The load bearing joints of the human body and particularly the ankle are often seriously damaged because of different pathological events. During the last 10 years a lot of total ankle prostheses have been studied and implanted. in consequence of the inadequate results obtained by arthrodesis (i.e. the fusion of the joint).The aim of this paper is to analyze mechanical features (functional, kinematic, and strength) of the ankle joint in order to provide optimized design criteria of an arthroprosthesis substituting the disabled joint. c 100

Many applications in orthopaedic surgery require the creation of personalised design models that can serve as the basis for navigation in computer aided surgery systems or be used to create a personalised model to perform structural analysis during pre-operative planning or post-operative follow-up. The paper introduces a method for developing a three-dimensional (3D) patient-specific model of a femur bone from an antero-posterior radiograph. A generic femur was employed and was altered on the basis of bone boundaries visible on radiographs. Morphological errors were evaluated against 3D models obtained from computed tomography (CT) scans. When only the antero-posterior radiograph was used, the average radius estimation error was 4.8 mm, the average percentage area estimation error was 14%, and the average percentage estimation error for inertial moments was 15%. If both the medial-lateral and the anterior-posterior radiographs were used, these errors were 2.0 mm, 5% and 7%, respectively. The procedure described can be profitably employed whenever CT scans are not available, such as during a retrospective analysis, or when CT scans cannot be justified because of X-ray exposure and cost considerations.

The internal bony structure of ten dentate human mandibles was examined on lateral radiograms, and the condylar shape measured with a digital electronic machine. The external surface was coated with photoelastic material. Each mandible was then placed in centric occlusion with brass replicas of the upper arch and the glenoid fossae and set in a supporting frame. Occlusal loads were simulated and the isoclinics recorded in plane-polarized light. The isostatic flow lines were constructed for each mandible. A relation was found between the mandibular structure and the distribution pattern of these lines.

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When a metallic material is highly stressed, its internal specific damping capacity increases showing a nonlinear behavior. In spite of this, the most part of experimental methods employ nonhomogeneous stress fields measuring only a volumetric average, often called structural damping. To overcome this problem the procedure herein presented extends the applicability of the plain traction or compression methods to higher frequency range (up to 300 Hz). The introduced methodology corrects for elastic energy and dissipated energy relative to the test machine and to the fixtures. The experimental procedure is based on the acquisition of a decay signal when the test machine excitation force has been removed. Two different methods to extract the pattern of internal damping versus material strain have been compared: one is based on least square exponential fitting while the other employs an autoregressive model. Best results have been obtained combining the two techniques taking into account also the variation of Young’s modulus with strain. The resulting curves of the loss factor as a function of strain amplitude for three steels and two cast irons are presented.

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