The spatial structure changes of thigh arterial trees after transfemoral amputation: case studies

After lower limb amputation, blood flow is a fundamental and crucial factor affecting the recovery of residual limb. The investigation on arterial spatial structure change is the first important step to achieve the systematic research on hemodynamic state. The objective of this study is to investigate the effect of different ambulation approach on the spatial structure changes of bilateral thigh arterial tree within the first year after unilateral transfemoral amputation. It was hypothesized that using a prosthesis would cause greater arterial tree displacement, especially in residual limb. In this study, the modified Hausdorff distance was applied to quantify the spatial difference of arterial tree in comparing the vessels displacement between two subjects who had different walking mode (one was prosthesis-user and the other was crutch-user), and between their sound and amputated limbs. Each subject was arranged to have 3 times of CT angiography on both thighs at the 4th, 8th and 12th months after surgery. The CT images were used for 3D reconstruction of arterial trees, and then their coordinate matrices were exported for pairwise Hausdorff distance computation. The results of data analysis demonstrated that the thigh artery system on both sides of the two subjects underwent spatial structure changes throughout the study period. Consistent with the hypothesis, patients' ambulation approach was a key impact factor on bilateral arterial tree displacement. The subject wearing prosthesis showed greater arterial tree displacement in the residual limb than in the sound limb, and the difference of bilateral displacement degree decreased over time. The subject using crutches showed the opposite results. This investigation suggested that using prosthesis not only could achieve the functional compensation of residual limb, but also might promote the joint physiological status adjustment of both lower limbs to accommodate a new bipedal gait pattern.