The dachshund, a chondrodystrophic dog breed, presents a unique challenge in the treatment of tibial fractures by having short and curvaceous tibiae, leading to high implant failure risk. In this study, intramedullary pins with full cerclage wires as an option in the treatment of oblique diaphyseal tibial fractures was studied in vitro. This fixation technique was biomechanically compared with the current gold standard in internal stabilization, namely bone plates and screws. Twenty tibiae recovered from adult dachshund cadavers were randomly allocated into two groups of ten bones each. Oblique fractures running in a proximo-cranial-disto-caudal direction in the middle third of the tibial diaphysis were simulated by osteotomy and each bone repaired by using one of the following methods: <ul> <li> Pre-bent intramedullary pin, filling 40% to 60% of the medullary cavity at its narrowest point, inserted normograde and combined with a set of three full cerclage wires (group 1).</li> <li> Lag screw at the osteotomy site, combined with a six hole 2.7 mm contoured dynamic compression plate and cortical screws in neutral mode (group 2).</li> </ul> Each test specimen was subjected to a two point single cycle axial compression test by applying a standardized, increasing compression load to the point of fixation failure or bone collapse. A stress-strain graph for each test specimen was drawn from the raw data. Radiographs and digital photographs were made pre-osteotomy, post-osteotomy, post-repair and post-test, and modes of failure noted for each test specimen. Stress (applied load) and strain (deformation) at yield, ultimate strength, and at failure were determined for each test specimen from the stress-strain graphs and the mean values statistically compared between the groups using the ANCOVA method. Significance levels of p < 0.05 were used, while p < 0.1 and p < 0.01 were also indicated. In group 1, 50% specimens failed due to unraveling or slippage with displacement of the cerclage wires, 30% due to bone fracture at a cerclage wire, and 20% due to bone fracture elsewhere. In group 2, 80% specimens failed due to bone fracture at one or more of the screw holes, whereas 20% failed due to bone fracture not directly associated with implants. No bone plate or screw underwent plastic (permanent) deformation, whereas 80% of the intramedullary pins and 30% of the cerclage wires underwent plastic deformation. Mean stress at the yield point in groups 1 and 2 were 0.323 MPa and 0.403 MPa respectively, at the point of ultimate strength 0.383 MPa and 0.431 MPa respectively, and at the failure point 0.345 MPa and 0.403 MPa respectively. Mean strain at the yield point in groups 1 and 2 were 0.296% and 0.362% respectively, at the point of ultimate strength 0.412% and 0.472% respectively, and at the failure point 0.713% and 0.838% respectively. Clinically, there was an indication that plates and screws were more resistant to deformation by the loads applied than intramedullary pins and cerclage wires. However, statistically, there were no significant differences in stress at yield (p = 0.299), ultimate strength (p = 0.275), or failure (p = 0.137) between the two groups. Similarly, there were no significant differences in strain at yield (p = 0.684), ultimate strength (p = 0.778), or failure (p = 0.505) between the two groups. Main limitations of the study were the relatively small number of specimens tested, the smoothness of the osteotomy cuts which limited interdigitation between the fragments, and that only three of the five recognized loads acting on bones in vivo, were tested in vitro. In conclusion, this study did not show enough evidence to prove a significant difference between the two methods of fixation. Therefore, it is suggested that intramedullary pins and full cerclage wires be used as an acceptable alternative to bone plates and screws in the treatment