Prosthetics Flashcards
What may cause gait deviations (BKA)?
Toe lever arm (If too short they will roll off frontat midstance)
heel lever arm
socket flexion (If they have contracture and it’s set to full extension it won’t fit them)
heel/keel stiffness
socket rotation (average person has slight external rotation)
external foot rotation
What is bench alignment (BKA)?
It is what socket and components are set in
All components capable of adjustment and modification for optimum fit
What is static alignment (BKA)?
Stationary alignment to establish: height, foot rotation, socket position (flexion, extension, adduction, abduction, AP position, ML position)
What is dynamic alignment (BKA)?
Watch them walk
Allows for minute adjustments to prosthesis
Customize alignment of prosthesis to patient’s needs and requirements
Ensures maximum activity and stability resulting in highest possible outcome
What is prosthetic cause of drop off (BKA)?
Short toe lever, excessive socket flexion, excessive DF, incorrect foot type
What is amputee cause of drop off? (BKA)
Gait habit, weak quads, knee flexion contracture
What is prosthetic cause of vaulting? (BKA)
long prosthetic, poor suspension, excessive PF of foot, excessive knee resistance or stability
What is amputee cause of vaulting? (BKA)
Gait habit, fear of catching toe, weak hip flexors on residual limb, improper initiation of hip flexors on residual limb
What is prosthetic cause of wide gait? (BKA)
prosthetic foot too far outset, excessive socket adduction
What is amputee cause of wide gait? (BKA)
insecurity- wants to widen base in attempt to increase stability
weak ML knee control
Gait habit
What is prosthetic cause of lateral shift? (BKA)
foot too far inset, insufficient socket adduction, short prosthesis
What is amputee cause of lateral shift? (BKA)
inadequate balance, weak knee, narrow gait base
What are observations that can be made if someone has a long prosthesis? (BKA)
Patient reports lower back pain
Patient reports they feel like they are walking up a hill
Noticeable rise and drop of shoulder on the effected side
Hesitation in gait timing from prosthetic mid-stance to sound side heel strike
What are observations that can be made if someone has short prosthesis? (BKA)
Patient reports lower back pain
Patient reports they feel like they are stepping into a hole
Noticeable rise and drop of shoulder on sound side
Uneven arm motion to accommodate uneven stride length
Appears like the patient may be vaulting
What observations can be made if someone has external foot rotation? (BKA)
Patient wants foot to match sound side Internal rotation of knee at toe off Induces "medial whip" Drop off at end of stance phase Low back pain Skin irritation due to rotational stress in socket
What are causes of gait deviations in AKA?
Toe lever arm (knee may buckle if this is too long or short) Heel lever arm Socket flexion (add additional 5 degrees to contracture they already have because it will help them get over their prosthetic and stretch their hip flexors, greater trochanter aligns with knee)
During stance and swing phase how is the AK prosthetic positioned?
Stance: foot axis is 5-7 degrees ER, Knee axis is 5-7 degrees ER
Swing: foot axis perpendicular to line of progression, knee axis perpendicular to line of progression, hip joint and pelvis IR 5-7 degrees
What is the TKA?
Trochanteric Knee Ankle
stationary alignment line to identify relative alignment between center of socket weight line, the rotation point of knee, and the functional rotation point of the ankle/foot
What is prosthetic cause of medial whip? (AKA)
ER of knee
Tight socket
Mis-aligned toe break (foot is too ER, throws the knee into medial whip)
What is amputee cause of medial whip? (AKA)
Gait habit
Socket not put on properly
ER of hip at toe off/hip flexion
What is prosthetic cause of lateral whip (AKA)?
IR of knee
Loose socket
Mis-aligned toe break
What is amputee cause of lateral whip (AKA)?
Gait habit
Socket not put on properly
IR of hip at toe off/hip flexion
What is prosthetic cause of abducted gait (AKA)?
Prosthesis too long
Medial wall too high
Insufficient femoral stability (want tight fit between trochanter and ramus connecting pubis and ischium)
Induces medial whip
What is amputee cause of abducted gait (AKA)?
Abduction contracture
Pore gait habit, patient insecure and desires wide base in belief it will increase stability
What is prosthetic cause of circumducted gait? (AKA)
Long prosthesis
Excessive knee friction
Excessive knee stability
What is amputee cause of circumducted gait? (AKA)
Lack of confidence in flexing knee
Abduction contracture
Weak hip flexors
Habit, using entire hip and pelvis to initiate gait
What is prosthetic cause of vaulting (AKA)?
Long prosthetic
poor suspension
Excessive PF of foot
Excessive knee resistance or stability
What is amputee cause of vaulting (AKA)?
