Different Types And Parts Of An Upper-Limb Prosthesis

Whether upper-limb difference is the result of an illness, injury or birth complication, the needs of those wearing upper-limb prosthetic devices can vary quite a bit. For example, some people may only require a prosthesis from the wrist down, while others may need something that replaces their entire arm from the shoulder.

Even when two people have similar residual limbs, the requirements they may have for their prostheses can be completely different based on their daily activities and lifestyles. This means there are many types of prosthetic arms and hands to suit all these various needs. Read on to learn the basics about the parts of an upper-limb prosthesis and how they may be configured.

There are three general classes of prostheses for those with upper-extremity differences. These are:

• Cosmetic — Despite the name, these prostheses can do more than simply mimic the appearance of the wearer’s natural limbs. Also known as passive prostheses, they can serve to help maintain a person’s balance or serve as a stabilizer for simple tasks such as writing. They do not feature any active movement in the hand or joints.
• Body-powered — These offer more functionality because they utilize the movement of the wearer’s shoulder, torso, and/or upper arm to operate cables that can open and close a hook, hand, and move a wrist or elbow. These allow the people using them to pick up and grip objects so they can more easily perform various daily tasks.
• Myoelectric — These are the most sophisticated type, featuring electric actuators that can grasp items more securely and with varying degrees of force. They typically use sensors to detect muscular movement (myoelectric signals, or “EMG”) for control.

Components of Upper-Limb Prostheses

Although each one is different, upper-limb prostheses typically feature the same basic components. The most common of these are:

• Terminal device — This refers to the prosthetic hand at the end of the prosthesis, which can be a hook, claw, or device that more closely resembles a hand.
• Interposing joints — These are the points at which the prosthesis can be moved and manipulated, typically at the elbow and wrist and within the terminal device.
• Socket — The point at which the prosthesis is attached to the wearer’s own body, these are cast to fit the person’s residual limb as comfortably and securely as possible.
• Suspension — Whether through the use of a harness, suction, or friction, this is the system through which the prosthetic limb is connected between the socket and residual limb.
• Control system — These can be body-powered, externally powered (such as myoelectric or myoelectric pattern recognition), or a hybrid of the two systems. This is how the wearer can control his or her prosthesis.

Expanding Into New Worlds

Technology is always advancing in the field of upper-limb prosthesis, and Coapt is leading the way. Our systems add artificial intelligence and myoelectric pattern recognition into the mix, enabling control systems for myoelectric prostheses to feel more intuitive and natural to the users. Our technology also offers ease for wearers to fine-tune the level of control they have over their devices, along with other benefits.