Hololimb: Mixed Reality to Alleviate Phantom Upper Limb Pain

Our research explored new technological solutions for the treatment of phantom limb pain (PLP). PLP is associated with functional and structural effects on the brain and induces reversible changes in the cortical representation of the painful limb, which can be alleviated by sensory stimulation convincing the brain of a healthy and functioning body. In particular, reducing the gap between the actual condition of the limb and its representation can bring the cortical reorganization to a functional state. This concept has informed the design of Hololimb, a Mixed Reality system based on Hololens 2. Hololimb enables the user to see a virtual limb (rendered by a holographic model) projected "over" the phantom limb, fully integrated with the view of their physical body and the surrounding environment. The holographic model can be customized to maximize similarity with the patient's limb and fit it with their body by adjusting the hologram to non-anatomical postures perceived by the patient and personalizing size, motion, color, and transparency. Hololimb also supports dynamic effects, such as letting the virtual phantom limb gradually disappear to support different forms of therapeutic interventions.