Gait habit, fear of catching toe
Weak hip flexors on residual limb
Improper initiation of hip flexors on residual limb
What is prosthetic cause of heel rise (AKA)?
inadequate extension aide (spring mechanism too tight)
insufficient knee friction
improper knee selection
What is amputee cause of heel rise (AKA)?
excessive use of hip flexors to initiate swing phase, overpowering knee unit
What is prosthetic cause of knee instability? AKA
excessive DF
knee in unstable position (TKA too far forward)
insufficient socket flexion (with contractures)
malalignment of foot
What is amputee cause of knee instability? AKA
weak hip extensors
hip flexion contracture
*safety mechanisms in the prosthesis are secondary to patient initiating muscular control
What is prosthetic cause of short steps? AKA
socket pain weak extension aid unstable knee excessive DF poor suspension
What is amputee cause of short steps? aKA
patient insecurity
weak hip muscles
poor balance
What is prosthetic cause of long steps? AKA
Excessive PF of foot
insufficient initial socket flexion
long toe lever arm
What is amputee cause of long steps? AKA
Flexion contracture
Patient insecurity
Pain on sound side
What is prosthetic cause of lateral shift? AKA
prosthetic foot too far inset
excessive socket adduction
What is amputee cause of lateral shift? AKA
weak hip abductors
narrow gait base
What is prosthetic cause of lateral trunk bend? AKA
foot too far outset
ineffective lateral socket containment
high medial wall
aligned in abduction
What is amputee cause of lateral trunk bend? AKA
inadequate balance
abduction contracture
short residual limb
gait habit
What is prosthetic cause of toe drag? AKA
long prosthesis
excessive PF
excessive knee friction
What is amputee cause of toe drag? AKA
weak hip flexors
weak hip abductors on sound side
poor posture
poor gait habits
What are observations to make when someone has a long prosthesis? AKA
patient reports lower back pain
patient reports they feel like they are walking up a hill
noticeable rise and drop of shoulder on the affected side
reduced swing of the arm on the effected side, exaggerated swing with arm on sound side
What are the four factors of gait?
Patient
Prosthetic alignment
Socket fit
Rehab teamwork
What are patient requirements for prosthetic knees?
Patient weight: max out at 500 lbs Patient height Patient functional age Type of amputation: knee disartic, AKA, hip disartic, hemi-pelvectomy, bilateral Patient age: peds, adult, geriatric
What is functional level 0 of knee?
no ability to walk or potential to ambulate or transfer
What is functional level 1 of knee?
ability or potential to transfer or ambulate on level surfaces at fixed cadence
What is functional level 2 of knee?
ability of potential for ambulation with ability to traverse low level barriers
What is functional level 3 of knee?
ability or potential to ambulate with variable cadence
What is functional level 4 of knee?
ability or potential to ambulate which exceeds basic ambulation skills
What are financial concerns for patients and the knee they choose?
initial investment maintenance replacement parts long term replacement future insurance status
What are the knee selection criteria?
Functional: stability factor, maintenance, durability
Patient priorities: function, durability, cosmetics, comfort
What are knee failure facts in regards to alignment?
Socket and components not set in appropriate alignment
Forces improperly interacting with components and causing premature wear
Patient has changed heal height adding stress to knee
What are knee failure facts for inappropriate use of prosthetic?
knee is stressed in conditions that the system is not designed for walking without shoes improper heel height water damage dust and dirt damage lack of maintenance
What are knee failure facts for patient selection of prosthetics?
Activity level doesn’t correspond to knee design
Weight or activity has increased since initial fitting
Patient doesn’t meet criteria for design and function of knee
How does changing shoes affect the knee?
if they change heel height it might cause knee to fail
CP has modified foot to accommodate shoe
How does improper knee adjustment lead to knee failure?
excessive friction and strong extension assist
stance screw too tight and swing screw too loose
installed with in-compatible components (foot, pylon connectors)
What are advantages and disadvantages for single axis knees?
less moving parts and simple design, lower fabrication costs
less stable at heel strike, one axis to absorb gait stress
What are advantages and disadvantages for polycentric knees?
inherent stability at heel strike, easy to initiate swing phase
tend to be heavier, increased maintenance
What functional level is manual lock knee for?
Levels 1-2
What are advantages and disadvantages of manual lock knees?
transfer prosthesis or limited walking on level surfaces, simple design, provides a non-flexing knee while standing/ambulating
patient must unlock knee to manually sit, if patient falls the knee will not collapse under them
Who gets friction knees?
Functional levels 1-2
What are advantages and disadvantages of friction knees?
transfer prosthesis or limited walking on level surfaces, simple design functionally acts like a simple door hinge
Friction setting allows for only one walking speed, friction plates wear and will require regular maintenance and replacement
Who gets stance control knees?
