Anna M. Ryniewicz

Microstructural and micromechanical tests of titanium biomaterials intended for prosthetic reconstructions.

PURPOSEnThe aim of the present paper was a question of structural identification and evaluation of strength parameters of Titanium (Ticp - grade 2) and its alloy (Ti6Al4V) which are used to serve as a base for those permanent prosthetic supplements which are later manufactured employing CAD/CAM systems.nnnMETHODSnMicrostructural tests of Ticp and Ti6Al4V were conducted using an optical microscope as well as a scanning microscope. Hardness was measured with the Vickers method. Micromechanical properties of samples: microhardness and Youngs modulus value, were measured with the Oliver and Pharr method.nnnRESULTSnBased on studies using optical microscopy it was observed that the Ticp from the milling technology had a single phase, granular microstructure. The Ti64 alloy had a two-phase, fine-grained microstructure with an acicular-lamellar character. The results of scanning tests show that titanium Ticp had a single phase structure. On its grain there was visible acicular martensite. The structure of the two phase Ti64 alloy consists of a β matrix as well as released α phase deposits in the shape of extended needles. Micromechanical tests demonstrated that the alloy of Ti64 in both methods showed twice as high the microhardness as Ticp. In studies of Youngs modulus of Ti64 alloy DMLS technology have lower value than titanium milling technology.nnnCONCLUSIONSnAccording to the results obtained, the following conclusion has been drawn: when strength aspect is discussed, the DMLS method is a preferred one in manufacturing load structures in dentistry and may be an alternate way for the CAD/CAM system used in decrement processing.

