Laboratory for Neuroengineering, Department of Health Science and Technology, Institute for Robotics and Intelligent Systems, ETH Zürich, 8092, Zürich, Switzerland.
Sci Rep. 2022 Oct 6;12(1):16696. doi: 10.1038/s41598-022-21057-y.
A non-optimal prosthesis integration into an amputee's body schema suggests some important functional and health consequences after lower limb amputation. These include low perception of a prosthesis as a part of the body, experiencing it as heavier than the natural limb, and cognitively exhausting use for users. Invasive approaches, exploiting the surgical implantation of electrodes in residual nerves, improved prosthesis integration by restoring natural and somatotopic sensory feedback in transfemoral amputees. A non-invasive alternative that avoids surgery would reduce costs and shorten certification time, significantly increasing the adoption of such systems. To explore this possibility, we compared results from a non-invasive, electro-cutaneous stimulation system to outcomes observed with the use of implants in above the knee amputees. This non-invasive solution was tested in transfemoral amputees through evaluation of their ability to perceive and recognize touch intensity and locations, or movements of a prosthesis, and its cognitive integration (through dual task performance and perceived prosthesis weight). While this managed to evoke the perception of different locations on the artificial foot, and closures of the leg, it was less performant than invasive solutions. Non-invasive stimulation induced similar improvements in dual motor and cognitive tasks compared to neural feedback. On the other hand, results demonstrate that remapped, evoked sensations are less informative and intuitive than the neural evoked somatotopic sensations. The device therefore fails to improve prosthesis embodiment together with its associated weight perception. This preliminary evaluation meaningfully highlights the drawbacks of non-invasive systems, but also demonstrates benefits when performing multiple tasks at once. Importantly, the improved dual task performance is consistent with invasive devices, taking steps towards the expedited development of a certified device for widespread use.
假肢与截肢者体觉图式的非最佳整合，表明下肢截肢后会产生一些重要的功能和健康后果。这些后果包括对假肢作为身体一部分的感知度低，感觉假肢比自然肢体更重，以及使用者在认知上使用起来很费力。通过在残肢神经中植入电极的侵入性方法，改善了假肢的整合，为股骨截肢者恢复了自然和躯体感觉反馈。非侵入性的替代方法可以避免手术，从而降低成本并缩短认证时间，显著增加此类系统的采用率。为了探索这种可能性，我们将非侵入性的电皮肤刺激系统的结果与在膝上截肢患者中使用植入物的结果进行了比较。通过评估他们感知和识别假肢触摸强度和位置或运动的能力，以及假肢的认知整合（通过双任务表现和感知假肢重量），我们在股骨截肢者中测试了这种非侵入性解决方案。虽然这种解决方案成功地引起了对人工脚上不同位置和腿部闭合的感知，但它的性能不如侵入性解决方案。与神经反馈相比，非侵入性刺激在双重运动和认知任务中引起的改善相似。另一方面，结果表明，重新映射的、诱发的感觉不如神经诱发的躯体感觉信息丰富和直观。因此，该设备无法改善假肢的体现感及其相关的重量感知。这种初步评估有意义地突出了非侵入性系统的缺点，但也展示了在同时执行多项任务时的优势。重要的是，改善的双重任务表现与侵入性设备一致，朝着加速开发可广泛使用的认证设备迈出了一步。
