Track 9. Tissue Engineering

6346 We-Th, no. 25 (P62) The Robin Heart telemanipulation user interface Z. Nawrat 1,3, R Kostka 1,2. 1Foundation of Cardiac Surgery Development, Zabrze, Poland, 2Silesian University of Technology, Gliwice, Poland, 3Silesian Medical Academy, Zabrze, Poland

Currently used cardiac surgery robots fulfil the function of manipulators, which main task is to detect and scale up or down the surgeon hand motions and precisely translate them to the movements of robot's arm equipped in appropriated tools. The basic advantages of cardio-robots are safe, reliable and repeatable operative results with less patient pain, trauma and recovery time. The Foundation of Cardiac Surgery Development FCSD have received in 2000 the grant to create robot for cardiac surgery application. The design and optimisation study of user robot interface is prepared in Biocybernetics Lab. and cooperating teams. There are few methods for control the telemanip- ulation system. The most natural for surgeon is the usage of interface based on laparoscopic handle mounted in special mechanical construction able to transfer via encoder signals and computer to arm and tool motors. There is a suitable solutions for surgeons working mostly using traditional methods. For the new generation of surgeons, familar with computer simulation games, it is possible to use manipulates based on joystic solution. The trajectory of operator handle (original and scaled) and trajectory of robot have been tested using of technological top semiconductor accelerometer and gyroscope sensors for acceleration and angle velocity measurements. Performance eval- uation of several versions of user interface for robotically assisted surgery application, base on registration and analysis of the real robot arm trajectory is presented. The basic task consisting in mapping the hand movements of surgeon (operator) into tool arm movement was characterized as well as additional important function (e.g. scaling, tremor removing) and parameters describing whole system were estimated. Advantages of verbal against tactile camera control were determined. In order to evaluate the ergonomy of different ways of surgeon-robot communication the comparison study for different model were carried out.

6054 We-Th, no. 26 (P62) Evaluation of newly developed algorithms for calculating anatomical landmarks from surface contours on the lower extremities C. Hetzer 1 , W. Rapp 1 , M. Witkowski 2, R. Sitnik 2, B. Haex 3, N. Bogeart 3, J. Vander Sloten 3, T. Horstmann 1 . 1Medical Clinic of Sport Medicine, University TEtbingen, Germany, 2Department of Micromechanics, University of Warsaw, Poland, 3Department of Biomechanics and Engineering Design, Katholieke University Leuven, Belgium

The surface contour of the lower leg was analyzed using the method of rasterstereography. Based on the projection of horizontal light lines significant anatomical landmarks were automatically detected by either concave or convex shape. Images from frontal view were recorded from 18 subjects. For landmark verification, plumbum markers were placed on top of patella, tibia tuberositas, caput tibae, midpoint between malleolus and at the femur. The markers were visible on the video image and as well on x-ray images which were needed due to clinical reasons in 6 subjects. The coordinates of the anatomical landmarks were calculated either manually digitising the point on the screen and automatically by special software algorithms. This software analysed the maximal values at a region of interest which should correlate with the manually marked landmarks. The results show average deviations between software and palpated coordi- nates for the patella of 7.2 mm, 6.6 mm for the tibia tuberositas, 10.3 mm for caput tibiae and 8.6 mm for the midpoint of malleolus. From the x-ray images it could be shown, that the automatically analysed coordinates correlates rather well with the location of the markers which were visible on the x-ray. It is obvious that the newly developed algorithms to detect anatomical land- marks from surface contours working well in subjects with a normal BMI. Especially in subjects with higher BMI the deviations were little bit higher. The coordinates from the landmarks can be used as a basis for the development of biomechanical models for the lower leg. The benefit of this can be seen in the automatically recording of anatomical landmarks without using external markers.

7599 We-Th, no. 27 (P62) Optimisation of three-dimensional imaging of the breast region with 3D laser scanners M. Eder, A. Zimmermann, G. Brockmann, L. Kovacs. Department of Plastic and Reconstructive Surgery, Klinikum rechts der Isar of the Technical University Munich, Munich, Germany

Background: The complex anatomic conditions of the female breast require three-dimensional (3D) surface imaging of the breast region in a normal standing position for quality assurance, surgery planning or surgery simulation. The aim of this study was to optimize the imaging technology for the breast

