Knee Prosthesis Patella Path Reduced Constraint Region

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Solution Overview

Problem

Conventional knee prosthetics often result in unnatural kinematics and pain due to constrained movement of the patella, leading to dissatisfaction and discomfort in patients post-total knee arthroplasty.

Innovation Solution

A femoral component with a reduced constraint region on the patella path, allowing increased freedom of movement for the patella in medial-lateral translation and internal-external rotation, mimicking natural patella movement, and a prosthetic patella with a raised portion to facilitate smooth transition into the trochlear groove during flexion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a conventional trochlear groove is used to constrain patella movement, then stability of the femoropatellar joint is improved, but freedom of movement of the patella deteriorates

Engineering Contradiction:

Improvestability of femoropatellar jointVSAvoidfreedom of movement of patella

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patella path is segmented into two distinct regions: a reduced constraint region superiorly and a trochlear groove inferiorly. This segmentation allows the patella to experience different constraint levels during different phases of knee motion, resolving the contradiction between stability and freedom of movement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the patella path are given different geometric qualities. The reduced constraint region has a shallower profile allowing greater freedom, while the trochlear groove has a deeper profile providing stability. This local differentiation resolves the contradiction by applying appropriate constraint levels to appropriate locations.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If the patella path is fully constrained by a trochlear groove, then control over patella position is improved, but natural kinematics deteriorates

Engineering Contradiction:

Improvecontrol over patella positionVSAvoidnatural kinematics

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The constraint system transitions dynamically from reduced constraint in the superior region to full constraint in the inferior region as the patella moves through its path. This dynamic progression allows natural kinematics during early motion while providing control during later motion phases.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Instead of applying full constraint throughout the entire patella path, constraint is applied partially - only in the inferior trochlear groove region. This partial action preserves natural kinematics where full constraint is unnecessary while providing control where needed.

Inventive Principle:

Principle #16Partial or excessive action

3Stability of the object's composition

If constraint regions are extended superiorly on the femoral component, then stability during extension is improved, but freedom of movement during extension deteriorates

Engineering Contradiction:

Improvestability during extensionVSAvoidfreedom of movement during extension

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The superior portion of the patella path is segmented as a distinct reduced constraint region, separate from the inferior trochlear groove. This segmentation ensures that extension movement occurs in a low-constraint environment, preserving freedom of movement while maintaining adequate stability through the raised portion geometry.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The constraint geometry is made asymmetric along the superior-inferior axis, with reduced constraint superiorly and increased constraint inferiorly. This asymmetric design allows optimal freedom during extension (superior) while providing stability during flexion (inferior), resolving the contradiction for extension-phase movement.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS20230310164A1Knee prosthesis with increased patella freedom of movement

Publication Date: 2023.10.05 SMITH & NEPHEW INC

AI summary

Knee implants and components thereof are disclosed. A femoral component of a knee implant may include a reduced constraint region arranged on a portion of a patella path. The reduced constraint region may be configured to provide increased freedom-of-movement of a patella traveling over the reduced constraint region. The increased freedom-of-movement may be with respect to medial-lateral movement and/or internal-external rotation of the patella. The patella path may include a constraint region (e.g., a trochlear groove) positioned inferiorly of the reduced constraint region. A patella may travel within the reduced constraint region during extension (or partial flexion) and within the trochlear groove during flexion. A prosthetic patella having a raised portion is also disclosed. The raised portion may be configured to facilitate engagement of the prosthetic patella with the trochlear groove of the femoral component as the patella transitions from the reduced constraint region to the trochlear groove.