Maritime University of Szczecin
Akademia Morska w Szczecinie
2010, 24(96) pp. 88–92 2010, 24(96) s. 88–92
Evaluation of wear processes of titanium plates used
for internal maxillofacial fixation
Ocena eksploatacyjna tytanowych płytek wykorzystywanych
do wewnetrznych zespoleń kości twarzoczaszki
Jarosław Sidun
Bialystok University of Technology, Mechanical Faculty Department of Materials Science and Biomedical Engineering
Politechnika Białostocka, Wydział Mechaniczny, Katedra Inżynierii Materiałowej i Technologii Maszyn 15-351 Białystok, ul. Wiejska 45c, e-mail: jareks@pb.edu.pl
Key words: exploitation, fretting, wear, maxillofacial fixation Abstract
The internal fixation of maxillofacial fractures with plates and distracters has gained growing popularity during the last decades. The design of implants for fracture fixation has undergone a gradual evolution over the years as researchers have tried to facilitate healing and decrease the rate of complications. Osteolysis is one of the foremost problems limiting the survival of current implantation procedures. It is induced by the wear particles and corrosion products which incite an inflammatory response resulting in bone resorption and eventual loosening and failure of the bone fixation. The future research will help to limit the effects of wear particles by identifying the most suitable bearing surfaces. The pathologic cascade of events triggered by wear particles may be a potential site of action for drugs intended to prevent or check the progression of the disease.
The paper presents a damages problems of the maxillofacial plate fixation. The surface failure at plate stabiliser elements showed typical damages for this system. Damages of screw’s steepl heads as well as the surface layers failure of the the coned seat on tie plates were observed. The surface failure at a screws were visible in a lesser degree. The biggest wear areas are visible on the cooperating surfaces of the plate sockets and the bone screw heads. Many types of damage characteristic of processes of corrosion damage and tribological wear, mainly abrasive, adhesive, and fretting wear, are observed here.
Słowa kluczowe: eksploatacja, fretting, zużycie, zespolenia kości twarzoczaszki Abstrakt
Zespolenia wewnętrzne kości twarzoczaszki z wykorzystaniem płytek wewnętrznych, jak również z użyciem dystraktorów zewnętrznych, w ostatnich latach stały się bardzo popularne. Projektowanie elementów zespo-leń kości znacznie ewaluowało, dając badaczom wiele informacji o współistniejących komplikacjach. Oste-oliza jest jednym z elementów ograniczających możliwości rozwoju procedur operacyjnych. Powoduje ona zużycie elementów i produkty korozji wywołujące współistniejące reakcje oraz stany zapalne będące następ-stwem ewentualnego obluzowania i uszkodzenia zespolonej kości. Badania efektów zużycia elementów zespoleń pozwolą w przyszłości na ograniczenie efektów zużycia oraz określenie najbardziej zużytych obszarów.
W pracy przedstawiono zagadnienia dotyczące uszkodzeń płytek do zespoleń kości twarzoczaszki. Uszkodzenia powierzchni elementów płytek zespalających użytych do wykonania zespoleń wskazują na charakterystyczne ślady uszkodzeń. Są to uszkodzenia warstwy wierzchniej gniazd stożkowych w płytkach zespalających. Mniejsze uszkodzenia obserwuje się na powierzchniach wkrętów. Największe uszkodzenia są widoczne na współpracujących powierzchniach gniazd płytek oraz głów wkrętów kostnych. Obserwuje się tu wiele rodzajów uszkodzeń charakterystycznych dla procesów korozyjnych i tribologicznych, takich jak zuży-cie śzuży-cierne, adhezyjne oraz frettingowe.
Introduction
Along with the development of technology, mainly motorization and active lifestyle of a con-temporary person, a substantial increase of a variety of injuries of organs responsible for locomotion can be observed. In the view of medical knowledge, in the cases of bone fractures it is essential to reduce the fracture and maintain it in such a position until healing occurs. The most beneficial method is to obtain a stable fixation of the fractured bone, which enables the patient to undergo therapeutic rehabili-tation as soon as possible. In the majority of clinical cases, difficulties are observed in long bone stabili-sation with the use of widely applied osteosynthesis methods.
Facial bone fractures are the most frequent con-sequence of head trauma resulting often from work, road or sports accidents, as well as physical assault. Those fractures present a significant therapeutic issue, mostly with proper setting and fixation of bone fragments. In case of insufficiently fixated fractures, the bone gap becomes larger and the heal-ing process is significantly impaired. Stable osteo-synthesis ensures a better fixation of the fracture, facilitates further functional treatment without the necessity of employing jaw immobilization, and shortens the estimated treatment time. The intro-duction of micro- or miniplates in facial bone treatment procedures is currently considered one of the most efficient methods of maxillofacial surgery. Ostheosynthesis with miniplates is recommended primarily in the cases of mandibular fractures.