of oblique mid-diaphyseal tibial fractures in chondrodystrophic dog breeds. / Die dachshund, ‘n chondrodistrofiese honderas, bied ‘n unieke uitdaging in die behandeling van frakture van die tibia, deurdat hulle tibias kort en krom is, wat lei tot ‘n hoë risiko van inplantaat mislukking. In hierdie studie is intramedullêre penne met vol sirkeldrade as ‘n keuse in die behandeling van skuins frakture van die tibiale skag in vitro bestudeer. Hierdie tegniek van herstel is vergelyk met die huidige goue standaard in interne stabilisering, naamlik beenplate en skroewe. Twintig tibias wat van volwasse dachshund kadawers herwin is, is lukraak aan twee groepe van tien bene elk toegewys. Skuins frakture in ‘n proksimo-kranio-disto-koudale rigting in die middelste derde van die tibiale skag is nageboots deur ‘n osteotomie, waarna elke been herstel is deur die gebruik van een van die volgende metodes: <ul> <li> Vooraf gebuigde intramedullêre pen, wat 40% tot 60% van die murgholte by die dunste punt vul, normograad geplaas en gekombineer met ‘n stel van drie vol sirkeldrade (groep 1).</li> <li> Trekskroef by die osteotomie area, gekombineer met ‘n ses-gat 2.7 mm gekontoerde dinamiese drukplaat en kortikale skroewe geplaas op neutrale wyse (groep 2).</li> </ul> Elke toetsmonster is onderwerp aan ‘n twee-punt enkel siklus aksiale druktoets deur die toepassing van ‘n gestandardiseerde, verhogende druklading tot by die punt van fiksasie breuk of kollaps van die been. ‘n Druk-spanning grafiek vir elke toetsmonster is vanaf die rou data saamgestel. X-straalfoto’s en digitale foto’s van elke been is pre-osteotomie, post-osteotomie, post-herstel and post-toets geneem en die maniere van faal vir elke toetsmonster aangeteken. Druk (toegepaste lading) en spanning (vervorming) by meegee (“yield”), treksterkte (“ultimate strength”) en faal (“failure”) is vir elke toetsmonster bepaal vanaf die druk-spanning grafieke en die gemiddelde waardes statisties vergelyk tussen die groepe deur gebruik te maak van die ANCOVA metode. Beduidenis vlakke van p < 0.05 is gebruik, terwyl p < 0.1 en p < 0.01 ook aangedui is. In groep 1 het 50% toetsmonsters gefaal as gevolg van losgaan of gly van die sirkeldrade met verplasing, 30% as gevolg van beenfrakture by ‘n sirkeldraad, en 20% as gevolg van beenfrakture elders. In groep 2 het 80% toetsmonsters gefaal as gevolg van beenfrakture by een of meer skroefgate, terwyl 20% gefaal het as gevolg van beenfrakture wat nie direk met die inplantate geassosieer is nie. Geen beenplaat of skroef het plastiese (permanente) vervorming ondergaan nie, terwyl 80% van die IM penne en 30% van die sirkeldrade plastiese vervorming ondergaan het. Gemiddelde druk by die meegeepunt in groepe 1 en 2 was 0.323 MPa en 0.403 MPa onderskeidelik, by die punt van treksterkte 0.383 MPa en 0.431 MPa onderskeidelik, en by die faalpunt 0.345 MPa en 0.403 MPa onderskeidelik. Gemiddelde spanning by die meegeepunt in groepe 1 en 2 was 0.296% en 0.362% onderskeidelik, by die punt van treksterkte 0.412% en 0.472% onderskeidelik, en by die faalpunt 0.713% en 0.838% onderskeidelik. Klinies was daar ‘n indikasie dat plate en skroewe meer weerstandbiedend was teen vervorming deur die toegepaste ladings as intramedullêre penne en sirkeldrade. Statisties was die druk wat die toetsmonster laat meegee (p = 0.299), en die druk by die treksterkte- (p = 0.275) en faalpunte (p = 0.137) egter nie beduidend verskillend tussen die twee groepe nie. Net so was die spanning by die meegee- (p = 0.684), treksterkte- (p = 0.778) en faalpunte (p = 0.505) nie beduidend verskillend tussen die twee groepe nie. Hoof beperkings van die studie was die relatief klein getal monsters wat getoets is, die gladheid van die osteotomie-snitte wat interdigitasie tussen die fragmente beperk het, en dat slegs drie van die vyf erkende ladings wat op bene in vivo inwerk, in vitro getoets kon word. Laastens het hierdie studie nie genoeg getuienis opgelewer om ‘n beduidende verskil te bewys trussen die twee metodes van herstel nie. Derhalwe word voorgestel dat IM-penne en vol sirkeldrade gebruik word as aanvarbare alternatief tot beenplate en skroewe in die behandeling van skuins midskag tibia frakture in chondrodistrofiese honderasse. / Dissertation (MSc)--University of Pretoria, 2012. / Companion Animal Clinical Studies / unrestricted

