Patient-Specific Ankle Cutting Guide With Bushing-Based Registration

Solution Overview

Problem

Existing patient specific instruments (PSI) face challenges in accurately positioning due to variations in bony landmarks under soft tissue, which are difficult to expose and require invasive dissection, leading to complexity and inconsistency in registration points.

Innovation Solution

The use of reference bushings to provide accurate registration points by advancing them into bones adjacent to the joint, allowing for the design and manufacture of patient specific cutting guides without disrupting soft tissue, and connecting these guides to the bushings for precise bone cuts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If bony landmarks are exposed by dissecting soft tissue to ensure consistent location, then registration accuracy is improved, but surgical time increases and tissue disruption occurs

Engineering Contradiction:

Improveregistration accuracyVSAvoidsurgical time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Reference bushings are advanced into the bone through the soft tissue before surgery to establish precise registration points. The 3D spatial location information is gathered in advance, allowing the patient-specific cutting guide to be manufactured beforehand with pre-defined attachment features that mate with the reference bushings, eliminating the need for time-consuming soft tissue dissection during surgery to expose bony landmarks.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Reference bushings serve as intermediary elements that are advanced through soft tissue to reach the bone. These bushings act as mediators between the soft tissue and the bone, providing accessible registration points that can be engaged by the patient-specific cutting guide without requiring direct exposure or dissection of the bony landmarks themselves.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If bony landmarks are exposed by dissecting soft tissue to ensure consistent location, then registration accuracy is improved, but invasiveness increases

Engineering Contradiction:

Improveregistration accuracyVSAvoidtissue disruption

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

Reference bushings are advanced into the bone through the soft tissue before surgery to establish precise registration points. The 3D spatial location information is gathered in advance, allowing the patient-specific cutting guide to be manufactured beforehand with pre-defined attachment features that mate with the reference bushings, eliminating the need for time-consuming soft tissue dissection during surgery to expose bony landmarks.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Reference bushings serve as intermediary elements that are advanced through soft tissue to reach the bone. These bushings act as mediators between the soft tissue and the bone, providing accessible registration points that can be engaged by the patient-specific cutting guide without requiring direct exposure or dissection of the bony landmarks themselves.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If patient specific guides are placed against soft tissue to avoid dissection, then invasiveness is reduced, but positioning accuracy deteriorates due to soft tissue compression

Engineering Contradiction:

Improvetissue disruptionVSAvoidpositioning accuracy

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

Reference bushings serve as intermediary elements that are advanced through soft tissue to reach the bone. These bushings act as mediators between the soft tissue and the bone, providing accessible registration points that can be engaged by the patient-specific cutting guide without requiring direct exposure or dissection of the bony landmarks themselves.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical system of directly placing the cutting guide against soft tissue with a system that uses reference bushings anchored in the bone. The cutting guide attaches to the bushings through defined mechanical interfaces (screws, pins, or snap-fit connections), eliminating the reliance on soft tissue as a mechanical support, which is prone to compression and displacement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12616488B2Patient specific instruments and methods for joint prosthesis

Publication Date: 2026.05.05 HOWMEDICA OSTEONICS CORP

AI summary

A system for preparing an ankle bone to receive an ankle prosthesis is provided. The system includes a patient specific cutting guide that has an anterior surface, a posterior surface, and at least one cutting feature extending through the guide from the anterior surface. The posterior surface comprising a first protrusion or other member that extends from a first end fixed to the posterior surface to a second end disposed away from the first end of the first protrusion. The posterior surface has a second protrusion or other member that extends from a first end fixed to the posterior surface to a second end disposed away from the first end of the second protrusion. The first and second protrusions are spaced apart and have a length such that when the patient specific cutting guide is coupled with first and second bone references, which can include bushings implantable in bones, a clearance gap is provided between the posterior surface and the ankle bone.