Pivotable Joint Balancing Instrument for Precise Bone Cut Alignment

Solution Overview

Problem

Surgeons face difficulties in achieving a balanced joint alignment during total joint replacement surgeries, particularly in total knee replacements, due to the interdependence of varus/valgus, slope, and cut depth parameters, often requiring multiple bone cuts which can lead to excessive bone removal or sub-optimal outcomes.

Innovation Solution

A surgical instrument with pivotable artificial articular surfaces that mimic the native joint surfaces, allowing for adjustable distraction and flexion angle, combined with a cutting block that is adjustable in slope and depth, to facilitate precise bone cuts aligned with the implant's standard plane.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple bone cuts are performed to achieve balanced joint alignment, then joint balance can be improved, but excessive bone removal occurs and procedure duration increases

Engineering Contradiction:

Improvejoint balanceVSAvoidbone removal

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The surgical instrument performs preliminary actions by establishing the correct slope and alignment of the first bone cut before subsequent cuts are made. The instrument is positioned on the prepared end of the first bone with its articular surface imitating the native surface, and the slope of the first bone cut is set according to the flexion angle of the joint, ensuring that subsequent cuts can be made with minimal adjustments and minimal bone removal.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The instrument allows for parameter changes in the slope and depth of bone cuts by adjusting the flexion angle of the joint. The slope of the cut is defined by a cutting block that is adjustable in slope and cutting depth, enabling the surgeon to optimize the cut parameters to achieve joint balance while minimizing bone removal.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If multiple bone cuts are performed to achieve balanced joint alignment, then joint balance can be improved, but procedure duration increases

Engineering Contradiction:

Improvejoint balanceVSAvoidprocedure duration

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The surgical instrument performs preliminary actions by establishing the correct slope and alignment of the first bone cut before subsequent cuts are made. The instrument is positioned on the prepared end of the first bone with its articular surface imitating the native surface, and the slope of the first bone cut is set according to the flexion angle of the joint, ensuring that subsequent cuts can be made with minimal adjustments and minimal bone removal.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The instrument allows for parameter changes in the slope and depth of bone cuts by adjusting the flexion angle of the joint. The slope of the cut is defined by a cutting block that is adjustable in slope and cutting depth, enabling the surgeon to optimize the cut parameters to achieve joint balance while minimizing bone removal.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If traditional surgical methods are used without adjustable articular surfaces, then device complexity is reduced, but manufacturing precision of bone cuts deteriorates

Engineering Contradiction:

Improvebone cut alignmentVSAvoidinstrument structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The surgical instrument uses an artificial articular surface that copies or imitates the native articular surface of the first bone. This allows the instrument to accurately reproduce the geometry and orientation of the native joint surface, enabling precise bone cut alignment without requiring overly complex measurement and calculation systems.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The artificial articular surface is pivotable in relation to the surgical instrument, allowing dynamic adjustment of the instrument's orientation. This pivoting capability enables the surgeon to adjust the instrument to match the specific anatomy of the patient's joint while maintaining manufacturing precision in the bone cuts.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS12582412B2Surgical instrument for alignment of bone cuts in total joint replacements

Publication Date: 2026.03.24 KICO KNEE INNOVATION CO PTY LTD

AI summary

This disclosure relates to surgical instruments for alignment of bone cuts during surgeries on joints and in particular, during total replacement of joints. The surgical instrument comprises a contact surface shaped to fit a prepared end of the first bone of the joint and an artificial articular surface that imitates the native articular surface of the first bone that has been removed by the preparation of the first bone. The artificial articular surface is pivotable in relation to the surgical instrument. The instrument can be fitted onto the prepared bone and coronal balancing can be performed. After fixing a further instrument to the second bone the joint can be balanced in flexion. At the optimal flexion angle, the slope and the cutting depth can be adjusted to achieve alignment. The further instrument is then used as a guide for cutting the second bone at the resulting cutting depth, slope and varus/valgus angle.