Development and evaluation of new cementless revision acetabular components for total hip arthroplasty / type TC / Objective: The aim of the clinical part of the study was to introduce a new revision oval cup type TC, and evaluate its reliability and utility in revision endoprosthesis. Due to the different structure of the implant, we aimed to objectively demonstrate the remodeling of bone tissue in its vicinity. In the experimental part of the work we verified the hypothesis that the use of locking screws has an effect on the bond strength of the implant with bone tissue, and therefore on the primary stability of the acetabular component. Method: We evaluated 31 patients that underwent revision hip surgery between 2004 and 2008. The mean follow-up was 7.1 years (range 5.3 to 9.3 years, minimum 5 years after surgery). Osteointegration of the implant and remodeling of bone tissue around the implant and its ribs were evaluated by digital radiography and computed tomography, and clinical results according to Harris. The experiment was based on the execution of pull-out tests after the implantation of TC cups in cadaveric bovine pelves. We evaluated the dependence of tensile forces in the axis of the implant on extraction of the metal cup from the bone bed. Four tests were conducted with the cup fixed...

Einführung: Zu den Immobilisationsmethoden bei Kieferfrakturen gehören die selbstbohrenden Schrauben (IMF-Schrauben). Diese könnten – wie jeder chirurgische Eingriff – zu Komplikationen führen. Eine dieser Komplikationen ist die Zahnwurzelverletzung. In dieser retrospektiven Studie werden die Patienten, bei denen im Rahmen der Versorgung von Unterkieferfrakturen in der Klinik der MKG-Uniklinik-Dresden im Zeitraum von 2011 bis 2015 IMF-Schrauben eingesetzt wurden, klinisch und radiologisch untersucht. Material und Methoden: Ausgewertet wurden die Patientenunterlagen und Röntgenaufnahmen. Bei der Nachuntersuchung wurden sowohl die subjektiven als auch die objektiven Auffälligkeiten der in Nähe der Schrauben stehenden Zähne erhoben. Der Lockerungsgrad, die Zahnverfärbung, die Perkussionsempfindlichkeit sowie die Vitalität der Zähne wurden geprüft. Bei klinisch behandlungsbedürftigen Befunden wurde eine Röntgendiagnostik durchgeführt und die Behandlung in Zusammenarbeit mit dem Hauszahnarzt veranlasst. Ergebnisse: 157 Patienten (49 Frauen/108 Männer) wurden in die Studie eingeschlossen. 633 Schrauben wurden insgesamt inseriert. Davon hatten 563 einen radiologischen Kontakt mit Zähnen. Von diesen Patienten wurden 34,3 % nachuntersucht. Die Nachbeobachtungszeit betrug von 33,3 Monate im Durchschnitt. Es kam bei 27 Schrauben zu einem radiologischen Wurzeldefekt (4,8 %), wovon sechs Fälle behandlungsbedürftig waren: ein avitaler Zahn, eine Pulpaverkalkung, eine interne Pulparesorption und drei Wurzelfrakturen. Im Rahmen der Behandlung dieser Fälle erfolgten eine Zahnextraktion, eine Wurzelkanalbehandlung und vier Zähne werden durch Hauszahnarzt beobachtet. Schlussfolgerung: Die IMF-Schrauben sind eine zuverlässige Methode zur Okklusionssicherung, die aber zu Zahnwurzelverletzungen führen könnte. Hier empfiehlt sich die klinische und radiologische Nachuntersuchung und die Einleitung einer entsprechenden Therapie falls erforderlich. Es ist wichtig, die Schrauben mit dosierter Kraft zwischen den Eckzähnen und ersten Molaren auf Höhe der mukogingivalen Linie einzubringen, um Zahnwurzel-, Nerv- und Kieferhöhlenverletzungen zu vermeiden.

