[3-dimensional photo-elastometric study of the patella (knee cap). Methodology and initial results]

Thanks to the photo-elastic method, the authors have described the disposition of the quadricipital tensile stresses in the human patella. Photo-elasticity allows the study of the relations between birefraction and stresses which exist in a transparent medium. Up to now, all the studies have been made on a plane model. The original feature of this study lies in the use of a three-dimensional model which, better than any plane photo-elasticimetry, makes it possible to display bone stresses in the three-dimensional space. After reminding some fundamental data, the authors describe the methodology and give the first qualitative results: in a frontal plane, tensile stresses are localised in the anterior two-thirds of the patella; on the contrary, pressure stresses can be observed in the posterior third. So the patella moves forward the tensile stresses of the knee.