RESUMEN
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.
Asunto(s)
Fémur/diagnóstico por imagen , Modelos Anatómicos , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Fémur/anatomía & histología , Humanos , Imagenología Tridimensional/métodos , Cirugía Asistida por Computador/métodos , Tomografía Computarizada por Rayos X/métodosAsunto(s)
Absorciometría de Fotón/métodos , Articulación de la Cadera/diagnóstico por imagen , Procesamiento de Imagen Asistido por Computador , Remodelación Ósea , Calibración , Intervalos de Confianza , Prótesis de Cadera , Humanos , Reproducibilidad de los Resultados , Proyectos de Investigación , Programas Informáticos , Grabación en VideoRESUMEN
Video-densitometric analysis has proved useful in the study of bone remodelling, however, for more efficient results, an investigation procedure that enables the comparison of X-rays is needed. In the present research an automated method has been developed which considerably speeds up the entire procedure through the implementation of specially designed C++ software. At present, a sequence of six X-rays can be analyzed in about 1 h irrespective of the number of areas to be investigated, which can be arbitrarily increased (200 or more). Analysis is fast as well as more reliable and accurate. In clinical practice, the results offer an effective support to observation on the biomechanical behaviour of bone implant systems.
Asunto(s)
Absorciometría de Fotón/métodos , Remodelación Ósea , Huesos/diagnóstico por imagen , Absorciometría de Fotón/estadística & datos numéricos , Huesos/fisiología , Estudios de Evaluación como Asunto , Prótesis de Cadera , Humanos , Intensificación de Imagen Radiográfica/métodos , Programas Informáticos , Diseño de SoftwareRESUMEN
The biodynamic total hip prosthesis which was devised in 1977-78 and implanted in 1979 was derived from a series of experimental studies and a lengthy clinical experience, both dating back to 1968. This prosthesis introduced two new and original concepts into the field of prosthetic hip surgery: 1) the biequatorial design of the cup; 2) the preservation of the femoral neck. This prosthetic system is based on maximum preservation of the bone stock as well as hip function. The biequatorial cup allows for positioning corresponding to that of the normal acetabulum. The femoral component incorporates features (collar, sagittal and frontal angulation, external surface, etc.) which facilitate proximal cortical fixation and cancellous metaphyseal biological anchoring, thus ensuring total adhesion. The average 3.5 years follow-up (maximum 7 years, minimum one year) in 280 cases confirms the effectiveness of this prosthesis and the validity of the basic principles on which it is founded.
Asunto(s)
Prótesis de Cadera , Adulto , Anciano , Cementos para Huesos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Diseño de PrótesisRESUMEN
Loosening of the prosthetic stem is one of the most frequent problems in arthroprosthetic replacement. Fixation at the bone/cement interface is therefore of crucial importance. This can be affected by several factors, one of which is the heat generated in the acrylic cement, which may exceed the level at which tissue viability is affected. The authors therefore investigated this phenomenon in theoretical models. These were related to the level and duration of temperature changes at four levels - inside the cement and at the interfaces between cement, implant, spongy bone and cortical bone. Graphs showing temperature peaks and duration are constructed in all the varying conditions and their implications discussed. These concern the viability of osteocytes and vascular tissue, and the mechanical strength of the cement. The implications on design and surgical technique are obvious and point to the need to use the thinnest layer of cement compatible with firm fixation.
Asunto(s)
Cementos para Huesos , Prótesis Articulares , Temperatura , Acrilatos , Articulación del Tobillo/cirugía , Cementación/efectos adversos , Humanos , Prótesis Articulares/efectos adversos , Modelos Biológicos , PolímerosRESUMEN
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.
Asunto(s)
Análisis del Estrés Dental , Mandíbula/anatomía & histología , Mandíbula/fisiología , Adulto , Computadores , Oclusión Dental Céntrica , Femenino , Humanos , Masculino , Cóndilo Mandibular/anatomía & histología , Cóndilo Mandibular/fisiología , Persona de Mediana Edad , Modelos Anatómicos , Resinas Sintéticas , Estrés MecánicoRESUMEN
The role of recent research started in Italy, funded by the National Research Council, is stressed. The newly built Bcg facilities at the Polytechnic of Turin are concisely described. Current experimental research concerns the evaluation of a new type of concave-convex Bcg bed. Results from three healthy male individuals are shown and briefly discussed.