Marco Viceconti

..Thus, is biomechanically possible that spontaneous femoral neck fractures occur during level walking, due to a combination of severe osteoporosis and severe neuromotor degradation...

....

..Preliminary tests showed that a stem with the addition of such fins presents good primary stability in all tested conditions...

..Aim of the present study is to quantify the minimum thickness of mechanically non-bearing regions around a cementless prosthesis necessary to loose the implant enough to activate interface tissue differentiation...

..The results obtained from simulations suggest that the strategy the hip replacement patient adopts to perform a given motor task, may be, for the implant stability, equally or even more critical than the type of motor task performed...

....

..For this reason, the automatic method should be chosen to develop the automatic positioning of a stem in a database of anatomies...

..8 mm and 16.7 deg for the 3D-rendering interface. The results of this study indicate an important effect of the type of visualization modality used to represent CT data on final accuracy of the planning operation...

..However, some of these methods can already be successfully used in various application contexts, and a few guidelines are drawn...

..The surgical planning performed with the Hip-Op system is accurate and repeatable, especially for the socket and for less experienced surgeons...

..openmaf.org) indicate that it is possible to develop effective environments for interactive visualisation of multiscale biomedical data...

..For the varus configuration, which lacks cortical support, the algorithm predicted a completed loosening...

..Thus, it may be concluded that the method presents a generality sufficient to cope with almost any orthopaedic application...

..The proposed approach is illustrated using the validation of a cemented epiphyseal stem as an example...

..The proposed method can be used to evaluate new designs in conditions more representative of the variability in clinical practice...

..The experimental and numerical results showed the validity of the new fixation concept, although a further optimisation of the geometry of the cement pockets is needed in order to further reduce the stresses in the cement...

..However, there is indirect evidence that simple anatomical information may not be sufficient for the surgeon to decide size and position of the implant in a repeatable manner...

..All the other models presented errors higher than 20 micrometer assumed in the present study as an accuracy threshold...

..Other important determinants were found to be the adoption of an incremental software engineering strategy, well suited for small to medium projects and the presence in the development staff of a technology transfer expert...

..From the results of this study, it may be concluded that three dimensional segmentation algorithms are useful not only in visualisation applications but also in the creation of geometry models...

..For this category, which includes artificial neural networks, Bayesian models and integrative models, the definition of a generic falsification strategy requires further investigation by researchers and philosophers of science...

..This methodology allows an accurate three-dimensional modelling of operated bone which have been implanted with high density metallic devices which produce relevant artefacts in post-operative CT images...

..These good results were achieved because of the integration of the vectorial description of the prosthetic component with the raster description of the CT data that allowed the designer to use all details available in the CT images...

..While the Data Manager is clearly still only at the prototype stage, we believe that it is already capable of being used to solve a large number of problems common to many biomedical engineering activities...

..The proposed method was used to convert the CT scan data set of a human femur into a valid CAD model; the resulting solid was two times more accurate than that obtained using the commonly used procedure based on 2D segmentation...

....

..Hence, the best way to achieve the dream of personalised, preventive, and participative medicine at sustainable costs will be through the integration of all available data, information and knowledge...

..After being evaluated in an internal clinical trial, the software is currently made available as freeware at http:// www.ior.it/hipop/...

..Stem size, based on templating and pre-operative planning software, only partially avoids stem mis-sizing. Mis-sizing can produce implant instability and/or wasting the wrong-sized stem...

..Concerns recently arose concerning the long-term endurance of such implants in active patients. In fact, it was suspected that cyclic loads applied by demanding patients could lead to fixation failure...

..To our knowledge, this study represents the most extensive collection of whole-bone biomechanical properties of lower limb bones...

..This study addresses the risk of femoral neck fracture associated with resurfacing hip prostheses. A novel cemented Proximal Epiphyseal Replacement (PER) featuring a short curved stem was investigated...

..3% and from 228% to 134% of the maximum measured strain, respectively. The stress fields predicted inside the bone were also significantly different. A new software implementing the second strategy was made available in the public domain...

..Similarity in wear tracks observed on tibial inserts and other retrieval studies, coupled with clinically consistent migration patterns for TKR, supports the efficacy of the new in vitro method presented...

....

