Tumorska modularna endoproteza zgloba kuka

Abstract

U prvom poglavlju je ukazano na potrebu ugradnje implantata u cilju ponovnog uspostavljanja normalnog funkcionisanja lokomotornog sistema čoveka. Na osnovu analize broja i strukture ugrađenih endoproteza zgloba kuka za 2014. i 2015. godinu na IOHB „Banjica“, Beograd, i Kliničkom centru Vojvodine Novi Sad, Klinika za ortopediju i traumatologiju, zaključuje se da ovi pokazatelji ukazuju na sličnost i uporedivost, sa podacima iz SAD, u odnosu na broj stanovnika. Drugo poglavlje, u uvodnom delu, sadrži sistematizaciju endoproteza zgloba kuka u skladu sa standardom ISO 7216. Nakon toga, dat je prikaz dosadašnjih rezultata primene tumorskih modularnih endoproteza. Pažnja je poklonjena opisu i varijantnosti konstrukcionih elemenata modularnih endoproteza zgloba kuka, kao i analizi izvedenih konstrukcionih rešenja. Prikaz dosadašnjih istraživanja je upotpunjen analizom patentnih rešenja modularnih endoproteza zgloba kuka. Na kraju, polazeći od prethodno sumiranih saznanja, i iskustva u razvoju protetičkih pomagala je definisan cilj istraživanja, osnovne hipoteze, materijal i metode. Treće poglavnje sadrži kratak prikaz koštanih tumora i istorijat tumorske endoproteze. Ukazuje se na komplikacije nakon ugradnje kao i na kriterijume za ugradnju tumorske endoproteze. Primarni i sekundarni tumori, neuspela aloartroplastika, prelomi preko ili ispod trohantera, patološki prelom, često prouzrukuju totalno razaranje gornjeg dela butne kosti, i ovi uslovi predstavljaju indikaciju za zamenu gornjeg dela butne kosti tumorskom endoprotezom. Cilj ugradnje tumorske endoproteze zgloba kuka je da se spase ekstremitet, očuva estetika i obezbedi zadovoljavajuća funkcionalnost i neutrališe prisustvo bola. Ne može se očekivati da endoprotetski sistem ima neograničen vek. Za pojedine delove koji su izloženi intenzivnom habanju u toku eksplatacije potrebno je obezbediti mogućnost jednostavne zamene uz minimalan hirurški zahvat. Sa biomehaničkog aspekta projektovanja, sistem fiksacije i konfiguracija tela endoproteze mora biti takav da minimizira naponsko stanje ili obezbedi povoljniju raspodelu napona. Četvrto poglavlje je posvećeno definisanju strukture i dimenzija komponenti sistema tumorske modularne endoproteze zgloba kuka. Ukazuje se na postupak i uticajne faktore na proces projektovanja, kao i na pouzdanost projektovanog rešenja. Posebna pažnja je posvećena dimenzionisanju donje komponente endoproteze sa stanovišta pojave koncentracije napona, kao i elementima za vezu i stezanje komponenti u jedinstven mehanički sistem. Dimenzije pojedinih komponenti su definisane na bazi statističkih razultata do sada ugrađenih tumorskih monolitnih endoproteza na IOHB „Banjica“ Beograd. U okviru petog poglavlja, prikazani su rezultati računarske analize statičkog ponašanja tela monolitne, odnosno donje komponente tumorske modularne endoproteze zgloba kuka. Prvo su prikazana preliminarna ipsitivanja pri statičkom opterećenju, i to računarsko simuliranje eksperimentalnih ispitivanja i sama eksperimentalna ispitivanja za obe vrste tumorskih endoproteza. Na bazi ovih rezultata izvršeno je remodelovanje donje komponente i umesto radijusa prelaza između kragne i tela - mesto maksimalnih napona u implantatu, definisan je