Evaluation of the Tracer CAD and T ring prosthetic shape capture systems

Research output: ThesisDoctoral Thesis


The quality of prosthetic socket fit can affect the function of the final prosthesis and may be compromised by errors during the residual limb shape capture. Plaster of Paris and Computer Aided Design (CAD) systems are currently used with the residual limb exposed to different conditions. Limited measure of accuracy or repeatability of CAD systems exist when compared to plaster of Paris methods. The thesis aims to evaluate the accuracy, repeatability and reliability of commonly used prosthetic CAD systems and compare results with traditional shape capture methods. A survey established that the most commonly used CAD systems are the Tracer CAD and Tring systems which use the same software but different principles of operation. Systems were evaluated using a series of models of known dimensions and volume. Each was measured by CAD systems and compared to a gold standard to evaluate accuracy and repeatability of diameter and volume measurement. Reliability between users was also compared and found to be high when assessing all models using both CAD systems (ICC > 0.984). Tracer CAD system repeata bility was good (CV<5%) for diameter and volume measurements on solid models but less repeatable in areas of a manikin which were easily deformed (CV 9.66%). Less repeatability of Tring volume measurement was observed particularly at distal levels. Plaster of Paris casting was more repeatable than CAD systems. Poorer repeatability of volume measurement was observed at the distal end of deformable and shaped models (CV= 8.97%). Plaster casts showed the best accuracy of diameter measurement of all systems on non deformable models ( < 1mm) and similar accuracy of volume measurement compared to Tracer CAD. The Tring was the least accurate system. Errors were largest on shaped and deformable models. Poorer accuracy was observed towards the distal end. Based on limited evidence, results indicate that methods of shape capture analysed do not show sufficient accuracy for prosthetic shape capture.
Original languageEnglish
Awarding Institution
  • Biomedical Engineering
  • McHugh, Brendan, Supervisor
  • Buis, Arjan, Supervisor
Place of PublicationGlasgow
Publication statusPublished - 2009


  • tracer CAD
  • T Ring
  • prosthetics shape
  • shape capture systems
  • prosthetic socket


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