An amputation between the elbow and wrist is called a transradial (across the radius) amputation. If the amputation is made through the wrist itself it is known as a wrist disarticulation. The major differences between these two levels are the overall length and the fact that no bone is cut in a wrist disarticulation.
With wrist disarticulation and longer transradial amputations, you may still have some rotation of the forearm (called pronation and supination); for shorter transradial amputations there might be a small amount of rotation but it will generally not provide much dexterity. With longer residual limbs the socket will usually extend around halfway up your forearm, whereas a short residual limb (less than roughly half of the original forearm length) the socket might extend to just above the elbow.
The prosthetic socket is usually made from fibreglass, but metal and leather can also be used (although these are much less common). To hold the prosthesis on to your limb, we can use a number of different methods:
There are two basic types of upper-limb prosthesis:
You might decide to have one of each to suit different activities. A dress limb looks cosmetically appealing but provides little functional use. They can be used for simple tasks such as holding something down (such as a piece of paper when writing), for stabilising an object against your body or other hand, and they give you symmetry and the ability to make gestures.
A functional or work limb may look a little more unusual but can give a great deal of functional improvement. They can be fitted with a range of alternative hand units (called terminal devices), including hooks, grippers and specific tools such as hammers, steering wheel attachments and cutlery. Some devices can be operated via a control cable that attaches to a strap around your shoulder; by moving your shoulders backwards and forwards, you pull or release the cable and the device opens or closes. We can also manufacture specialised prosthetic arms for performing a specific task, such as cycling, kayaking, holding a camera and such like. Ask your prosthetist for advice if you have a particular request.
While some functional hand units are mechanically activated, others are operated electronically. These myoelectric (Greek: myo, muscle) use sensors in the socket to detect movement in certain muscle. This contraction of muscle generates a signal that turns on a small motor in the hand, moving the fingers or wrist. These prostheses are very expensive and are not suitable for everyone, but can offer a great deal of function and control. The latest hand units include several pre-programmed modes that allow you to perform specific tasks such as turning a key in a lock, carrying a bag or typing.
For further information or if you would like to make an appointment with a member of our clinical prosthetic team, please call APOS on 091 796983