introducing a compliant barrel structure that can deform under load. This parameter change allows the system to maintain fixation stability while reducing peak stresses at the implant-bone interface through controlled deformation, preventing micro-crack formation that would occur in a completely rigid system.
Solution Approach 2:
The system employs a composite structure combining the screw, barrel, and surrounding bone as a multi-material system. The barrel's material properties are designed to provide controlled compliance, creating a composite system that balances fixation stability with stress distribution to prevent interface micro-cracks.
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 reduces the incidence of femoral head cut-out, enhances patient comfort, and improves force distribution, leading to better healing outcomes and reduced wear-related issues.
Implementation Method 1
a compliant member positioned or positionable at least partially in the plate member and configured to be reversibly deformed in response to a load applied to the head of the proximal femur, to change an angular orientation of the fixation element with respect to the plate member
Data Source
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AI summary
System, including methods, devices, and kits, for hip fixation. The system may include a fixation element configured to be placed obliquely into a proximal femur and anchored in a head of the proximal femur. The system also may include a plate member including (a) a mounting portion configured to be placed on and attached to a lateral cortex of the proximal femur and (b) a barrel portion configured to be placed into a lateral region of the proximal femur and positioned around a portion of the fixation element. The system further may include a compliant member positioned or positionable at least partially in the plate member and configured to be reversibly deformed in response to a load applied to the head of the proximal femur, to change an angular orientation of the fixation element with respect to the plate member.