Functional levels 1-3
What are advantages and disadvantages of stance control knees?
Provides added stability during a misstep or uneven surfaces, breaking mechanism locks the knee during stance phase, most popular knee fit in US, light weight
Break will wear and knee will fail without proper adjustment and maintenance
Who gets hydraulic swing phase knee?
functional level 3-4
What are advantages and disadvantages of hydraulic swing knee?
Hydraulic mechanism provides resistance to flexion/extension during swing phase, provides variable cadence, ability to change walking speeds without hesitation
Tend to be heavier due to hydraulic fluids in cylinder, require regular maintenance
Who gets hydraulic swing and stance knees?
Functional level 3-4
What are advantages and disadvantages of hydraulic swing and stance knees?
Hydraulic mechanism provides resistance to flexion/extension during swing and stance phase, provides stumble recovery and ability to walk down stairs and ramps
tend to be heavier due to hydraulic fluids, require regular maintenance
Who gets microprocessor swing knees?
Functional level 3-4
What are advantages and disadvantages of microprocessor swing knees?
provides resistance to flexion/extension during swing phase, enables variable cadence, ability to change walking speeds without hesitation, on board microprocessor analyzes gait and selects appropriate resistance for smooth swing phase, provides variable cadence and ability to change walking speeds without hesitation
Added expense due to computer technology, maintenance is essential
Who gets microprocessor swing/stance knees?
functional level 3-4, some level 2s requiring added stability
What are advantages and disadvantages of swing/stance knees?
On board computer analysis gait 50x/second and performs continuous hydraulic adjustments to ensure stability, security, and efficiency in swing and stance, provides microprocessor hydraulic controlled stance and swing phase function, stance stability is engaged and disengaged as necessary, provides maximum cadence response over a wide range of functional applications, approved by medicare and VA
added expense due to computer technology
maintenance is essential
What do microprocessor knees provide?
comfort, security, stability, function, freedom
What are the comfort aspects of microprocessor knees?
reduces need to focus on every step
enables wearer to walk with more natural gait allowing normalized muscle interaction
How does a microprocessor knee provide security?
ensures knee is in most appropriate stability setting allowing security of performing ADLs
Analyzes gait 50x/sec to make instantaneous adjustments for every step and movement
What are stability aspects behind microprocessor knees?
ensures knee and prosthesis is always in the most stable and appropriate adjustment
provides ultimate in stumble recovery and instantaneous stability
How does a microprocessor knee help with function?
confidence and stability to walk on stairs, curbs and day to day obstacles
initiates stance feature to provide maximum stability and knee control
How does a microprocessor knee provide freedom?
climb and descend slopes and ramps with ease
continually adjusts hydraulic controls to right stance and swing settings
Patient has freedom to focus on life with confidence in prosthesis
How does a microprocessor knee work?
computer analyzes gait 50-1000 times per second
calculates knee angle and ankle strain
system does continuous hydraulic adjustments
dynamic valve controls multiple inputs, stance engaged and disengaged as necessary
provides maximum cadence response
stance flexion feature adjustable
How does the hydraulic stance extension, dampening work?
reduces impact to skeletal structure at heel strike
initiates a natural and smoother transition to mid stance
mimics natural gait dynamics
beneficial from going down ramps and stairs
How does the microprocessor knee stay charged?
lithium ion battery recharger
necessary to power the microprocessor
solar adaptor in testing stages
standardized item for UE prosthetics
What does the microprocessor knee do in normal gait?
prevents knee from bending or collapsing at heel contact
knee will enable STANCE FLEXION which is like a shock absorber which allows for normal gait
this is better because with non computer knees they have to be forced back into extension to prevent falls
How does the microprocessor knee help with sitting and standing?
Computer senses when person wants to sit down and the internal sensors will adjust resistance and allow the wearer to ride the knee down to the seat.
When standing the computer will allow knee to extend to full upright providing maximum resistance to bending.
If person lost balance while standing the knee would sense it and provide resistance preventing a fall.
What does microprocessor knees do with stairs?
microprocessor will initiate stair mode
knee ensures maximum stability to resist flexion as affected side contacts lower stair
microprocessor provides appropriate knee bending which allows wearer to go down steps
How do microprocessors deal with ramps?
initiates ramp mode
allows wearer to walk down slopes without fear of knee bending or collapsing
How does the microprocessor knee help with uneven terrain?
stumble recovery stance control prevents falls
microprocessor is monitoring position of knee
if prosthesis experiences stumble or unexpected conditions it will initiate stumble recovery
What is the C-leg?
preferred knee for bilateral and very short residual limbs and hip disarticulations.
