Cutting Block Tracking for Precise Bone Resection Alignment

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Solution Overview

Problem

Current orthopedic surgery methods for joint replacement, such as total knee replacement, are cumbersome and costly due to the complex process of aligning cutting blocks, which require high machining tolerances and involve invasive tracker attachment to bones, increasing setup time and infection risk.

Innovation Solution

A navigation system that attaches tracking devices directly to pre-mounted cut guides instead of the patient's bones, using a frame with multiple markers and mounting points to facilitate precise bone cuts and reduce invasive pinning.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If tracking devices are attached directly to patient's bones using invasive pinning methods, then real-time tracking precision is improved, but infection risk and surgical invasiveness increase

Engineering Contradiction:
Improvetracking precisionVSAvoidinfection risk
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces cutting blocks as intermediary objects that attach to bones through less invasive means (clamps, adhesives, or external fixators) rather than direct bone pinning. These cutting blocks serve as mediators that hold the tracking devices, eliminating the need for invasive skeletal pinning while maintaining tracking capability. The intermediary cutting blocks reduce infection risk by avoiding penetration of the bone cortex while still providing stable mounting surfaces for trackers.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Manufacturing precision

If complex mechanical alignment mechanisms with high machining tolerances are used for cutting blocks, then alignment precision is improved, but device complexity and cost increase

Engineering Contradiction:
Improvealignment precisionVSAvoidmechanical mechanism complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical alignment mechanisms with computer-based navigation and imaging systems. Instead of relying on intricate mechanical reference systems and high-precision machined surfaces, the solution uses optical trackers, cameras, and software to achieve precise alignment and positioning. This substitution of mechanical systems with computational methods reduces device complexity while maintaining or improving alignment accuracy.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If manual alignment of cutting blocks is performed, then ease of operation is improved, but alignment precision and setup time are worsened

Engineering Contradiction:
Improvemanual alignment easeVSAvoidalignment precision
Core Design Contradiction:
Ease of operationVSManufacturing precision

Solution Approach 1:

The cutting blocks serve as intermediaries that combine ease of manual attachment with precision tracking capabilities. They can be easily attached using simple clamps or adhesives, yet they incorporate mounting surfaces for tracking devices that enable precise alignment through computer navigation. This intermediary approach allows surgeons to manually position blocks easily while the tracking system provides real-time feedback for precise alignment.

Inventive Principle:
Principle #24Intermediary (Mediator)

4Stability of the object's composition

If invasive bone pinning is used for tracker attachment, then tracking stability is improved, but surgical invasiveness and setup time increase

Engineering Contradiction:
Improvetracking stabilityVSAvoidsetup time
Core Design Contradiction:
Stability of the object's compositionVSLoss of time

Solution Approach 1:

The cutting blocks are attached to bones in advance of tracker attachment, serving as pre-prepared mounting surfaces. This preliminary action allows trackers to be quickly mounted on the already-secured cutting blocks without requiring time-consuming invasive pinning procedures during the critical tracking setup phase. The cutting blocks are positioned and secured beforehand, eliminating the need for intraoperative bone penetration.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP3793454B1System for tracking resection planes
Publication Date: 2026.04.01 SMITH & NEPHEW INC
  • EP3793454B1 patent drawingFigure 1
  • EP3793454B1 patent drawingFigure 2
  • EP3793454B1 patent drawingFigure 3

AI summary

A system for tracking resection planes during a surgical procedure includes a cutting block and a position tracker. The cutting block is configured to be mounted on an anterior surface of a bone during the surgical procedure. The cutting block comprises at least one slot configured to position a resection tool during the surgical procedure. The position tracker is configured to be directly attached to the cutting block after the cutting block is mounted on the anterior surface to allow positional tracking of the cutting block by a tracking device during the surgical procedure.