Surgical Saw Blade Lock Teeth to Eliminate Backlash

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Solution Overview

Problem

Surgical sagittal saws and blades often experience blade slap and backlash, leading to inefficiencies in cutting bone, potential fracturing of the saw head, and deformation of the blade, which can reduce precision and increase the risk of complications during surgery.

Innovation Solution

The surgical saw and blade system incorporates lock teeth on the blade that are softer than the rest of the blade, which deform and coin when compressed between the saw head's anvil and press, eliminating clearance between the blade and saw head, ensuring they move as a single unit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the blade is dimensioned to fit closely in the slot for easy insertion and removal, then ease of operation is improved, but blade slap and backlash occur causing reduced reliability

Engineering Contradiction:
Improveease of blade insertion and removalVSAvoidblade attachment stability
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The invention changes the physical state of the lock teeth by deforming them from their original shape to a coined shape that engages with the saw head. This parameter change transforms the blade attachment from a loose fit to a locked engagement, eliminating blade slap and backlash while maintaining ease of operation through the simple deformation action.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The lock teeth transition from a static, rigid structure to a dynamic, deformable structure during attachment. The teeth are coined or deformed to engage with the saw head, creating a secure connection. This dynamic adaptation allows the blade to be firmly attached during use while still enabling easy removal through reverse deformation.

Inventive Principle:
Principle #15Dynamics

2Ease of operation

If the blade moves independently of the saw head due to clearance, then ease of blade insertion is improved, but cutting precision deteriorates due to backlash

Engineering Contradiction:
Improveblade insertion easeVSAvoidcutting precision
Core Design Contradiction:
Ease of operationVSManufacturing precision

Solution Approach 1:

The deformation of lock teeth changes the positional parameter of the blade relative to the saw head. By coining the teeth into the engaged position, the blade is locked in a precise position that eliminates clearance and backlash, ensuring cutting precision while maintaining ease of insertion through the simple deformation process.

Inventive Principle:
Principle #35Parameter changes

3Reliability

If the blade is firmly attached to eliminate blade slap, then reliability is improved, but blade deformation and saw head fracturing risk increase

Engineering Contradiction:
Improveblade attachment stabilityVSAvoidblade and saw head structural integrity
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The invention applies local quality by making only the lock teeth deformable while keeping the rest of the blade structure rigid. The lock teeth are specifically designed to be softer and more ductile, allowing them to deform and engage with the saw head without causing stress concentrations that would lead to blade deformation or saw head fracturing.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The material property parameter of the lock teeth is changed to be softer and more ductile than the rest of the blade. This parameter change allows the teeth to deform in a controlled manner during attachment, absorbing stresses that would otherwise propagate through the entire blade structure and cause failure.

Inventive Principle:
Principle #35Parameter changes

4Reliability

If lock teeth are softer to allow deformation for secure attachment, then reliability is improved, but blade strength deteriorates

Engineering Contradiction:
Improveblade attachment stabilityVSAvoidoverall blade strength
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The invention applies local quality by making only the lock teeth deformable while keeping the rest of the blade structure rigid. The lock teeth are specifically designed to be softer and more ductile, allowing them to deform and engage with the saw head without causing stress concentrations that would lead to blade deformation or saw head fracturing.

Inventive Principle:
Principle #3Local quality

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

This solution eliminates blade slap and backlash, enhancing the precision and efficiency of bone cuts, reducing the risk of saw head fracturing and blade deformation, and ensuring consistent attachment of the blade to the saw head.

Implementation Method 1

lock teeth formed out of material that deforms when the blade is secured to the saw

Methodology Applied
Scientific EffectDeformation: Deformation

Implementation Method 2

lock teeth on the blade that are softer than the rest of the blade, which deform and coin when compressed between the saw head's anvil and press

Methodology Applied
Scientific EffectPlasticity: Plasticity

Data Source

PatentEP3572013B1Surgical saw and complementary saw blade, the blade including lock teeth formed out of material that deforms when the blade is secured to the saw
Publication Date: 2025.03.19 STRYKER CORP
  • EP3572013B1 patent drawingFigure 1
  • EP3572013B1 patent drawingFigure 2~4
  • EP3572013B1 patent drawingFigure 3

AI summary

A surgical saw (40) includes a body (42), a coupling assembly (66,102,122,134) moveably mounted to the body adapted to releasably hold a saw blade (140, 140a, 140b, 140c, 202, 202a, 240, 246), to the coupling assembly, and a motor (62) internal to the body that is connected to the coupling assembly so as to cause the reciprocating movement of the coupling assembly and the like reciprocating movement of the saw blade held by the coupling assembly. The coupling assembly includes an anvil (70) and a press (102). Said press is capable of movement towards and away from the anvil. Said anvil or said press is formed with at least one channel (80) and the other of said press or anvil includes at least one press foot (114) capable of being received in the channel. The coupling assembly further includes an assembly for selectively bringing the press towards and away from the anvil so that, when the press is brought towards the anvil, the press foot presses a lock tooth (150, 150a, 180, 210, 214, 218) associated with the blade into the channel so that the at least one of the press or anvil coins the lock tooth.