Trans-Tibial Prosthetics Flashcards
4 major causes of amputation
- Vascular disease and infection
- Trauma
- Tumors
- Congenital limb difference
in order of prevalence
Greatest risk factors for amputation
Vascular disease .
- Contributing to 2/3 LE amputations
55% requiring amputation of 2nd LE within 2-3 years
Often see progression from a CROW boot and eventually transitioning to prosthesis .
Role of prosthetist
- Design, fabrication, and fit of prosthesis
- Monitor prosthetic use and trouble shoot issues
- Monitor non-amputated limb, precursors to amputation
- Master’s degree. Need license.
Pre-prosthetic concerns (after amputation but before getting prostheses)
- Delayed healing
— dysvascular
— poor nutrition/habits
— falls - Fluctuating edema
- Shape
- Contractures
- Adherent soft tissues
What is first course of action for edema control on residual limb
Shrinkers sock
— reduces edema, good for shaping, and allows for easy inspection
ACE wraps for edema control?
- reduce edema
- good for shaping
- always accurate if applied correctly.
- good to teach all patients to do on their own.
What is removable rigid dressing
- used more in inpatient side of things. Like a helmet for the amputated limb
- reduces edema
- shapes limb
- protection
- allows for inspection
- education
How to decide on prosthetic design
Consider a team approach
- what PLOF, CLOF, are they going to be walking with a walker or with no AD, what are they gonna do in the future
- K level - way to assess someone’s functional level before getting a prosthesis
- sound side use — can they stand without a prosthesis on the residual limb side?
Outcome measures
- helps give insight into prosthetic design
- K level
PLUS-M
TUG
4xsqSt
Examples of consideration based on amputation level
Through-bone versus disarticulation
Anticipated componentry
Confusion from from dysvascular cases
— disarticulation is separating the joint itself.
— the level of amputation will cause the type of prosthesis recommended to change
2 forms of initial prosthesis
- Preparatory
- Definitive
Preparatory prosthesis
- Slightly less cost
- Provides early ambulation
- Lower tech components
- Less cosmetic
Definitive prosthesis
- more cosmetic
- lighter weight
- ability to use higher tech components like the suspension, feet, knees that can offer more function
Components of TT prosthesis
- Socket
- Protective cover
- Pylon
- Foot
- Suspension
Look at slide for pic
Socket part
- most important aspect
- custom made — casting, hand modifications, also CAD/CAM tech can help to make it
- lots of designs
Foot part
- provides BOS
- several designs
- act as springs
Pylon part
- integrates socket to foot
- allows for alignment and height adjustment
- various materials
- may be finished with a cover
Suspension part
- means of attachment to anatomy
- actual weight vs perceived weight. If it’s attached well to the limb the perceived weight could be less
- impact on proprioception
- several options
2 Transtibial socket designs
- Patellar tendon bearing (PTB)
- Total surface bearing (TSB)
What is a patellar tendon bearing socket
Uses specific weight bearing areas
100% body weight supported in socket. Have to distribute it through the surface area of the socket.
- Utilizes flexion in the socket to distribute load not just on distal end but anterior surface too
- Utilizes pressure tolerant areas
- Avoids pressure sensitive areas
Pressure tolerant areas
- Patellar lig
- Pre-tibial muscles
- Medial flare of tibia
- Shaft of fibula
- Gastroc
- Popliteal fossa
WANT TO SEE RED HERE ITS WHERE THE WEIGHT SHOULD BE
Pressure sensitive areas
- Anterior/distal tibia
- Fibular head
- Crest of tibia
- Perineal N
- Distal cut fibula
- Lateral tibial condyle
7 hamstrings
Really don’t wanna see red here and esp if it lasts more than 30 mintues
PTB pressure distribution
Socket flexion is used. The socket is tilted 5-10 degrees to establish total contact
Indications for PTB socket
- Medium to long residual limb length
2, ease of donning - Especially prominent anatomy
Indications for PTB SC
He said he doesn’t use this a lot
- used for…
— short residual limbs
— increased ML support
— anatomical, self-suspending
Indications for PTB-SCSP
- Higher ML trim lines
— increased ML stability
— anatomical, self-suspending - Anterior trim line proximal to patella
- Indicated for very short residual limbs (tibial tubercle)
- Controls knee hyperextension (quad bar is introduced to prevent hyperextension)
Indications for joints and corsets
- Increase ML support
- Decreased weight bearing on residual limb
- Tri-planar stabilization through knee
- Previous user
- if someone has laxity through the knee or if someone is unable to bear the entire weight through their amputated limb then we introduce this
What is a total surface bearing socket
- Works on principle that liquid is non-compressible
- Distribute forces throughout surface of limb (P=f/a)
- Must use liner — like a silicon sock
What are the options for TT suspension
- Cuff strap and waist belt
- Supracondylar wedge, anatomical
- Suspension sleeve
- Locking — pin or lanyard
- Suction
- Vacuum
Describe cuff strap and waist belt
- Easy to adjust — connects to patients waist belt
- Used with standard PTB
- Sock fit — you don’t have to use a liner
- Underserved populations — materials can be used anywhere
- Cumbersome - idk what this means
Describe supracondylar wedges
- Specific shape to achieve suspension
- Requires tight PML
- Eliminates the waist belt.
clip locks them into the socket
Describe suspension sleeve
- Neoprene, urethane, gel, silicone
- Pull or roll onto thigh
- Air tight seal allows for suction
- Heat/prespiration — is it sweaty or no?
