Assessing conformal thin film growth under nonstochastic deposition conditions: application of a phenomenological model of roughness replication to synthetic topographic images.

In this work, a simple method to follow the evolution of the surface of thin films during growth on substrates characterised by high roughness is detailed. To account for real cases as much as possible, the approach presented is based on the hypothesis that deposition takes place under nonstochastic conditions, such as those typical of many thin film processes in industry and technology. In this context, previous models for roughness replication, which are mainly based on idealised deposition conditions, cannot be applied and thus ad hoc approaches are required for achieving quantitative predictions. Here it is suggested that under nonstochastic conditions a phenomenological relation can be proposed, mainly based on local roughening of surface, to monitor the statistical similarity between the film and the substrate during growth or, in other words, to detect changes of the bare substrate morphological profile occurring during the film growth on top. Such approximation is based on surface representation in terms of power spectral density of surface heights, derived from topographic images; in this work, such method will be tested on two separate batches of synthetic images which simulate thin films growth onto a real rough substrate. In particular, two growth models will be implemented: the first reproduces the surface profile obtained during an atomic force microscopy measurement by using a simple geometrical envelope of surface, regardless the thin film growth mechanism; the second reproduces the columnar growth expected under nonstochastic deposition conditions. It will be shown that the approach introduced is capable to highlight differences between the two batches and, in the second case, to quantitatively account for the replication of the substrate roughness during growth. The results obtained here are potentially interesting in that they account essentially for the geometrical features of the surfaces, and as such they can be applied to synthetic depositions that reproduce different thin film depositions and experimental contexts.

Thin film deposition onto rough surfaces is widespread among many industrial and technological applications such as photovoltaics, microelectronics, optics and biomedicine just to mention a few. In such cases, compared to substrate morphology, film deposition may be required to improve certain surface functionalities through roughening or smoothing of the pristine substrate morphology to accomplish different needs or applications. This raises a simple and legitimate question: how could the degree of replication of the substrate morphology after film deposition be determined? Quantitative approaches to this issue involve statistical descriptions of the two interfaces in terms of power spectral densities retrieved from scanning probe microscopy images of the surface. However, this requires an in-depth knowledge of the physics behind the process of film formation, leading to a complication in that models providing quantitative predictions for film conformality are based on ideal deposition conditions; thus, numerical results remained so far restricted to the case of atomically flat, and mostly unrealistic, surfaces. To tackle into this subject, an approximation is suggested that is based on phenomenological considerations and on the hypothesis that deposition is nonideal. On these premises, a simple conformality factor derived from a linear relation is introduced to relate the substrate and the evolving film morphology. Such approach is then applied to simulated atomic force microscopy images which describe the film growth onto a real substrate. Two models will be implemented: the first uses a simple geometrical envelope of the surface that uniquely matches with experiments without keeping into account the mechanism of growth, while the second reproduces the columnar growth expected under real deposition conditions. The application of conformality factors to the images so obtained shows that the second model accomplishes well to the final goal of obtaining quantitative results and enables to retrieve quantitative information especially in case of micro or nanometrically structured surfaces.

Virtual simulation of an osseointegrated trans-humeral prosthesis: A falling scenario.

INTRODUCTION: Traditional prosthetic solutions expose the amputee to numerous problems that limit his ability to safely perform the normal activities of daily life. In order to eliminate the problems related to the use of the traditional prosthesis with socket, a new technique was developed for fixing the prosthesis to the amputees based on the principle of osseointegration. The aim of this paper is to study and analyze the stress distribution on the interface between a trans-humeral osseointegrated prosthetic implant and the residual bone, identifying the most stressed areas and thus foreseeing possible failure phenomena of the entire prosthetic system and, after, to compare the stress distribution on three different prosthetic designs that differ from each other for some geometric characteristics. MATERIALS AND METHODS: A healthy individual mimics two fall scenarios of which the trans-humeral amputees can most likely be victims: Static fall and Dynamic fall. A force platform (P-6000, BTS Bioengineering) is required for load data acquisition. The CAD model of the trans-humeral osseointegrated implant was created following the guidelines of the OPRA implant. The bone model was created starting from the CAT scan of a left humerus. The FEM simulation was conducted throught a linear analysis. RESULTS: Both during static fall and dynamic fall, similar trends have been observed for the reaction force Fz, the torque moment Tz, the bending moments Mx and My. From the analysis of the von Mises stress distribution it was found that the stress distribution is more homogeneous in the case where the thread of the fixture is made by a triangular profile with height of the thread equal to 0.5 mm. However, it can be seen that, when passing from a thread with height of 0.5 mm to a 1 mm, there is a slight decrease in the stress on the whole contact zone between the fixture and the humerus. The same improvement can also be seen in the case of trapezoidal threading. CONCLUSION: By modifying the height and/or by varying the thread profile, are obtained slightly better results with respect to the case with a 0.5 mm height triangular thread.

