Background & Aims

Postamputation pain (PAP) – in terms of phantom limb pain (PLP) and residual limb pain (RLP) – is a common phenomenon after limb amputation (Diers et al., 2022). Prosthesis embodiment – i.e., the perception of a prosthesis being a part of the body (Bekrater-Bodmann, 2020) – is negatively related to PAP (Bekrater-Bodmann et al., 2021), indicating that correction of body perception, in terms of a higher sense of integrity, has beneficial effects. It has been suggested that the rubber limb illusion – a paradigm applying correlated visuotactile stimuli to induce the perception of an artificial limb belonging to an amputee’s body – represents an experimental model for prosthesis embodiment (Ehrsson et al., 2008) and could thus give important impulses for PAP treatment. However, given methodological constraints of existing rubber limb illusion setups, the role of PAP for eliciting this kind of illusion is unclear as is its relationship to prosthesis embodiment.

Methods

The author developed a new rubber limb illusion paradigm for manipulating body perception in lower limb amputees: participants were asked to observe an intact or an amputated artificial lower limb that was touched in synchrony or asynchrony with the hidden residual limb in a 2 (factor limb; intact vs. amputated) *2 (factor stimulation; synchronous vs. asynchronous) repeated measures design. The sense of integrity and vividness of touch (i.e., the authenticity of the observed tactile stimulation) was assessed with questionnaires. Data were analyzed using variance analytical and regression analytical statistical approaches. Prevalence of PAP, with a focus on the differential effects of PLP and RLP, was added to the models. Experimental data on the sense of integrity were correlated to prosthesis embodiment as assessed with the Prosthesis Embodiment Scale (Bekrater-Bodmann et al., 2023).

Results

Data of N=34 unilateral lower limb amputees (mean age: 55±10 years) were included, with 71% reporting PAP (PLP: 44%; RLP: 29%). There was a significant limb*stimulation interaction (p=.014) on the sense of integrity, i.e., looking at an intact artificial limb under synchronous stimulation elicited the highest ratings. Adding PAP to the statistical model revealed a significant stimulation*PAP interaction (p=.017), with PAP participants showing a more pronounced synchronous stimulation effect compared to PAP-free participants. This effect was driven by PLP rather than RLP (p=.002 vs. p=.452 for the interaction, respectively). The same pattern was found for vividness of touch (p=.022 for PAP, p=.001 for PLP, p=.539 for RLP), which itself was positively related to the sense of integrity (r=.59, p<.001). Although prosthesis embodiment was negatively related to PAP (one-tailed p=.027 for the group difference), it did not significantly correlate with the sense of integrity (r=.182, p=.303).

Conclusions

The results suggest that PLP is associated with enhanced proneness to adapt the participant’s sense of integrity in accordance with visuotactile stimulation. The similar pattern for vividness of touch indicates that (peripherally or centrally) reduced tactile resolution capacity of the residual limb (see also Flor et al., 2001) – and thus less sensitivity to multisensory incongruence – might contribute to this effect. Interestingly, the experimentally induced sense of integrity and prosthesis embodiment were not correlated (see also Zbinden & Ortiz-Catalan, 2021), suggesting different sensorimotor processes underlying both phenomena. However, the data also indicate that PAP-associated reductions in prosthesis embodiment might be compensated by appropriate multimodal stimulation conditions. Based on the present findings, prostheses equipped with tactile feedback might be particularly promising for amputees suffering from PLP.

References

Bekrater-Bodmann, R. (2020). Perceptual correlates of successful body–prosthesis interaction in lower limb amputees: psychometric characterisation and development of the Prosthesis Embodiment Scale. Scientific Reports, 10(1), 14203.
Bekrater-Bodmann, R., Kehl, I., Giordano, A., & Franchignoni, F. (2023). Rasch validation of the German version of the Prosthesis Embodiment Scale for lower limb amputees and proposal of a revised version. Disability and Rehabilitation, Online ahead of print.
Bekrater-Bodmann, R., Reinhard, I., Diers, M., Fuchs, X., & Flor, H. (2021). Relationship of prosthesis ownership and phantom limb pain: results of a survey in 2383 limb amputees. Pain, 162(2), 630-640.
Diers, M., Krumm, B., Fuchs, X., Bekrater-Bodmann, R., Milde, C., Trojan, J., … & Flor, H. (2022). The prevalence and characteristics of phantom limb pain and non-painful phantom phenomena in a nationwide survey of 3,374 unilateral limb amputees. The Journal of Pain, 23(3), 411-423.
Ehrsson, H. H., Rosén, B., Stockselius, A., Ragnö, C., Köhler, P., & Lundborg, G. (2008). Upper limb amputees can be induced to experience a rubber hand as their own. Brain, 131(12), 3443-3452.
Flor, H., Denke, C., Schaefer, M., & Grüsser, S. (2001). Effect of sensory discrimination training on cortical reorganisation and phantom limb pain. The Lancet, 357(9270), 1763-1764.
Zbinden, J., & Ortiz-Catalan, M. (2021). The rubber hand illusion is a fallible method to study ownership of prosthetic limbs. Scientific Reports, 11(1), 4423.

Presenting Author

Robin Bekrater-Bodmann

Poster Authors

Robin Bekrater-Bodmann

Prof. Dr.

RWTH Aachen University

Lead Author

E-mail

Topics

  • Specific Pain Conditions/Pain in Specific Populations: Pain in Amputees