Upper Limb Prosthetics

My goal with this was not to provide definitions as much as explanations of terms and concepts and how they are used in prosthetics.  Prosthetic terms are listed first, then Anatomical/Medical terms, and abbreviations at the bottom

Prosthetic Terminology



3rd party payer
- Insurance, Medicare or other 'health coverage'

Amplifier or "amp" - Used in conjunction with or as a part of the electrode assembly in a myo-electric system.  Different types filter out ambient electrical activity or amplify the EMG signal.

Body powered - using body motion and strength to directly operate a prosthesis.  For more information, visit the Body Powered page.

Bowden cable - the name of the cable used in body powered prostheses to control operation of the terminal device.

Co-contraction - the contraction or activation of two muscles at once.  This can be used as a signal to switch between two different actions or functions of the prosthesis.  For example, switching between the hand and the wrist.

Component - a device or part of the prosthesis.  A hand, elbow, or wrist are examples of components

Control Strategy - The program used for operating an externally powered prosthesis.  Refers to combination of digital vs proportional, 1 site vs 2 site, etc. For more explanation, see the
Externally Powered page.

Cosmetic glove - covering for an upper limb prosthesis

Digital control - can be thought of as a simple on/off, like a light switch.  signal present = on, absent = off

Doffing - taking off a prosthesis

Donning - putting on a prosthesis

Donning Sleeve - A tube of slippery fabric that looks like a wind-sock. Used to help pull your tissue into the socket in a way so that it won't come off easily.  Usually used with suction suspension.

Dual control- a split or dual bowden cable and housing system that allows the cable to control the elbow or TD depending on whether the elbow is locked.  If the elbow is locked, pull on the cable will control the TD.  If it is unlocked, pull on the cable will bend the elbow.

Excursion:  is a description of distance generated by the relative movement of 2 body parts.  For example:  when you hunch or round your shoulders, you are widening the distance between your shoulder blades.  That increase in distance is the 'excursion' you have generated. 

Externally Powered- or "powered".  A prosthesis in which movement is generated by motors and powered by a battery (not by you-hence the 'external').  They are often referred to as "myoelectric."  However, "myoelectric" technically only means powered prostheses that use electrodes as the input device.  Other input devices include Force Sensing Resistors, Linear Transducer, and Switches.  For more information, visit the
Externally powered page.

Figure 8 harness - harness that provides suspension and control of a body powered prosthesis

Figure 9 harness - harness used in self-suspending below-elbow prostheses to control the prosthesis

Force Sensing Resister - a 'touch pad'. An input device for externally powered prostheses that measures compressive force. (Something pushing on it).  It can be used in proportional control. For more information, visit the
Externally Powered page.

Gain - measure of sensitivity of an electrode or the magnification of the electrical signal it picks up.  A person with a weak signal will need a higher gain.  As the signal gets stronger, we can turn the gain down.

Hybrid - this is obviously a general word with many uses, but in upper limb prosthetics we use it to refer to a prosthesis that has both body powered and externally-powered elements.

Interface - the inner surface of the prosthesis that makes contact with the body, or the way a prosthesis attaches to the body.  Certain designs of interfaces are called "sockets."

In-put Device- a method of generating a signal for a microprocessor to use to operate an externally powered prosthesis.  For more information, visit the
Externally Powered page. 

Linear Transducer - an input device for externally powered prostheses that measures movement or 'excursion' (see above) and translates it into a signal to control a myo-prosthesis.  Can be used in proportional control.  For more information, visit the
Externally Powered page.

Low Profile
- we use it as meaning 'doesn't take up much room'.  For example: a person with a long residual limb will need 'low profile' components so that the prosthesis isn't longer than the other limb

Microprocessor - simply put, the "brains" of an externally powered device.  It takes signals and uses them to control a prosthesis.   Microprocessors are what is programmed with the 'control strategy' 

Modular Prosthesis- a prosthesis assembled from components, usually endoskeletal with soft foam covering.  Lightweight.

