Tibial Baseplate Pockets and Keel for Stronger Cement Fixation

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Solution Overview

Problem

Existing tibial prostheses face challenges in achieving better bonding with bone cement, leading to micro-motion and reduced durability, while also requiring complex surgical procedures for switching between cemented and non-cemented apparatuses.

Innovation Solution

The tibial baseplate features a keel and fins with specific geometries and surface textures that enhance cement bonding, allowing for both cemented and non-cemented fixation options with shared sizes and geometries, reducing surgical complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the tibial baseplate uses a smooth surface, then the manufacturing is easier, but the bonding with bone cement is insufficient leading to micro-motion

Engineering Contradiction:

Improvebonding with bone cementVSAvoidsurface preparation

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The tibial baseplate incorporates distal-facing surfaces with specific surface roughness (Ra of about 5.0 microns) at the distal pocket and inner pockets, while other areas may have different surface characteristics. This localized surface quality enhancement improves bone cement bonding precisely where needed without complicating the entire manufacturing process.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The distal pocket and inner pockets are designed with channel structures that receive bone cement, creating a porous-like interface between the prosthesis and bone cement. The channel geometry and surface roughness work together to enhance mechanical interlocking and bonding strength.

Inventive Principle:

Principle #31Porous materials

2Strength

If the tibial baseplate uses complex distal features for cement bonding, then the bonding and rigidity improve, but the device complexity increases

Engineering Contradiction:

Improverigidity and torsional strengthVSAvoiddistal features geometry

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The distal features are segmented into distinct functional zones: a distal pocket with specific roughness, multiple inner pockets with channels, and a keel structure. Each segment serves a specific purpose in enhancing bonding or rigidity, allowing the complexity to be distributed and managed systematically.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The distal features serve multiple functions simultaneously: the distal-facing surfaces provide bonding area, the channels guide and contain bone cement, the keel provides structural rigidity, and the overall geometry enhances torsional strength. This multi-functionality reduces the need for additional separate components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If the surgeon uses separate stock sizes for cemented and non-cemented apparatuses, then the fixation options are optimized, but the surgical complexity and time increase

Engineering Contradiction:

Improvefixation durabilityVSAvoidsurgical time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The tibial baseplate is designed with universal stock sizes that can accommodate both cemented and non-cemented fixation methods. The same prosthesis size and geometry can be used regardless of the fixation choice, eliminating the need for separate inventory systems and reducing surgical decision complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The design allows dynamic selection of fixation method (cemented or non-cemented) intraoperatively without requiring different prosthesis sizes or geometries. The surgeon can adapt the fixation approach based on intraoperative findings while using the same sized prosthesis, providing flexibility without compromising durability.

Inventive Principle:

Principle #15Dynamics

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

Improved bonding and rigidity of the tibial baseplate, along with reduced micro-motion and simplified surgical options, enhance durability and efficiency in knee arthroplasty procedures.

Implementation Method 1

The tibial tray includes distal-facing surfaces that have a surface roughness (Ra) equal to about 5.0 microns

Methodology Applied

Scientific EffectSurface roughness: Abrasion

Implementation Method 2

Each inner pocket includes a channel sized to receive bone cement

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 3

facilitate better bonding with bone cement

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentEP4327784B1Tibial prosthesis with distal features for cemented fixation

Publication Date: 2025.12.31 ZIMMER INC

Figure 1A~1B
Figure 1C~1D
Figure 1E~1G

AI summary

A tibial prosthesis that includes a baseplate (100) and a tibial keel (108). The baseplate including: a distal surface (104) sized and shaped to substantially cover a proximal resected surface of a tibia; a proximal surface (102) opposite the distal surface, the proximal surface having a lateral compartment (116) and a medial compartment (114) opposite the lateral compartment; a periphery (106) extending between the distal surface and the proximal surface; a first pocket (124) formed in the baseplate and recessed from the distal surface, wherein the first pocket is configured to receive a bone cement therein; a second pocket (126) formed in the baseplate and recessed from the first pocket, wherein the second pocket is configured to receive a portion of the bone cement. The tibial keel extending distally from the distal surface to define a longitudinal tibial keel axis (S1).