Arthroplasty Implant Button Cap Screw Fixation
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Solution Overview
Problem
Current arthroplasty implants for joints in the foot and hand are inadequate and prone to positional shifts, lacking effective stabilization and retention mechanisms.
Innovation Solution
A three-component arthroplasty implant comprising a bone screw, a button, and a cap, with features like knurling, spherical pockets, and retention structures (undercuts or tangs) to stabilize and secure the implant in place, preventing rotation and ensuring concentric alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional single-component arthroplasty implants are used, then the implantation process is simple, but the implant is prone to positional shifts and lacks effective stabilization
Solution Approach 1:
The implant is divided into three separate components: a button with knurling for bone fixation, a cap with spherical head for articulation, and a bone screw for anchoring. This segmentation allows each component to perform its specific function optimally while together providing stable fixation that prevents positional shifts
Solution Approach 2:
The bone screw is inserted through the center hole of the button, and the cap is placed over the button, creating a nested arrangement where components fit within or upon each other. This nested structure ensures proper alignment and concentric positioning of all components during implantation
2Reliability
If traditional arthroplasty implants without retention structures are used, then the implantation process is straightforward, but the implant is susceptible to rotation after implantation
Solution Approach 1:
The cap includes an asymmetric tang extending from its lateral surface, and the button includes a corresponding asymmetric retention structure. This asymmetric geometry prevents rotation of the cap relative to the button and bone, as the tang can only engage in one specific orientation
Solution Approach 2:
The cap features a spherical head that articulates with the bone, and the button has a spherical pocket that receives the bone screw head. These curved surfaces provide stable articulation while the asymmetric tang prevents rotational movement around the spherical joint
3Reliability
If traditional arthroplasty implants without concentric alignment features are used, then the implantation process is simple, but the implant components may not remain concentric, leading to instability
Solution Approach 1:
The button is designed with a cylindrical shape and the cap with a matching cylindrical outer surface, creating a geometric fit that naturally maintains concentric alignment. The spherical head of the cap fits within the spherical pocket of the button, ensuring that all components remain centered on the same axis during movement and articulation
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 implant provides stable and secure articulation surfaces for joints, reducing the likelihood of positional shifts and enhancing the durability and functionality of joint replacements in the foot and hand.
Implementation Method 1
The button incorporates knurling on its distal end to fixate onto bone
Implementation Method 2
a spherical pocket to mate with the bone screw for stabilization
Implementation Method 3
a proximal retention structure to mate with the cap... In one form, the proximal retention feature is an undercut. In another form, the proximal retention feature is a tang
Data Source
AI summary
Arthroplasty implants replace an articulating surface of a bone joint such as bone joints of the foot, and is characterized by a three-component device comprising a bone screw, a button, and a cap. The button incorporates knurling on its distal end to fixate onto bone, a center hole, a spherical pocket to mate with the bone screw for stabilization, and a proximal retention structure to mate with the cap. The bone screw incorporates distal bone (cortical) threads or threading, a spherical head, and a drive structure used to insert the bone screw through the hole of the button and into the bone (e.g. a distal segment of the first metatarsal). The cap incorporates a distal mating structure that retains the cap onto the button, a proximal smooth spherical head that mates with the distal surface of the bone (e.g. a phalange bone), and a tang that prevents rotation after implantation.