Paggetti Flavia, Gherardini Marta, Ianniciello Valerio, Cirelli Simone, Cipriani Christian
IEEE Trans Biomed Eng. 2025 Jul;72(7):2168-2177. doi: 10.1109/TBME.2025.3536854.
The myokinetic control interface for limb protheses involves implanting small permanent magnets in the residual muscles of the stump, retrieving their displacement induced by muscle contraction using external magnetic sensors, and mapping such displacements to motor commands. We have previously shown the feasibility of tracking several magnets implanted in an anatomically relevant workspace. However, to clinically translate the interface, strategies to address different kinds of external disturbances compromising its functioning are mandatory. Among these, physical disturbances, viz. relative displacement between the sensors and the magnets not due to voluntary contraction, could significantly hinder the interface usability.
Here we propose three rejection methods sought to mitigate this problem: one aims to realign the sensors and the magnets when a disturbance is detected, through numerical approximation methods; the others exploit differential measurements. We applied these concepts to upper limb prostheses, by mimicking the presence of physical disturbances in simulations and through a physical setup, reproducing four target muscles of a human forearm to be potentially implanted. Finally, we evaluated the rejection ability of one of those methods during the first-in-human implementation of the myokinetic interface.
All methods proved capable of rejecting the disturbances, showing median localization errors below 10% the displacement undergone during contraction.
Results suggest that the optimal rejection method is application-specific, and provide hints for assessing different factors influencing the best choice.
Other than being crucial for the myokinetic interface development, these outcomes also provide interesting insights for many biomedical applications exploiting remote magnetic tracking.
肢体假肢的肌动控制接口涉及在残肢的残余肌肉中植入小型永久磁铁，使用外部磁传感器获取由肌肉收缩引起的磁铁位移，并将此类位移映射为运动指令。我们之前已经证明了跟踪植入在解剖学相关工作空间中的多个磁铁的可行性。然而，为了将该接口临床转化，必须制定应对损害其功能的不同类型外部干扰的策略。其中，物理干扰，即传感器与磁铁之间并非由自主收缩引起的相对位移，可能会严重阻碍该接口的可用性。
在此，我们提出三种抑制方法来缓解这一问题：一种方法旨在通过数值近似方法在检测到干扰时重新对齐传感器和磁铁；另外两种方法利用差分测量。我们通过在模拟中模拟物理干扰的存在并通过物理装置，将这些概念应用于上肢假肢，该物理装置再现了人类前臂中可能植入的四块目标肌肉。最后，我们在肌动控制接口的首次人体应用中评估了其中一种方法的抑制能力。
所有方法都证明能够抑制干扰，收缩过程中位移的中位定位误差低于10%。
结果表明，最佳抑制方法因应用而异，并为评估影响最佳选择的不同因素提供了线索。
这些结果不仅对肌动控制接口的开发至关重要，还为许多利用远程磁跟踪的生物医学应用提供了有趣的见解。