I och med att klimatfrågan blir allt viktigare ökar även intresset för miljövänligt byggande. Förbyggnader av högre karaktär är förädlade träprodukter något som syns mer av på marknaden.Element av KL-trä, korslimmat trä, är en stabil träprodukt med stora användningsområden förhela byggnaden men dessa måste på något sätt förankras i varandra. För att få en djupareförståelse om hur förband i KL-trä verkar i en skarv utvärderar detta examensarbete totalt åtta(8) stycken olika skarvtyper teoretiskt, varav några mer ingående. De mekaniska- ochekonomiska egenskaperna jämförs för att bedöma bästa kapaciteten ochanvändningsområdet för olika bjälklag.De skarvar som beaktas är bland annat plywoodskarven där en plywoodremsa läggs ned i etturfräst spår i överkant längs KL-träskivans långsida. Halvt i halvt-skarven med urfräsning tillhalva djupet i över- och underkant för att passas ihop och rakskarv med skråskruvning. IRakskarv 2D skråskruvas skruven 45° i YZ-planet, Rakskarv 3D skruvas också i 45° men där vridsäven skruven 45° i XY-planet. Skarvarna behandlas för tillämpning i bjälklag för flerbostadshus,parkeringshus och tak. Genom att testa olika teoretiska beräkningsmetoder, från Eurokod ochvidare forskning inom ämnet, kontrollera hur dessa skiljer sig emot tidigare gjorda tester. Föratt jämföra skarvarnas kapacitet har en fem (5) meter lång skarv i en mindre konstruktion med200 mm tjocka KL-träskivor använts som referens. Fästdonen har begränsats till ett fåtal därvinkeln mot virkets yta varierar. Kostnaden för tillverkning, montage och fästdon sätts emotkapaciteten för att kunna jämföra vilken skarv som är mest kostnadseffektiv, då det alltid ären viktig fråga inom projekt.Kostnaden för Rakskarv 3D är 63 % av kostnaden för en Plywoodskarv 12 mm. För att klarapåfrestningen från tvärkraften behövs cirka 18 stycken SW-D-skruvar men upp emot 95stycken ankarspikar. Resultatet blev att den mest kostnadseffektiva skarven ur tillverkningochmontageperspektiv samt behovet av smide per löpmeter är Rakskarv 3D. För skarvtypermed SW-D skruv blir ofta den horisontella skjuvkraften dimensionerande då de vertikalakrafterna är lägre och utdragsbärförmågan är hög för dubbelgängad skruv. För bjälklag ibostäder är Rakskarv 2D att rekommendera, då den är en beprövad metod som har godkapacitet och är snabb att montera. Att också vrida skruvarna 0-45° i XY-planet, Rakskarv 3D,för att möta tvärkrafterna har positiv inverkan. Även för takbjälklag är rakskarven det bättrealternativet. Vad gäller parkeringsbjälklag rekommenderas också Rakskarv 3D även om Halvti halvt har likvärdiga mekaniska egenskaper på grund av pris och c/c-avstånd.Stora skillnader mellan beräkningsmetoder och tester framkommer för både kapacitet ochstyvhet. Vid horisontell skjuvning kan detta leda till att utfallet av brottmod, som normalt blir”f” enligt tester, blir fel. Högsta horisontella styvhet enligt beräkningarna har Halvt i halvt,däremot är enligt tester Rakskarv 3D den med högst styvhet. Utifrån detta kan man ifrågasättahur säkra beräkningsmetoderna verkligen är eller om variationen i träet för stora. Bortser manifrån att Rakskarv 3D får låga värden på kapaciteten enligt beräkningar och bara tittar tillutförda tester tillsammans med vetenskapliga publikationer är den allmänt ett bra val avskarvmetod. / As the climate issue becomes more important, the interest in environmentally friendlyconstruction also increases. For buildings of higher character, refined wood products aresomething that is more common at the market. Elements of cross-laminated timber (CLT) arestable wood products with large uses for the entire building, but these must in some way beanchored in each other. To gain a deeper understanding of how joints in CLT works, this thesisis evaluating a total of eight (8) different types of joints theoretically, some of which are moredetailed. The mechanical- and economical properties are compared to assess the best capacityand area of application for different slabs.The joints that are considered include the spline joint, where a plywood strip is laid down in amilled groove at the top along the long side of the CLT slab. Half-lap joint, with cut to halfdepth at top and bottom to fit together, and butt joint with screw in shear. In Butt joint 2D,the screw is screwed 45 ° in the YZ plane, Butt joint 3D is also screwed in 45 ° but the screw isalso turned 45 ° in the XY plane. The joints are treated for application in flooring for apartmentbuildings, parking garages and roofs. By testing different theoretical methods of calculation,from Eurocode and