Paper Submission & Registration
8th Dutch Bio-Medical Engineering Conference
16:30   Implants
Chair: Antoine Nonclercq
15 mins
Optimization surgical mandibular body fracture treatment using finite element method and polymeric model testing: effect of osteosynthesis plate positioning and mandibular body height decrease on unilateral stright-line mandibular body fracture stability
Omid Daqiq, Rudolf R M Bos, Baucke van Minnen
Abstract: The aim of this study is optimizing surgical treatment for mandibular body fracture with different plate positioning and different mandibular body height, using finite element method (FEM) and polymeric model testing, therefore develop a guideline for the plate selection and positioning based on FEM in order to improve the clinical outcome. This study investigates two problems regarding the use of osteosynthesis systems for mandibular body fracture fixation stability, namely the effect of plate positioning and the effect of mandibular body height decrease. Extracted computed tomography (CT) images of cadaveric mandibles with heights of resp. 21, 15, and 10 mm were used to create a FEM-model in Comsol software. The FEM-model included a standard commercially available 6-hole 2 mm titanium miniplate with a length of 36.3 mm and 6 x 2 mm miniscrews with a length of 18.4 mm. Different assemblies were studied defined by different plate positioning on different mandibular body heights in which a unilateral straight-line fracture was modelled. The model was verified by mesh refining. The FEM outcome was compared with a series of mechanical tests with polymeric mandible models fixed in a customized device and loaded with a mechanical test bench. Furthermore, all outcomes were compared with earlier publications. The outcomes of FEM analysis and polymeric model testing were highly comparable and similar to earlier publications. Firstly, the optimal location for osteosynthesis plate positioning appears to be the upper border of the mandibular body due to the tensile force on the plate and compression force at the lower border of the fracture site. Secondly, A lower mandibular body height introduces increased instability and thus requires a stronger fixation. Finally, current surgical treatments for mandibular body fracture can be studied and optimized with the use of FEM analysis.
15 mins
The effect of interference fit on primary stability of cementless TKA tibial components
Esther Sanchez, Christoph Schilling, Thomas M. Grupp, Alexander Giurea, Nico Verdonschot, Dennis Janssen
Abstract: INTRODUCTION: Total knee arthroplasty (TKA) is the most common and successful surgical procedure to treat osteoarthritis. However, the tibial component is considered the weak link, showing more aseptic loosening than the femoral component. The fixation of cementless tibial components depends on the difference in dimensions between the tibial implant and the tibial cavity prepared during surgery, also known as the interference fit. The optimal amount of interference fit to achieve good initial stability is still unclear. Therefore, this study investigates the effect of using tibial components with different interference fit on primary stability by measuring the micromotions and gaps at the bone-implant interface. METHODS: Two cementless e.motion® tibial components (Aesculap AG) with 350µm and 700µm interference fit were implanted in six pairs of human cadaveric tibia (47-60 years). The Orthoload peak loads of gait (1960N) and squat (1935N) were applied to the specimens with a custom made load applicator. The micromotions and opening/closing gaps were measured with Digital Image Correlation (DIC) in 6 different regions of interest (ROIs). Two General Linear Mixed Models were created with micromotions and gaps as dependent variables, the ROIs, bone quality, loading conditions, and implant design as independent variables, and the specimens as the subject variables. RESULTS: No significant difference was found for the micromotions between the two interference fits (gait p = 0.755, squat p = 0.232), or for closing gaps (gait p = 0.474, squat p = 0.269). In contrast, significant differences were found between the ROIs. Closing gaps (negative values) were seen for most of the ROIs. The posterior ROIs (PM and PL) showed more closing than seen in the anterior ROIs (AM and AL) for both loading configurations. CONCLUSION: The results demonstrate that increasing interference fit does not automatically influence the primary stability of a tibial TKA component. The exact relation between interference fit and primary implant stability still remains subject to debate and requires further evaluation, possibly utilizing a computational technique approach. SIGNIFICANCE: It is necessary to ensure good primary stability between the bone and the implant for better long-term fixation and reduce the risk of implant loosening.
