Podłużne harmoniczne fale sprężysto-elektryczne w porowatych kościach długich wypełnionych płynem fizjologicznym

Transmission of elasto-electric longitudinal harmonic waves in porous long bones filled with physiological fluid is investigated. The complete set of equations of the problem is obtained on the basic of the Biot theory of elastic waves in fluid-saturated porous media and the linear equations of electrokinetics, by means of quantities analogous to those in the theory of electrical transmission lines. Experimental findings from the biomechanical literature, supporting applicability of the proposed description, are presented. The electric signal associated with the propagation of longitudinal elastic waves in a wet long bone shaft can potientially be used for monitoring these waves during their application in e.g. bone porosity measurements.Przedmiotem pracy jest zagadnienie transmisji sprężysto-elektrycznych podłużnych fal harmonicznych w porowatych kościach długich wypełnionych płynem fizjologicznym. Zbiorczy układ równań zagadnienia wyprowadzono na podstawie Biotowskiej teorii propagacji fal sprężystych w ośrodkach porowatych nasyconych cieczą oraz liniowych liniowych równań elektrokinetyki, stosując opis za pomocą wielkości analogicznych do stosowanych w teorii elektrycznych linii przesyłowych. Uzasadniono przydatność zaproponowanego modelu teoretycznego przywołując z literatury wyniki badań eksperymentalnych dotyczące bioelektromechaniki kości. Sygnał elektryczny towarzyszący propagacji podłużnych fal sprężystych w trzonie kości długiej nasyconej płynem fizjologicznym mógłby, przypuszczalnie, zostać użyty celem monitorowania tych fal w zastosowaniu ich np. do pomiaru porowatości kości

Preliminary study of structural-electrical properties in the low frequency range of experimental biomaterial models of long bones in a pathological state

