Residual-limb shape change: three-dimensional CT scan measurement and depiction in vivo.

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.