..The presented method is hence robust enough to be used for investigating the mechanical behavior of bones with subject-specific finite-element models derived from CT data taken in vivo...

..For the socket the average differences increased to 8 mm and 10 degrees. The study shows the need for a more informative planning environment and for intra-operative supports, especially when deformed anatomies are involved...

..More work is needed in the future to integrate all levels fully, while following a sound scientific method to assess the relevance and validity of such an integrated model...

..The scope of this study was to investigate whether stem undersizing and a thin cement mantle are sufficient to cause implant loosening...

..This validated model can support realistic simulations to examine physiological load configurations and the effects of variations in prosthesis design and implantation technique...

..The convergence behaviour of the model was not worsened by the introduction of inhomogeneous material properties. The software was made available in the public domain...

..The full coupling between the thermal and the mechanical conditions used in this study appears to be necessary if accurate predictions of the polyethylene deformation are required...

..The K(IC) mean value was 1.38 MPa x m1/2. These experimental results provide the set of necessary inputs for numerical studies aimed to investigate the damage accumulation process in the mantle fixing cemented prostheses...

..However we can consider the possibility that sub-optimal activations of the muscular system play a role in spontaneous fractures not associated with falls...

....

..The secondary aim was to compare osteoarthritic and non-pathological bone considering the correlation between structure and bone volume fraction...

..It then uses one particular project, the Living Human Project, to illustrate the type of advances that are taking place to further the aims of the VPH and similar initiatives worldwide...

..The resulting system is thus directed to prostheses manufacturers and addresses a market segment that appears to have a steady growth in the future...

..The Framework is based on a collection of portable libraries and it can be compiled on any platform that supports OpenGL, including Windows, MacOS X and any flavor of Unix/linux...

..The model predictions found an indirect clinical validation when the child was allowed to perform short unprotected walks and did not experience any fracture...

..Such a difference was comparable to the fluctuations observed between different parts of the curve. Therefore, it can be concluded that the proximal femur has a linear-elastic behavior up to fracture, for physiological strain-rates...

..This study aimed to determine the short- and long-term effects of embalming, using a solution with 4% formalin concentration, on the mechanical properties of human cortical bone...

..This study has demonstrated that the application of VR environment for pre-operative planning of total hip replacement may help to shorten the duration of the positioning and to yield consistent results even with first-time users...

..A similar conclusion can be drawn for age, although a larger donor sample size would be necessary to definitively exclude the existence of a slight effect...

..Consequently, it is suggested that TMD can be managed as a constant in computational models, varying only BV in relation to clinical densitometric analysis...

..The proposed approach of considering both tissue anisotropy and inhomogeneity improved the accuracy in predicting the mechanical behaviour of cancellous bone tissue and should be suitable for more general loading conditions...

..The few cement cracks found were mainly localized in proximity of a proximal drainage hole. It is foreseen that when this detail is optimized, long-term endurance will further improve...

..The effective dose is comparable to that of a standard pelvic CT exam. Adjusting the axial CT scan parameters the effective dose can be reduced, however lowering the accuracy of 3-D bone geometry reconstruction...

....

..Modular necks tested with higher load magnitudes and those coupled with larger, stiffer femoral stems were readily distinguished and showed significantly larger areas of burnished smooth and textured damage...

..is preferable when the full bone surface is accessible (typically during in vitro tests). Conversely, no advantage in terms of repeatability seems to exist between the reference frames proposed by Cappozzo et al. and ISB...

....

..A maximum principal strain criterion can thus be defined a suitable candidate for the in vivo risk factor assessment on long bones...

..In fact, ash density was found to be a good predictor of strength and stiffness, also for cortical bone collected from children. Finally, the present findings support the hypothesis that compressive yield strain is an invariant...

..This angle should be reduced as much as possible (in the present work the average value was 6.6+/-3.3 degrees), in any case measured, and always reported together with the mechanical parameters of cancellous bone...

..Moreover, the in vivo testing demonstrated that the developed methods provide reasonable quantitative indicators of the stem positioning in the femoral CT dataset...

..Thus, we can conclude that skeletal virtual palpation can be performed directly on the CT dataset, as far as the virtual palpation is performed with a multimodal display interface...