Microscopic tribological analysis of the knee joint

The aim of the conducted research was the evaluation of the topography and the structure of the superficial layer of meniscus and articular cartilage. These are surfaces that optimise the friction and lubrication process in the knee joint. The animal samples of the menisci and the articular cartilage were examined. The research was performed using scanning electron microscopes and an atomic force microscope. The structure of the surface of meniscus and articular cartilage is very regular. The collagenous fibres, which are embedded in the ground substance, are parallel to the surface. The undulation of the surface was observed. In the area of the anterior horn on tibia side of both menisci as well as in the anterior area of tibial plateau, the concavity and convexity pattern is evident. The observed cavities enable the accumulation of the synovial fluid. The synovial fluid plays the role of the lubricant in the knee joint, and its presence is highly desired during the load transmission. Słowa kluczowe: staw kolanowy, łąkotka, chrząstka stawowa, SEM, AFM. Streszczenie Celem przeprowadzonych badań była ocena topografii i struktury łąkotek oraz powierzchni stawowych, które zabezpieczają i optymalizują proces tarcia i smarowania w stawie kolanowym. Materiałem badań były łąkotki pobrane z prawidłowych stawów zwierzęcych oraz tkanka chrzęstna wypreparowana z powierzchni stawowych. Badania były realizowane na mikroskopach skaningowych oraz mikroskopie sił atomowych. Struktura warstwy wierzchniej chrząstki włóknistej oraz szklistej wykazała dużą regularność. Włókna kolagenowe biegnące równolegle do powierzchni i zatopione w substancji podstawnej tworzą łagodnie pofalowaną strukturę. Układ wgłębień i wzniesień jest najbardziej wyraźny na części przedniej plateau kości piszczelowej oraz w obszarze rogu przedniego łąkotek, po stronie kontaktującej się z plateau kości piszczelowej. W zaobserwowanych wgłębieniach może gromadzić się ciecz synowialna, która pełni rolę środka smarnego, i której obecność jest wysoce pożądana podczas przenoszenia obciążeń wewnątrz stawu kolanowego. * AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, al. Mickiewicza 30, 30-059 Kraków, Poland. ** Cracow University of Technology, Faculty of Mechanical Engineering, Laboratory of Coordinate Metrology, al. Jana Pawła II 37, 30-001 Kraków, Poland. *** AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, al. Mickiewicza 30, 30-059 Kraków, Poland. **** AGH University of Science and Technology, Faculty of Non-Ferrous Metals, al. Mickiewicza 30, 30-059 Kraków, Poland. INTRODUCTION The knee joint menisci are located between the joint surfaces of femur condyles and tibial plateau [L. 1, 2] (Fig. 1). Those medial and lateral fibrocartilaginous structures are responsible for the proper knee joint biomechanics [L. 3, 4]. The joint stability, the movement coordination, the security of maximal knee flexion and extension open the long list of meniscus functions. The meniscus is also involved in the lubrication mechanism and the spreading of synovial fluid. Moreover, it distributes the load and plays a role of a shock absorber. The menisci protect the articular cartilage of the joint surfaces of tibial plateau and femur condyles. The proper meniscus assures the correct interaction between the joint surfaces of the femur distal end and the tibia proximal end, and, the meniscal lesion induces the faulty femorotibial contact area [L. 5]. The structure and functions of knee meniscus are common for the mammal species and are sex independent [L. 6, 7]. 148 ISSN 0208-7774 T R I B O L O G I A 3/2017 Fig. 1. The MRI of the left knee joint, the studied areas marked in colour: red – menisci, yellow – articular cartilage of femur condyles, blue – articular cartilage of tibial plateau: a) coronal section, b) sagittal section Rys. 1. Obraz MRI lewego stawu kolanowego, obszary badawcze zaznaczone kolorem: czerwony – łąkotki, żółty – chrząstka stawowa na kłykciach kości udowej, niebieski – chrząstka stawowa na plateau kości piszczelowej, a) przekrój w płaszczyźnie czołowej, b) przekrój w płaszczyźnie strzałkowej Fig. 2. The SEM picture of the meniscus lateralis cross section: a) the middle part of the meniscus, b) close-up on the superficial layer and the structure below, the area is marked in red on picture a) Rys. 2. Obraz SEM łąkotki bocznej w przekroju: a) środkowa część łąkotki, b) zbliżenie na obszar warstw wierzchniej oraz struktur pod warstwą wierzchnią, obszar zaznaczony na czerwono na zdjęciu a) The arrangement of the collagen fibres within the knee joint menisci is still under discussion. It is commonly agreed [L. 6, 8–12] that three types of layers can be distinguished within the meniscal body. However, there is no consensus about the collagenous structure of those layers. This study was focused on the superficial layer of the meniscus (Fig. 2). The tibial and femoral contact surfaces [L. 10–12] are described as similar to each other. The meniscal surface is depicted as consisting of grooves and ribs. The collagenous fibres of random orientation are parallel to the surface. Injury of the knee meniscus is very common [L. 2, 3, 13]. The young patients mainly suffer from trauma connected with the contact-sport activity. Among adults, trauma is usually coupled with degenerative disease. Both meniscus and articular cartilage of joint surface have a poor regenerative potential [L. 13–16] and their injury causes the development of osteoarthritis. At the very first stage of osteoarthritis, no symptoms occur, which makes it hard to diagnose. During the development of the disease, the articular cartilage and deeper bone structures are subsequently deformed. Therefore, the load distributions and joint stability are firmly disturbed. The chronic and acute pain makes the locomotion impossible. Currently, there is no method which allows the regeneration of the joint surfaces. The patient is doomed to the implantation. The aim of the conducted research was the evaluation of the topography and the structure of the superficial layer of meniscus and articular cartilage. These are surfaces that optimise the friction and lubrication process in the knee joint. The knowledge of the cartilage structure is essential for the identification of tribological phenomena, which accompany the interaction of the joint surfaces [L. 17–24]. a) b) 149 ISSN 0208-7774 T R I B O L O G I A 3/2017 MATERIALS AND METHODS The areas of the topographic scanning electron microscopy (SEM) study (Fig. 3) were chosen based on the contact areas, which were diagnosed by the magnetic resonance imaging (MRI) and direct observations during the joint separation. The MRI is the noninvasive diagnostic method that allows one to define the interaction and the contact area of the joint surfaces [L. 25–28] (Fig. 1). Each meniscus was examined on both sides at six points (Fig 3). Three of those points were located on the inner edge. The first point is on the anterior horn, the second is midway, and the third one is on the posterior horn. The other three were located respectively in the middle of the meniscus width. The topography of the tibial plateau surface (Fig. 3b) was evaluated by means of two approaches. The first examination was performed in three points: on the anterior, the middle, and the posterior areas of the lateral condyle. The medial condyle topography was studied along the C line. The SEM study of the topography of the menisci and the articular cartilage was performed using the Laboratory of Scanning Microscopy at the AGH University of Science and Technology using Scanning Electron Microscope Hitachi S-3400N. The swine samples were soaked in 4% formalin for 5 days prior to examination. An electron backscatter (BSE) detector was used, and the scan parameters were as follows: probe current 60, accelerating voltage 20 kV, and a low vacuum in the range between 130 and 200 Pa. Fig. 3. The research areas of the superficial layer of the knee menisci and the joint surfaces are marked by a black circle. Letter A indicates the anterior horn of the lateral meniscus and the medial meniscus as well as the anterior area of lateral side of tibial plateau, letter P – respectively the posterior horn and posterior area of tibial plateau, letter M – the middle area. Line C shows the direction, which was used during the evaluation of the topographical changes of medial side of tibial plateau. Number 1, 2, 3 corresponds to Figure 4 b, c, d respectively: a) the menisci and the femur condyles of the right knee joint, b) the menisci and the tibial plateau of the right knee joint, c) the medial menisci of the left knee joint prepared to SEM study of the femur side surface, d) the medial menisci of the left knee joint prepared to SEM study of the tibia side surface Rys. 3. Obszary badawcze warstwy wierzchniej łąkotek oraz powierzchni stawowych oznaczone czarnym okręgiem. Literą A oznaczono obszar rogu przedniego na łąkotkach przyśrodkowej i bocznej oraz część przednią bocznej powierzchni plateau kości piszczelowej, literą P – odpowiednio obszar rogu tylnego oraz część tylną plateau, literą M – część środkową. Linia C wyznacza kierunek badania zmian topograficznych na powierzchni przyśrodkowej części plateau kości piszczelowej. Do numerów 1, 2, 3 odnoszą się odpowiednio Rysunki 4 b, c oraz d: a) łąkotki oraz kłykcie kości udowej prawego stawu kolanowego, b) łąkotki oraz plateau kości piszczelowej prawego stawu kolanowego, c) łąkotka przyśrodkowa lewego stawu kolanowego przygotowana do badania SEM warstwy wierzchniej od strony kłykci kości udowej, d) łąkotka przyśrodkowa lewego stawu kolanowego przygotowana do badania SEM warstwy wierzchniej od strony kłykci kości piszczelowej c) d) a) b) 150 ISSN 0208-7774 T R I B O L O G I A 3/2017 The distribution of elements on the section of the femur was analysed by means of a Scanning Electron Microscopy JEOL 5400 in cooperat