optimalni bionički profil prelaza. Nakon izrade donjih komponenti od različitih materijala i različitih profila prelaza realizovana su završna ispitivanja komponenti tumorske modularne endoproteze pri statičkom opterećenju. I kod završnog ispitivanja prvo je izvršeno računarsko modelovanje a nakon toga i eksperimentalno ispitivanje. Pri eksperimentalnom ispitivanju meren je napon u jedanaest mernih tačaka po profilu prelaza između kragne i tela. Dobijeni rezultati su poređeni sa računarskim modeliranjem i konstatovano je zadovoljavajuće poklapanje raspodele i maksimalnih napona po profilu prelaza između kragne i tela endoproteze. Za slučaj delovanja dinamičkog opterećenja izvršena su eksperimentalna laboratorijska ispitivanja. Pri ovom ispitivanju definisane su sledeće promenljive: 1. vrsta endoproteze: monolitna i modularna, 2. materijal: superlegure čelika 316LVM i titanijuma Ti6Al4V, 3. oblik prelaza: sa radijusom i optimizirani prelaz. Cilj ovog ispitivanja ja da se utvrdi broj ciklusa koji će dovesti do početka razlabavljenja tela endoproteze pri maksimalnim uslovima opterećenja, tj. da li navedene promenljive daju statistički značajnu razliku u broju ciklusa do pojave razlabavljenja, kasne mehaničke komplikacije koja prethodi lomu usled zamora materijala, ili zahteva reviziju. Pri ovom ispitivanju fizički prototipovi endoproteza su, izloženi jednosmerno promenljivoj sili, Fmax=2500N, amplitude 2000N i frekvencije 15-20 Hz. Vršena je vizuelena kontrola pojave radiolucentne linije između tela endoproteze i koštanog cementa, odnosno kosti, kao pouzdani znak početka razlabavljenja, kao i Rtg snimaka od strane ortopedskih hirurga nakon svakih 500.000 ciklusa, za sve uzorke. Analiza rezultata nakon ispitivanja pri dinamičkom opterećenju uzoraka izrađenih od superlegure čelika 316LVM i uzoraka izrađenih od superlegure titanijuma Ti6Al4V ukazuje na visoku pouzdanost odnosno nizak nivo rizika da može doći do razlabavljenja i do pojave loma usled zamora materijala. Profil prelaza sa velikog na mali prečnik za slučaj radijusa i optimizirani bionički profil nisu pokazali značajnu statističku razliku kod ispitivanja pri dinamičkom opterećenju. Na kraju je pojava razlabavlja utvrđivana i inženjerskom metodom. Nakon ispitivanja dinamičkim opterećenjem fizički prototipovi endoproteza su ponovo izloženi statičkom opterećenju i konstatovano je da nema značajnijih promena u raspodeli i vrednostima maksimalnih napona, što ukazuje da nije došlo da pojave razlabavljenja. Kroz šesto poglavlje dat je kratak opis biokompatabilnih materijala, legura čelika 316LVM, kobalta CoCrMo, titanijuma Ti6A14V „eli“, poroznih i keramičkih materijala, materijala od plastične mase, kompozita i bioreseptivih materijala. Nakon toga su prikazani rezultati ispitivanja biokompatabilnosti materijala koji su primenjeni za izradu elemenata modularnog sistema endoproteza. Rezultati ispitivanja su pokazali da materijali i tehnološki proces proizvodnje zadovoljavaju sa stanovišta biokompatabilnosti. Sedmo poglavlje sadrži zaključke, na osnovu rezultata pojedinih poglavlja i izvedenih istraživanja. Nakon toga dati su pravci budućih istraživanja. Osmo poglavlje sadrži pregled korišćene literature, koju čini 68 literaturnih naslova od kojih je najveći broj citiran u radu.

