A vibrotactile stimulation system for improving postural control and knee joint proprioception in lower-limb amputees

The lack of sensory feedback in lower-limb amputees is the major cause of (i) amputees difficulty to keep balance, (ii) suboptimal performance in gait functions and (iii) increased energy consumption. This also hugely affects their participation in the activities of daily living. Improving postural control functions in people with lower-limb amputation has the aim to enhance their quality of life and is achieved through the restoration of their lost sensory feedback. The objective of this paper is to propose a stimulation system for restoring plantar pressure perception and knee-joint proprioception in lower-limb amputees. The proposed approach is based on the combined use of two FSRs, two accelerometers and two or three vibrotactile actuators. For validating the system, two experimental sessions were carried out on sixteen healthy subjects and one lower-limb amputee. They were aimed to (i) assess if vibrotactile feedback can improve balance control in lower-limb amputees and (ii) investigate the potentiality of the vibrotactile perception as a means to restore amputees' knee-joint proprioception. Quantitative indices capable of describing users' performance were extracted from the processed data and a statistical analysis was performed to compare different types of sensory feedback: i.e. (i) augmented visuo-proprioceptive feedback, no feedback, forearm vibrotactile feedback and low-back vibrotactile feedback in the 1st experimental session and (ii) forearm continuous vibrotactile feedback, low-back continuous vibrotactile feedback, forearm discrete vibrotactile feedback, and low-back discrete vibrotactile feedback in the 2nd experimental session. The achieved results on the vibrotactile stimulation were encouraging for both applications, i.e. restoring amputees' plantar pressure perception and knee-joint proprioception.