The use of multiple-component systems in orthopedic surgery gives the surgeon increased flexibility in choosing the optimal implant, but introduces the possibility of interfacial corrosion [1]. The corrosion of implant materials is therefore a topic of major significance in biomaterials science. One of the aspect of corrosion it’s relation to mechanical fixation. The second one is osteolysis of adjacent bone limiting the time of survival of implants [2].
The quality of the fixation and the resulting complications mostly depend on the biomechanical parameters of the fixation in question, ie., indivi-dual geometry of the miniplate and its mechanical properties, as well as the fixation technique and the surgeon's skill. Inappropriately chosen fixation system might lead to excessive overuse of its ele-ments and adhesion complications. Excessive wear of the materials used results in lesions in the sur-rounding tissue [3, 4, 5].
The contemporary literature shows that the metal fatigue and chronic inflammation along with
granulomatous tissue are connected with increased presence of elements responsible for the reactions described above [5, 6].
Materials and methods
Research was conducted on a group of 30 samples of plate fixation of maxillofacial fractures (Fig. 1). Research material was obtained from areas of direct contact with the implant. Bone fragments was obtained during remowal metalic elements of fixation. Samples were tested for existing chemical makeup with the use of a scanning microscope Hitachi S-3000N (Japan), equipped with an X-ray spectrometer type NSS (Noran System Six) and a freezing table for biological sections. The tests were conducted at speeding voltage of 15kV and measure time of 100 secunds.
Fig. 1 A sample view of abrasive damage as a result of the so-called fretting
Rys. 1. Przykładowy widok uszkodzeń będących wynikiem zużycia frettingowego
Results
The tests of the surfaces of the parts of the mini-plates used to perform the fixations are indicative of characteristic damage marks. As a result of the macro- and microscopic observation, two basic types of damage were observed. The damage of the first type have a form characteristic to tribological wear. Macroscopically, these are marks of friction occurring both on the surfaces of the conical holes in the bracing plates and connector sockets as well as the bone screw heads which cooperate with them. Damage of the second type have a form char-acteristic to corrosion wear. Macroscopically, they are matt places, with some spots of pitting, visible with the naked eye, occurring on the surfaces of the holes in the bracing plates and connector sockets as well as their corresponding bone screw heads.
The fretting-corrosion is a combined damage mechanism involving corrosion at points where two moving metal surfaces make rubbing contact. It occurs essentially when the interface is subjected to vibrations (repeated relative movement of the two contacting surfaces) and to compressive loads.
The amplitude of the relative movement is very small, typically of the order of a few microns. When the frictional movement in a corrosive me-dium is continuous, the resulting process is termed tribocorrosion.
Obtained results indicate the penetration of ions of metal from the implant surface into the osseous tissue. I Some instances of corrosion focus were observed on the surface of the implants themselves, an issue related to corrosion fatigue caused by low-cycle, inconstant pressure in a chemically active environment such as a living organism. Maximum concentration of elements in the tested bone structures was,07–3.89% Ti; 0.05–0.9% Al; 0.05–0.2% Fe; 0.54–0.79% Mo (Fig. 3). Figure 2 shows a sample chemical makeup analysis using the NSS x-ray microanalysis and analogous bone structure sample photograph.
Abrasive wear marks resulting mainly from mi-cromachining are formed when connecting screws and bone screws are turned while their conical heads are tightened to the plate sockets, which is evident from the wear form and occurrence. Beside
Fig. 3. The concentration chemical elements in the tested bone structures
Rys. 3. Zestawienie zawartości pierwiastków w strukturze badanej kości
that, the passive layer of the surfaces undergoes mechanical damage (abrasion). Wear processes
Fe Al Ti Mo –0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 P erc en tag e of ch em ica l e lem en ts
C-K O-K Na-K Mg-K Al-K P-K Cl-K K-K Ca-K Fe-K Mo-L
Point 1 63.01 25.57 0.62 0.19 0.11 2.74 0.59 0.19 6.13 0.19 0.66
Point 2 69.91 24.48 0.53 0.53 0.66 0.91 0.84 0.46 0.59 1.09
Point 3 69.93 23.13 0.63 0.17 0.08 1.18 0.72 0.28 2.66 0.27 0.96
Fig. 2 A scanning microsope image of the fixation area corresponding spectrum of the chemical makeup obtained from the NSS x-ray microanalysis
Rys. 2. Obraz tkanki z okolic zespolenia uzyskany z mikroskopu skaningowego z odpowiadającym widmem składu chemicznego z mikroanalizatora rentgenowskiego NSS
develop particularly intensively in the microcontact areas of fixing parts. Spontaneous screwing out of bone screws under the influence of low-cyclic changeable loadings which a stabiliser undergoes in the period of being used, cannot be excluded, ei-ther, as the reasons for abrasive wear. The initial tension of connecting screws and tightening of bone screws should be as big as for screw micromove-ments or loosening, and thus decreasing the screw tightening, not to take place. It is, however, known that screwed joints can screw out under the influ-ence of changeable loadings. Abrasive processes can be intensified through the presence in the abra-sive area of hard wear particles functioning as a ‘free abrasive’ (the so-called secondary wear).
