How do sock ply changes affect residual-limb fluid volume in people with transtibial amputation?

Abstract

The purpose of this research was to investigate the influence of sock addition and removal on residual-limb fluid volume in people using prosthetic limbs. We used bioimpedance analysis to measure residual-limb extracellular fluid volume on 28 transtibial amputee subjects during 30 min test sessions. Upon addition of a one-ply polyester sock, residual-limb fluid volume changes ranged from -4.0% to 0.8% (mean -0.9 +/- 1.3%) of the initial limb fluid volume. Changes for sock removal ranged from -1.2% to 2.8% (mean 0.5 +/- 0.8%). Subjects who reduced in fluid volume with both addition and removal of a sock and subjects with high positive ratios between the fluid-volume loss upon sock addition and gain upon sock removal (high add/remove [AR] ratios) tended to have arterial disease, were obese, and were smokers. Subjects with low positive AR ratios, subjects who increased in fluid volume both with sock addition and removal, and a single subject who increased in fluid volume with sock addition and decreased with sock removal tended to be nonsmokers and either individuals in good health without complications or individuals without arterial problems. Results are relevant for the anticipation of limb volume changes during prosthetic fitting and toward the design of adjustable-socket technologies.

Figures

FIGURE 1. Electrode placement for bioimpedance testing

The outer two electrodes injected current while the inner two electrodes sensed voltage.

FIGURE 2. Bar charts of percent residual limb fluid volume change

The number of subjects for different ranges of percent fluid volume change for sock addition (gray bars) and sock removal (white bars) are shown.

FIGURE 3. a-d. Example results for each group

Exemplary data for one subject from each group are presented. For clarity, only data during walks are shown. 10-point moving mean plots are presented. (a) Group 1: reduction in limb fluid volume both when the sock was added and removed; (b) Group 2: reduction in limb fluid volume when the sock was added and increase in limb fluid volume when it was removed; (c) Group 3: increase in limb fluid volume both when the sock was added and removed; (d) Group 4: increase in limb fluid volume when the sock was added and decrease in limb fluid volume when it was removed.

FIGURE 4. Subject groups and health status

Percent limb fluid volume changes for sock addition (dark blue bars) and sock removal (light orange bars) are shown for all 28 subjects. Groups 1 to 4 were defined based on the directions of fluid volume change, as described in the text. The numbers to the left of the graph are the AR ratios, i.e. quotients of percent fluid volume change upon sock addition divided by the percent fluid volume change upon sock removal. The table to the right of the bar graph indicates: subjects in good health (g), presence of a health condition: a= arterial disease or peripheral vascular disease; v= venous insufficiency; h= high blood pressure; d= diabetic; z= other condition (z1= heart arrhythmia; z2 = lifetime antibiotics because of residual limb infection; z3= renal failure and dialysis; z4=congestive heart failure). A ‘-’ indicates that ASGP testing was not conducted. People who were overweight (25<BMI<30) (o) and obese (BMI>30) (O) are indicated in the ‘O’ column, and smokers (s) are indicated in the ‘S’ column. Reasons for amputation (R) include trauma (t), vascular (arterial) disease (vd), spina bifida (b), Larsson’s syndrome (L), cancer (c).