..The proposed method is general, robust, automated, and accurate enough to be used in bone FE modelling from diagnostic data, and prospectively in applications such as statistical shape modelling...

..These regions mostly contain minimum values in BV/TV, which were found to predict ultimate stress better than average BV/TV...

....

..However, above this number of cycles, stem preheating seems to reduce the probability of failure. These findings are discussed in the text...

..This innovative set-up was able to reproduce stable and reliable measurements. The results obtained encourage further investigations of this set-up for long-term assessment and using different combinations of materials...

....

..The results showed that the examined VR technology does not show a sufficient positioning accuracy to be considered for clinical assessment...

..This observation seems to confirm that along the fibula shaft the orientation of collagen fibers within the osteons is consistent with the loading conditions which the bone undergoes...

..This study demonstrated a good repeatability among the stations of the knee simulator obtaining weight loss values congruent with those found by other authors using similar test conditions...

..Failure load should be reported as a fraction of donor's body-weight to reduce variability. The proposed method can be used to investigate the reason and mechanism of failure of natural and operated proximal femurs...

..Hence, the present study confirms that it is possible to accurately predict the level of primary stability achieved for cementless stems using numerical models that account for patient specificity and surgical variability...

..New cements can be assessed in comparison with other cements with known (positive/negative) clinical outcome, tested with the same protocol...

..This research demonstrated that adding one single biomechanical indicator to the standard clinical measurements improves the identification of patients at-risk of femoral neck fracture...

..6%, peak error=35%). The results showed that it is possible to automatically generate accurate finite element models of bones from CT data and that the strategy of material properties mapping has a significant influence on its accuracy...

..Although this study had a limited sample size, it provides novel pre-clinical indications about the potential of ceramic TKR femoral components...

....

..The cantilever beam model suggested that, although the autograft is currently subjected to subcritical stresses. morphological evolution could increase the risk of fracture in the next few years if a normal level of loading were allowed...

..Conversely, alterations were moderate where the strain was higher. Thus, prosthesis-to-bone load transfer of both devices has been elucidated; the prototype preserved a stress distribution closer to the physiological condition...

..The result was efficient, repeatable and easy to use software for the evaluation of the femoral neck fracture risk to be inserted in the daily clinical practice providing a useful tool for the improvement of fracture prediction...

....

..The aims of this study were to investigate the initial strength and failure mode of different tendon grasping techniques and to evaluate an alternative stitch proposed for arthroscopic repair of rotator cuff tendons...

..The antibiotics added to bone cements may, however, have detrimental effects on the mechanical properties of the cement...

..LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence...

..7). Multifactorial analysis demonstrated that stem size was influenced by sex, age, and height, but not by weight. Besides this, there was an interaction between sex and age: in women, but not in men, the stem size increased with aging...

..Meshless methods, which do not rely on a pre-defined topological discretisation of the domain, might greatly improve the numerical process automation, but currently their application to biomechanics is negligible...

..Medical images can be showed on the device display, but also transferred to a high-resolution monitor. Large amount of data can be dictated and translated by remote continuous speech recognition...

..8%) in comparison to the left one (23.2%) in the left-footed patients. The authors suggested that, in left-footed patients, the right side was subjected to greater stress...

..The purpose of this study is to report a reprocessing protocol applied to explanted osteosynthesis devices obtained at a leading trauma care hospital...

..The presented results show, in addition, that the adoption of a single density-elasticity relationship over the whole bone density range is adequate to obtain an accuracy that is already suitable for many applications...

..All simulations show a peak strain at the femoral neck region with a strain distribution typical of a fall on the side. The proposed method seems to supply a useful tool for the in vivo analysis of the risk of hip fracture...

..Since it is possible to mould specimens without macroporosity, it seems recommendable to reject specimens with macroporosity on the fracture surface before calculating the KIc value of bone cement...

..The in vitro wear of meniscal components can be assessed using a four-station joint simulator. The study was aimed at comparing wear patterns obtained in vitro with those observed in implant retrievals with the same design...

..The study demonstrates that the Bayes linear classifier can be a valid alternative to multiple logistic regression in the classification of osteoporotic patients...

..Once properly integrated in an easy-to-use application, the described method could finally make feasible many clinical applications of finite element analysis...