Kuiken TA et al. (2007) Targeted reinnervation for enhanced prosthetic arm function in a woman with proximal amputation: a case study. Lancet 369: 371–380

Current myoelectric prostheses give slow and awkward movements and little sensory feedback. A new nerve transfer procedure has given a woman much improved control of her prosthetic arm, as well as sensory feedback to the missing limb.

The patient had previously undergone left arm amputation at the humeral neck following a motorcycle accident. Using a procedure known as 'targeted reinnervation', surgeons have rerouted motor nerves that originally went to her amputated limb (the ulnar, median, musculocutaneous, and distal radial nerves) to the pectoral and serratus muscles in her chest. Now, when she thinks about moving her arm, an electrical signal is sent along the rerouted nerves, activating the surface muscles. Electrodes resting on the skin over the reinnervated muscle pick up this signal and send it to the artificial limb so that it moves. The patient quickly learned 'intuitive' control of the arm, with simultaneous movement in the hand, wrist and elbow. Dexterity and coordination were both much better than with her previous myoelectric prosthesis.

In a second part of the procedure, the distal ends of two sensory nerves to chest skin overlying the reinnervated muscle were cut and connected to the amputated nerves allowing the hand sensory nerve fibers to reinnervate this skin. When pressure was applied to different areas of the chest skin, the patient then perceived this as being to different digits of her missing hand; she also had some sensations of vibration and temperature. Further development of this technology—for example, placement of sensors on the digits of the artificial limb—could provide patients with a sense of pressure and temperature in their prosthetic limbs.