How cartilage status can be related to joint loads in anterior cruciate ligament reconstruction: a preliminary analysis including MRI t2 mapping and joint biomechanics.

The knee is the largest and most complex joint in the human body. Traumatic events, such as anterior cruciate ligament (ACL) tear, can lead to an alteration of joint tissues homeostasis. Literature reports an evident correlation between abnormal joint biomechanics and the status of articular tissues. These alterations, due to a sub-optimal ACL reconstruction, may result in an increasing risk of developing degenerative pathologies, such as osteoarthritis. Thus, the identification of the optimal surgical technique is a highly demanding issue in ACL reconstruction. The aim of this study was to analyze the correlation between joint cartilage conditions and knee biomechanics in ACL reconstructions, by integrating MRI T2 mapping investigations, radiostereophotogrammetry-based gait analysis and subject-specific musculoskeletal modelling.

Total knee replacement: intraoperative and postoperative kinematic assessment.

BACKGROUND AND AIM: The main goals of the total knee arthroplasty (TKA) is to reduce the perceived pain and  restore knee mobility and function in case of osteoarthritic knees joints. Literature shows how the three major causes of TKA failures are related to wear, loosening and instability and this is due to a problem of imbalance and malalignment. Intraoperative and postoperative kinematics analysis could be of benefit for improving surgery outcome. The aim of the present paper is to give an overview of the two set-up with the highest accuracy for intraoperative and postoperative TKA kinematics evaluation, currently in use at Istituto Ortopedico Rizzoli. Introperative and Postoperative Evaluation: For intraoperative evaluation it has been presented a navigation system with a specifically developed software, while for the postoperative it has been presented the roentgen stereophotogrammetric analysis (RSA). The navigation system consists in a laptop connected with an optoelectronic localizer (Polaris, Northern Digital Inc, Canada).  Two reference arrays with passive optical markers and a marked probe are used to localize the knee joint in the 3D space and track the joint kinematics. The RSA is a radiographic technique used in orthopaedic field for measuring micromotion at bone/prosthesis interface or for joint kinematics evaluation. The RSA uses two X-ray sources synchronized with two digital flat-panels. CONCLUSIONS: The present paper shows that using the navigation system allows the surgeon to easily perform kinematic and alignment evaluation during TKA surgery while the RSA allows a quantitative evaluation of the joint kinematics during the recovery time.

DOES TOTAL KNEE REPLACEMENT MODIFY FLEXION AXIS OF THE KNEE ON FRONTAL AND AXIAL PLANE REGARDLESS FROM LIMB ALIGNMENT?

The optimal reference for rotational positioning of femoral component in total knee replacement (TKR) is debated. Navigation has been suggested for intra-op acquisition of patient’s specific kinematics and functional flexion axis (FFA). The main purpose of the present study is to prospectively investigate whether pre-operative FFA in patients with osteoarthritis (OA) and varus alignment changes after TKR and whether a correlation exists between post-op FFA and pre-op alignment. A navigated TKR was performed in 108 patients using a specific software to acquire passive joint kinematics before and after TKR. The knee was cycled through three passive range of motions (PROM), from 0° to 120°. FFA was computed using the mean helical axis algorithm. The angle between FFA and surgical TEA was determined on frontal (αf) and axial (αa) plane. The pre- and post-op hip-knee-ankle angle (HKA) was determined. Post-op FFA was different from pre-op FFA only on frontal plane. No significant difference was found on axial plane. No correlation was found between HKA-pre and αA-pre. A significant correlation was found between HKA-pre and αF–pre. The study concluded that TKR modifies FFA only on frontal plane. No difference was found on axial plane. Pre-op FFA is in a more varus position respect to TEA. The position of FFA on frontal plane is dependent on limb alignment. The present study has demonstrated TKR modifies the position of FFA only on frontal plane. The position of FFA on axial plane is not dependent on the amount of varus deformity and is not influenced by TKR. Level of evidence, IV, case series.