275 lb weight limit
has a second mode that allows wearer to covert knee to set of pre-determined knee settings for special activities.
What is the compact knee?
has same stance of C-leg, and same swing as SNS
provides maximum stability and control
How do they assess who needs a microprocessor knee?
PAVET category scoring
Determined by accumulated score of ADL, functional, physical, and consideration categories
What companies is the microprocessor knee approved by?
FDA, Medicare, VA, insurance companies, US army
Why would someone need a microprocessor knee?
improve balance, confidence in large crowds, walk up and down ramps, change speeds during walking, walk on uneven terrain, conserve energy during the day, freedom to live an active lifestyle without having to think about walking, perform ADLs
What is purpose of heel rocker in gait?
controlled PF, absorb loading forces, reduces knee flexion moment, maintain forward progression
What is the ankle rocker?
stable tripod foot-flat posture (heel, 1 and 5 MT), maintain forward progression
What is forefoot rocker?
forefoot locks and becomes rigid, heel rise against rigid forefoot level, energy storage in the PFs
What are medicare functional levels for feet?
K0-K4
method of rating functional abilities and potential to ambulate
determined by the physician, often with input prosthetist
can change over time (never underestimate)
bilateral considerations
What is K0 foot?
patient does not have ability or potential to ambulate, prosthesis does not enhance quality of life
bed or chair restricted
no prosthetic needed
What is K1 foot?
Potential to ambulate on level surface on fixed cadence
Limited or unlimited household walking
Foot: SACH or single axis
What is a K2 foot?
Potential for ambulation in lower-level environmental barriers, limited community ambulatory
Foot: flexible keel or multiaxial ankle/foot
What is a K3 foot?
Potential for variable cadence and community ambulation with most environmental barriers, activity that demands prosthetic use beyond simple locomotion
Foot: energy storing, multiaxial/dynamic response, flexfoot, flexwalk
What is a K4 foot?
potential for ambulation that exceeds basic ambulatory skills, for children active adults or athletes
Foot: no limitations
Is there a best foot?
there is no single best prosthetic foot
the best foot for someone is within their functional abilities and needs
Needs may change though course of rehab
What must you consider for K1 feet?
implications of rigid ankle/stiff heel: flexion moment at knee, potentially unstable especially with weak knee extensors
consider how forces are resisted in socket: residual tibia extends into socket, creates localized pressures
What does a Sachs foot do?
Solid Ankle Cushion Heel- enables safety
stiff heel creates potentially dangerous knee flexion moment.
compressive heel reduces flexion moment, shifts GRF anterior
simple, inexpensive, durable
What is a single axis foot?
Mechanical axis with bumpers; resistance to PF and DF
Reduces flexion moment; shifts GRF anteriorly quicker
Rapid foot flat, increased weight, increased maintenance
What is posterior bumper for? What if this was too stiff?
Eccentric DF. knee would buckle
What is anterior bumper? What if it was too soft?
Eccentric PF. Fall off front of prosthetic
What movements does multi-axial foot provide?
PF and DF, inversion and eversion, internal and external rotation
Preferred for uneven terrain
Absorbs gait torque to reduce shearing forces on residual limb
What are K3 foots?
energy storing foot, dynamic response ankle with multiaxial ankle unit, flex walk, flex foot, shank foot with loading pylon
How does the K3 foot work?
Initial contact opens to allow PF
internal keel structure absorbs energy during mid stance and terminal stance
Releases energy at pre swing to provide smoother gait
What are benefits of K3 feet?
benefits more apparent at faster speeds
smoother dynamics during gait
reduced impact on the sound side heel strike
How does endoskeletal construction help with feet?
facilitates multiple alignment options/changes
allows feet to be interchangeable
What are heel height considerations for transtibial prosthesis?
Prosthesis aligned to single heel height, change in shoes can affect alignment
Heel too high: anterior translation, excessive knee flexion, going down hill
Heel too low: posterior translation, knee extension, walking up hill
What are heel height considerations for transfemoral prostheses?
considerable attention given to position of knee over foot
What is a rotational torque adaptor?
reduces shearing forces, built into the foot or attached as separate component, provides rotation mobility for standing and twisting movements
What is a vertical shock absorber?
built into the foot or attached as separate component
Reduce impact forces during stance phase
Reduce shear forces within socket
Improve prosthetic rotational forces at heel strike
What are running feet?
J-shaped springs
Absorb energy during loading
Release energy at toe off
Not good for regular walking: too stiff, no heel
Is there a foot with adjustable heel?
Heel Height Adjustable Foot
Patient can accommodate various shoes by changing heights
It doesn’t change overall prosthetic alignment