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region with a 3D laser scanner, to evaluate the reproducibility and accuracy of the method. Methods: Avoiding potential human artefacts, such as movement, we tested the most favorable imaging technology on dummy models for scanner-related factors such as the scanner position in comparison with the torso and the number of scanners and single shots. The influence of different factors of the breast region, such as varying breast shapes or pre-marking of anatomical landmarks, was also first investigated on dummies. The dummy models re- sults were compared to the investigations on test persons, and the accuracy of measurements on the virtual models was compared with a coincidence analysis of the manually measured values. Results: Best reproducibility and accuracy of breast region measurements were achieved when landmarks were marked before taking the shots, and when shots at 300 left and 300 right, relative to the sagittal line, were taken with two connected scanners mounted with a +100 upward. However, the reproducibility of the measurements on test persons was significantly lower than those measured on dummies. Conclusions: Correct settings for 3D surface imaging of the breast region with a laser scanner can achieve an acceptable degree of reproducibility and accuracy. 3D surface imaging could develop into a very important instrument for clinical evaluation, surgical planning and eventually even for simulating operations, not only in the field of Plastic and Reconstructive Surgery.

Track 9

Tissue Engineering

7799 We-Th, no. 1 (P63) Evaluation of human osteoblast-like cell adhesion strength on Ti substrates functionalized by bioactive peptide grafting A. Bagno 1 , M. Dettin 1 , A. Piovan 1 , P. Brun 2, R. Gambaretto 1 , G. Fontana 3, C. Di Bello 1 , G. Pal52, I. Castagliuolo 2. 1Department of Chemical Process Engineering, University of Padova, Padova, Italy, 2Department of Histology, Microbiology and Medical Biotechnology, University of Padova, Padova, Italy, 3Department of Medical and Surgical Specialties, University of Padova, Padova, Italy

Endosseous devices in dental, orthopedic and maxillofacial applications, might be designed to support, guide and enhance osteoblast adhesion [1,2]. In fact, cell adhesion is fundamental for implant osseointegration. A recent strategy to improve endosseous implant integration is based on biomimetic surfaces [3], able to present adhesive factors to cells. In the present study, biomimetic surfaces are obtained by covalently grafting two adhesive peptides on oxidized titanium substrates after silanization: (i) an RGD-containing peptide; (ii) a pep- tide mapped on human vitronectin. They act via different mechanisms [4]. The amount of human osteoblast-like cells adhered onto peptide-grafted and not grafted surfaces is estimated as well as the strength of cell binding [5]: results allow comparing the capacity of the bioactive surfaces in promoting cell adhesion.

References [1] Dettin M, Conconi MT, Gambaretto R, Pasquato A, Folin M, Di Bello C, Parnig-

otto PR Novel osteoblast adhesive peptides for dental/orthopedic biomaterials. J Biomed Mater Res 2002; 60: 466-71.

[2] Bagno A, Genovese M, Luchini A, Dettin M, Conconi MT, Menti AM, Parnig- otto PP, Di Bello C. Contact profilometry and correspondence analysis to correlate surface properties and cell adhesion in vitro of uncoated and coated Ti and Ti6AI4V disks. Biomaterials 2004; 25: 2437-45.

[3] Rezania A, Healy KE. Biomimetic peptide surfaces that regulate adhesion, spreading, cytoskeletal organization, and mineralization of the matrix deposited by osteoblast-like cells. Biotechnol Prog 1999; 15: 19-32.

[4] Dettin M, Conconi MT, Gambaretto R, Bagno A, Di Bello C, Menti AM, Grandi C, Parnigotto PR Effect of synthetic peptides on osteoblast adhesion. Biomaterials 2005; 26: 4507-15.

[5] Bigerelle M, Anselme K. Statistical correlation between cell adhesion and proliferation on biocompatible metallic materials. J Biomed Mater Res 2005; 72A: 36-46.

7488 We-Th, no. 2 (P63) Effects of mechanical loading and crosslinking density on gene expression of chondrocytes encapsulated in hydrogels G. Nicodemus, S.J. Bryant. Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO, USA

Loss or damage of articular cartilage at the surfaces of diarthrodial joints can result in pain and eventual loss of mobility. Tissue engineering is a promising approach that aims to regenerate new living tissues. Photopolymerizable hydrogels based on poly(ethylene glycol) (PEG) are attractive materials for

