Compliant Hip Fixation Element for Femoral Head Cut-Out Prevention
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Solution Overview
Problem
Current hip fixation devices, such as nail-based and plate-based systems, often fail to provide stable fixation, leading to femoral head damage due to screw migration, resulting in cut-out and fracture instability, which can hinder effective healing.
Innovation Solution
A compliant hip fixation system featuring a deformable fixation element with a reversibly deformable region and an optional stiffening insert, allowing the element to slide parallel to its long axis and reduce deformability, thereby distributing load more evenly and reducing the risk of micro-crack formation and implant cut-out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid fixation device is used to provide stable support, then structural strength is improved, but the risk of femoral head cut-out increases due to inability to accommodate bone resorption and micromotion
Solution Approach 1:
The fixation device incorporates a compliant mechanism that transitions from a rigid structure to a dynamic system capable of controlled deformation. The device includes flexible elements and movable components that allow adaptation to bone resorption and micromotion while maintaining fixation strength, thereby reducing the risk of cut-out.
Solution Approach 2:
The device utilizes materials and structures with variable mechanical properties, including compliant elements with controlled flexibility and stiffening mechanisms that can adjust their rigidity. This allows the fixation device to provide initial stability while gradually adapting to physiological conditions, balancing strength and reliability.
2Adaptability or versatility
If a compliant fixation element is used to reduce cut-out risk, then adaptability to bone changes is improved, but fixation stability deteriorates due to excessive deformability
Solution Approach 1:
The fixation device is divided into distinct functional segments: compliant elements for adaptation, stiffening mechanisms for stability, and locking components for final fixation. This segmentation allows each part to perform its specific function optimally, achieving both adaptability and stability.
Solution Approach 2:
The device incorporates preliminary stabilization features that provide immediate fixation stability upon implantation, followed by gradual adaptation through controlled deformation. Stiffening elements are pre-positioned to maintain stability while compliant portions gradually adapt to bone changes over time.
3Productivity
If the screw is permitted to slide in the nail or barrel to enable dynamic compression, then fracture healing is improved, but screw migration occurs causing femoral head damage
Solution Approach 1:
An intermediary mechanism is introduced between the screw and the nail/barrel, consisting of controlled compliance elements and guiding features. This intermediary allows the screw to migrate sufficiently for dynamic compression while preventing excessive migration that would cause cut-out, mediating between the two opposing requirements.
Solution Approach 2:
The screw-nail interface is designed with dynamic characteristics, allowing controlled movement during the healing process. The compliance mechanism enables initial screw migration for compression while progressively restricting movement as healing progresses, optimizing both fracture healing and preventing femoral head damage.
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 dampening, leading to better fracture healing outcomes and reduced wear-related complications.
Implementation Method 1
a reversibly deformable compliant region
Implementation Method 2
slideable with respect to the support member parallel to a long axis defined by the fixation element
Implementation Method 3
a stiffening insert that is insertable into the fixation element to reduce a deformability of the compliant region
Data Source
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.