Ankle Components & Transtibial Amputation Flashcards
What is the name of a non-articulating prosthetic foot?
SACH (Solid- ankle- cushioned heel)
Typically patients in K1 level will get what type of prosthetic feet?
- SACH feet
- Single axis feet
What are the articulating feet?
- Single Axis feet
- Multi-axial feet
- Dynamic response/energy storing feet
- Multi-axial dynamic response feet
- Microprocessor
Typically patients in K2 level will get what type of prosthetic feet?
Multi-axial feet
Typically patients in K3 level will get what type of feet?
- Dynamic response/energy storing feet
- Multi-axial dynamic response feet
Typically patients in K4 level will get what type of feet?
- Microprocessor
Describe a SACH
- Light weight
- Inexpensive
- Wooden or metal keel that extends to the MTP joints
- Rubber heel allows for shock absorption
- Allows for plantarflexion at loading response
What is a keel?
Rigid, which provides midstance stability but little lateral movement
What is a SACH Foot?
Soft rubber heel wedge that mimics ankle action by compressing under load during the early part of the stance phase of walking
How does the wearer prevent the knee from buckling when using a SACH foot?
The wearer must actively control the prosthesis to prevent the knee from buckling
What mobility is allowed by a SACH Foot?
Ankle joint that allows the foot to move up & down, enhancing knee stability
What motion is allowed by the single axis foot?
- Some sagittal motion allowed and controlled by interchangeable anterior & posterior bumpers
- DF 5-7°
- PF 15°
- No transverse or frontal plane movement
Which type of foot may be more appropriate for individual where stability is a concern (Single axis or SACH) and why?
- Single axis
- Reduces the effort required to prevent buckling
What are the disadvantages of single axis compared to SACH?
- Heavier
- More maintenance required than SACH
What motion does multi-axis foot allow?
- Pronation & supination (eversion/Inversion)
- Sagittal DF/PF
What does multi-axis foot allow the wearer to be able to do?
- Cope with uneven terrain
What are the disadvantages of multi-axis foot?
- More expensive
- Can be heavier
Describe a multi-axis foot in regards to movement and protection
- Similar to single axis foot in terms of weight, durability & cost
- Multi-axis foot conforms better to uneven surface
- can move from side to side in addition to up and down
- Added ankle motion absorbs some of the stresses of walking, this helps to protect both the skin & the prosthesis from wear & tear
How does the leaf spring work in dynamic response/energy storage?
- Leaf spring stores energy during rocker & releases energy
- As cadence or activity increases the dynamic response increased, & results in greater energy return
Who is the ideal patient for a multi-axial dynamic response foot?
- Vary walking speed, change directions quickly or walk long distance
- People with active lifestyles
How does the multi - axial dynamic response foot store & release energy during walking cycle?
By absorbing energy in the keep during the “roll-over” phase and then springing back to provide a subjective sense of push off for the wearer
Some dynamic response feet feature a split-toe design, what does this do?
- Further increases stability by mimicking the inversion/eversion movements of the human ankle & foot
What does the comfort and responsiveness of dynamic response foot encourage?
Individual to advance from a more moderate activity level to a higher activity level, given the more natural feel of walking with this type of prosthetic foot
What does the microprocessor foot automatically do?
- Provides DF during swing phase that allows sufficient ground clearance
- Active ankle motion allows user to tuck both feet behind their knees when getting up from a chair
- PF foot for more natural appearance when seated
What are the advantages of a microprocessor foot?
- Provides push off
- Increased ability to self-select gait speed
- Less energy expenditure
What are disadvantages of Microprocessor foot?
- Poor battery life
- Heavy
- Expensive
What should be considered when choosing the appropriate foot?
- Prosthetic user activity level
- Ability or potential to reach a higher level
- Cosmetic appearance-toes, veins, medial/lateral malleoli
- Ability to resist moisture
- Heel height
- Vocational/recreational
- Maintenance/ distance to prosthetist
What is a transtibial amputation and what motion are lost?
