Week 2: Upper Extremity Prosthetics

future developments: osseointegration

surgically implant rod/fixture into center of bone; abutment sticks out of limb and is connected directly to prosthetic component

future developments: Targeted muscle reinnervation (TMR)

take the nerves and redirect them to pectoral muscles so when pt. pretends to do motion with missing limb, the nerve that would've been associated with that motion is activated for high level pt.

excursion of harness

the distance that the intact segment of the body must travel to activate the terminal device

wrist terminal devices are connected via...(2)

threaded stud or quick disconnect (the latter of which is better for changing out devices if you switch between tasks)

terminal body powered hands: commonly used prehension pattern

three-jaw chuck

which digit provides 50% of hand function?

thumb

terminal body powered hooks: visual field

better with hooks than mechanical hands (especially canted shape, which is curved; Lyre is straighter and less visually helpful)

transhumeral harnessing: what does it control?

both elbow and terminal device function

inside-locking elbows: what is locking mechanism triggered by?

cable/string

hinges for transradial prostheses: purpose

connect forearm to tricep cuff, which goes around upper arm

transradial harnessing: what is figure of 9 good for?

control only -- no suspension (only used when socket design is self-suspending)

voluntary opening body powered terminal device: user must overcome ______ in order to open the device

full grip strength (regardless of what is required for the task)

future developments: HiFi Socket design

good for prosthetic fit and outcome; stabilizes bone within limb and prevents rotation in the socket

what does passive terminal devices include? (3)

hands mitts devises designed for sport, recreation, vocation

voluntary closing body powered terminal device: ____ pinch forces can be achieved

higher pinch forces can be achieved (not limited by rubber bands/springs)

single DOF hands: what does it consist of (3)?

inner actuator mechanism, outer hand-shaped form, cosmetic glove cover

terminal body powered hands: usually used as _______ hand for social occasions

interchangeable

voluntary opening body powered terminal device: grip strength remains constant until...

it is modulated by the user

inside-locking elbows: what is it? where is it attached

joint + locking mechanism inside outer shell; installed distal to residual limb

possible myoelectric control strategies (3)

single-sit (one site, cx muscle once and it does one thing/cx again and it does opposite) dual site (one signal open/one closed) pattern recognition (multiple electrodes, muscle cx causes pattern which creates action)

myoelectric signals

signals associated with muscular contraction in the residual limb which can be picked up by external electrodes placed against the skin inside the prosthetic socket

transhumeral harnessing: _____ cable responsible for two actions

single cable responsible for 2 actions (split cable housing)

which hinges are indicated for very short transradial limbs, which require very high trimlines but cause flexion ROM restriction?

step up hinges

how is UE eval different from lower extremity? (4)

still looking for the basic info; however goals should be more specific (does patient type? have public facing job? require to use tools? want to work out) greater focus on activity specific prosthesis cognition is esp. important for myoelectric devices mental health more imp.

single DOF hooks: prehension patterns

tip, lateral, cylindrical

purpose of wrist terminal devices

to attach and position the terminal device

transhumeral harnessing: when elbow is _______, control cable activates elbow function

unlocked

multiple DOF hands: how many functional grasping patterns

up to 30

transhumeral harnessing: shoulder saddle

used when heavy lifting is required; used to disperse forces across a greater SA using the chest wall and IL shoulder

voluntary closing body powered terminal device: describe tension needed to maintain grasp

user must apply constant cable tension to maintain it (can start feeling very heavy)

shoulder myoelectric elbows

very heavy

myoelectric elbows

very heavy; need enough muscle control to allow for different motions (most pt. w/ above elbow amputation do passive/body powered elbow + myoelectric hand)

transradial harnessing: what is shoulder saddle good for?

when heavy lifting is frequently required (uses chest wall and IL shoulder to support weight/force)

important factors to consider in component selection of myoelectric prostheses (11)

