wrist units and elbow units

Question 1

types of rigid elbow hinges

Answer 1

Single-Axis Hinges.
Polycentric Hinges.
Step-Up Hinges.
Stump-Activated Locking Hinge

Question 2

flexible hinges are used usually on what kind of patients?

Answer 2

long residual limb and bilateral

Question 3

what are flexible hinges used for?

Answer 3

facilitate the transmissions of this residual forearm rotation (50%) to the terminal device.

Question 4

what materials are flexible hinges made of?

Answer 4

metal, leather or dacron webbing

Question 5

attachment points of flexible hinges?

Answer 5

prox. triceps pads,, distally prosthetic forearm

Question 6

Amputations at or above the mid-forearm level cause: 2 things

Answer 6

Limitation to the possibility of transmitting active supination or pronation to the terminal device.
Increase in the possibility of the socket to rotates about the residual limb.

Question 7

to prevent socket-residual limb rotation we use …… hinges?

Answer 7

rigid

Question 8

types of mechanical wrist units

Answer 8

Friction Wrist Units
Constant-Friction Wrist Units
Quick-Change Wrist Units (Quick disconnect Wrist Unit)
Wrist Flexion
Rotational Wrists
Ball-and-Socket Wrist

Question 9

friction wrist unit is available in two shapes, which one is more cosmetically looking and provides smoother transition?

Answer 9

oval shaped friction wrist units

Question 10

friction wrist units are made of

Answer 10

aluminum and stainless steel

Question 11

how is friction obtained in friction wrist unit? and how?

Answer 11

through a rubber washer, by changing the hand orientation

Question 12

how does the hand orientation affect the friction in wrist unit?

Answer 12

when TD stud is screwed into the unit, rubber washer is compressed and causes friction
as TD is unscrewed friction is reduced

Question 13

in constant-friction wrist unit, how much does each shape have sizes?

Answer 13

circle: 4 (inf. child. adult. med.)
oval: 2 (med. adult)

Question 14

in constant-friction wrist unit, what is the mechanism?

Answer 14

these units employ a nylon-threaded insert with steel lead threads. Turning a small set screw in the body of the wrist causes the nylon thread to be deformed against the stud of the terminal device, thus creating constant friction

Question 15

why is wrist flexion important?

Answer 15

midline activities

crucial for bilateral amputees

Question 16

Has three locking positions at zero, 30, and 50 degrees of volar flexion.
This unit is significantly heavier than the Flexion Wrist
what is it?

Answer 16

Sierra wrist flexion unit

Question 17

Replaces the common constant-friction wrist
Allows manual prepositioning of the TD in neutral, 30 degrees of volar flexion, or 50 degrees of volar flexion.
The TD can also rotate about its mounting stud in any of the positions.
what is it ?

Answer 17

Hosmer-Dorrance wrist unit

Question 18

what makes the rotational wrists go back to neutral position after manually supinating/pronation?

Answer 18

tension on the terminal device control cable

Question 19

what gives rotational wrists an advantage at other types?

Answer 19

when locked in position, they provide greater resistance to rotation than do friction units

Question 20

how does a ball-and-socket wrist work?

Answer 20

The unit permits universal prepositioning of the terminal device with constant friction.
The magnitude of the friction loading can be easily adjusted by the amputee