Coupled-Uncoupled Sleeve for Prosthetic Knee Stem

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Solution Overview

Problem

Over-broaching of the metaphysis in long bones during prosthetic implantation can result in a deeper broached channel than desired, leading to gaps between the sleeve and the broached channel, which inhibits bone ingrowth and requires additional components or bone resection, causing loss of healthy bone.

Innovation Solution

A sleeve configured to be used as either coupled or uncoupled from the tibial or femoral stem housing, allowing intraoperative evaluation to determine the appropriate configuration, with the uncoupled sleeve acting as a cone to fill gaps with bone cement and engage the metaphyseal bone, thereby promoting bone ingrowth and stabilization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the broach or reamer is operated too far along the axis of the bone, then the broached channel becomes deeper, but this creates a gap between the sleeve and the broached channel that eliminates axial support and inhibits bone ingrowth

Engineering Contradiction:

Improvedepth of broached channelVSAvoidaxial support and bone ingrowth

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The sleeve is divided into two functional segments: a proximal coupled portion that attaches to the stem housing and provides axial support, and a distal uncoupled portion that extends into the broached channel to engage the bone. This segmentation allows the sleeve to maintain reliable axial support while accommodating variable broaching depths without creating harmful gaps.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sleeve transitions from a static, fixed-position component to a dynamic, adaptable structure that can function in different configurations. The coupled-uncoupled design allows the distal portion to move independently and adapt to the actual depth and position of the broached channel, ensuring reliable bone engagement regardless of broaching variations.

Inventive Principle:

Principle #15Dynamics

2Reliability

If further resection is performed to eliminate the gap and position the broached channel at the desirable depth, then the sleeve can contact the cancellous bone, but this results in loss of healthy bone and may require additional components

Engineering Contradiction:

Improvesleeve contact with cancellous boneVSAvoidloss of healthy bone

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The sleeve is pre-configured with a coupled-uncoupled structure that anticipates potential broaching depth issues. By having the distal uncoupled portion ready to extend independently into the broached channel, the design ensures reliable bone contact is achieved without requiring additional bone resection or supplemental components like spacers.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The sleeve's effective positioning parameters are changed by allowing the distal portion to operate independently from the proximal attachment point. This parameter change enables the sleeve to adapt to variable broaching depths and ensure reliable bone engagement without altering the bone itself through additional resection.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If the sleeve is attached to the stem housing, then it can be positioned close to the tibial tray, but this may not allow proper engagement with the metaphyseal bone if the broached channel is too deep

Engineering Contradiction:

Improvepositioning of sleeve near tibial trayVSAvoidengagement with metaphyseal bone

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The sleeve is segmented into a proximal coupled portion for easy attachment to the stem housing and positioning near the tibial tray, and a distal uncoupled portion that can extend independently to engage the metaphyseal bone. This segmentation resolves the contradiction by allowing both easy positioning and reliable bone engagement to occur simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The uncoupled distal portion of the sleeve acts as an intermediary element between the coupled proximal portion and the metaphyseal bone. It bridges the gap created by deep broaching, maintaining the simple coupled attachment while ensuring reliable bone engagement through its independent extension into the channel.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10987225B2Systems and methods for attaching sleeve or cone in prosthetic implant having a stem

Publication Date: 2021.04.27 ZIMMER INC

AI summary

A prosthetic implant system for reconstructing a knee joint comprises a prosthetic implant and sleeve. The prosthetic implant comprises a tibial tray component for reconstructing a tibia of the knee joint, and a stem configured to extend from the tibial tray component to anchor the tibial tray component in the tibia of the knee joint. The sleeve comprises an outer wall configured to engage with bone, and an inner bore configured to receive the stem. The inner bore is shaped to couple to the prosthetic implant at a first location proximate the tibial tray component while surrounding the stem, and uncouple from the prosthetic implant at a second location spaced from the first location while still surrounding the stem. Methods employing the prosthetic implant system can comprise intraoperatively determining to use the sleeve in a coupled or un-coupled configuration based on a depth of a broach into a broached channel.