○ Availability ○ Weight ○ Cost ○ Cosmesis ○ Noise ○ Durability ○Reparability/Warranty/ Service ○ Compatibility ○ Limb Length -- may not have enough residual limb length for SA contact with electrode ○ Gadget Tolerance ○ Environmental Factors

drawbacks of terminal body powered hands (4)

○ Frictional loss of force ○ Glove restriction of motion ○ Limited pinch force ○ Contours that block visual inspection (bulky)

main objectives in acute care (5)

-STM -scar management -wound care -desensitization (gentle tapping) -manage surgical pain

terminal body powered hooks: materials

-aluminum, stainless steel, titanium, composites (versatile)

advantages of myoelectric prostheses (5)

-doesn't require gross body movements -increased grip strength -increased envelope of operation (Can reach out arms in front of them) -improved control -improved cosmesis

types of hinges for transradial prostheses (see details) (6)

-flexible -single axis -polycentric -step up -residual limb activated locking hinges -outside locking hinges

types of wrist (5)

-friction -constant-friction -quick disconnect -rotational -flexion what you choose depends on how device is activated and how much motion you allow at wrist for terminal device ; good wrist reduces sound side compensation at the shoulder

2 types of elbows for ED and transhumeral amputation

-friction elbows -inside-locking elbows

transhumeral harnessing: what are the control motions (2)

-glenohumeral flexion -biscapular abduction

transradial harnessing: how does figure of 8 create power generation? (2)

-glenohumeral flexion of IL shoulder -biscapular abduction

types of prosthetic suspensions (3)

-harnessing -liner (lanyard/pin) -anatomical (suspend against bony prominences)

transhumeral amputation: what does increased residual limb length provide? (3)

-increased surface area -more leverage -interaction without a prosthesis (allows for opposition)

elements of pre-prosthetic care (7)

-limb shaping (shrinker/compressive device) -strengthening (core, both upper extremities) -ROM -endurance -mental health considerations -myoelectric specific training (EMG signals, co-contraction / signal separation) -getting prosthetists, PTs, and OTs involved as early as possible

transradial amputation: what does increased residual limb length provide? (4)

-more surface area -better leverage -extended area for force to be distributed on -more pronation/supination ROM (helps reduce compensation at the shoulder)

types of prosthetic design (3)

-passive -body powered -myoelectric

single DOF hooks: additional features

-passive radial/ulnar deviation and/or wrist flexion/extension

passive terminal devices do not have...

active/cable-controlled grasp (only moves if you move the other hand)

force of harness

amount of power the body must generate to activate terminal device

Krukenberg operation

amputation that separates ulna and radius (transradial amputation) to create a pincer surface area so patient still can grab onto something while maintaining proprioception, sensation, temperature (no prosthesis but helps with function)

voluntary opening body powered terminal device: for delicate objects, user must maintain...

appropriate tension to prevent crushing the object

passive hands may include _____ or ______ fingers

bendable or spring loaded (i.e. for a motorcycle handle)

pathway of motor control (7)

- Muscular activity --> - Surface EMG sensor (electrode) --> - Amplifier (increases activity that is seen) --> - Processor (decides what to do based on input) --> - Power source (creates motion) --> - Prosthesis motor (creates activation) --> - Activation of the prosthesis

what complex things can the intact upper limb do? (5)

-perform both FM and GM tasks -contribute to communication & body language -28 simult. DOF -sightless proprioception (position, heat, moisture, pressure) -visually appealing, lightweight, waterproof, self0healing no prosthesis can do ALL of these things; additionally, the best device for the patient may not be the most technically advanced

finger/partial hand prosthesis: functional

-provide intuitive grasp; restores length of finger and hand; provides grip strength

considerations for shoulder disarticulation amputation (4)

-relatively uncommon -related to malignant lesions, trauma, congenital etiologies; causes complete loss of UE -often reject prosthetic use (cumbersome, heavy, sockets = uncomfortable) -may have small part of humeral head and neck remaining to preserve cosmesis

disadvantages of myoelectric prostheses (4)

-reliance on external power source -increased weight -damage -increased cost

transhumeral harnessing: body motions to lock/unlock elbow (3)

