Modular Elbow Implant Intraoperative Constraint Selection

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Solution Overview

Problem

Current elbow replacement devices lack the ability to intraoperatively adjust soft tissue tension and provide mechanical constraint for varus/valgus motion, and they do not allow for the selection of linked or unlinked constraints, cemented or cementless fixation, which limits their effectiveness and durability.

Innovation Solution

A modular elbow replacement system that allows surgeons to select between linked or unlinked constraints and cemented or cementless fixation, featuring a connection on the ulnar and humeral stems, enabling intraoperative adjustment of soft tissue tension and articular surface geometry that shifts contact points during varus/valgus motion to increase restoring moment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a fixed constraint design (linked or unlinked) is used in elbow replacement, then the device structure is simple, but it cannot accommodate varying patient anatomy and conditions requiring intraoperative adjustment

Engineering Contradiction:

Improveability to accommodate varying patient anatomy and conditionsVSAvoidmodular construction with multiple selectable components

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The elbow replacement system is divided into separate modular components including a humeral component, ulnar component, and selectable constraint mechanisms. This segmentation allows surgeons to choose and assemble appropriate components during surgery based on patient-specific needs, resolving the contradiction between adaptability and complexity by making the system configurable rather than fixed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system incorporates dynamic selectability where the constraint type (linked or unlinked) can be chosen and adjusted during the surgical procedure itself. This dynamic approach allows the device to adapt to intraoperative findings and patient anatomy, transforming a static design into a flexible, adjustable system that balances versatility with manageable complexity.

Inventive Principle:

Principle #15Dynamics

2Reliability

If polyethylene bushings are used in linked elbow replacements, then mechanical constraint is provided, but wear and deformation occur causing decreased function and osteolysis

Engineering Contradiction:

Improvedurability of mechanical constraintVSAvoidwear particles causing osteolysis and function degradation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention changes the material parameters and friction characteristics of the constraint interface by using alternative bearing surfaces or coatings on the humeral and ulnar components. This parameter change reduces wear particle generation while maintaining the necessary mechanical constraint, directly addressing the reliability issue without the harmful side effects of polyethylene degradation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system employs composite material constructions in the bearing surfaces, combining materials with complementary properties to achieve low wear, high strength, and biocompatibility. This composite approach provides durable mechanical constraint while minimizing the generation of osteolytic wear particles, resolving the contradiction between reliability and harmful byproducts.

Inventive Principle:

Principle #40Composite materials

3Stability of the object's composition

If cemented fixation is used in elbow replacements, then initial stability is achieved, but long-term durability and bone integration are reduced

Engineering Contradiction:

Improveinitial stability of implant fixationVSAvoidlong-term durability and bone integration

Core Design Contradiction:

Stability of the object's compositionVSDuration of action of stationary object

Solution Approach 1:

The fixation system applies different surface qualities to different regions of the implant components. Cemented fixation is applied locally at specific interfaces where immediate stability is critical, while porous or textured surfaces are provided in bone-contact regions to promote long-term osseointegration. This local differentiation resolves the contradiction between initial stability and long-term durability by optimizing each region for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The implant components are pre-prepared with surface treatments, porous coatings, or osteoinductive features before implantation. This preliminary action ensures that when the implant is placed, both immediate stability (through initial fixation) and long-term bone integration (through pre-engineered bone-ingrowth surfaces) are achieved simultaneously, eliminating the trade-off between cemented stability and biological fixation durability.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP3463199B1Elbow replacement apparatus

Publication Date: 2023.07.26 LIMACORPORATE SPA

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AI summary

Apparatus and methods for total elbow replacement are provided to allow a surgeon to intraoperatively select a linked or unlinked constraint by utilizing a connection located on the body of the ulnar (110) and/or humeral (101) stem. Additional modularity also allows the selection of a cemented or cementless stem as described herein. The modularity and adjustability provides a number of advantages.