Impact of transradial amputation and brachial plexus injury on vibrotactile sensation capacity of the upper extremity

BACKGROUND: The sense of touch is fundamental for interacting with our surroundings, yet its restoration after sensory loss remains challenging. Haptic feedback, often delivered through vibrotactile stimulation, can help restore somatosensory information. While tactile perception on the arm is well characterized in healthy individuals, quantitative psychometric data are scarce for conditions involving severe peripheral disruption such as transradial amputation (TR) and brachial plexus injury (BPI), where denervation and cortical reorganization may reduce residual sensitivity. METHODS: We systematically assessed the vibrotactile sensation capacity of the six relevant dermatomes (C3-T2) at the lower arm, upper arm, and shoulder regions of persons with TR and BPI. Psychometric tests were performed to determine the perception capacity (sensation threshold, just noticeable difference), and an online control task was conducted to assess the interpretation of feedback (delay and tracking error). The obtained results were compared to the benchmark data measured in healthy non-disabled individuals. RESULTS: Within this small exploratory cohort, we found no significant differences in sensory capacity of persons with TR compared to the benchmark, in any outcome measure, and this was consistent across all arm segments. In contrast, persons with BPI demonstrated a significantly lower sensation perception in the distal regions (lower and upper arm), while the perception at the shoulder area was close to that of the benchmark. Unexpectedly, sensitivity was higher at the upper than the lower arm in persons with BPI, even though pan-plexus avulsion would be expected to cause complete sensory disconnection in both regions. CONCLUSIONS: The results suggest that vibrotactile sensation may remain partly preserved in proximal regions despite sensory impairment. Given the small sample and limited statistical power, these findings should be regarded as preliminary but may inform future designs of vibrotactile feedback interfaces.