NEW WAYS FOR DESIGNING OF THE EXTERNAL FIXATORS INTENDED FOR THE

TREATMENT OF OPEN AND UNSTABLE FRACTURES IN TRAUMATOLOGY

Karel FRYDRÝŠEK, Assoc. prof., M.Sc., Ph.D., ING-PAED IGIP

Department of Mechanics of Materials

Faculty of Mechanical Engineering

VŠB - Technical University of Ostrava,

Czech Republic

ERASMUS staying, University of Vigo, Spain

Source: internet

http://aplmech.vsb.cz/zevni-fixace/

HISTORY Hippocrates (almost 2400 years ago described a form of external fixation to splint a fracture

of the tibia). Jean-Francois Malgaigne (1840 - described a spike driven into the tibia and held by straps

to immobilise a fractured tibia, 1843 - used a claw-like device to percutaneously hold the fragments of a fractured patella).

Clayton Parkhill (1894), Albine Lambotte (1902) - modern concept of unilateral external fixation.

Raoul Hoffmann (1938) - external fixators are clinically relevant, first application of minimally invasive surgery.

Gavril Ilizarov (1950) - new method for treating fractures, circular fixators, deformities and other bone defects.

1950 - today - (application of steels, aluminium, titanium, unilateral, circular and hybrid fixators, animals).

Source: internet

INTRODUCTION

Fixators can be applied in traumatology, surgery and orthopaedics for treatments of humans and animals such as: open and unstable (complicated) fractures, limb lengthening, deformity correction, consequences of poliomyelitis, foot deformities, hip reconstructions, etc.

External fixation: Holes are drilled into bones around the fracture and bolts or wires are screwed into the holes. Outside the body, rods and curved pieces of metal with special joints connect the bolts to make a stiff support. The bone can be set in the proper anatomical configuration.

External fixation is usually used when internal fixation is contraindicated, or as a temporary solution. During its use, it is also possible to use the broken limbs and even walk.

NEW WAYS FOR DESIGNING EXTERNAL FIXATORSScientific and technical developments, together with medical care and medical practice, bring new demands for designs of external fixators. These demands should be solved by:

1. applications of new smart materials,2. new design,3. measuring of the real loadings,4. numerical modelling and experiments.

These points which are mutually connected are discussed in the following slides.

Source: internet

According to current studies and research, performed at VŠB – Technical University of Ostrava and Traumatology Centre of the University Hospital of Ostrava (Ostrava, Czech Republic), the current design of external fixators can be modified.

1. APPLICATIONS OF NEW SMART MATERIALSNew smart materials should satisfy the following requirements:

Can you see the fracture? Are the bones in correct position?

1.1 Low x-ray absorption (i.e. x-ray invisible) for the outer parts of fixators. The outer parts of fixators are usually made of metal, which are visible in x-ray diagnostic. Sometimes, the surgeons must repeat x-ray diagnostics (from different spatial points of view) during the operation, because it is difficult to see the broken limbs. Therefore, it is important to make the outer parts x-ray invisible, which leads to shortening the operating time and reducing radiation exposure for patients and surgeons.

1. APPLICATIONS OF NEW SMART MATERIALS1.2 Application of nanoadditives containing selected metal-based

nanoparticles on the surface of the outer parts of the fixators may allow for growth inhibition of several pathogens present on human skin and thus prevent or reduce possible infection. Nanotechnology allows a built-in antibacterial protection for solid products, coatings and fibres. Antibacterial protection gives products an added level of protection against damaging microbes such as, bacteria, mould and mildew that can cause cross-contamination and product deterioration. Antibacterial nanotechnology, combined with regular cleaning practices, helps to improve hygiene standards and provides extra protection wherever it is used.

1.3 Proper mechanical properties (stiffness of the whole system of fixators, fatigue testing, etc.) is based on laboratory testing of new smart materials.

Experiments in our laboratories

1. APPLICATIONS OF NEW SMART MATERIALS1.4 Weight optimalization - to avoid the overloading of limbs fixed by

external construction. This is based on the application of numerical methods and experiments.

It is possible to satisfy all these demands with a new material which uses proper plastics (polymers), because some current solutions based on light metals (aluminium, titanium etc.) are visible in x-ray diagnostic, heavy and expensive etc. The prospective polymer could be polyurethane.

1. APPLICATIONS OF NEW SMART MATERIALSHowever, the most useful applications are composites based on the mentioned polymer and reinforced by carbon nanotubes (CNT) – CNT bionano-composites. CNT are allotropes of carbon with a cylindrical nanostructure (fullerene structural family). These cylindrical carbon molecules have novel properties, making them potentially useful in nanotechnology, electronics, optics, mechanical and civil engineering, military, automotive industry etc.). Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometres (approximately 1/50000 th. of the width of a human hair), while they can be up to 18 centimetres in length (as of 2010). Moreover, nanotubes naturally align themselves into "ropes" held together by van der Waals forces.

Single-wall carbon nanotubes (SWCNT)

Multi-wall carbon nanotubes (MWCNT)

Scanning electron microscope image of CNT bundles

Advantage of this type of material is also in its x-ray invisibility.

1. APPLICATIONS OF NEW SMART MATERIALSThe chosen materials are polyurethanes filled by MWCNT and SWCNT. They have good mechanical (static and dynamic) properties.

Making bionano-composites in our laboratory

1. APPLICATIONS OF NEW SMART MATERIALS

polyurethanes filled by SWCNT

2. NEW DESIGN

A new design should be made according to shape, ecological perspective, a patient's comfort, reducing the time of the surgical operation and reducing the weight and overall cost.

NewOld

2.1 Previosly mentioned reinforced polymers are

easy recycled.

2.2 Aesthetics of fixators also have impacts on the psyche of the patients (i.e. "friendly-looking design of fixators"). For example, patients usually have better feelings, easier motion and physiotherapy with fixators made up from lighter plastics than heavier metals.

2. NEW DESIGN

Source: internet

2.3 Decreasing the weight (metals are heavier than plastics).

2.3 Easy to assembly (reducing the time of operation).

Source: internet

How long does it take to assembly?

A new proposed design cannot be more specifically described here for confidentiality reasons.

3. MEASURING OF THE REAL LOADINGSDuring the patient’s treatment measurements of the real loadings and stiffness of the external fixators (laboratory measurement and measurement in vivo - painlessly) and data processing are needed. The original type of measuring is very important for future possible enhancements.

This is based on strain gauge measurement and the Simulation-Based Reliability Assessment (SBRA) Method (i.e. probabilistic approach). Using the SBRA method, the probability of failure (i.e. the probability of an undesirable situation) is obtained mainly by analyzing the reliability function. Application of the SBRA method is a modern and innovative trend in mechanics.

This new solution promises new (so far not investigated) information about real loadings of external fixators during the treatments of patients.

4. NUMERICAL MODELLING AND EXPERIMENTSNumerical modelling and experiments as support for research and design, are a very important part of the solution (i.e. application of the Finite Elements Method and SBRA Method).

Thank you for your attention

http://aplmech.vsb.cz/zevni-fixace/

This work was supported by the Ministry of Industry and Trade of the Czech Republic as the part of project № MPO FR-TI3/818 named “External Fixation”.

We are searching for Ph.D. students in Ostrava.