New Types of External Fixators Intended for the Treatment of Open and Unstable Fractures Nové typy zevních fixátorů určených pro léčbu otevřených a nestabilních zlomenin Leopold PLEVA 1, Karel FRYDRÝŠEK 2, Pavel KOŠTIAL 3, Vladimír JEČMÍNEK4, Roman MADEJA5 Abstract: This paper deals with a new ways for designing of the external fixators applied in traumatological surgery. These fixators can be applied for the treatment of open and unstable fractures or for lengthening human or animal bones etc. New design is based on the development of todays techniques (i.e. shape and weight optimalization, application of smart materials, low x-ray absorption, antibacterial protection, patient's comfort, reducing the duration of the surgical treatment as well as the cost). Abstrakt: Článek se zabývá novýni způsoby konstrukce zevních fixátorů používaných v traumatologii. Tyto fixátory lze použít pro léčbu otevřených a nestabilních zlomenin nebo pro prodlužování kostí lidí nebo zvířat atp. Nová konstrukce je založena na rozvoji dnešních technik (tj. optimalizace tvaru a hmotnosti, aplikace “smart” materiálů, nízka rentgenová absorbce, antibakteriální ochrana, pacientovo pohodlí, zkracování chirurgických úkonů a výrobní ceny). Keywords: external fixator, traumatology, fractures of bones, surgery, design, construction, material, mechanical behaviour Klíčová slova: zevní fixátory, traumatologie, zlomeniny kostí, chirurgie, konstrukce, materiál, mechanické vlastnosti.
1. Introduction According to the current studies and research, performed at VŠB – Technical University of Ostrava and Traumatology Centre of the University Hospital of Ostrava, for example see references [1] to [5], the current design of external fixators (based on the Ilizarov techniques) can be modified.
1
Assoc. prof. MUDr. Leopold Pleva, Ph.D.; Traumatology Centre, University Hospital of Ostrava, 17. listopadu 1790, 708 52 Ostrava-Poruba,
[email protected]. 2 Assoc. prof. M.Sc. Karel Frydrýšek, Ph.D., ING-PAED IGIP; Department of Mechanics of Materials; Faculty of Mechanical Engineering, VŠB - Technical University of Ostrava, 17. listopadu 15, 708 33, Ostrava, Czech Republic,
[email protected]. 3 prof. RNDr. Pavel Koštial, Ph.D., Department of Material Engineering; Faculty of Metalurgy and Materials Engineering, VŠB - Technical University of Ostrava, 17. listopadu 15, 708 33, Ostrava, Czech Republic,
[email protected]. 4 MUDr. Vladimír Ječmínek, Ph.D.; Traumatology Centre, University Hospital of Ostrava, 17. listopadu 1790, 708 52 Ostrava-Poruba,
[email protected]. 5 MUDr. Roman MADEJA; Traumatology Centre, University Hospital of Ostrava, 17. listopadu 1790, 708 52 Ostrava-Poruba,
[email protected].
Ilizarov and other techniques can be applied in traumatology, surgery and orthopaedics. Such as: treatment of open and unstable (complicated) fractures, limb lengthening, deformity correction, consequences of poliomyelitis, foot deformities, hip reconstructions, etc. Hence, external fixators can be used for treatment of humans and animals. External fixation, see Fig. 1, is a surgical treatment usually used to set bone fractures in which a cast (plaster) would not allow proper alignment of the fracture. In this kind of reduction, holes are drilled into uninjured areas of bones around the fracture and special 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 complicated fracture can be set in the proper anatomical configuration. Since the bolts pierce the skin, proper cleaning to prevent infection at the site of surgery must be performed. External fixation is usually used when internal fixation is contraindicated, or as a temporary solution. During its use, it is also possible to use and exercise the broken limbs and even walk.
Fig.1 Examples of external fixators. 2. New Ways for Designs of External Fixators Scientific and technical developments, together with medical care and medical practice, bring new demands for designs of the external fixators. These demands are: 1. Applications of new smart materials which satisfy the following requirements: • low x-ray absorption (i.e. x-ray invisible) for outer parts of fixators, see Fig. 2. • antibacterial protection - application of nanotechnologies on the surface of the parts of the fixators prevent infection. • proper mechanical properties (stiffness of the whole system of fixators, fatigue testing, etc.). • weight optimalization - to avoid the overloading of limbs fixed by external construction. 2. New design according to shape, ecological perspective, patient's comfort, reducing the time of the surgical operation and reducing the overall cost. Technical aesthetics of fixators also have impacts to psyche of the patients (i.e. "friendly-looking design of fixators").