further research in the subject, check how these differ from previous tests.To compare the capacity of the joints, a five (5) meter long joint in a smaller structure with a200 mm thick CLT slab has been used as reference. The fasteners have been limited to a fewwhere the angle to the surface of the wood varies. The cost of production, assembly andfasteners is set against the capacity to be able to compare which joint is the most costeffective,as it is always an important issue within projects.The cost of a 3D joint is 63% of the cost of a 12 mm spline joint. In order to cope with the strainfrom the transverse force, about 18 SW-D screws are needed, but up to 95 anchor nails. Theresult was that the most cost-effective joint from the manufacturing- and assemblyperspective, as well as the need for fastener per meter was Butt joint 3D. For joint types withSW-D screws, the horizontal shear force is often dimensioned as the vertical forces are lowerand the withdrawal capacity is high for double threaded screws. For slab in homes, Butt joint2D is recommended, as it is a proven method that has good capacity and is quick to assemble.Also turning the screws 0-45 ° in the XY plane, like Butt joint 3D, to meet the transverse forceshas a positive effect. Even for roof joists, the butt joint is the better option. Regarding jointsin parking garages, Butt joint 3D is also recommended even though Half-lap joint has similarmechanical characteristics due to the price and c/c- distances.Differences between calculation methods and tests appear for both capacity and stiffness.Horizontal shear can result in wrong type of failure, which normally becomes "f" according totests. The highest horizontal stiffness according to the calculations has Half-lap joint, however,according to tests Butt joint 3D is the one with the highest stiffness. Based on this, one canquestion how accurate the calculation methods really are or whether the variation in wood istoo great. Apart from the fact that Butt joint 3D receives low values of capacity according tocalculations and only looks at tests carried out together with scientific publications, it isgenerally a good choice of joint method.

Intresset för flervåningshus i trä ökar stadigt. Trä är ett lätt och mjukt material vilket är problematiskt med avseende på stomstabilisering och horisontella deformationer. Syftet har varit att undersöka förbandstyper för KL-trä och huvudfrågan var hur stommens horisontella deformationer påverkas av infästningstyperna och deras styvhet. En jämförande studie av självborrande skruvar och beräkning av deras förskjutningsmodul har utförts. En modell på 22 våningar med en stomme av KL-trä modellerades i RFEM. Analyser genomfördes för olika värden på förskjutningsmodul för att kunna jämföra de horisontella deformationerna. Resultatet visade på att deformationerna blev små och att skillnaden mellan olika förskjutningsmoduler gav en knappt märkbar skillnad i horisontell deformation, trots att variationen av värdet på förskjutningsmodulerna var stor. Detta kan förklaras av att modellen i sig är väldigt stabil, vilket främst skulle kunna bero på fasadelementens vertikala förskjutning och höjd. Andra bidragande orsaker var att modellen saknade urtag för dörrar och fönster, KL-elementens tjocklek samt att pågjutning av betong applicerades på varje våning. / The interest for multi storey buildings with timber is growing. Timber is a material that is light and ductile, characteristics that make timber a challenging material in terms of horizontal stabilization and horizontal displacements. The purpose was to examine connectors for CLT and the main question was how the horizontal displacement of the frame is affected by the connectors and their stiffness. A parametric study for self-tapping screws and calculation of their slip modulus was carried out. A model of a 22-storey building with a CLT frame was modelled in RFEM. Analyses were run for different values of the slip modulus for comparison of the horizontal displacements connected to each slip modulus. The results show that the deformations were small and that the differences in slip modulus only caused small differences in horizontal deformations even though the variation in slip modulus was wide. The reason for this could be due to the modelling; the model in itself is very stiff, possibly as a result of the façade panels’ vertical adjustment and height. Other factors contributing were the lack of openings for doors and windows in the model, the thickness of the CLT panels as well as the concrete decks on all floors.

