Validation reliability and responsiveness of a new surface topography instrument


A new system developed to record and measure the shape of the back has been tested in regular use at the Nuffield Orthopaedic Centre in Oxford. A striped pattern is projected onto the back and a single digital photograph is taken. Analysis of the distortion of the stripes relative to their pattern on a flat reference plane allows the three-dimensional shape of the back to be calculated. A number of parameters are then extracted from the surface data and presented in a report for the clinician. All images and calculated parameters are stored in a database. At subsequent visits previous results can be retrieved from the database so that parameters can be plotted against time for monitoring the deformity. If a patient is measured twice there will be variations in the results caused by stance, posture, breathing and muscle tension.

The main aim of this project was to measure the variability in parameters measured from the three-dimensional back shape caused by these natural variations. Only changes in parameters greater than their measured variability can be regarded as indicative of progression of the deformity.

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