15 mins
Adhesives for fixation of polycarbonate urethane implants to the bone
Pardis Farjam, Edsko E.G. Hekman, Jeroen Rouwkema, Gijsbertus J Verkerke
Abstract: The use of polyurethane in medical applications has been reported and evaluated by several authors. For use in orthopaedics, there is particularly one member of the polyurethane family, the polycarbonate-urethane (PCU), which has great potential. PCU demonstrated promising characteristics to be used in orthopaedic implants. These include; good biocompatibility and mechanical properties, similarities to natural cartilage, and good wear properties. This makes the use of polycarbonate-urethane in orthopaedic applications compelling. They can be involved in a diverse range of orthopaedic implants including but not limited to joint replacement implants. Success in the application of an orthopaedic implant depends on multiple factors. Implant design, surface configuration, fixation method and surgical procedure play critical roles to decrease the failure rate of implantation. An insufficient fixation technique may cause serious issues such as movement, delamination, deformation and detachment of an implant which leads to failure of the implant and thus the requirement for additional treatment. Utilizing an adhesive as the fixation technique would revolutionize the field of orthopaedic surgery. Adhesives form an anchorage based on a chemical and/or physical bonding rather than relying on bulky mechanical interlockings which are currently the golden fixation technique. So employing adhesives as the anchorage tool brings numerous advantages, such as: preserving the integrity of the tissue and the implant with introducing no invasiveness, possibility to be delivered via minimal-invasive techniques and offering simple and precise applicability. We currently are designing a novel joint replacement prosthesis, build from PCU which adhesives could realise its firm fixation to bone. Purpose In this study we will evaluate commercial biocompatible adhesives as a candidate fixation technique for PCU based orthopaedic implants. Method We will analyse adhesion strength of a biocompatible cyanoacrylate-based adhesive in PCU-bone bond by performing mechanical in vitro tests. The tests will be conducted according to ASTM standards; F2258 for strength properties of tissue adhesives in tension and F2255 for strength properties of tissue adhesives in lap-shear by tension loading.
15 mins
Label-free stimulated Raman scattering imaging reveals silicone breast implant material in tissue
Ludo van Haasterecht, Liron Zada, Robert Schmidt, Erik de Bakker, Ellis Barbé, Dick Vethaak, Susan Gibbs, Johannes de Boer, Frank Niessen, Paul van Zuijlen, Marloes Groot, Freek Ariese
Abstract: Millions of women worldwide have silicone breast implants. It has been reported that implant failure occurs in approximately ten percent of patients within 10 years, while the extent to which silicone debris from breast implants impacts women's long-term health is not fully understood. Research into the role of silicone debris in breast implant-associated ailments is difficult as no sensitive detection technique exists. We show the feasibility and sensitivity of stimulated Raman scattering (SRS) imaging to specifically detect silicone material in stained histopathological slides, without additional sample treatment. SRS imaging entails the synchronized action of two overlapping laser beams of a different wavelength. This results in stronger signals than conventional Raman scattering, circumvents fluorescence from the sample and cover slip, while speeding up the detection enormously. These characteristics make SRS an excellent technique for label-free vibrational imaging of biological tissues. Histology slides of four periprosthetic capsules were obtained after implant removal, as well as an enlarged axillary lymph node from a patient with a ruptured implant. Image acquisition consisted of obtaining a bright-field picture of the entire histological slide, after which the sample was scanned at two different wavenumbers, which were specifically chosen to maximize the contrast between silicone and the surrounding tissue. These images were coregistered to reveal the distribution of silicone material in the tissue. All four implant capsules contained measurable amounts of silicone. The lymph node tissue displayed an abnormal vacuolated aspect and abundant silicone material, illustrating the migration of implant material to distant organs. The capsule from a non-ruptured implant, initially included as a potentially negative control, unexpectedly revealed large agglomerations of silicone. This method facilitates research into immunological mechanisms present in the tissue surrounding implants, while simultaneously providing a quantitative evaluation of silicone content. Comparing these data for different implant types, surgical techniques and patient characteristics should result in a better understanding of the role that implant debris plays in pathophysiological mechanisms related to silicone breast implants.

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