Identification of the Cause of the Stem Neck Fracture in the Hip Joint Endoprosthesis

Abstract Endoprosthesis stem fractures are among the rarest complications that occur after hip joint arthroplasty. The aim of this paper is to evaluate the causes of the fractures of the Aura II stem neck, which is an element of an endoprosthesis implanted in a patient. In order to achieve it, a radiogram was evaluated, the FEM analysis was carried out for the hip joint replaced using the Aura II prosthesis and scanning tests as well as a chemical analysis were performed for the focus of fatigue. The tests performed indicate that the most probable causes leading to the fatigue fracture of the Aura II stem under examination were material defects in the process of casting and forging (forging the material with delamination and the presence of brittle oxides and carbides) that resulted in a significant reduction of strength and resistance to corrosion. In the light of an unprecedented stem neck fracture, this information should be an indication for non-destructive tests of ready-made stems aiming to discover the material and technological defects that may arise in the process of casting and drop forging.

Regeneration of knee joint menisci – methods review

Abstract At present, there is no need to convince anyone that menisci are crucial structures dealing with a huge number of responsibilities, and its absence in a knee joint results in irretrievable chondral damage. A lot of methods have been recently developed to treat meniscal tears: physical therapy as a first and, for some cases, a last step, bonding by biodegradable sutures, screws, or arrows, collagen and polyurethane scaffolds designed for partial meniscus replacement, and finally allograft transplantation. However, all of them have numerous limitations and can be used in specific conditions only. That is the reason why partial and total meniscectomy is up to this time a common operation in the case of degenerative or complex meniscus tears despite its well-known degenerative consequences. Trials to overcome those limitations are ongoing, and the challenge to invent a long-term successful regeneration method or to design a substitute that well mimics an anatomical meniscus is still in front of us.

Modeling of lumbar spine equipped with fixator

Abstract Anatomical model of fragment of lumbar spine and rod fixator with screw attachment were made. Numerical analyses (use of finite element method) were executed. Results show that stresses in the analyzed structure depend on the size of the fixator used. Authors suggest further research.