- Removal of the lower extremity below the knee joint
- Loss of active foot & ankle motions
Where is the fibular transected to avoid distal fibula pain?
1-2 cm shorter than the tibia
How much length of the tibia is preserved with a short transtibial amputation and what motion is difficult?
- Less than 20% of tibial length
- Small moment arm making knee extension difficult
How much length of the tibia is preserved with a standard transtibial amputation ?
20 - 50%
How much of the tibia is required below the knee joint for optimal fitting of prosthesis?
At least 8cm
How much length is preserved in long transtibial amputation?
50% of tibial length
Why is long transtibial amputation not usually advised?
Poor blood supply to the distal leg
What is the ideal length of the tibia after transtibial amputation?
12-15 cm
What occurs during surgery in an Ewing Amputation?
Agonist-antagnonist Myoneural interface (AMIs) are created by linking muscle pairs within the residual limb
What is the aim of the Ewing amputation?
- Aimed to provide proprioceptive feedback & better control of prosthetic device
- Embodiment
What are pressure sensitive area after transtibial amputations?
- Fibular head
- End of fibula
- shin bone
- end of tibia
- Hamstring tendons
What are the two socket designs for transtibial prosthetic?
- Paterllar Tendon bearing (PTB)
- Total surface bearing
What are the suspension systems for transtibial?
- Thigh corset
- Pin system
- Suction suspension
- Vacuum Assisted socket system
Where is indentation in patellar tendon bearing?
- Patellar tendon
How is the suspension system generated in patellar tendon bearing socket?
At medial & lateral areas of the femoral condyles
Where does the medial & lateral walls extend in patellar tendon bearing?
Extend above femoral condyles
What are the challenges of the patellar tendon bearing?
- Active amputees the PTB trim lines/suspension too restrictive (limiting knee flexion)
- Can piston
- Some amputees can’t tolerate pressure on their patellar tendon
How is suspension generated in total surface bearing socket?
Means of adhesion between residual limb and silicon liner
Where is weight distributed in total surface bearing socket?
over the residual limb surface
What are the advantages of total surface bearing socket?
- Active amputees- lower trim lines
- Reduced pistoning due to total contact
- Increase proprioception due to WB
- Suspension is between in the socket using locking pins of suction
- Believed to be more comfy
What are the disadvantages of total surface bearing?
- Can have challenges for 1st amputees due to volume changes in 12-18 months
- Challenges for individuals on dialysis
- Challenges for individuals with short residual limbs (<10 cm long)
- Pain at distal of residual limb
- Increased perspiration (silicon liner)
- Not preferred for individual with visual/sensory disturbances or hemiparesis due to difficulties donning/doffing
- Excessive soft tissue (uncomfy)
What is pistoning?
Undesirable motion, residual limb moves up and down within socket
What is suspension?
Method by which the artificial limb is attached to the body
What are the disadvantages of thigh corset?
- heavier
- May cause pistoning
- Difficult to don
- Not as common
What is the advantages of the pin system suspension system?
- Helps with pistoning
- Unrestricted knee flexion & minimal pistoning
When is the pin system suspension system indicated?
Scarred or sensitive limbs
T/F: The pin system is commonly used
True
What are the advantages of sleeve suspension?
- Cosmetic
- Airtight
- Showering
- Unrestricted knee motion
What are the disadvantages of sleeve suspension?
- Not durable
- Hygiene problems
- Need good hand function to don/doff
What is the advantage and disadvantage of suction suspension systems?
- Advantage: Can add sock ply as needed for volume fluctuations
- Disadvantage: Pistoning can occur
What are the benefits of vacuum-assisted socket system?
- Promote fluid exchange
- Reduce moisture build up
- Regulates volume fluctuations
- Increases proprioceptive awareness of the residual limb
- Helps to control pistoning
- May help with wound healing
What are the disadvantages of the vaccum- assisted socket system?
- Expensive
- Heavier
- Can be noisy