Myoelectric - an type of externally powered prosthesis that uses muscle signals and electrodes to control it.

Myosite - a place on the residual limb or body that we can pick up the electrical signal generated by a muscle contraction.  We place an electrode there to pick up the signal.

Passive Hand - a hand that resembles the absent hand, but that does not have any moving parts.  Because of this they can be made light.  Sometimes they have bendable fingers and elbows, and a special emphasis is put on cosmesis. 

Passive prosthesis- prosthesis that usually has movable/positional components that you can move with your other hand, but do not have active motion themselves

Pistoning - when your residual limb moves around within the prosthesis in the on/off or in/out direction. 

Ply - a term used to describe the thickness of a prosthetic sock.  Usually numbered 1-5 (though a few are made up to 10) Thin socks are lower numbers, like 1 or 2.  Thicker socks are 5.  When someone asks you how many 'ply' you are wearing, they mean what combination of socks:  a 1, 3, and a 5 together are 8 ply.  Is also sometimes used as an estimation of socket fit.  The more ply you are wearing, the looser the socket is on its own = the less it fits.  

Prehensors- Terminal Device that grasps and holds.  Usually used to describe TD's that are neither hooks nor hands.

Preparatory Prosthesis - an unfinished functional prosthesis.  Worn for a period of time at the beginning of the rehab process.

Proportional control - strategy of controlling an externally powered prosthesis in which the strength or speed of the signal controls the strength or speed of the prosthetic component (in proportion to the signal)

Prosthetic socks - special coverings designed for residual limbs.  They are usually soft, stretchy, and seamless.  Classified by the thickness or 'ply'. (see below)

Shrinker - stretchy compressive sock worn over the residual limb to help control edema/reduce swelling

Socket - type of interface that encases the residual limb

Suspension system - method of holding on a prosthesis. 

Switch - input device for externally powered prostheses.  Used with digital control.  For more explanation, visit the
Externally Powered page

Terminal Device - the component on the end of the prosthesis meant to provide a function that the hand used to provide.

Threshold - this word obviously has many meanings, in prosthetics it is used to describe the level a myo/electrical signal has to reach before it triggers a response.  It is necessary to have a threshold to prevent accidental activation of the prosthesis from slight movements or just ambient electrical 'noise'.

Touch pad - an input device for externally powered prostheses that measures compressive force, or how hard something pushes on it.  Can provide proportional control.  For more explanation, visit the
Externally Powered page.

Triple Control - Body powered control scheme for above elbow systems, referring to the control of elbow, elbow lock, and

Terminal Device - prosthetic component on the end of the prosthesis to perform a function that the hand used to do.  (I don't want to say replace the hand, because none of them really can.  And I don't want to say approximate a hand, because some of them look nothing like hands) Body powered or externally powered hooks and hands, and activity specific attachments are examples of terminal devices.

Wrist rotator - externally powered prosthetic component that provides wrist rotation.


Anatomical/Medical Terms


Adherent Scar Tissue
- scar tissue that is formed in the healing process that sticks (adheres) to underlying tissue such as muscle or bone.  Can increases the chance of pain or skin breakdown

Atrophy - reduction in the size of a muscle, usually from disuse.  If you don't use a muscle, it atrophies.

Axilla - armpit

Bilateral - both sides.  A person with amputations of both arms has bilateral amputations.

Bulbous - a residual limb that is larger at the end than it is in the middle. 

Condyles - where the bones flare out near the ends.  those knobby ends (like the widest part of the elbow) are the condyles.  If we make a  socket that fits tightly around them we can use it as a method of keeping the prosthesis on.

Congenital - present at birth

Contracture- the shortening of a muscle.  If you keep your knee bent for a long time (such as when sitting in a wheelchair) you may end up with a flexion contracture, in which the muscles that flex/bend the knee (the hamstrings) have adapted to that bent position and shortened, so that the knee can no longer be fully straightened.

