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Rehabilitation Engineering I > Lecture 6 - Exoprosthetics > Flashcards

Lecture 6 - Exoprosthetics Flashcards

1
Q

What are the main causes of amputations? In order of most to least common.

A
  1. vascular disease
  2. trauma
  3. miscellaneous (malignant tumors)
  4. infection, sepsis
  5. congenital malformation
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2
Q

What does the choice of a prosthesis depend on?

A
  • Mobility of use (age, weight, interest in sport)
  • Type & level of amputation
  • Condition of residual limb (muscle function?)
  • Cosmetic expectations
  • Costs, affordability (covered by insurance?)
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3
Q

Describe the different Mobility Grades for leg prostheses.

A

Grade 0: Prosthesis not applicable. Bedd-ridden or wheelchair-bound.
Grade 1: Prosthesis for simple sit-to-stance transfers, indoor walking (slow speeds)
Grade 2: Prosthesis for limited outdoor walking (slow speeds)
Grade 3: Prosthesis for normal outdoor walking (normal speeds)
Grade 4: Prosthesis for special outdoor activities (e.g. sport)

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4
Q

Describe the inverted pendulum model without a knee joint.

A
  • Hip joint moves along circular path (center of rotation at the ankle)
  • Up & down movement of hip joint is rather high (not optimal)
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5
Q

Describe the role of the knee joint in gait.

A
  • Flex swing leg
  • Flex a little (5-10 degrees) in stance leg
  • Further reduce up and down movement of the hip joint (less energy needed to move trunk up and down)
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6
Q

Describe the role of the pelvis during gait.

A

The pelvis helps move the trunk up and down in a way that further minimizes levels of acceleration.

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7
Q

Describe the role of the foot during gait.

A
  • Helps smoothen trajectory of the trunk

- Smooth trajectory of proximal end of shank only occurs if muscles in ankle and foot are acting appropriately

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8
Q

List the stages of the stance phase of gait.

A
  1. Initial contact (heel strike)
  2. Loading response
  3. Midstance
  4. Terminal stance
  5. Pre-swing
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9
Q

List the stages of the swing phase of gait.

A
  1. Initial swing (starts with toe-off)
  2. Midswing
  3. Terminal swing
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10
Q

What is the function of initial contact during stance phase?

A

Shock absorption

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11
Q

What is the function of the loading response during stance phase?

A

Store energy (dorsiflexion torque)

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12
Q

What is the function of the mid stance?

A

Smooth motion

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13
Q

What is the function of the terminal stance?

A

Release energy (plantarflexion torque)

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14
Q

What is the function of the pre-swing stage?

A

Release energy (plantarflexion torque)

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15
Q

What is the function of the swing phase?

A

Plantarflexion torque

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16
Q

What is the function of mid-swing?

A

Lift leg for foot clearance (dorsiflexion)

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17
Q

What is the function of terminal swing?

A

Heel strike preparation (ankle co-contraction)

18
Q

What are the foot and ankle requirements for a foot prosthetic during the stance phase?

A
  • Energy (“shock”) absorption, dissipation
  • Provide good foot-ground contact (flat on ground, no slip)
  • Smooth foot rolling phases
  • Store kinetic energy by elastic components (transfer from power uptake to power release)
19
Q

What are the foot and ankle requirements for a foot prosthetic during the swing phase?

A

Dorsiflexion to obtain high foot clearance and avoid toe drag and stumbling

20
Q

What are the basic characteristics of a SACH foot? (Solid Ankle Cushioned Heel)

A
  1. emerged 1957
  2. solid ankle joint (keel and lower leg often wooden)
  3. non-articulated rubber heel
  4. provides energy absorption at impact
  5. rigid keel may increase energy expenditure
  6. tendency to fall backward with softer heels
  7. slow rolling down movement of foot
  8. simple, cheap, reliable
  9. good for amputees with limited mobility
21
Q

What are the basic characteristics of a Jaipur foot?

A
  1. emerged 1968
  2. greater range of motion - allows for dorsiflexion & inversion-eversion
  3. rubber core
  4. wooden keel & ankle
  5. vulcanized rubber coating
  6. low cost: $45
  7. water resistant
  8. quick to fit and manufacture
22
Q

What are the basic characteristics of a Single-Axis foot? (compared to SACH)

A
  1. faster rolling down movement
  2. increased knee stability
  3. preferred for amputees with short stump, painful stump, weak muscles
  4. requires maintenance
  5. slightly more expensive than SACH (more complex)
  6. has single-axis joint and plantar flexion bumper
23
Q

What are the basic characteristics of a Multi-axial foot?

A
  1. allows pronation/supination and eversion/inversion to better cope with uneven terrain
  2. ankle torque absorber can be added
  3. more expensive than SACH and single-axis foot
  4. for persons with higher mobility grades
24
Q

What are the basic characteristics of a Elastic Keel foot?

