Adaptation to altered balance conditions in unilateral amputees due to atherosclerosis: a randomized controlled study

Abstract

Background: Amputation impairs the ability to balance. We examined adaptation strategies in balance following dysvascularity-induced unilateral tibial amputation in skilled prosthetic users (SPU) and first fitted amputees (FFA) (N = 28).

Methods: Excursions of center of pressure (COP) were determined during 20 s quiet standing using a stabilometry system with eyes-open on both legs or on the non-affected leg(s).

Main measures: COP trajectories and time functions; distribution of reaction forces between the two legs; inclination angles obtained through second order regression analysis using stabilogram data.

Results: FFA vs SPU demonstrated 27.8% greater postural sway in bilateral stance (p = 0.0004). Postural sway area was smaller in FFA standing on the non-affected leg compared with SPU (p = 0.028). The slope of the regression line indicating postural stability was nearly identical in FFA and SPU and the direction of regression line was opposite for the left and right leg amputees.

Conclusion: Of the two adaptation strategies in balance, the first appears before amputation due to pain and fatigue in the affected leg. This strategy appears in the form of reduced postural sway while standing on the non-affected leg. The second adaptation occurs during rehabilitation and regular use of the prosthesis resulting in normal weightbearing associated with reduced postural sway on two legs and return to the normal postural stability on one leg.

Figure 1

Stabilograms. Left: stabilogram indicating COP excursions and the radius of the characteristic circle containing 95% of the scanned points of the stabilogram. Right: total (T), AP and ML COP excursion lengths (m) in the function of the time during 20 s quite stance.

Figure 2

Representative stabilograms indicating AP (y) and ML (x) excursions of COP. A: COP excursion of a patient who had left lower leg amputation. The correlation coefficient is R_xy = 0.75 (p <0.001). The regression line tends from the (left) prosthesis heel towards the right (intact) sole and the angle of regression line is  a = 53°. B: COP excursion of a right leg amputee. The correlation coefficient is: R_xy = 0.72 (p <0.001) and the angle of regression line is    a = -48°. The regression line trends from the (right) prostheses heel towards the left intact sole. The quadrants of the coordinate system are marked with numbers: 1, 2, 3 and 4.