Disarticulation - amputation through a joint.  No bone is cut.

Distal - more 'distant' from the center of the body.  Your hand is distal to your elbow, which is distal to your shoulder.  Your foot is distal to your knee, which is distal to your hip.

Edema -   A collection of fluid in a body part causing it to swell.  After an amputation surgery, you will have edema in your residual limb.

Extension - Usually means to straighten a joint, but some joints don't really straighten, they just bend in different directions.

Flexion
- usually to bend a joint, but again, not always.  Since I only have to talk about the arm, here, I'm just going to specify what's what:         

Fingers:  
Wrist:
Elbow:

Flexion = bend
Flexion = wrist down
Flexion = bend

Extenstion = straighten
Extension = wrist up or back
Extension = straighten

Shoulder: Flexion = raise arm straight in front of you
               Extension = push arm straight back behind you
                        
Heterotropic Ossification - formation of extra bone growths in soft tissue, like muscle. 

Medial- closer to the midline of the body (vertical line through your nose and belly button).  Your eye is medial to your ear

Lateral- farther from the midline of the body.  Your ear is lateral to your eye

Prehension - to hold or grasp

Proprioception - the sense of being able to feel one's limbs in space

Proximal - closer to the center of the body.  Your shoulder is proximal to your elbow, which is proximal to your hand.  Your hip is proximal to your knee which is proximal to your foot.

Neuroma- ball of nerve tissue that forms after a nerve is cut.  Technically, this always happens, but when we use the term in prosthetics, we are usually mean a neuroma that is causing problems.    It has grown too large, or is in an unfortunate place where it gets aggravated frequently and causes pain.

Phantom pain - the sensation of pain, sometimes severe, in your absent body part.

Phantom sensation - the feeling that you can still feel your absent body part.  Present in most people with amputations.

Pronation - the movement of rotating your arm to turn from palm up to palm down.

Protraction - the act of hunching or rounding your shoulders thus spreading apart your shoulder blades.  This is the main action used to control body-powered prostheses.

Range of Motion - the extent to which you can move a joint.  Can be full or partial.  Usually measured in degrees (as in a circle)

Scapula - shoulder blade

Supination- the movement of rotating your arm to turn from palm down to palm up.

Supracondylar- "above the condyles" Describes a socket design that fits tightly around and above the condyles (see above)

Transcarpal - amputation between the wrist and hand.

Transhumeral - Through the humerus/upper arm; above-elbow.  Named for the bone that is cut in an above elbow amputation

Transradial - through the radius/forearm; below elbow.  Named for a bone that is cut in a below elbow amputation

Unilateral - one side

Wrist Disarticulation - amputation through the wrist 


 Abbreviations

ACA

Amputee coalition of America

ACCI

Anatomically Controlled and Contoured Interface

ACS

Anatomically Contoured Socket

AE

Above-elbow, transhumeral, through the upper arm

AFB


Automatic Forearm Balance - a feature of some body-powered elbow-forearm assemblies to make flexing the elbow easier

BE  

Below-elbow, trans-radial, through the forearm

CAD-CAM

Computer Aided Design - Computer Aided Manufacturing. Creating a 3D image of your residual limb with a scanner and using it to make your prosthesis

CP

Certified Prosthetist

CPO

Certified Prosthetist/Orthotist

FSR

 Force Sensing Resister

EMG

ElectroMyoGram - type of electrical signal picked up by electrodes in myoelectric prostheses

ETD

 Electronic Terminal Device

HO

Heterotropic Ossification

LP

Low Profile

OT

Occupational therapist

PT

Physical therapist

ROM

Range of Motion

TD

 Terminal Device

TH

Trans-humeral

TMR

 Targeted Muscle Re-innervation

TR

 Transradial

TRAC

 Transradial Anatomically Contoured (Socket)

UE

 relating to the Upper Extremity or Upper Extremity Amputation

UL

 relating to the Upper Limb or Upper Limb Amputation