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Residual-limb shape change: three-dimensional CT scan measurement and depiction in vivo
K E Smith1, P K Commean, M W Vannier
1Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, MO 63110, USA.
Purpose:
To perform quantitative evaluation of lower-extremity prosthesis fit by using spiral computed tomography (CT).
Materials And Methods:
Two spiral CT scans were obtained at each of two different sessions in seven adult patients who had undergone amputation below the knee. A rigid-body transformation of the tibia was computed and used to align paired (intra- and intersession) spiral CT data sets for each individual in a common coordinate system. Paired scans in each individual were compared to assess registration and precision of soft-tissue change measurement. Clinical prosthesis fit evaluation was demonstrated in an adult amputee volunteer who underwent CT evaluation while wearing two different prostheses.
Results:
In the seven patients examined, more than 90% of the measured soft-tissue volume displacements between sessions could be explained as true differences. Precision error of soft-tissue volume change was approximately 13 cm3, or approximately 1% error relative to the mean volume. Volumetric changes due to different prostheses were substantially larger than the random error.
Conclusion:
Registration of CT volumetric data sets to quantify residual-limb soft-tissue envelope change in lower-limb prosthetics is precise and can be used to detect the effect of prosthesis shape alterations.