Compliant Hip Fixation Element for Dynamic Compression
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Solution Overview
Problem
Current hip fixation systems, such as nail-based and plate-based fixation devices, often fail to provide stable fixation, leading to femoral head damage due to screw migration, resulting in cut-out or splitting, which can hinder fracture healing.
Innovation Solution
A hip fixation system comprising a support member with an intramedullary nail or plate member and a reversibly deformable fixation element that is slideable parallel to its long axis, along with a stiffening insert to reduce deformability, thereby reducing peak loads and preventing micro-crack formation at the implant-bone interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the screw is permitted to slide parallel to its long axis in the nail or barrel to enable dynamic compression of the fracture, then fracture healing is improved, 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 fixation element is designed with a compliant region that allows controlled deformation under load, changing the mechanical parameters of the system to enable dynamic compression while limiting excessive migration that causes cut-out. The compliant region deformability parameter is optimized to balance fracture compression benefits with femoral head protection.
Solution Approach 2:
The fixation element incorporates a compliant region made of elastomeric material combined with a stiffening insert, creating a composite structure that provides both flexibility for dynamic compression and rigidity to prevent excessive migration and cut-out of the femoral head.
2Stability of the object's composition
If the fixation element is made rigid to provide stable fixation, then screw stability is improved, but peak loads at the implant-bone interface increase causing micro-crack formation
Solution Approach 1:
The fixation element's stiffness parameter is optimized by incorporating a compliant region that deforms under load to reduce peak stresses at the implant-bone interface, preventing micro-crack formation while maintaining sufficient stability through the stiffening insert.
Solution Approach 2:
The compliant region acts as a cushioning element that absorbs and distributes mechanical loads before they reach the implant-bone interface, reducing peak stresses and preventing micro-crack formation in advance.
3Object-affected harmful factors
If the compliant region is made more deformable to reduce peak loads, then load distribution is improved, but the fixation element becomes less stable
Solution Approach 1:
The fixation element combines an elastomeric compliant region with a stiffening insert to create a composite structure that provides both deformability for load distribution and rigidity for stability, optimizing the balance between these competing requirements.
Solution Approach 2:
Different regions of the fixation element have different mechanical properties: the compliant region provides deformability for load distribution, while the stiffening insert provides rigidity for stability, creating local quality variations that optimize overall performance.
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, improves patient comfort, and enhances fracture healing by providing better load distribution and dampening, while minimizing swarf creation through wear.
Implementation Method 1
a reversibly deformable fixation element... with a reversibly deformable compliant region
Implementation Method 2
a stiffening insert that is insertable into the fixation element to reduce a deformability of the compliant region
Implementation Method 3
the fixation element... is slideable with respect to the support member parallel to a long axis defined by the fixation element
Data Source
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AI summary
System, including methods, devices, and kits, for hip fixation. The system may include a support member defining an aperture and including an intramedullary nail for a proximal femur or a plate member for a proximal femur. The system also may include a fixation element having a compliant region and configured to be received in the aperture of the support member such that the fixation element extends out of the support member from the aperture and into a head of the proximal femur and is slideable with respect to the support member along a long axis defined by the fixation element. The system further may include a set of stiffening inserts each insertable into the fixation element and configured to stiffen the compliant region differently from one another.