This study consists of three self-standing parts, each dealing with a different aspect of design of composite steel-concrete flexural members. The first part deals with a new type of shear connection in composite joists. Composite steel-concrete flexural members have increasingly become popular in design and construction of floor systems, structural frames, and bridges. A particularly popular system features composite trusses (joists) that can span large lengths and provide empty web space for installation of typical utility conduits. One of the prominent problems with respect to composite joists has been the installation of welded shear connection due to demanding welding requirements and the need for significant welding equipment at the job site. This part of the study presents a new type of shear connection developed at Virginia Tech— standoff screws. Results of experimental and analytical research are presented, as well as the development of a recommended design methodology. The second part deals with reliability of composite beams. Constant research advances in the field of composite steel-concrete beam design have resulted in numerous enhancements and changes to the American design practice, embodied in the composite construction provisions of the AISC Specification (AISC 1999). Results of a comprehensive reliability study of composite beams are presented. The study considers specification changes since the original reliability study by Galambos et al. (1976), considers a larger database of experimental data, and analyses recent proposals for changes in design of shear connection. Comparison of three different design methods is presented based on a study of 15,064 composite beam cases. A method to consider effect of degree of shear connection on strength reduction factor is proposed. Finally, while basic analysis theories between the two are similar, requirements for determining the strength of composite beams in Eurocode 4 (CEN 1992) and 1999 AISC Specification (AISC 1999) differ in many respects. This is particularly true when considering the design of shear connections. This part of the dissertation explores those differences through a comparative step-by-step discussion of major design aspects, and accompanying numerical example. Several shortcomings of 1999 AISC Specification are identified and adjustments proposed. / Ph. D.

Die Einführung der Computer-assistierten Navigation von Pedikelschrauben an der Wirbelsäule in den klinischen Alltag konnte in mehreren Studien eine signifikante Senkung der Fehlplatzierungsraten auf deutlich unter 10% zeigen. Es existieren aber nur spärliche Daten bezüglich der Navigation an der Brustwirbelsäule und deren Anwendung bei unfallchirurgischen Patienten, typischerweise mit frischen Frakturen. Ziel dieser Arbeit war es, die Genauigkeit der CT-basierten Navigation von Pedikelschrauben an der Brustwirbelsäule mit Hilfe eines optoelektronischen Navigationssystems bei Patienten mit Frakturen, Tumoren und Entzündungen im Vergleich zur konventionellen Technik zu untersuchen. Dazu wurden bei 85 Patienten 324 Pedikelschrauben, 211 navigiert und 113 konventionell, an der Brustwirbelsäule gesetzt. Die Navigation erfolgte mit einem optoelektronischen System, wobei zusätzlich ein Bildverstärker zur Lagekontrolle verwendet wurde. Postoperativ wurde die Pedikelschraubenplatzierung mit Hilfe von Computertomogrammen dargestellt und durch einen unabhängigen Radiologen ausgewertet. In der navigierten Gruppe wurden 174 (82,5%) Schrauben korrekt platziert. In der konventionellen Gruppe waren es mit 77 (68,1%) Schrauben signifikant weniger (p < 0,003). Allerdings ließen sich erhebliche Fehllagen von über 4 mm in 1,9% der Fälle trotz Navigation nicht vermeiden. Die zusätzliche Röntgendurchleuchtung vermied vor allem die Navigation falscher Wirbelkörper sowie Abweichungen der Schrauben nach kaudal bzw. kranial. / Several studies have shown that computer assisted pedicle screw insertion in spinal surgery can decrease pedicle perforation rate significantly to less than 10%. However, few data exist concerning the accuracy of pedicle screw navigation in the thoracic spine in trauma patients. The goal of this study was to evaluate the accuracy of CT-based computer assisted pedicle screw insertion in the thoracic spine in patients with fractures, metastases and spondylodiscitis compared to conventional technique. 324 pedicle screws were inserted in the thoracic spines of 85 patients. 211 screws were placed using a CT-based optoelectronic navigation system assisted by an image intensifier. 113 screws were placed with conventional technique. Screw positions were evaluated with postoperative CT-scans by an independent radiologist. In the computer assisted group 174 (82,5%) screws were found completely within their pedicles compared with 77 (68,1%) correctly placed srews in the conventional group (p < 0,003). Despite of using the navigation system 1,9% of the computer assisted screws perforated the pedicle wall more than 4 mm. The additional use of the image intensifier helped identifying the correct vertebral body and avoided cranial or caudal pedicle wall perforations.