$576 Journal o f Biomechanics 2006, Vol. 39 (Suppl 1) Poster Presentations

tissue engineering for their ability to be gelled in situ with controlled architecture and desired macroscopic properties. In designing an in situ forming cell- scaffold, it is important to understand the impact of mechanical loading on articular chondrocytes within the scaffolds. Specifically, this study examines the influence of gel properties, in the form of the crosslinking density (px), on chondrocyte gene expression in response to loading. Hydrogels were fabricated by varying PEG macromer concentration from 10 to 20% (w/w) to create gels with low and high crosslinking, respectively. Freshly isolated bovine articular chondrocytes were encapsulated in the PEG hydrogels and subjected to dynamic compressive strains (1 Hz, 15% amplitude strain, 24 hours). Gene expression was examined by real time PCR for extracellular matrix genes: collagen II, aggrecan, collagen I and normalized to a ribosomal housekeeping gene (L30). Relative gene expression for collagen II and aggrecan were 1000- fold higher compared to collagen I for all experimental conditions indicating that the native chondrocytes phenotype was maintained. In the absence of loading, relative gene expressions for collagen I and II were significantly higher in gels with increased Px. For example, collagen II relative gene expression was 0.53±0.07 and 0.86±0.08 for the low and high crosslinked systems, respec- tively. Under dynamic loading a slight, but not significant (p = 0.09) increase in collagen I and II expression was observed with increased crosslinking density when normalized to their respective unloaded controls. In conclusion, our studies indicate that crosslinking density significantly alters collagen I and II gene expression while loading has a slight, but not significant effect. Through careful manipulations in gel properties, chondrocyte gene expression may be modulated to achieve a desired response.

7499 We-Th, no. 3 (P63) Water Jet Cutting, an alternative method for cutting cartilage M. Honl, V.K. Shekhawat, C. Pacione, T. Schwenke, M.A. Wimmer. Rush University Medical Center, Chicago, IL, USA

Introduction: Autologous osteochondral transfer is an option for the treatment of articular defects. Chondrocyte viability at graft and recipient edges is stated to be an important determinant of the success of repair. As a tool, water jet (W J) provides a cold cutting process. This study evaluates the feasibility of performing cutting on articular cartilage tissue by the use of plain water jetting. Materials and Methods: Fresh full thickness cartilage explants were obtained from the knee joints of 5 young calves (6-8 months old). Full thickness cartilage explants were removed from the femoral condyles. The intensifier pump allowed pressure variations between 100 and 700 bars. The nozzle (O=0.2mm) was mounted on a gantry with two degrees of freedom. The cutting experiments were performed in displacement control mode, with carti- lage held stationary and the nozzle moving at a traverse speed of 1 mm/s. To calculate the energy typically required for consistent material removal, 40 cartilage samples were cut at various pressure levels using the water jet. Depths of the cut were measured by a Vernier caliper. In the second part of the study 40 osteochondral cylinders were obtained from the femoral condyles using: (a) 8 mm diameter Arthrex OATS punch, (b) 8 mm diameter diamond coated drill punch and (c) the water jet cutting device. Plugs were then assessed for cell viability along the cut periphery by performing live- dead cell staining and viewing under the confocal laser scanning microscope. Results: There was a significant correlation between pressure and cut depth (p<0.001). At a relatively high transverse speed of 1 mm/s cartilage was cut smoothly and easily. The typical material removal energy for bovine cartilage is 7.38.109 J/m 3. The margin of superficial zone cell death at the curved edge was significantly greater in the OATS punch group (390±18 ~tm) and in the diamond drill group (440±18 ~tm), when compared to the WJ group (10±4 ~tm, p < 0.001) Discussion: The dead at the cutting edge was greatly for WJ cut samples, making it a promising technology for cartilage repair. The results of the present study suggest that water jet cutting has the potential to be developed as an alternative means to prepare the cartilage for patients undergoing cartilage transplantation.

6818 We-Th, no. 4 (P63) In v ivo cartilage regeneration using a scaf fo ld- f ree 3-D synthetic tissue cultured from synov ium-der ived cells D. Katakai 1 , H. Fujie 1 , M. Imura 1 , W. Ando 2, K. Tateishi 2, H. Yoshikawa 2, N. Nakamura 2. 1Biomechanics Lab, Kogakuin University, Tokyo, Japan, 2Department of Orthopaedic Surgery, Osaka University Medical School, Osaka, Japan

Introduction: Synovial cells have been reported to have the ability to pro- liferate over many passages without losing their multilineage differentiation potential [1]. We have been establishing a novel scaffold-free 3-D synthetic tissue (3DST), composed of synovial cells and their native extracellular matrix for cartilage tissue engineering [2]. The mechanical properties of porcine cartilage regenerated in vivo with the 3DST were determined.