Definitely, the mechanism of wearing through tacking of the 1st (adhesive) type cannot be excluded, either. It is a process of damaging the surfaces of the cooperating parts intensively when friction takes place, in the conditions of great load-ings and plastic strain of the upper layer, especially the highest roughness surface peaks. Local metallic tacking (connecting) of both the abrasive surfaces take place then, and the surfaces are damaged with metal particles being torn off or the metal being smeared on the abrasive surface.
Figure 4 illustrates an abrasive damage as a re-sult of the so-called fretting. Wear through fretting is a phenomenon of damaging the top layer, con-sisting in forming of local material loss areas in the elements undergoing vibration or slight contact slip. Wear through fretting accompanies, among others, cooperation of connections of the pin, screw head r rivet type. Products of fretting are particles in the range of 0.01–0.1 m, usually. A very significant
consequence of fretting, beside abrasive wear pro-ducts, is indent (pit) formation on the surface. The indents may be small (when the products leave the contact area), or constitute little areas of deep pitting (when the products are not removed). The character of such damage depends on the num-ber of cycles, the amount of wear products, ampli-tude, load, and humidity (Fig. 5).
Fig. 5. Image showing plate wear obtained from the metallo-graphic microscope Nicon MA200 (Japan), mag. 100x Rys. 5. Obraz przedstawiający zużycie płytki uzyskany z mi-kroskopu Nicon MA200 (Japonia), pow. 100x
a)
b)
a) b)
Fig. 4. A two basic types of damage: a) of the first type (a form characteristic to tribological wear), mag. 100x, b) of the second type (a form characteristic to corrosion wear), mag. 500x
Rys. 4. Dwa podstawowe typy uszkodzeń eksploatacyjnych: a) pierwszego rodzaju (charakterystyczne dla zużycia tribologcznego), pow. 100x, b) drugiego rodzaju (charakterystyczne dla zużycia korozyjnego), pow. 500x
Conclusion
The results indicate the passing of chemical elements (Fe, Al, Ti, Mb) from the implant surface into the osseous tissue. Some instances of corrosion focus were observed on the surface of the implants themselves, an issue related to corrosion fatigue caused by low-cycle, inconstant pressure in a chemically active environment such as a living organism.
The observations and analyses carried out indi-cate that the surfaces of the miniplates used for the maxillofacial fixation are characterized by a dam-age. The greatest wear areas are visible on the co-responding surfaces of the plate sockets and the bone screw heads. Many types of damage charac-teristic to processes of corrosion damage and tri-bological wear, mainly abrasive, adhesive, and fretting wear, are observed here. The abrasive wear marks are found in the contact areas of the cooper-ating parts. Wear processes are most probably initi-ated as early as during the operation while a plates is mounted. The mechanisms of adhesive wearing cannot be excluded, either. It is a process of damag-ing the surfaces of the cooperatdamag-ing parts intensively when friction takes place, in the conditions of great loadings and plastic strain of the upper layer. The phenomenon of fretting is caused by interactive microshifting of the bracing plate and the screw head.
Acknowledgement
The scientific research was supported by the Polish Ministry of Educational Science from resources for science in years 2008–2011 under the research project no N N507 439834.
References
1. ZAFFE D., BERTOLDI C., KONSOLO U.: Accumulation of
aluminium in lamer bone after implantation of titanum plater, Ti-6Al-4V screws, hydroxyapatite granules, Bioma-terials 2004, 25, 3837–3844.
2. AGRAWAL S.: Osteolysis-basic science, incidence and
diag-nosis. Current Orthopaedics 2004, 18, 220–231.
3. HATTON P.V., BROOK I.M.: The role of electron micros-copy in the evaluation of biomaterials. European Micros-copy and Analysis 1998, January, 39–41.
4. KRISCHAK G.D.,GEBHART F.,MOHR W.,KRIVAN V.,I GNA-TIUK A.,BECH A.,WACHTER N.J.,REUTER P.,ARAND M., KINZL L.,CLAUS L.E.: Diffrence in metallic weaar
distribu-tion released from commercially pure titanium compared with stainless steel plates, arch Orthop Trauma Surg. 2004, 124, 104–113.
5. VOGGENREITER G., LEITING S., BRAUER H., LEITING P.,
MAJETSCHAK M., BARDENHEUER M.,OBERTACHE V.:
Im-muno – inflammatory tissue reaction to stainless – steel and titanum plates used for internal of long bones, Biomaterials 2003, 24, 247–257.
6. WINNER C., GLUCH H.: Aseptic Loosening After CD
Instrumentation in the Treatment of Scoliosis: A Report about Eight Cases. Journal of Spinal Disorder 1998, 11, 440–443.
Recenzent: dr hab. med. Robert Latosiewicz Uniwersytet Medyczny w Lublinie
