Reverse Total Hip Prosthesis Design for Dislocation Prevention
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Solution Overview
Problem
Current total hip replacement designs are prone to dislocation, particularly posterior dislocation, due to the traditional ball-and-socket biomechanics, which can be devastating for patients, and existing reverse hip prosthesis designs have shown high failure rates or practical limitations such as acetabular loosening and soft tissue entrapment.
Innovation Solution
A reverse total hip replacement design that reverses the biomechanics by making the femoral component cup-shaped and the acetabular component ball-shaped, allowing for a medialized center of rotation, reduced force requirements for abductor muscles, and enabling fastener fixation that avoids vital structures, with a targeting guide for accurate alignment and minimal bone resection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ball-and-socket hip replacement design is used, then the joint can replicate natural hip biomechanics, but the dislocation rate increases to 1-2%
Solution Approach 1:
The patent applies the reverse joint prosthesis principle by inverting the traditional ball-and-socket configuration. The acetabular component becomes the ball (spherical segment with spherical articulating surface) and the femoral component becomes the cup (cup-shaped articulating surface). This inversion fundamentally changes the dislocation mechanics, making anterior dislocation the primary risk instead of posterior dislocation, thereby reducing the overall dislocation rate while maintaining joint stability.
2Stability of the object's composition
If larger femoral heads are used to reduce dislocation, then joint stability improves, but the cup liner must be made thinner which compromises structural integrity
Solution Approach 1:
By inverting the joint configuration, the patent eliminates the need to thin the cup liner to accommodate larger heads. The spherical segment acetabular component with its spherical articulating surface provides inherent stability while the cup-shaped femoral component maintains adequate liner thickness for structural integrity.
3Reliability
If conventional total hip replacement is performed, then the femoral head is replaced, but significant bone resection including reaming of the medial acetabular wall is required
Solution Approach 1:
The reverse configuration allows the spherical segment acetabular component to be positioned without requiring extensive reaming of the medial acetabular wall. The unique geometry of the spherical segment with its spherical articulating surface enables implantation that preserves native bone stock while achieving reliable implant fixation.
Solution Approach 2:
The targeting guide is used to pre-plan and establish the optimal position and orientation of the spherical segment acetabular component before final implantation. This preliminary positioning action ensures correct alignment and minimizes the need for extensive bone resection to achieve proper implant placement.
4Force
If the center of rotation is not medialized, then abductor muscle leverage is maintained, but the moment arm increases requiring more muscle force
Solution Approach 1:
The inverted joint configuration with the spherical segment acetabular component medialized center of rotation reduces the moment arm of the abductor muscles. This geometric inversion optimizes the lever mechanics, decreasing the force required from the abductor muscles while maintaining effective hip abduction function.
Data Source
AI summary
A reverse total hip prosthesis is characterized by a femoral cup component and an acetabular ball component and is used for reconstruction of a hip joint. The prosthesis reverses the mechanics across the joint medializing the center of rotation, preventing dislocation in a posterior direction. Both ball and socket portions of the components lie outside of bone enabling larger sizing of the femoral and acetabular components improving stability, regardless of the size of the patient's anatomy. A method for reverse hip prosthesis implantation eliminates reaming through the base of the acetabulum preserving acetabular bone stock.