Prosthetic Limbs Today, From Body-Powered to Bionic

More than two million people in the United States live with limb loss, according to the Amputee Coalition, with diabetes and vascular disease the most common causes. Prosthetic technology has changed a great deal over the past three decades, and today there are several distinct types of artificial limbs, each suited to different needs and budgets.

Body-powered prostheses

The oldest modern design uses a harness and cable. Moving the shoulder or upper arm pulls the cable, which opens and closes a hook or hand. Body-powered arms are durable, relatively affordable and give the user a sense of the grip force through the cable, which many people value. They can be tiring to use for long periods.

Myoelectric arms and hands

Myoelectric prostheses use sensors placed against the skin to pick up the small electrical signals produced when muscles in the remaining limb contract. A motor then moves the hand, wrist or elbow. Advanced hands can switch between several grip patterns. They look more natural and require less physical effort, but they are heavier, need charging and cost far more. Prices often run into tens of thousands of dollars.

Microprocessor knees and ankles

For leg amputations above the knee, microprocessor-controlled knees adjust their resistance many times per second based on sensor readings, which helps users walk on slopes and stairs and reduces falls. The C-Leg, introduced by Ottobock in 1997, was among the first widely used examples. Powered ankles that actively push off are also available but less common.

Osseointegration

Instead of a socket that fits over the limb, osseointegration anchors a metal implant directly into the bone, with a connector that passes through the skin. Users often report better control and a sense of the ground through the bone. In 2020 the FDA authorized the OPRA implant system for certain people with above-knee amputations who can't use a socket. Risks include infection where the implant exits the skin.

Targeted muscle reinnervation

In this surgery, nerves that once controlled the missing limb are rerouted to nearby muscles. When the person thinks about moving the missing hand, those muscles contract and produce signals a myoelectric prosthesis can read, allowing more intuitive control. The technique, developed in the early 2000s at what is now the Shirley Ryan AbilityLab in Chicago, has also been found to reduce phantom limb pain for many patients.

3D-printed and low-cost devices

Volunteer networks such as e-NABLE design and print simple mechanical hands, often for children who outgrow devices quickly. These are not a substitute for clinical prosthetic care, but they have widened access in places where conventional devices are out of reach.

Restoring the sense of touch

One of the biggest limitations of prosthetic hands is that users can't feel what they're holding, so they have to watch the hand constantly. Research teams, including groups at Case Western Reserve University and the University of Utah, have implanted electrodes on nerves in the residual limb that send signals back to the brain when sensors in the prosthetic hand touch something. Volunteers in these studies have described feeling pressure in their missing fingers and have handled delicate objects more easily. These systems are still experimental.

Phantom limb pain

Most people who lose a limb experience phantom sensations, and many feel pain that seems to come from the missing limb. Treatments include medication, mirror therapy (watching a reflection of the intact limb move to "trick" the brain), and surgical approaches such as targeted muscle reinnervation. Pain often eases over the first year but can persist.

Changing needs over time

A prosthesis isn't a one-time purchase. The residual limb changes shape, especially in the first year after amputation and with weight changes, so sockets need adjusting or replacing. Children need new devices frequently as they grow. Most prosthetic components are expected to last a few years with regular maintenance.

Getting a prosthesis

Fitting involves a physician, a prosthetist who builds and adjusts the device, and usually a physical or occupational therapist. Insurance coverage varies widely, especially for microprocessor and myoelectric devices, so documentation of how a device will improve daily function is often needed for approval.