A technique for calibrating measurements from photographs of sliced specimens

Determining the geometry of articular joint surfaces is critical to the study of human joint mechanics. Photographs of sliced specimens (PSS) is currently one of the most popular methods used to determine surface geometry. This study sought to improve the photographs of sliced specimens method through a new calibration technique that includes a mathematical model and a precise plastic grating (calibration grid). Simulations showed that calibration results for x and y coordinates using the new technique attained a high degree of accuracy that was independent of camera and projector lens quality, degree of parallelity between the projector and digitizing table and selection of the area to be calibrated.