- Knee ROM restriction — something we have to prepare patients for. Also need to realize it could be the limitation of the suspension sleeve that shows decreased knee flexion ROM not the actual patient’s soft tissue restriction
Describe a locking liner
- Gel locking liner
- Always distal lock-in mechanism on the liner
- Audible click, secure before stand which is a huge benefit — you don’t need a suspension sleeve because the thickness of the liner and you rely on the click thing
Challenges for locking liners
- Distal elongation, pistoling — during swing
- Locking mechanism can be problematic
- Must don consistently — pin has to be in the same spot every time for it to work
-if someone is stuck, try tapping on the lock to release it or if they are using it with socks and sometimes the sock can get caught in the pin so fix that
Describe suction
- Uses a liner that has a rounded bottom to it, so nothing on distal end like the locking liner
- Great quality of suspension
- Addition of thigh sleeve
- Lightweight
- Low build heigh recruitment
- Most common mechanism for athletes/runners
Challenges of suction
- Knee ROM restriction because of the material behind the knee
- Sleeve damage
Describe suction seal in
- Suction achieved without suspension sleeve
- Often in TF
- Improved knee ROM — helps get around the bunching of fabric behind the knee
- May be problematic with honey anatomy
Describe vacuum
- Really close to suction but now we have a pump that gets the air out and creates negative pressure system
- Highest level of suspension
- Air is actively drawn out of airtight socket, pulling soft tissue to inner socket wall
— shear forces, adherent scarring, grafts - Requires air seal with sleeve
- Total contact is essential — imp with vacuum so you don’t harm the soft tissue
Benefits of vacuum
- Decreased volume fluctuation
- Moisture control
- Improved linkage between anatomy and prosthesis
- Wound healing - anecdotal - again idk this word
How do you maintain prosthetic fit
- Sock ply (volume) management
- Can use them to maintain proper fit with volume fluctuation — as the day goes on the limb can get smaller so they have to pack extra socks
- May change throughout the day
- Various many/not enough
Maintainence of prosthesis over time
- Ongoing relationship
- Adapt as patient changes and evolves
What are the foot options
- SACH
- Single axis
- Flexible keel
- Multi-axial
- Dynamic response
lowest to highest activity
What is foot function
- Yielding into inversion/eversión — esp for different surfaces
- Transverse rotation — so forces aren’t imposed on the anatomy through the socket
- Shock absorption — don’t want that translating upstream
- Active push off, energy return — accepts weight when loaded and stores energy until push off to help propel forward
What are the foot selection criteria
- Residual limb characteristics: length and skin integrity
- Funding
- Weight: patient’s weight and weight of component
- Proximal control, external forces
- Vocation
- Hobbies, activities prior to amputation
- Functional level
What are K levels
medicare terminology, way to describes someone’s function
K0 - K4
K0
Patient has no ability or potential to ambulate or transfer — no prosthetic candidate
K1
Transfer or ambulate on level surfaces with a fixed cadence
K2
Ambulation with ability to traverse low level barriers - most commonly household ambulatory or flat ground short distance community ambulator
K3
Ambulate with VARIABLE CADENCE, activities beyond simple locomotion
big thing we have to ensure they can do before referral for prosthesis
K4
High impact or energy levels, sports
What is a SACH
Solid ankle cushioned heel
K1 people
No inversion/eversión yielding
Cushioned heel — initial contact to midstance (softer heel cushion)
Anterior keel — midstance to terminal stance
What is a single axis foot
K1
Single axis joint allows PF/DF
Cushioned heel and solid keel
Stability — yields to floor at loading response and reduces knee flexion moment through early stance.
Increased weight for prosthesis
What is a flexible keel foot
K2
Absorption of motion in inversion/eversión and transverse rotation
More compliance here because the keel itself has movement to it and weight bearing capacity so it smooths out transitions throughout stance phase.
What is a Multi-axial foot
K2/3
Good for uneven terrain compliance, may be modular
Impact absorption, reduces forces on residual limb
What is a dynamic response foot
K3/4
Carbon composite heel/toe lever
Low/high profile
Categorized to patient weight/impact
Spring type energy storing and return back to body
this material really supports someone changing their cadence
What are specialty feet
- Microprocessor foot/ankle
- Hydraulic foot/ankle
- Adjustable heel height
- Running/fitness feet
- Swimming
Transtibial biomechanics
- Maximize weight bearing capacity of the residual limb
- Maintain ML stability between residual limb and socket during midstance
- Encourages knee flexion throughout stance phase, supported and controlled progression
a lot of it has to do with where we put the foot — we want to create a natural varus moment at the knee
More on Maximizing weight bearing capacity through residual limb
- Allows for full weight shift onto prosthesis
- Pressure sensitive/tolerant areas — LOAD the tolerant areas and RELIEVE the sensitive areas
- Socket flexion consideration
- Total contact, hydrostatic loading
What is the socket flexion consideration
Want to increase the vertical loading area for distributed weight bearing
What is the total contact consideration
Distal end should have contact with socket — larger surface area, minimize distal edema, increase proprioception
Concepts to improve weight bearing
- Joints/corsets
- Total surface bearing
- Ertl procedure
How do you achieve ML stability
- Looking for slight genu varum at midstance
- Thrust in either direction needs to be corrected
super don’t wanna see valgus - Again — load pressure tolerant areas and relieve pressure sensitive areas
Stability factors
- Alignment of componentry
- Socket design
- Socket fit
- Limb length
- Body weight, impact level
Alignment considerations
- Orientation of each component
- Tri-planar
- Optimize safety and efficiency
- May be linked to socket discomfort
- Adjustability as someone progresses
*good tip — look at the pylon and check for it to be vertical at midstance
Varus moment vs. Valgus moment in coronal alignment
Varus moment
- foot too inset
- insufficient socket Adduction
- short prosthesis
Valgus moment
- foot too outset
- excessive socket Adduction
Sagittal alignment areas
Drop off — excessive DF, foot too posterior
Knee Hyperextension moment — excessive PF, foot too anterior