Przedstawiono wyniki doświadczalnych badań porównawczych dotyczących metod wytworzenia biomateriałowego modelu kości długich w stanie patologicznym, tj. nie w pełni zmineralizowanych (stan osteomalacji) oraz o obniżonym kościotworzeniu (stan osteoporotyczny), otrzymanego na bazie wołowych kości udowych, z wykorzystaniem stosowanych w inżynierii biomateriałów metod częściowego odbiałczania i częściowego odwapniania. Ten biomateriałowi model kości długich jest niezbędny do prowadzenia doświadczalnych badań właściwości strukturalno--elektrycznych kości długich w celu zbudowania prototypowego systemu pomiarowo-obliczeniowego do wyznaczania gęstości i parametrów porosprężystych kości długich prawidłowych i osteoporotycznych oryginalną nieinwazyjną metodą elektroosteodensytometrii (zgłoszenie patentowe krajowe i międzynarodowe). Proces odbiałczania prowadzono porównawczo z użyciem roztworów NaOCl, H2O2, KOH i NaOH, natomiast proces odwapniania próbek kości wołowych prowadzono porównawczo z użyciem roztworów HNO3, HCl i EDTA oraz w mieszaninie roztworów HNO3 i HCHO. Zbadano kinetykę przeprowadzonych procesów, monitorując stężenia białka oraz wapnia w zastosowanych roztworach w funkcji czasu. Na podstawie zbadanych przebiegów procesów możemy obecnie zarekomendować do wytworzenia biomateriałowych modeli doświadczalnych kości długich w stanie patologicznym: o obniżonym kościotworzeniu – odbiałczanie z użyciem 7% roztworu nadtlenku wodoru (H2O2), a dla nie w pełni zmineralizowanych – odwapnianie z użyciem 0,5 M roztworu kwasu solnego (HCl). Przedstawiono pilotażowe wyniki doświadczalnej analizy właściwości strukturalno-elektrycznych biomateriałowego modelu kości długiej w stanie obniżonego kościotworzenia (badano trzy częściowo odbiałczone kości udowe wołowe) z wypełnieniem porów modelu wieloelektrolitowym płynem fizjologicznym Ringera, w zakresie niskich częstotliwości (od 20 Hz do 10 kHz) i w zależności od lokalizacji badanej próbki wzdłuż trzonu kości długiej. Stwierdzono, że: 1) wartości modułu impedancji elektrycznej jednostkowej |Z1| [Ω/cm] trzonu modelowej kości długiej osteoporotycznej maleją bardzo wyraźnie w funkcji częstotliwości w zakresie od 20 Hz do 500 Hz; od częstotliwości 500 Hz do 2 kHz zmiany wartości |Z1| są niewielkie, a powyżej częstotliwości 2 kHz wartość modułu impedancji jednostkowej |Z1| praktycznie nie zależy od zmian częstotliwości; 2) średnia wartość modułu impedancji elektrycznej jednostkowej |Z1| trzonu modelowej kości długiej osteoporotycznej okazała się względnie stała wzdłuż długości trzonu kości i wynosiła ok. 670 Ω/cm dla częstotliwości 100 Hz oraz ok. 630 Ω/cm dla częstotliwości 10 kHz. Otrzymane pilotażowe wyniki pomiarów parametrów elektrycznych określających właściwości strukturalno-elektryczne kości długich osteoporotycznych wymagają potwierdzenia na większej liczbie próbek trzonowo-kostnych częściowo odbiałczanych; planujemy też poszerzenie analizy doświadczalnej właściwości strukturalno--elektrycznych kości długich o obniżonej mineralizacji (częściowo odwapnionych).We present the results of a comparative experimental study on methods considered for the manufacture of a biomaterial model of long bones in a pathological state, i.e. insufficiently mineralized bone (osteomalacia) and reduced osteogenesis (osteoporosis), obtained from bovine femoral bone, using methods applied in the engineering of biomaterials such as partial deproteinization and partial demineralization. The biomaterial model is required for experimental research into the structural-electrical properties of long bones, which will be carried out to build a prototype for a measurement system for the evaluation of bone densitometry and poroelastic properties with the use of an original and non-invasive method of electroosseodensitometry (Polish and international patent applications). The kinetics of chemical bone deproteinization processes in NaOCl, H2O2, KOH and NaOH solutions and chemical bone demineralization processes in HNO3, HCl, EDTA solutions and in a mixture of HNO3 and HCHO were comparatively studied and the protein and calcium contents were monitored as a function of time. On the basis of the functional graphs obtained from the observed processes, we can currently recommend the following conditions for manufacturing a biomaterial model of long bones in a pathological state: deproteinization using a 7% solution of hydrogen peroxide (H2O2) to produce a model of bone in a state of reduced osteogenesis and decalcification with 0.5 M hydrochloric acid (HCl) to produce a model of insufficiently mineralized bone. The results of a pilot experimental analysis of the structural-electrical properties of the biomaterial model of long bones are presented for a state of reduced bone formation (osteoporotic; three partially deproteinized bovine femurs were examined). The bone pores of the model were filled with physiological multielectrolyte Ringer’s saline and assessed in a low frequency range (20 Hz to 10 kHz) as a function of the location of bone shaft samples along the diaphysis. It was found that: 1) values of the modulus of the unit electrical impedance |Z1| [Ω/cm] of the bone shaft of the model osteoporotic long bone decreased very clearly as a function of frequency in the range from 20 Hz to ca. 500 kHz; from a frequency of 500 Hz to 2 kHz, the changes in the |Z1| value were small, and above 2 kHz, the |Z1| value practically did not depend on frequency changes. 2) The mean value of the modulus of the unit electrical impedance |Z1| of the bone shaft of the model osteoporotic long bone was found to be relatively constant along the length of the bone shaft and was about 670 Ω/cm for a frequency of 100 Hz and about 630 Ω/cm for a frequency of 10 kHz. The results of the preliminary study on the structural-electrical properties of long bone shafts in a pathological (osteoporotic) state require confirmation in a full experimental study on a larger number of model osteoporotic long bones; we are also planning to extend the experimental analysis to the structural-electrical properties of long bones with impaired mineralization (partially decalcified)

Computer Aided Stereometric Evaluation of Porostructuralosteoconductive Properties of Intra-Osseous Implant Porous Coatings