-scapular depression (down) -glenohumeral extension (back) -glenohumeral abduction (out)

multiple DOF hands: how does switching b/w grasp patterns become accomplished? (4)

-single-peak trigger -double-peak trigger -co-contraction input signals -external switches/grip chips

other considerations for transhumeral amputation (3)

-skin integrity -ST coverage -muscular strength/myodesis (muscles must attach well to residual limb)

functions of passive terminal device (4)

-support / stabilization of objects -restoration of some bimanual activities -use of utensils, tools, grooming instruments -functional extension of residual limb to match sound side

single DOF hands: prehensive patterns (4)

-three-jaw chuck -palmar -power -cylindrical

2 types of body powered/activated terminal devices

1) voluntary opening (closed at rest) 2) voluntary closing (open at rest)

single DOF hands: describe the motors

1-2 motors to oppose thumb against digits 2 and 3; digits 4/5 are passive

transhumeral harnessing: how must patient operate device? (3 steps)

1. position forearm passively with the other hand or through cable system 2. lock elbow -- either pull cable with other hand or use another motion 3. activate TD by pulling cable again

multiple DOF hands: # motors

5-6 (more DOF but may decrease oppositional force and cause decreased battery lift)

terminal passive devices typically _______ and requires ______ harnessing

LW no harnessing

single DOF hands: articulation occurs at...

MCP and CMC joint

what are purposes of harnessing? (2)

Movement from an intact body segment causes a transfer of force that actuates body-powered componentry may also provide suspension of the prosthesis on the body

future developments: pattern recognition (COAPT)

Multiple electrodes, muscle cx causes pattern which creates action no insurance code

voluntary closing body powered terminal device: requires more _____

excursion

which transradial hinges are good for long residual limbs?

flexible

voluntary closing body powered terminal device: manipulation of delicate objects requires ________ compared to voluntary closing

less work

transhumeral harnessing: nudge switch

lever which can be used to create an action when insufficient excursion or forces is available via harnessing (pt. cannot produce enough of their own force) typically use chin for it

multiple DOF hands: what is it best for?

light/medium duty activities

friction elbows: weight

lightweight (simple to operate)

transhumeral harnessing: when elbow is _______, control cable activates terminal device function

locked

voluntary closing body powered terminal device: who is it better for?

longer residual limb, more distal amputation levels

friction elbows: who is it good for?

low-impact, pediatric, cosmetic restoration, BP injuries

multiple DOF hands: drawbacks

more complicated, heavier

transhumeral harnessing: shoulder saddle drawbacks

not as effective force transmission

friction elbows: cognition required?

not much

terminal body powered hands: how functional are they?

not very functional

single DOF hands: motion

open/close prehension (one motion back and forth -- opposing the thumb and first two fingers)

passive prosthesis v. cosmetic

passive lacks actively controlled grasping capability (may or may not be visually appealing) cosmetic is visually appealing/lifelike

friction elbows: what do they require?

passive positioning of forearm -- require you to move forearm and position it in space with other hand or by pushing against another option

which transradial hinges provide increased stability for short limbs?

polycentric

voluntary closing body powered terminal device: graded ______ or _______ is possible

prehension or tension

what do wrist terminal devices primarily facilitate?

pronation/supination (but, some units allow flexion, extension or other movements)

terminal body powered hooks: sizes

ranges from infant to adult; comes in many shapes depending on function needed

finger/partial hand prosthesis: silicone

realistic looking device on top of limb --> provides both cosmetic (good for mental health) and functional (opposition, protection) benefits

which hinges are indicated for very short transradial residual limbs that cannot operate conventional prosthesis?

residual limb activated locking hinges

transhumeral harnessing: can use ____ expansion to strengthen anchor points

rib cage

single DOF hands: IP joints

rigid

wrist shapes (2)

round or oval

voluntary opening body powered terminal device: what is grip strength created by?

rubber bands or strings holding the device closed

single DOF hooks: difference from hand

sacrifices cosmesis for robust design; stronger prehensor pinch forces; increased visual feedback