Reverse Hip Prosthesis with Threaded Acetabular Cup and Ball
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Solution Overview
Problem
Despite advances in design and materials, hip replacement systems often fail or require revision earlier than desired due to inadequate fitment, stability, and joint range of motion, necessitating improvements for longevity and adjustability.
Innovation Solution
A reverse hip prosthesis system with an acetabular cup arrangement and femoral stem configuration that includes adjustable components, such as threaded attachments and polymeric inserts, to ensure optimal sizing and stability, utilizing materials like high-density polyethylene and self-lubricating surfaces for improved wear resistance and articulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fixed-size acetabular cup is used, then the device structure is simple, but the fitment precision and adaptability to different patients are inadequate
Solution Approach 1:
The acetabular cup is divided into two separate components: a shell (anchor portion) and an insert. The shell provides structural support and is anchored to the acetabulum, while the insert provides the articulating surface and comes in multiple sizes. This segmentation allows the shell to remain a single standard size while the insert can be selected to match the patient's specific anatomical requirements, thereby improving fitment precision without significantly increasing overall device complexity.
Solution Approach 2:
The insert is designed to be inserted into and contained within the shell, forming a nested structure. The insert can be press-fit, interference-fit, or mechanically locked into the shell. This nesting arrangement allows the smaller insert component to be selected in different sizes while the outer shell remains a standardized component, resolving the contradiction between precision fitment and device simplicity.
2Stability of the object's composition
If a reverse hip configuration is used, then joint stability is improved, but the complexity of the prosthesis structure increases
Solution Approach 1:
The reverse hip configuration inverts the traditional hip prosthesis arrangement by placing the ball component on the acetabular side and the cup component on the femoral side. This inversion improves joint stability by better distributing loads and reducing the risk of dislocation. The shell-insert structure further simplifies this inverted configuration by allowing modular assembly, where the insert containing the ball can be separately optimized while the shell provides the acetabular anchor.
3Adaptability or versatility
If modular components with multiple sizes are provided, then adaptability to different patients is improved, but the quantity of components and device complexity increase
Solution Approach 1:
The prosthesis is segmented into modular components (shell and insert) where only the insert requires multiple size variations. The shell can be a standardized component suitable for most patients, while the insert is available in multiple sizes to accommodate different anatomical requirements. This selective segmentation provides adaptability without requiring multiple size variations of all components, thereby limiting the increase in device complexity.
4Duration of action of stationary object
If wearable polymeric materials are used for the insert, then wear resistance is improved, but the structural strength is reduced
Solution Approach 1:
Different materials with optimized properties are assigned to different parts of the acetabular cup. The shell is made from a strong, rigid material (such as metal or highly cross-linked polyethylene) to provide structural support and anchoring strength. The insert is made from a wear-resistant polymeric material (such as ultra-high-molecular-weight polyethylene or cross-linked polyethylene) to provide a low-friction articulating surface. This local differentiation of material properties allows each component to be optimized for its specific function, achieving both wear resistance and structural strength.
Solution Approach 2:
The acetabular cup system utilizes a composite construction combining different materials with complementary properties. The shell may be made from metal (such as titanium or cobalt-chromium alloy) or rigid polymer, while the insert is made from wear-resistant polymer. This composite approach allows the strong shell to provide structural integrity while the polymer insert provides wear resistance and low friction, achieving both requirements simultaneously.
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 provides enhanced adjustability, stability, and extended longevity by ensuring a precise fit and reduced wear, facilitating easier repair and replacement while maintaining joint mobility.
Implementation Method 1
The insert may include a self-lubricating material provided at least at a surface
Implementation Method 2
An acetabular ball may be configured for threaded attachment to the acetabular cup arrangement
Data Source
AI summary
A reverse hip prosthesis include an acetabular cup arrangement configured for insertion into an acetabulum of a patient and fixation therein, an acetabular ball configured for threaded attachment to the acetabular cup arrangement, a femoral stem configured for insertion into an intramedullary femoral canal of the patient, and a femoral cup arrangement configured for attachment to the femoral stem and to operatively receive the acetabular ball therein. The acetabular cup arrangement includes an anchor portion which becomes fixed to the patient's acetabulum and is the largest size suitable for the patient, and an insert which comes in different sizes and are connectable to the anchor portion, so that the most appropriate insert for the patient may be used. The acetabular cup arrangement and ball are interconnected with a threaded stem that also functions as an artificial Ligamentum Teres.