Interchangeable Patellar Prostheses with Standardized Securement

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Solution Overview

Problem

Existing knee arthroplasty systems require modification of the natural patella's securement features when switching between differently sized patellar prostheses, which can be time-consuming and prone to malpositioning due to the need for re-drilling holes and altering attachment surfaces.

Innovation Solution

The development of patellar prostheses with dissimilar perimeter shapes, such as circular and elongate designs, that share identical securement features and fixation post arrangements, allowing for interchangeable use without modifying the natural patella's attachment surface, along with a trial prosthesis that can rotate to optimize positioning during range of motion testing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If differently sized patellar prostheses utilize different securement mechanisms, then each prosthesis can be optimized for its specific size and shape, but intraoperative switching between sizes requires altering the securement features formed in the natural patella which increases surgical time and risk of malpositioning

Engineering Contradiction:

Improveinterchangeability of patellar prosthesesVSAvoidsurgical time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent applies universality by designing all patellar prostheses (regardless of size or shape variations) to use the same securement feature configuration. The fixation posts are positioned at standardized locations that work across circular, oval, and anatomically-contoured prostheses, eliminating the need to create new securement features when switching between different prosthesis sizes during surgery.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If differently sized patellar prostheses utilize different securement mechanisms, then each prosthesis can be optimized for its specific size and shape, but altering the attachment surface of the natural patella increases the risk of malpositioning

Engineering Contradiction:

Improveinterchangeability of patellar prosthesesVSAvoidpositioning accuracy

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by establishing the securement features (fixation post positions and depths) once during the surgical procedure. These pre-established features then serve as reliable reference points for implanting any size or type of patellar prosthesis, eliminating the need for repeated drilling and re-positioning that could lead to malpositioning.

Inventive Principle:

Principle #10Preliminary action

3Loss of time

If all patellar prostheses use identical securement features, then intraoperative switching between sizes becomes efficient and safe, but the securement mechanism must work effectively across dissimilar perimeter shapes

Engineering Contradiction:

Improvesurgical timeVSAvoidcompatibility across prosthesis designs

Core Design Contradiction:

Loss of timeVSAdaptability or versatility

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Reliability

Engineering Contradiction:

Improvepositioning accuracyVSAvoidcompatibility across prosthesis designs

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies asymmetry by positioning the fixation posts in non-symmetric locations that account for the varying shapes of different patellar prostheses. The posts are placed at specific offsets from the center (e.g., 2mm, 4mm, 6mm) to accommodate circular, oval, and anatomically-contoured designs while maintaining a consistent securement pattern that ensures reliable positioning across all prosthesis types.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentEP2648655B1Prosthetic patella

Publication Date: 2017.06.28 ZIMMER INC

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AI summary

A system of prosthetic patellar components including first and second prosthetic patellar components having dissimilar perimeter shapes and which are interchangeably useable without altering the securement feature formed on the natural patella or the position of the apex of the articulating surface of the prosthetic patella is described. A keyed securement feature as well as a patellar implant having a single offset mounting post for facilitating the proper placement of a patellar prosthesis on a natural patella based on patella tracking are also described.