The most advanced prosthetic arm currently available to patients is the LUKE Arm, developed by Mobius Bionics. With up to 10 powered degrees of freedom, it remains the only prosthetic arm cleared by the FDA that offers powered movement at the shoulder, elbow, wrist, and individual hand grips in a single system. But the field is moving fast, and several newer technologies are pushing well beyond what the LUKE Arm can do, with laboratory prototypes now matching the full dexterity of a human hand.
The LUKE Arm: Current Gold Standard
Named after Luke Skywalker, the LUKE Arm was originally developed through a DARPA-funded program and is manufactured by Mobius Bionics. In its maximum configuration (for shoulder-level amputations), it provides 10 powered degrees of freedom, including a powered shoulder, upper arm rotation, and wrist flexion. The hand itself offers four individually controlled degrees of freedom with multiple preprogrammed grips.
The system comes in three configurations depending on the level of amputation. A below-elbow (radial) version weighs 1.4 kg, while the full shoulder configuration weighs 4.7 kg. It runs on rechargeable lithium-ion batteries with capacities up to 7,000 mAh for the upper-arm version. What sets it apart from simpler myoelectric arms is that users can control multiple joints simultaneously rather than toggling between one movement at a time.
A Lighter, More Dexterous Prototype
A prosthetic hand published in Nature Communications in 2025 represents a significant leap in dexterity. Researchers built a hand with 19 degrees of freedom, controlled by 38 shape-memory alloy actuators. For context, the LUKE Arm’s hand has four. This prototype can perform 33 standard grasping modes plus 6 advanced modes designed for fine manipulation tasks.
Shape-memory alloys work by changing shape when heated and returning to their original form when cooled, mimicking how muscles contract and relax. These alloys pack far more power per gram than electric motors. Electric motors deliver about 100 watts per kilogram, while shape-memory alloys deliver around 1,000. That tenfold advantage is why the hand portion (wrist to fingertips) weighs just 0.22 kg, roughly half a pound, which is dramatically lighter than anything commercially available.
The hand includes real-time joint angle sensing in every finger, feeding data into a closed-loop control system. It also features voice control powered by a recognition system with 95% accuracy and millisecond response times, supporting over 60 languages. During 30 minutes of continuous use, the interior surface temperature stays at 27.2°C, which is safe and comfortable against skin. This hand is not yet commercially available, but it demonstrates where the technology is heading.
How Users Control Advanced Arms
Traditional myoelectric prostheses read electrical signals from a single pair of remaining muscles in the residual limb. This works, but it limits the user to one movement at a time. You flex one muscle to close the hand, another to open it, and if you want to move the elbow, you have to switch modes.
A surgical technique called targeted muscle reinnervation has changed this. Surgeons reroute the nerves that once controlled the missing arm to new muscle sites in the residual limb or chest. After the nerves grow into their new muscle targets (typically over several months), those muscles respond to the same brain signals that originally moved the hand, wrist, or elbow. When the user thinks about closing their hand, a specific muscle contracts, and sensors on the prosthesis detect that signal. Because multiple nerves are rerouted to separate muscles, users can control several joints simultaneously and intuitively, rather than cycling through movements one at a time.
Newer AI-based control systems add another layer of capability. Machine learning algorithms analyze patterns in muscle signals to predict which grip type the user intends. Some experimental systems pair this with a small camera on the prosthesis that identifies objects in the user’s visual field, then automatically selects the best grip. In one study, combining muscle signal classification with computer vision boosted grasp accuracy from 85.5% to 90%, reducing the mental effort required from the user.
The Push to Restore Touch
One of the biggest gaps between a biological arm and even the most advanced prosthetic is sensory feedback. Without it, users must watch their prosthetic hand constantly to know how tightly they’re gripping. Three main approaches are being used to solve this problem.
- Vibrotactile feedback uses small vibrating motors on the skin to signal grip pressure or contact. These systems are compact and energy-efficient, though the sensations can feel somewhat imprecise and users may become desensitized over time.
- Mechanotactile feedback applies direct pressure or skin stretch to convey information. This more closely mimics natural touch and is useful for conveying a sense of position, but the hardware tends to be bulkier.
- Electrotactile feedback delivers small electrical pulses through skin electrodes to stimulate sensory nerves. It can produce precise and varied signals but requires careful calibration to avoid discomfort.
The most promising approach bypasses the skin entirely. Researchers have implanted electrodes directly into peripheral nerves, delivering sensory signals straight to the nervous system. This produces more naturalistic sensation than any surface-based method and has even been shown to reduce phantom limb pain. These implanted systems remain experimental, but they point toward prosthetics that genuinely feel like part of the body.
Bone-Anchored Attachment
How a prosthetic arm connects to the body matters as much as what the arm itself can do. Traditional socket-based attachments wrap around the residual limb, and they frequently cause discomfort, skin irritation, and unreliable fit, especially as the residual limb changes shape over time. Many users abandon their prostheses because of socket problems alone.
Osseointegration offers an alternative: a titanium implant is surgically inserted into the bone of the residual limb, and the prosthesis clicks directly onto it. Studies tracking patients for up to 10 years show significantly better mobility, more daily prosthetic use, and improved quality of life compared to socket users. The tradeoff is a rising rate of mechanical complications over time. At 10 years, only 17% of patients had avoided some form of mechanical issue with the implant, though serious problems like deep infection or implant revision were much less common (revision-free survival was 83% at 10 years).
Grip Force: Stronger Than Human
Prosthetic hands are actually far stronger than biological ones. Standard prosthetic hands apply contact forces up to 24.7 newtons at the fingertips, compared to just 3.8 newtons for a human hand performing the same grip. That six-to-one strength advantage sounds impressive, but it’s actually a problem. Without good sensory feedback, users can easily crush delicate objects. Newer adaptive-grasp prosthetic hands produce forces closer to 4.7 newtons, much more comparable to a human hand, by distributing pressure more evenly across the fingers.
What Advanced Arms Cost
The price of a prosthetic arm varies enormously depending on the technology and level of amputation. Multi-articulating myoelectric hands like the Open Bionics Hero Arm (available for below-elbow differences) are at the more accessible end, with over 50% of insured users getting them fully covered. More advanced systems like the LUKE Arm cost significantly more, and pricing depends on configuration, clinical fitting, and rehabilitation needs.
The Atom Touch, an upcoming prosthetic arm from Atom Bodies, aims to be the first commercially viable arm with individual finger control, full human range of motion, built-in touch sensors, and a non-invasive AI neural interface. It is marketed as lighter than a human arm and uses a load-balanced harness to distribute weight across the torso. The Atom Touch has not yet launched, but its listed feature set, if delivered, would represent a major step toward closing the gap between commercial products and laboratory prototypes.
How Far the Gap Has Closed
A human arm and hand have roughly 27 degrees of freedom. The best commercial prosthetic (the LUKE Arm) offers 10. The Nature Communications prototype reaches 19. The remaining gap is closing through lighter actuators, smarter AI control, and sensory feedback that increasingly mimics real touch. The core challenge is no longer building a hand that can physically perform complex movements. It is building a control system that lets users access that dexterity without exhausting mental effort, and doing it in a package that is light enough, affordable enough, and durable enough for everyday life.