Saw Template Coupling to Rasp Body for Hip Resection

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Solution Overview

Problem

Current medical instruments for implanting hip joint endoprostheses lack a stable reference point, leading to angle errors and offset issues during femur resection, which can result in suboptimal anchoring of the prosthesis shaft in the femur bone.

Innovation Solution

The design incorporates interacting latching elements between the saw template and the rasp body, allowing for a defined coupling and secure attachment, enabling precise resection of the femur bone based on the prosthetic shaft's end or osteointegrative coating, with a coupling device that can be easily cleaned and reused.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a saw template is used without a fixed reference point on the femur, then the resection can be performed, but significant angular errors and misalignment of the resection height occur

Engineering Contradiction:
Improveresection operationVSAvoidangular alignment and resection height
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The rasp body serves as an intermediary reference element that is first inserted into the femoral cavity to establish a fixed reference position. The saw template then couples to this rasp body via coupling elements, using the rasp body as a mediator to transfer the reference position from the bone to the saw template, thereby eliminating angular errors and resection height misalignment.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The rasp body is inserted into the femoral cavity before the sawing operation to pre-establish the reference position and orientation. This preliminary action creates a stable baseline that the subsequent saw template can reference, ensuring accurate angular alignment and resection height before the actual cutting begins.

Inventive Principle:
Principle #10Preliminary action

2Reliability

If the saw template is temporarily coupled with the rasp body using locking elements, then secure attachment is achieved, but the coupling device complexity increases

Engineering Contradiction:
Improvecoupling stabilityVSAvoidlocking mechanism
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The coupling mechanism is segmented into separate coupling elements: a first coupling element on the saw template and a second coupling element on the rasp body. These separate elements can be independently positioned and engaged, simplifying the overall design while maintaining secure attachment through modular locking points rather than a complex integrated system.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The locking elements are designed to automatically engage and lock the saw template to the rasp body when the coupling elements are brought into alignment. The system self-secures through the interaction of the locking elements without requiring additional complex fastening mechanisms or manual intervention beyond the initial coupling action.

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP3570759B1Medical apparatus comprising sawing template
Publication Date: 2023.08.23 AESCULAP AG

AI summary

The aim of the invention is to improve a medical apparatus for implanting a hip joint endoprosthesis, said apparatus comprising at least one sawing template containing at least one guiding slit for a saw blade, such that prostheses shafts can be optimally anchored in the femur bone. To this end, the sawing template comprises at least one first coupling element for temporarily coupling the sawing template to a second coupling element of a rasp body of a prosthesis rasp in a coupling position.