The proper interaction of bone tissue - the natural porous biomaterial - with a porous coated intra-osseous implant is conditioned, among others, by the implant porous coating poroaccessibility for bone tissue adaptive ingrowth. The poroaccessibility is the ability of implant porous coating outer layer to accommodate the ingrowing bone tissue filling in its pore space and effective new formed bone mineralizing in the pores to form a biomechanically functional bone-implant fixation. The functional features of the microtopography of intra-osseous implant porous surfaces together with the porosity of pore space of the outer layer of the porous coating are called by bioengineers the porostructural-osteoconductive properties of the porous coated implant. The properties are crucial for successful adaptive bone tissue ingrowth and further long-term (secondary) biomechanical stability of the boneimplant interface. The poroaccessibility of intra-osseous implants porous coating outer layers is characterized by - the introduced in our previous papers - set of stereometric parameters of poroaccessibility: the effective volumetric porosity φVef, the index of the porous coating space capacity VPM, the representative surface porosity φSrep, the representative pore size pSrep, the representative angle of the poroaccessibility Ωrep and the bone-implant interface adhesive surface enlargement index ψ. Presented in this paper, an original method of evaluation of the porostructural-osteoconductive properties of intra-osseous implant porous coatings outer layer by means of the parameters of poroaccessibility was preliminary verified during experimental tests performed on the representative examples of porous coated femoral stems and acetabular cups of various hip endoprostheses. The computer-aided stereometric evaluation of the microstructure of implant porous coatings outer layer can be now realized by the authoring application software PoroAccess_1.0 elaborated in our research team in Java programming language

Computer aided stereometric evaluation of porostructural-osteoconductive properties of intra-osseous implant porous coatings

The proper interaction of bone tissue - the natural porous biomaterial - with a porous coated intra-osseous implant is conditioned, among others, by the implant porous coating poroaccessibility for bone tissue adaptive ingrowth. The poroaccessibility is the ability of implant porous coating outer layer to accommodate the ingrowing bone tissue filling in its pore space and effective new formed bone mineralizing in the pores to form a biomechanically functional bone-implant fixation. The functional features of the microtopography of intra-osseous implant porous surfaces together with the porosity of pore space of the outer layer of the porous coating are called by bioengineers the porostructural-osteoconductive properties of the porous coated implant. The properties are crucial for successful adaptive bone tissue ingrowth and further long-term (secondary) biomechanical stability of the boneimplant interface. The poroaccessibility of intra-osseous implants porous coating outer layers is characterized by - the introduced in our previous papers - set of stereometric parameters of poroaccessibility: the effective volumetric porosity φVef, the index of the porous coating space capacity VPM, the representative surface porosity φSrep, the representative pore size pSrep, the representative angle of the poroaccessibility Ωrep and the bone-implant interface adhesive surface enlargement index ψ. Presented in this paper, an original method of evaluation of the porostructural-osteoconductive properties of intra-osseous implant porous coatings outer layer by means of the parameters of poroaccessibility was preliminary verified during experimental tests performed on the representative examples of porous coated femoral stems and acetabular cups of various hip endoprostheses. The computer-aided stereometric evaluation of the microstructure of implant porous coatings outer layer can be now realized by the authoring application software PoroAccess_1.0 elaborated in our research team in Java programming language

Computer aided evaluation of poroaccessibility of porous coatings outer layer on intra-osseous implants

