Enabling natural forearm rotation by a novel attachment device for transradial bone-anchored prostheses

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UNIVERSITÀ DEGLI STUDI DI PISA

Facoltà di Ingegneria

Dipartimento di ingegneria dell’Informazione

Tesi di Laurea Magistrale in

INGEGNERIA BIOMEDICA

Enabling natural forearm rotation by a novel attachment

device for transradial bone-anchored prostheses

Relatore

Dott. Ing. Marco Controzzi Prof. Max Ortiz Catalan

Candidato Irene Boni

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Table of Content

ACKNOWLEDGMENTS 2 ABSTRACT 5 1. INTRODUCTION 6 1.1 OSSEOINTEGRATION 6

1.2 THE PUCK SYSTEM 8

1.3 SCOPE OF THIS THESIS 9

1.4 PRONATION AND SUPINATION 9

1.4.1 THE FOREARM: ANATOMY 9

1.4.2 FOREARM MOTION ANALYSIS 10

1.4.3 RESIDUAL MOTION AND LOAD DISTRIBUTION ON AMPUTEE 14

1.5 ROTADOR1 15

1.5.1 ROTADOR1 -‐ DESIGN 15

1.5.2 ROTADOR1 -‐ ASSESSMENT AND VALIDATION 17

1.5.3 CONSIDERATIONS 18

2. PSYCHOPHYSICS TESTS 22

2.1 LOADING TEST 23

2.1.1 METHODS 23

2.1.2 RESULTS 25

2.2 PRONATION/SUPINATION TEST 27

2.2.1 METHODS 27

2.2.2 RESULTS 28

3. ROTADOR2 – MECHANICAL DESIGN PROCESS 30

3.1 PRODUCT DEFINITION 30

3.2 CONCEPT GENERATION 31

3.3 CONCEPT EVALUATION 35

3.4 CONCEPT OPTIMIZATION 38

3.4.1 PIN DEFLECTION 38

3.4.2 AXIAL STRESS TO THE PIN 42

3.4.3 BENDING STRESS TO THE PIN 43

3.5 PROTOTYPE 44

4. ROTADOR2 – ASSESSMENT AND VALIDATION 46

4.1 RANGE OF MOTION 46

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5. CONCLUSION AND FUTURE WORK 52

REFERENCES 54

ANNEX I – DRAWINGS 57

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5 Osseointegration is an anchorage mechanism between prosthetic components and bones. It has become an important phenomenon in the treatment of limb amputees. Osseointegrated transradial prostheses have the potential to preserve the natural range of wrist rotation by allowing controlled freedom of motion between implants in the forearm bones. This improved prosthetic function would prevent compensatory movements that deteriorate posture and potentially lead to secondary health problems over time. So far, no reliable mechanical solutions have been developed that preserve forearm rotation.

In this thesis, psychophysics tests have been performed by a transradial amputee, with limited freedom of movement to the osseointegrated implants.

Based on the results obtained from psychophysics tests, a new version of attachment device (called Rotador2) was developed.

Next, the reliability of this device was evaluated. Results showed that Rotador2 preserved the full range of motion, enabled loading of the implants without an unpleasant experience of the patient, enabled equally load distribution over implants.

Future work to be done is related to test the device with more patients and validate Rotador2 to daily use over time. The attachment device will be used by patients taking part in the DeTOP project, supported by the European Commission GA#687905.