A
  1. SAFE foot (Solid Ankle Flexible Endoskeleton)
  2. Elastic keel for better energy conservation
  3. Smooth roll-over
  4. Slightly delay in push-off
  5. Lightweight, easy to use, and slightly more expensive than SACH foot
25
Q

What are the basic characteristics of a stored energy foot or Flexfoot?

A
  1. leaf spring (metal or nylon) keel
  2. flexible ankle joint
  3. stores energy at beginning and release it at end of stance phase
  4. preferred for fast cadences and high activity level (enhanced push-off)
  5. stiffness adjustable to amputee’s body weight, activity, ability
26
Q

What are the basic characteristics of the rise legs from India?

A
  1. comparable to stored energy foot
  2. made from cane (Rattan)
  3. low cost
27
Q

What does an actuated ankle joint do?

A
  1. generates joint torque leading to a smooth and powerful push off
  2. mimics natural foot motion and increased ground clearance
28
Q

What are knee joint requirements of a knee prosthesis during the stance phase?

A
  • support against gravity to provide stability
  • impact absorption at foot contact and loading response phase
  • keep body center of mass on constant height
  • dissipate/generate kinetic energy at defined phases
29
Q

What are knee joint requirements of a knee prosthesis during the swing phase?

A
  • flex knee joint to obtain sufficient foot clearance
  • decelerate shank during terminal swing
  • adaptation to different cadences and gait patterns (walking, running, ascending/descending stairs)
30
Q

Describe 3 ways to make an artificial knee joint stable.

A
  1. Change the loading vector orientation
    - Change gait pattern (walk like on ice to reduce horizontal GRF)
  2. Produce a counter torque against flexion torque
    - Lock knee joint (produce large blocking torque)
    - Insert spring and damper (produce a passive viscoelastic torque)
    - Insert motor (produce an active torque)
  3. Change Center of Rotation
    - multicentric joint (move center of rotation to a stable region)
31
Q

List the basic characteristics of a manual locking knee prostheses.

A
  • No flexion during walking
  • No energy conservation or dissipation
  • Knee bonding only possible with a manual release for sitting (e.g. via remote release cable)
  • Bilateral application possible, but both patient hands required
32
Q

Give an advantage and 2 disadvantages of manual locking knee prostheses.

A

+ Always stable and safe

  • Unnatural and energy-consuming gait
  • Patient falls into chair after release
33
Q

What are the 2 basic principles of a weight activated locking knee prosthesis?

A
  1. Spring mechanism activated when loaded during stance but released during swing
  2. Body-weight engages a brake to prevent knee from buckling (friction lock)
34
Q

What are the advantages of a weight activated locking knee prosthesis?

A
  • very stable, therefore prescribed as patient’s 1st prosthesis
  • preferred for patients with poor hip control
35
Q

What are the disadvantages of a weight activated locking knee prosthesis?

A
  • locking mechanism loose over time, thus maintenance required
  • unnatural gait pattern
  • no flexion during stance phase
  • prosthesis must be fully unloaded before sitting down
36
Q

What are the basic characteristics of a polycentric knee prosthesis?

A
  • during loading: COR posterior and proximal during extension (increased stability)
  • during late stance: COR anterior
  • instantaneous COR mimics the evolute of a normal knee
  • better unlocking at toe-off
  • shortens slightly during flexion, which provides additional toe clearance
37
Q

What are the basic characteristics of a knee prosthesis with passive damping via fluidic systems?

A
  • in combination with different joint systems (e.g. polycentric)
  • piston in cylinder presses oil or air through a little valve (hole)
  • provides a speed dependent damping force
  • natural impact absorption during heel strike
  • damping can be adjusted by the user
  • different walking speeds and cadences possible
  • leads natural walking pattern, for active patients
  • increases weight and costs
38
Q

List the different amputation levels for upper extremity prosthetics.

A
  1. Finger
  2. Partial hand (transmetacarpal)
  3. Entire hand
  4. Wrist disarticulation (transcarpal)
  5. Below elbow (transradial)
  6. Through elbow
  7. Above elbow (transhumeral)
  8. Shoulder disarticulation
39
Q

What functions must upper extremity prostheses fulfill?

A
  1. spatial movements of objects (hold and move)
  2. manipulation of objects (touch, press, grip)
  3. gesture
  4. perception and exploration
  5. cosmetics
40
Q

How do upper extremity prostheses compare to lower extremity prostheses?

A
  • non-periodic, non-ballistic movements
  • challenge of energy storage/generation
  • many different grips required
  • sensory feedback important
  • aesthetics, level of realism important
41
Q

List important hand grips.

A
  1. Finger push
  2. Flat-hand push
  3. Pinch/key grip
  4. Span grip
  5. Disk/precesion grip
  6. Hook grip
  7. Power/cylinder grip
42
Q

Give examples of powered prostheses.

A
  • Body-powered: via contralateral shoulder
  • Motor-powered myoelectric hand prosthesis
  • Targeted muscle reinnervation: neurally controlled, 8 DOF, nerves relocated, electrodes convert signals of motion intention, sensory feedback, natural control

Rehabilitation Engineering I (12 decks)

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