Abstract
AimTo examine tactile sensitivity in the leg and foot sole of below-knee amputees (diabetic n = 3, traumatic n = 1), and healthy control subjects (n = 4), and examine the association between sensation and balance.MethodVibration perception threshold (VPT; 3, 40, 250Hz) and monofilaments (MF) were used to examine vibration and light touch sensitivity on the intact limb, residual limb, and homologous locations on controls. A functional reach test was performed to assess functional balance.ResultsTactile sensitivity was lower for diabetic amputee subjects compared to age matched controls for both VPT and MF; which was expected due to presence of diabetic peripheral neuropathy. In contrast, the traumatic amputee participant showed increased sensitivity for VPT at 40Hz and 250Hz vibration in both the intact and residual limbs compared to controls. Amputees with lower tactile sensitivity had shorter reach distances compared to those with higher sensitivity.ConclusionChanges in tactile sensitivity in the residual limb of trans-tibial amputees may have implications for the interaction between the amputee and the prosthetic device. The decreased skin sensitivity observed in the residual limb of subjects with diabetes is of concern as changes in skin sensitivity may be important in 1) identification/prevention of excessive pressure and 2) for functional stability. Interestingly, we saw increased residual limb skin sensitivity in the individual with the traumatic amputation. Although not measured directly in the present study, this increase in tactile sensitivity may be related to cortical reorganisation, which is known to occur following amputation, and would support similar findings observed in upper limb amputees.
Highlights
Sensory feedback from the glabrous skin on the foot soles has been shown to contribute to the maintenance of standing balance and control of gait [1]
Tactile sensitivity was lower for diabetic amputee subjects compared to age matched controls for both vibration perception threshold (VPT) and MF; which was expected due to presence of diabetic peripheral neuropathy
The traumatic amputee participant showed increased sensitivity for VPT at 40Hz and 250Hz vibration in both the intact and residual limbs compared to controls
Summary
Sensory feedback from the glabrous skin on the foot soles has been shown to contribute to the maintenance of standing balance and control of gait [1]. At the onset of rehabilitation, amputees exhibit an increased dependence on vision during upright stance [7] This increased dependence on vision returns to baseline following eight months of balance training [7], and it has been suggested that an up-regulation of other sensory systems, such as proprioceptive feedback from the intact skin may help compensate for the loss of sensory feedback caused by the amputation [7, 8]. It is reasonable that cutaneous afferent feedback originating within the prosthetic may become up-regulated (given more functional weighting) as it takes on the task of weight bearing, and sensory role of the amputated foot This up-regulation of residual limb skin feedback could exhibit as reduced perception or two-point discrimination thresholds. While the exact link between altered cortical representations and changes in tactile sensation has yet to be identified, these cortical changes may represent an adaptation to the loss of sensory feedback following amputation [15, 18]
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