3. Measuring of the real loadings and stiffnesses of the external fixators during treatment of the patient (laboratory measurement and measurement in vivo) and its processing (strain gauge measurement, statistics, application of SBRA – Simulation-Based Reliability Assessment Method, see [6]. This is very important for future possible enhancements. 4. Numerical modelling as a support of the research, for example see Fig. 3.Text in English. Text in English. Text in English. Text in English. Text in English. Text in English.
Fig.2 Problems with high x-ray absorption (it is difficult to see broken limbs).
Fig.3 Example of numerical modelling. It is possible to satisfy all these demands by a new construction using proper plastics (polymers), because some current solutions based on light metals (aluminium) are visible in x-
ray diagnostic (see Fig. 2). The most useful are composites based on plastics reinforced by carbon nanotubes. The chosen properties of nanotubes and other materials are collected in Table 1. From Tab. 1, it is possible to clearly see the excellent mechanical properties of both single wall carbon nanotubes (SWCNT) as well as multi wall carbon nanotubes (MWCNT). Material: SWCNT MWCNT Steel Epoxy Wood
Young's modulus /GPa/: 1054 1200 208 3.5 16
Tensile strength /GPa/: 150 150 0.4 0.005 0.008
Density /g/cm3/: 1.4 2.6 7.8 1.25 0.6
Tab.1 The chosen material properties of nanotubes.
Tab.2 Material properties of pure polyurethane.
The authors of the European patent [7] described the realization of cables comprising polyethylene, polypropylene or mixture thereof, CNT, conductive carbon, copolymer of acrylonitrile and butadiene. The authors of the European patent [8] describe the preparation of CNT oriented composites in different metallic and non-metallic matrices. The patent [9] describes the reinforcing of synthetic, natural, styrene-butadiene rubber by CNT or graphitic nanofibers. Review of CNT-polymer composites is given in the work [10]. Very prospective materials for asked solutions are polyuretanes filled by MWCNT and SWCNT. They have quite good mechanical (static and dynamic) properties and low x-ray absorption (i.e. high invisibility). A material list is presented in Table 2. Conclusions New ways to design external fixators, based on the results of previous research, were presented. Hence, the new designs and materials of fixators will satisfy the ambitious demands of modern surgery. University Hospital of Ostrava together with VŠB - Technical University are now in the start of a process of new design of external fixators. Hence, they are in cooperation with ProSpon and Medin companies. References [1] Rozum, K.: Zevní fixátory pro léčbu otevřených nestabilních zlomenin (External Fixators for the Treatment Open Unstable Fractures), inaugural work written in Czech language, Faculty of Mechanical Engineering, VŠB – Technical University of Ostrava, Czech Republic, 2008, ISBN 978-80-248-1670-8, pp.43. [2] Pleva, L: Zevní fixátor k léčení zlomenin acetabula, (External Fixator for Treatment of Acetabulum Fractures, závěrečná zpráva projektu IGA MZ ČR, reg. č. 3522-4, written in Czech language, FNsP – Ostrava-Poruba, Czech Republic, 1999, pp.77. [3] Podešva, R.: Modelování zevních fixátorů pro léčbu otevřených nestabilních zlomenin s využitím výpočetní techniky (External Fixture Simulation for Treatment of Open Unstable Fractures with Computer Equipment Utilization), dissertation thesis written in Czech language, Faculty of Mechanical Engineering, VŠB – Technical University of Ostrava, Czech Republic, 2002, pp.89. [4] Stacha, R: Vývoj zevního fixátoru na loket včetně experimentálního ověření a počítačového modelování (Development of External Fixator for an Elbow Including Experimental Check and Computer Simulations), dissertation thesis written in Czech language, Faculty of Mechanical Engineering, VŠB – Technical University of Ostrava, Czech Republic, 2005, pp.98. [5] Kovařčík, F.: Vývoj zevního fixátoru na acetabulum, včetně počítačového modelování a experimentálního ověřování, dissertation thesis written in Czech language, Faculty of Mechanical Engineering, VŠB – Technical University of Ostrava, Czech Republic, 2005, pp.106. [6] Frydrýšek, K.: Aplikace pravděpodobnostní metody SBRA ve vědecko-technické praxi (Application of Probabilistic SBRA Method in the Scientific and Technical Practice), inaugural dissertation in the branch of Applied Mechanics, written in Czech language, Faculty of Mechanical Engineering, VŠB-Technical University of Ostrava, Ostrava, Czech Republic, 2009, pp.144. [7] Well-Kuo, L., Marios, A.: Patent EP 1052654 A1. [8] Kikutchi, M., Harada, I., Mizuno, K., Tanuma, I., Ogawa, M, Aizawa S., Aoike, Y., Shizuku, T.: Patent EP 1548057 A1.
[9] Kim, Y: Patent WO03/060002 A1. [10] Coleman, J., N. et all: Carbon 44, 2006, pp.1642.
