Lower Extremity Prosthetics Flashcards
Reasons for LE Prosthetics:
Disease 70% vascular related
Trauma 22%
Congenital birth defects 4%
Tumors 4%
Check Socket or Diagnostic Socket
A transparent socket used to aid in assessing prosthetic fit.
Definitive Prosthesis
A prosthesis that is intended for long term usage, comfort, fit, cosmetic appeal and durability. Usually fit once the residual limb stabilizes.
Pistoning
refers to the residual limb moving up and down within the socket while walking
Preparatory Prosthesis
Initial prosthesis that may or may not include definitive components. It is intended for temporary use to allow the patient to begin therapy for gait training. It is expected that it will need to be replaced within 3-9 months due to changes in the residual limb
Socket liner
soft interface used between the hard socket and residual limb. These can be made of various types of gel, socks or soft foams
Suspension Sleeve
an elastic tube made of varying materials that is first pulled over the outside of the prosthesis and then rolled up onto the thigh once the prosthesis is put on
C-Leg
The Otto Bock C-Leg features a swing and stance phase control system that senses weight bearing and positioning to provide the knee’s microprocessor information about the amputee’s gait, thus promoting smoother ambulation. The outer shell houses a hydraulic cylinder, microchip, and rechargeable battery
energy storing foot
A prosthetic foot designed with a flexible heel. The heel stores energy when weight is
applied to it and releases this energy when weight is transferred to the other foot
Ischial containment socket
In some amputation cases, usually those of the HP or HD, this socket is used to
support the ischium
multiaxis foot
The multi-rotational axis allows for inversion and eversion of the foot, and it is effective for walking on uneven surfaces.
pylon
A rigid structure, usually tubular, between the socket or knee unit and the foot that provides a weight bearing, shock-absorbing support shaft for the prosthesis
suction socket
Mainly for use by AK level amputees, this socket is designed to provide suspension by means of negative pressure vacuuming. This is achieved by forcing air out of the socket through a one-way valve when donning and using the prosthesis. In order for this type of socket to work properly, the soft tissues of the residual limb must precisely fit the contours of the socket. Suction sockets work very well for those whose residual limbs maintain a constant shape and size
Apply post-operative protector:
0-4 weeks
Incision fully healed; cast for prosthesis
5-9 weeks
Sutures removed; limb shaping
3-5 weeks
Pre-prosthetic training period from presurgery to temporary device
0-2 weeks (could start before)
Ongoing therapy and prosthetic adjustments
4 months-6/7 months
Receive permanent prosthesis
6/7 months-1 year
Primary post-operative concerns:
Protection of residual limb Compression-reduce post surgical edema Maintenance of ROM Pain Management- Pain vs Phantom pain/sensation Maintain Strength and cardiac reserves
Types of protection for residual limb:
simple splint
post operative cast
removable post operative cast
weight-bearing post operative device
Post-op evaluation
History Living situation Support network Work Goals
Tubular Gauze
Used for bulbous, sensitive limbs
double layering of material
same advantages and disadvantages as ace wrapping
uniform compression
Prosthetic Shrinker
Compression sock that is used to help control swelling in the residual limb and help shape the limb in preparation for prosthetic fitting
Prosthetic Socks
Socks of varying thicknesses or ply. The higher the ply number, the thicker the sock. They allow a patient to manage small volume changes in limb size and add to the comfort of prosthesis. They can be made of different materials, including wool, silicone and synthetic fibers
Compression garments:
ace wrapping
shrinkers
post operative casts
Who are our patients?
60% are 45 years or older
85% lose limbs to diabetes or related vascular disease
Multiple chronic health concerns
Deconditioned, Flexion contractures, Overweight
What determines the
prosthetic Rx?
Functional ‘K’ level Physical Concerns Vocational and Leisure Activities Cognitive skills Home environment / distance from prosthetic center Insurance Coverage
Physical Concerns of prosthetic Rx?
Level of amputation
Disease pathologies
Body weight
Skin integrity
Functional Level 0
no ability or potential for weight bearing or transfer
Functional Level 1
Ability or potential to transfer and ambulate within the household with an assistive device
Functional level 2
Community ambulator with the ability or potential to traverse minor environmental barriers, fixed cadence
Functional Level 3
Community ambulator with the ability or potential to traverse all environmental barriers with a variable cadence
Functional Level 4
ability or potential for prosthetic ambulation that exceeds basic ambulation skills, exhibiting high impact, stress, or energy levels. Typical of the prosthetic demands of the child, active adult, or athlete
Physical Concerns
Amputation length Weight restrictions on components Vocational and Leisure Activities Skin Integrity Peripheral Neuropathy/ hand strength Disease pathologies
Socket design
Muscle contouring
Total contact
Socket interface
Socks
Gel liners
Suspension
Sleeve
Suction
Pin locks
Belts
Principals of
Socket Design
Contour, relief and support for functioning muscles
Stabilize Skeletal Structure
Position Muscles to optimize strength
Minimize applied pressures to neurovascular structures
Distribute forces within socket over the entire limb
Trans-tibial Socket design and Interface
Patellar Tendon Bearing (PTB)
Total Surface Bearing (TSB)
Where is weight bearing concentrated in PTB?
patellar tendon
medial tibial flare
gastrocnemius
PTB complaints:
excessive pressure in popliteal fossa or patella tendon
Older style of Prosthetic sockets developed in 1959 after WWII
Total Surface Bearing (TSB)
Pressure distributed over entire limb surface.
The entire surface ofthe residual-limb is in total contact with socket while every unit area isunder compression to its proportionate tolerable level
Hydrostatic Design Sockets
considered TSB
Bearing design but they utilized compression chambers to achieve a uniform fit.
Fluid in chambers utilized Pascal law of fluids that apply pressure uniformly in all directions.