The mevalonate pathway is an important biosynthetic pathway, found in all cells of virtually all known pro- as well as eukaryotic organisms. This thesis is an investigation into the use of two drugs, originally developed for different applications, but both affecting the mevalonate pathway, in to models of fracture repair. Using two different rodent models of fracture repair, a commonly used cholesterol lowering drug (statin) and two drugs used to treat osteoporosis (bisphosphonate) were applied both systemically as well as locally in order to enhance fracture repair. Papers I and II investigate the potential of simvastatin to improve the healing of femoral fractures in mice. Papers III and IV explore the use of two bisphosphonates to improve early fixation of stainless steel screws into rat bone. The statin simvastatin lead to an increased strength of the healing cellus. The application of bisphosphonates increased early screw fixation. It seems clear that both drugs have uses in orthopaedic applications. One interesting avenue of further research would be to combine the two classes of drugs and see if we can get the benefits while at the same time diminishing the drawbacks.

The dissertation investigates the behaviour of timber-concrete connections with inclined screws – the load carrying capacity and deformability. The essen¬tial objects of investigation are the load carrying capacity of inclined screws; the modules of connection slip deformation, and the mechanical properties of mate¬rials and ware of which the connection is made. The load-carrying capacity of the connection depends on the properties of the material of connected member and the connectors, on which depends the strength and stiffness of the composite member. The main aim of dissertation is to create the connection load carrying capacity predicting model, based on the more realistic behaviour of the material of connected members; to prepare the simplified approach for load-carrying capacity predicting model for composite timber-concrete connections within at any angle in respect to timber grain in¬clined crews. The paper approaches a few major tasks such as the choice of suitable load-carrying capacity predicting base model; preparing it to composite timber-con¬crete connections with inclined screws; the experimental investigation of con¬nection with inclined screws under long- and short term loading; the experi¬mental investigation of properties of connected materials and type of used con¬nectors; the evaluation of created predictive model based on results also of other researchers experimental investigations. / Disertacijoje nagrinėjama kompozitinės medinės-betoninės jungties su įžambiai šlyties plokštumai orientuotais medsraigčiais elgsena – laikomoji galia ir deformacinės savybės. Pagrindiniai tyrimų objektai yra įžambiai medienos pluoštui orientuotų medsraigčių laikomoji galia, slinkties deformacijų moduliai ir mechaninės jungtį sudarančių elementų savybės, veikiančios jungties elgseną. Nuo medsraigčio ašies posvyrio kampo, deformacinių po medsraigčiu glemžiamos ir ištraukiamos medienos ir lenkiamo medsraigčio savybių priklauso ir jungties irties pobūdis, laikomoji galia ir slinkties deformacijų moduliai, o nuo pastarųjų – kompozitinio elemento stiprumas ir standumas. Pagrindinis disertacijos tikslas yra sukurti skaičiavimo modelį tokių jungčių laikomajai galiai nuspėti, kuo tiksliau atsižvelgiant į medžiagų ir elementų mechanines savybes; pateikti supaprastintą skaičiuojamąjį modelį, skirtą bet kokiu kampu medienos pluošto atžvilgiu įsriegtų medsraigčių laikomajai galiai nuspėti. Darbe sprendžiami keli pagrindiniai uždaviniai: tinkamo pamatinio jungties laikomąją galią vertinančio skaičiuojamojo modelio parinkimas, jo pritaikymas įžambiai medienos pluoštui orientuotiems medsraigčiams; trumpalaikis ir ilgalaikis eksperimentinis įžambinės medsraigtinės jungties laikomosios galios tyrimas ir vertinimas; kitų autorių eksperimentinių rezultatų vertinimas sukurtajam jungties laikomąją galią vertinančiam modeliui pagrįsti.