Methods: Synovial cells obtained from the synovial membrane of porcine knee joints were cultured in DMEM in monolayer. Seven days after the injection of ascorbic acid 2-phosphate, the synthesized matrices were allowed active contraction for 8 hours to develop 3-D synthetic tissues (3DSTs). A round shaped cartilage defect of 8 mm of diameter and 1.5 mm of depth was created on the medial condyle of the femur. The defect was filled with the 3DST, and the porcine were allowed cage activity. Six months after the surgery, a cylindrically shaped cartilage-subchondral bone specimen of 4 mm of diameter and 5 -8 mm of depth was extracted and subjected to a quasi-static compression test and a dynamic creep test. Results & Discussion: At 100 ~tm/s of compression rate, the tangent modulus of the regenerated cartilage with 3DST was significantly higher than those of control cartilage and regenerated cartilage without 3DST. However, the significant difference was disappeared at 4 ~tm/s of compression rate. Dynamic creep deformation of the regenerated cartilage with 3DST was remained control level for the initial 10s, but thereafter the deformation was significantly increased to the level of regenerated cartilage without 3DST. It was suggested that the extracellular matrices produced by the 3DST included much water, which resulted in time-dependent viscoelastic behaviors in response to quasi- static and dynamic Ioadings.

References [1] De Bari C, et al. Arthritis Rheum. 2001. [2] Ando W, et al. 51st ORS, 2005.

6191 We-Th, no. 5 (P63) Adhes ion o f pr imer cells for cartilage tissue engineering E. Eisenbarth 1 , A. Schmidt 1 , O. Krummhauer 2, D. Toykan 2, R. Janssen 2. 1Hamburg University of Technology, Biomechanics Section, Hamburg, Germany, 2Hamburg University of Technology, Advanced Ceramic Group, Hamburg, Germany

According to the Tissue Engineering concept of Meenen and Poertner [1] for the synthesis of porcine cartilage, primer cells are used to enable the contact between carrier material (CAP) and tissue engineered cartilage. A precondition for a Ioadable connection between carrier and cartilage is a tight adhesion of the primer cell monolayer on the CaP-carrier. The adhesion properties of the primer monolayer depend on the used cell type and the surface structure of the carrier. In order to find an optimized combination of primer cell type and surface modification, Hydroxyapatite with variations in porosity and linear surface structures were used as carrier materials. The adhesion of porcine chondrocytes and osteoblast on the structured HA carriers was compared due to spreading area of the cells, stress fiber portion within the cells, contact guidance and collagen I synthesis. Osteoblasts showed an average spreading area on the porous CaP carriers of 2837~tm 2 (s= 1328), compared to Chondrocytes with 620~tm 2 (s=331). The content of F-Actin within the osteoblasts was 464 % that of the chondrocytes on the porous carriers. On the linear structured CaP carriers showed 36% of the osteoblasts contact guidance, but no chondrocytes were linearly orientated to the grinding corrugations on the surface. After five days in contact with the porous CaP carriers the cells did not grow into the pore structures of the porous carrier and decreased their contact area to the porous substrates compared with the contact area of the cells to the linear structured samples. The results allow the conclusion to be drawn that osteoblasts show a tighter adhesion onto the linear structured CaP carriers than chondrocytes and the cell adhesion is better on the linear structured carriers than on the porous CaP substrates.

References [1] P6rtner R., NageI-Heyer St., Goepfert Ch., Adamietz P., Meenen N.M. Bioreactor

design for tissue engineering. Journal of Bioengineering and Bioscience 2005; 100(3): 235-245.

5578 We-Th, no. 6 (P63) Effect o f intermit tent loading on redifferentiation of chondrocytes and cartilage formation K. Wiegandt 1 , J. Heyland 1 , C. Goepfert 1 , S. NageI-Heyer 1 , U. Schumacher 2, R. P6rtner 1 . 1 Institute of Bioprocess- and Biochemical Engineering, Hamburg University of Technology, Hamburg, Germany, 2Department of Anatomy Ih Experimental Morphology, University Medical Center Hamburg-Eppendo~ Hamburg, Germany

Since cartilage is exposed to intermittent hydrostatic pressure due to everyday activities, it is hypothesized that loading causes a stimulating effect on the metabolism of chondrocytes. Thus, the aim of this study was to investigate the influence of intermittent hydrostatic loading on the redifferentiation of chondrocytes during cartilage formation in vitro. Cartilage-carrier-constructs were generated according to a 3-phases-system by NageI-Heyer et al. using adult porcine chondrocytes. Therefore, cells were expanded in T-flasks until passage 3, afterwards cultivated in an alginate gel for two weeks, recovered from the gel and seeded onto a microporous