On Friday, the Food and Drug Administration (FDA) approved the sale and marketing of a prosthetic arm called the DEKA Arm System, which uses electronic signals from the wearer’s muscles to induce up to 10 different movements in the prosthetic. Electrodes attached to the arm above the prosthesis detect muscle contractions and send those signals to a processor, which translates the contractions into movements that the arm should execute. The prosthetic weighs the same as an adult arm, and its design is modular so that it can be fitted to accommodate many different needs. Specifically, the FDA notes that the prosthetic can be used for “limb loss occurring at the shoulder joint, mid-upper arm, or mid-lower arm. It cannot be configured for limb loss at the elbow or wrist joint.”