Disertacijoje nagrinėjama kompozitinės medinės-betoninės jungties su įžambiai šlyties plokštumai orientuotais medsraigčiais elgsena – laikomoji galia ir deformacinės savybės. Pagrindiniai tyrimų objektai yra įžambiai medienos pluoštui orientuotų medsraigčių laikomoji galia, slinkties deformacijų moduliai ir mechaninės jungtį sudarančių elementų savybės, veikiančios jungties elgseną. Nuo medsraigčio ašies posvyrio kampo, deformacinių po medsraigčiu glemžiamos ir ištraukiamos medienos ir lenkiamo medsraigčio savybių priklauso ir jungties irties pobūdis, laikomoji galia ir slinkties deformacijų moduliai, o nuo pastarųjų – kompozitinio elemento stiprumas ir standumas. Pagrindinis disertacijos tikslas yra sukurti skaičiavimo modelį tokių jungčių laikomajai galiai nuspėti, kuo tiksliau atsižvelgiant į medžiagų ir elementų mechanines savybes; pateikti supaprastintą skaičiuojamąjį modelį, skirtą bet kokiu kampu medienos pluošto atžvilgiu įsriegtų medsraigčių laikomajai galiai nuspėti. Darbe sprendžiami keli pagrindiniai uždaviniai: tinkamo pamatinio jungties laikomąją galią vertinančio skaičiuojamojo modelio parinkimas, jo pritaikymas įžambiai medienos pluoštui orientuotiems medsraigčiams; trumpalaikis ir ilgalaikis eksperimentinis įžambinės medsraigtinės jungties laikomosios galios tyrimas ir vertinimas; kitų autorių eksperimentinių rezultatų vertinimas sukurtajam jungties laikomąją galią vertinančiam modeliui pagrįsti. / The dissertation investigates the behaviour of timber-concrete connections with inclined screws – the load carrying capacity and deformability. The essen¬tial objects of investigation are the load carrying capacity of inclined screws; the modules of connection slip deformation, and the mechanical properties of mate¬rials and ware of which the connection is made. The load-carrying capacity of the connection depends on the properties of the material of connected member and the connectors, on which depends the strength and stiffness of the composite member. The main aim of dissertation is to create the connection load carrying capacity predicting model, based on the more realistic behaviour of the material of connected members; to prepare the simplified approach for load-carrying capacity predicting model for composite timber-concrete connections within at any angle in respect to timber grain in¬clined crews. The paper approaches a few major tasks such as the choice of suitable load-carrying capacity predicting base model; preparing it to composite timber-con¬crete connections with inclined screws; the experimental investigation of con¬nection with inclined screws under long- and short term loading; the experi¬mental investigation of properties of connected materials and type of used con¬nectors; the evaluation of created predictive model based on results also of other researchers experimental investigations.