The poroaccessibility of intra-osseous implant coating is the ability of the porous coating outer layer to accommodate the ingrowing bone tissue filling its pore space and effective new bone formation mineralizing in the pores to form biomechanically functional bone - implant fixation. The poroaccessibility determines the functional features of intra-osseous implant porous coating which are called its structural-osteoinductive properties [6, 8]. The structural-osteoinductive properties can be characterized by the set of three-dimensional parameters of poroaccessibility describing the functional properties of microgeometry of implant porous coatings: the effective volumetric porosity φ Vef , the index of the porous coating space capacity VPM, the representative surface porosity φ Srep, the representative pores size pSrep, the representative angle of the poroaccessibility Ωrep and the bone-implant interface adhesive surface enlargement index ψ [3,7,1]. The original method of stereometric evaluation of the microstructural properties of intra-osseous implants porous coatings by means of the parameters of poroaccessibility [4] is based the 3D roughness profilometry and was preliminary verified during experimental tests performed on the representative examples of porous coated femoral stems and acetabular cups of various hip endoprostheses [2,5,9]. In this paper we present the possibilities of computer aiding for evaluation of the poroaccessibility of porous coating outer layer of intra-osseous implants illustrated by the measurement data from the experimental tests performed on porous coated components of various hip endoprostheses. The computer aided evaluation of the microstructure of implant porous coatings can be realized b y t he authoring application software PoroAccess_1. 0 elaborated for our purposes in our research team in Java programming language. The screen of the application software is presented in FIG. 1. The PoroAccess_1.0 software lets to perform the dynamic analysis of the surface porosity φS in function of the pores depth pd which is showed as the map of porosity situated on the right side of the screen (see FIG. 1). The application software imports results from the series of contact profilometry measurements as the 2D matrices in ASC II format and calculates the values of the poroaccessibility parameters of porous coating outer layer according to the mathematical formulas given in [3,11]. The applications software also has the module enabling 3D visualization of measured region of porous coating outer layer as the isometric plot. The presented methodology provides the characterization of the effective part of porous coating – its outer layer, which is full of pores open for penetrating bone tissue with the diameter of many macro pores surpassing 100 μm. Such size of pores, according to clinical research [1], is beneficial for bone tissue to grow into the coating, so the pore space of the porous coating outer layer participates in creating biomechanically functional bone-porous implant fixation. The set of poroaccessibility parameters characterizes some major aspects of porous coating outer layer features. The parameters describe spatial (φVef, φSrep), volumetric (VPM), hybrid (pdef, ΩMMrep) and some functional (physicochemical) properties of implant porous coatings outer layer, e.g. enhancement of the adhesive properties (ψ), which can be indirectly interpreted in the aspect of its structural-osteoinductive properties [10]. The presented methodology of characterization of implant porous coatings with use of the poroaccessibility parameters is going to be applied as a specific tool in research on designing porous coatings with functionally graded pore distribution and designed poroaccessibility. Nowadays, the best potential to manufacture implant porous coatings with designed poroaccessibility have Direct Metal Manufacturing (DMM) technologies like Selective Laser Sintering / Melting (SLS/M) or Electron Beam Melting (EBM), so the next stage of this research is the investigation on the possibilities to manufacture the porous coating with designed poroaccessibility in one of DMM technologies. The biostructural evaluation of the manufactured in DMM technologies porous coatings together with its biological evaluation in NHOst cultures is expected to provide more information about the representative features of the microstructure of the porous coatings and allow to evaluate the most advantageous poroaccessibility of their pore spaces for potential bone tissue ingrowth to be verified in further in vivo test on animal models

Prototype of innovating bone tissue preserving THRA endoprosthesis with multi-spiked connecting scaffold manufactured in selective laser melting technology

The paper presents the prototype of innovating bone tissue preserving THRA endoprosthesis with multi-spiked connecting scaffold - the main result of our research project: "Experimental investigation and design of the constructional properties of bone-porous implants fixations" (4T07C05629, Polish Ministry of Science, finished in February 2008) presented also as plenary lecture at the 18th International Conference "Biomaterials in Medicine and Veterinary Medicine" in Rytro (Poland), 2008. Three-dimensional selective laser melting (SLM), a direct metal manufacturing (DMM) technology from rapid prototyping/rapid manufacturing (PR/RM) group, was successfully applied to manufacture these prototypes of Ti6AI7Nb powder. We share our observations and remarks on the prototypes manufacturing in SLM laser additive technology

Investigations of microstructure of porous coated orthopaedic implants in the aspect of the structural-adaptive compatibility of bone-porous implant interface. Part 1, Critical view on bone-implant fixation problem

The biomechanical construction of orthopaedic implants, e.g. construction of an artificial hip joint, is characterized by a set of material, geometrical and dynamic properties, designed to fulfil required assumptions. From the biomechanical point of view the problem of structuralbiomechanical compatibility between impalnt and bone is a key-question in respect of the role performed in the skeleton. At first in the matter, the problem of structural-adaptive compatibility of orthopaedic implants porous coatings with bone tissue (natural porous biomaterial) should be stated. This problem deals with osteoinductive properties of biomaterial. The osteoinductive properties of biomaterial are determined, among others, by the poroaccessibility of porous coating for adaptive ingrowth of bone tissue into its pore space which is influenced by mechanical load history. The aim of bone ingrowth into pore space of a coating is to achieve the proper and permanent fixation of the implant in its bony surroundings. This part of the paper presents insight view into the problem of bone-implant fixation, and a critical review of the traditional approach to investigations on the cementless implant fixation conditioned by the bone tissue ingrowth, which were carried out on the basis of one-phase biomechanical model of bone