In the first chapter, the need of implant insertion was apostrophed, with the purpose to achieve normal functioning of human locomotory system. On the base of analysis of the number and the structure of implanted hip endoprosthesis during the years 2014. and 2015. at IOHB “Banjica”, Belgrade, and at Clinical center of Vojvodina, Novi Sad, Clinic of orthopedy and traumatology, it was concluded that the data, related to the number of citizens, show to be similar and comparable with those from the USA. In the second chapter, in the preface section, the systematization of hip endoprosthesis according to the norm ISO 7216 was presented. After that, the results of historical application of modular tumor endoprosthesis was presented. The attention was paid to the description and structure element variants of modular hip endoprosthesis, and also to the analyses of existing prosthesis constructions. The results of up to now conducted research were additionally enriched with patented variants of modular hip endoprosthesis. At the end, based on previously summed knowledge and experiences in the field of development of prosthetic aids, the goal of the research was determined, so as basic hypothesis, materials and methods. Third chapter comprises short description of bone tumors and historic development of tumor endoprosthesis. The complications after implantation were discussed and also the criteria for the implantation of tumor prosthesis. Primary and secondary tumors, failed arthroplasty, fractures across or beneath trochanter and pathologic fractures are frequent causes of total destruction of the upper portion of the femur and require the replacement of it with tumor prosthesis. The aim of hip tumor prosthesis implantation is to save the limb, to preserve esthetic, to provide satisfactory functionality and to neutralize the pain. It is not possible to expect that endoprosthetic system achieves en infinitely long service life. For some of the components, which are during the service exposed to intensive wear and tear, it is necessary to provide the possibility of simple replacement, with the need for a minimal surgical intervention. From the aspect of biomechanical design, the fixation system and body configuration of an endoprosthesis must be such, as to minimize stress level and to provide for a convenient stress distribution. The fourth chapter is dedicated to the definition of the structure and components’ dimensions for a system of modular hip endoprosthesis. It was dealt with the procedure and with the influencefull factors on a design process and also with the reliability of a designed solution. Special care was devoted to the dimensioning of the upper portion of endoprosthesis from the standpoint of stress concentration and to the elements for the connection and joining the elements in a compact mechanical system. The measures of certain components were defined on the base of statistic analysis of up to now implanted monolithic tumor endoprosthesis at IOHB “Banjica”, Belgrade. Within fifth chapter, the results of computer analysis of static behavior of the body of monolithic component (lower section) of modular tumor hip endoprosthesis was presented. As the first, the results of preliminary examinations with static load were presented, both the computer simulation of experimental testing and the results of real experimental testing, for both types of tumor endoprosthesis. On the base of these results, the remodeling of the lower component was undertaken so that instead of the connection of a collar and the prosthesis body with the shape of a constant radius (the spot with the maximum stress in the prosthesis), an optimal bionically shaped connection was defined. After the production of lower prosthesis components from different materials and with the different shapes, the final examinations of the components of modular tumor hip endoprosthesis under static load were performed. For the final examinations, in the first step also the computer modeling was performed, and consequently experimental testing. When performing experimental testing, the stress level was determined at eleven measuring spots, on the prosthesis section between the collar and the body. Acquired results were compared to the results acquired through computer modeling and an adequate overlapping of stress distribution and maximum stress in the region between the collar and the prosthesis body was detected. For the case of dynamic load, the laboratory experimental examinations were performed. For these examinations the following variables were determined: 1. endoprosthesis type: monolithic and modular, 2. material: steel superalloy 316LVM and of titanium Ti6Al4V, 3. shape of a connection between the collar and prosthesis body: with constant radius and with the optimized shape. The aim of this examination was to determine the number of cycles which would lead to the beginning of the loosening of the prosthesis body under the conditions of maximum load or, with other words, it was to be determined if mentioned variables provide for significant statistic difference in cycle numbers to the point of prosthesis loosening, to the consequent mechanic complication predicting material fatigue failure or demanding surgical revision. When conducting the examination, physical models of endoprosthesis were exposed to the influence of unidirectionally changing force with the parameters of Fmax = 2500N, Fampl = 2000N, frequency 15-20 Hz. After every 500.000 load cycles, for all the samples, the appearance of a radiolucent line between the prosthesis body and bone cement and the bone itself, as the reliable sign of the loosening onset, was visually checked on Rtg shots by orthopedic surgeons. The analysis of the results for behavior under dynamic load, for the samples from steel superalloy 316LVM and from titanium Ti6Al4V shows that they posses high reliability and that there is a low probability that the loosening and the fatigue failure will occur. When examined under dynamic load, prosthesis section with the change from small diameter to large diameter, for the case with constant radius and for the case with optimized bionic profile, have not shown statistically significant difference. At the end, the loosening appearance was examined under the application of engineering methods. After exposing the prosthesis to the dynamic load, physical prototypes of prosthesis were anew exposed to static load and it was confirmed that there is no significant change in the distribution and the level of maximum stress, what was the proof that no loosening has occurred. Within the sixth chapter, the short description of biocompatible materials was given, of steel alloy 316LVM, cobalt CoCrMo, titanium Ti6Al4V “eli”, of porous and ceramic materials, plastic materials, composites and bioreceptive materials. Subsequently, the results of biocompatibility examination of materials which were applied for the production of the elements of modular endoprosthesis system were presented. The acquired results have proved that the materials and the production process are satisfactory from the standpoint of biocompatibility. Seventh chapter comprises the conclusions, based on specific previous chapters and the research results. After that, the suggestions for the future research were outlined. Eight chapter comprises an overview of used literature, with 68 titles, most of which were cited in this work.