Minimally Invasive Surgery and Interventional Techniques
Department of Biomechanical Engineering - Delft University of Technology
Prof.dr. Jenny Dankelman
Design of a 3D Patient Specific Osteotomy
11 July 2017

Design of a 3D Patient Specific Osteotomy




The aim of Orthopedic Surgery is to prevent and correct dysfunctions of the skeleton, repair bone fractures and resect bone tumors. In case of tumor resection or reconstructive surgery, the surgeon makes an operative plan based on patient data. Nowadays these surgeries are often planned using computer programs to visualise the anatomy of the patient area to be intervened and to template the different types of reconstructive options, i.e tumor prosthesis. CT and MRI patient data is mostly used as input to visualise 3D models on the screen of a computer but other imaging modalities are also possible. Based on the 3D models the surgeon can design the surgery in detail, special emphasises on the margins of the tumour, the level of osteotomy and the implant to reconstruct. This is called the pre-operative plan. Next step is to translate the pre-operative plan to the real surgery. An important step in this translation is the match between the coordinate system of the computer 3D model and the physical coordinate system of the patient. This process is called registration. There are three main ways to translate the pre-operative plan to the patients anatomy:

Manually: by using anatomical landmarks and rulers to mark the resection lines on the patient

Computer Assisted Navigation Surgery, using basic surface matching or more advanced mobile CT equipment, other special instruments, computer and screens to guide the surgeon during the surgery

Patient Specific Osteotomy instruments.


This project relates to Patient Specific Osteotomy instruments that are designed using 3D visualisation techniques and manufactured using 3D printers. We call this technique 3D PSO. 3D PSOs are instruments that are placed on the bone of the patient to be intervened, fitting in a unique position. They contain specific mechanical constructions to guide the instruments used for osteotomy (i.e. oscillating saw, drill, osteotome, etc).


Your responsibilities

You will work in a multidisciplinary team with students of other faculties/disciplines to develop a 3D PSO. The total design is divided into several student assignments. Your part of the design needs to be aligned with the other parts of the project that results in a final well-integrated

total design. Your performance will be evaluated based on your own output and the alignment of your work with the total design in a 80/20 relationship. This way you can manage your assignment with a reasonable independence of the performance of the other members of the team and at the same time you are motivated for the team results.


Assignment 1: Test Patient Specific Osteotomy Instrument

We are designing a 3D PSO instrument and want to test the accuracy of the instrument as well as the usability of the instruments by the surgeons. The assignment consists of:

writing the test specifications for each test level (see further in the document)

perform the tests

Find solutions and updates of the design to achieve better results of the tests

write the report to obtain permission from the ethical committee to realise the clinical test on patients.

find out regulatory requirements for the certification of these instruments.

report the results

The tests will be performed at three levels/environments:

technical test: to evaluate the technical concept

cadaveric/animal lab test: this test will be performed by surgeons. The goal is to let the users to evaluate the functionality of the instruments in a lab environment

clinical test: evaluation of the instruments in real surgeries.


Your Profile

1. You are in the final stage of a major course in the field of

(Bio)Mechanical Design / BioMedical Engineering

2. Have basic knowledge or interest on medical devices

3. Knowledge/interest in regulatory requirements

4. Skills in Computer Added Design

5. Advanced knowledge of mechanical design

6. Can work independently as well as part of a team


Assignment 2: Design osteotomy tool specifically for 3D PSOs.

Your assignment is to design an osteotomy tool optimised for surgeries

using 3D PSOs. The design includes:

Mechanism minimise wobbling of the 3D PSO

Mechanisms to limit dimensions of the resection

Ability to perform curved resection profiles

Your Profile

Similar to the profile for assignment 1.

Assignment 3: Advanced Manufacturing Customisation of the Cutting Guide.

Given a 3D patient bone model with the pre-operative surgery plan (designed by the surgeon) design an algorithm and write the code to automatically design a 3D PSO.

Your Profile

You are in the final stage of a major course in the field of Industrial

Design / Advanced Manufacturing / Computational Design

Have basic knowledge on medical devices

Skills in Computer Added Design

Advanced knowledge of Advanced Manufacturing algorithms

Programming skills: C++

Can work independently as well as part of a team

Assignment 4: Design a natural user interface that offers the surgeon an intuitive way for analysing the 3D patent model and design the surgery plan.

Your Profile

You are in the final stage of a major course in the field of Computer Graphics and Visualisation

Have basic knowledge on medical devices

Knowledge of Computer Added Design

Programming skills: C++, Augmented Reality, Graphic design and


Can work independently as well as part of a team




Dr. P.D.S. Dijkstra, Orthopaedic Surgery

Dr. ir. B.L. Kaptein, Bio-Mechanical Engineering


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