Probabilistic model of ligaments and tendons: quasistatic linear stretching.

Ligaments and tendons have a significant role in the musculoskeletal system and are frequently subjected to injury. This study presents a model of collagen fibers, based on the study of a statistical distribution of fibers when they are subjected to quasistatic linear stretching. With respect to other methodologies, this model is able to describe the behavior of the bundle using less ad hoc hypotheses and is able to describe all the quasistatic stretch-load responses of the bundle, including the yield and failure regions described in the literature. It has two other important results: the first is that it is able to correlate the mechanical behavior of the bundle with its internal structure, and it suggests a methodology to deduce the fibers population distribution directly from the tensile-test data. The second is that it can follow fibers' structure evolution during the stretching and it is possible to study the internal adaptation of fibers in physiological and pathological conditions.

Validation of a new protocol for computer-assisted evaluation of kinematics of double-bundle ACL reconstruction.

BACKGROUND: Computer-assisted surgery is useful to increase the precision of anterior cruciate ligament (ACL) surgical procedure, but could be even more important in evaluating the global performance of reconstructed ACL. This paper describes a new protocol for an accurate and extensive computer-assisted evaluation of single- and double-bundle reconstructions of ACL. METHODS: The protocol consists of the acquisition of the leg axes, ACL and graft insertions by a navigation system, and tracking of the knee motion during the classical kinematic test of knee stability. These data are elaborated by computer software in order to compute graft biomechanical behaviour and the knee kinematics and estimate the performance of the intervention. FINDINGS: The proposed protocol was validated on three cadaver knees. It resulted minimally invasive, effective to describe graft kinematic performance and able to provide a 3D reliable description of the reconstructed knee. INTERPRETATION: The protocol is an extension of the present evaluation of computer-assisted packages and includes additional kinematic tests and computations. The scientist-reader can find important details on tested computations to implement a similar computer-assisted procedure for new applications in knee surgery, while the surgeon can find in this procedure a means to improve the evaluation of ACL reconstruction and identify the residual laxity.

Prueba bactericida con ultraestructura para el diagnostico de enfermedad granulomatosa cronica. / Bacterial testing with leucocyte ultrastructure in chronic granulomatous disease diagnosis

Se presenta el caso de un nino de 4 anos de edad con cuadro clinico y anatomopatologico compatible con enfermedad granulomatosa cronica. Se realizaron las pruebas de nitroazul de tetrazolio (NBT) y bactericida leucocitaria con exame ultraestructural. Las dos pruebas anteriores confirmaron el defecto de la funcion bactericida-oxidativa leucocitaria. El examen con microscopio electronico fue utilizado para hacer diagnostico diferencial con otras enfermedades de los fagocitos que presentan alteraciones ultraestructurales

Prueba bactericida con ultraestructura para el diagnostico de enfermedad granulomatosa cronica. / Bacterial testing with leucocyte ultrastructure in chronic granulomatous disease diagnosis

Se presenta el caso de un nino de 4 anos de edad con cuadro clinico y anatomopatologico compatible con enfermedad granulomatosa cronica. Se realizaron las pruebas de nitroazul de tetrazolio (NBT) y bactericida leucocitaria con exame ultraestructural. Las dos pruebas anteriores confirmaron el defecto de la funcion bactericida-oxidativa leucocitaria. El examen con microscopio electronico fue utilizado para hacer diagnostico diferencial con otras enfermedades de los fagocitos que presentan alteraciones ultraestructurales