Also uses a silicone suction suspension sleeve
Socks
maintain socket fit
Nylon Sheaths:
help wick perspiration from skin
Gel Liners
provide protection against shear and pressure and can be integrated into suspension. Key component of TSB sockets. High friction inner and low friction outer allows decrease skin shear
Types of gel liners
Silicone elastomers, silicone gels, urethanes
Transtibial Suspension
Cuff / Waist belt / Joints & Lacer PTB SC/SP Sleeve – many variations Locking liners/seal in Active suction
Sleeve Suspension
Older style of prosthesis suspension but a versatile
Neoprene, Latex, Gel lined sleeve that fits over the top of the prosthesis
Not durable
Create negative pressure seal
Work w/other suspension methods
Three suspensory forces attributed to the sleeve are
- negative pressure created during the swing phase,
- friction between the residual limb and the socket, and
- longitudinal tension in the sleeve
Sleeve suspension advantages
Simple and effective means of suspension.
Helps minimize socket pistoning.
Does not create proximal constriction.
Sleeve suspension disadvantages
Provides no added knee stability.
Suspension is greatly decreased if the sleeve is punctured.
Perspiration may build up under the sleeve and create skin irritation or hygiene problems.
Must be replaced regularly.
Sleeves may restrict full knee flexion and require good hand function to don and doff.
Elevated vacuum systems try to
reduce pistoning, perspiration and provide better linkage between user and prosthesis.
Benefits of Elevated Vacuum Systems:
Better pistoning
Better cirulation
Soft tissue hydrated
Trans-femoral socket design
Quadrilateral
Ischial Containment
M.A.S.
Quadrilateral Socket
Wide M-L / narrow A-P
Weight bearing through ischium and Gluteal muscles
Can be used effectively by healthy, muscular individuals
Ischial Containment
Narrow M-L dimension
Ischium and ramus contained within socket
Maintains natural femoral adduction
Increased medial lateral stability during ambulation
Muscle Contouring
built-in relief for concentrated pressure points
an aggressive, more intimate fit of the pelvis bone
improved M-L control
increased A-P stability
reduced socket rotation on the
Controls alignment of Femur
anatomically correct channels to encourage muscle contraction during gait
ability to increase muscle tone in residual limb
MAS Socket: Marlo Anatomical Socket Medial Ramus Ischial Containment
Narrow M-L Anatomical Socket Shape
Good M-L control due to boney lock
Increased Range of Motion throughout gait cycle
Increased sitting Comfort
Double Wall Socket for Transfemoral
Socket within a socket
transfemoral prosthesis that fits intimatelyand provides increased control and security
largerrange of motion
Trans-femoral Suspension Belts:
Silesian
Elastic Removable
Waist belt with pelvic band and hip joint
Trans-femoral Suspension Suction:
Incorporated into socket
Incorporated into liners
Trans-femoral belt suspension:
May be used as primary or auxiliary form of suspension
Rotational stability / mediolateral pelvic stability may be enhanced with the addition of hip joint
Advantages of belt suspension
Can be simply applied
Rotational control for shorter limb length
Positive point of attachment over contra-lateral pelvic crest
Disadvantage of belt suspension:
Can cause skin irritation
Silesian Belt can not be removed for laundering
Removable belts are bulky and retain body heat
Trans-femoral suction suspension:
Air expulsion valve facilitates suspension by negative air pressure applied with sock or other pull on device
applied with lotion or other lubricant
Disadvantages of Trans-femoral suction suspension
Must Have stable limb volumes
Less effective on limbs with irregular contours or scars
Short residual limbs may require secondary suspension
Perspiration can be a problem
Advantages of Trans-femoral suction suspension
Increased Proprioception
Less vertical displacement of prosthesis during ambulation
Disadvantages of suction liners:
Can cause fleshy limbs to elongate during swing
Lock mechanisms add additional length to socket
Liners need meticulous hygiene to avoid odors and skin irritation
Advantage of suction liner:
Easy donning
Can be adjusted for volume fluctuations
Flexible
Socket and Frame
Construction
Improved comfort at brim
Ability to modify for volume fluctuation
Cut outs in frame allow for increased sitting comfort, as well as active muscle contraction during gait
Function of Prosthetic Knees
Provide Security against collapse when prosthesis is loaded
Provide shock absorption at heel strike
Flex during preswing and swing phase to advance prosthesis
Slow down extension during terminal swing to prevent damage to knee joint
Functional level 1 choices of Prosthetic knees:
locking knee
single axis friction
safety-knee-stance; activated breaking mechanism
Manual Lock
Functional Level 1 – 2
Transfer prosthesis or limited walking on level surfaces
Simple design, provides a non-flexing knee while standing/ambulating
Patient must unlock knee manually to sit
If patient falls, the knee will not collapse under them
“knee of last resort”
Friction Knee
Functional level 1 - 2
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
Single Axis
Less moving parts and simple design
Lower fabrication costs
Less stable at heel strike
One axis to absorb gait stress
Polycentric
Inherent stability at heel strike Easy to initiate swing phase Tend to be heavier Increased maintenance Greater inherent mechanical stability resulting in greater stance stability Good choice for short residual limbs
Stance Control Knee
Functional Level 1-2-3
Provides added stability during a missteps or uneven surfaces
Breaking mechanism locks the knee during stance phase
Most popular knee fit in USA
Light weight
Break will wear and knee will fail without proper adjustment and maintenance
Locks’ in up to 20 degrees of flexion
Best suited to geriatric or individuals with weak hip extensors
Fluid and Pneumatic Swing Control
Extension and flexion resistance controlled for more efficient gait
Eliminates terminal impact
Heavier
More expense
Some models include stance flexion
Hydraulic can be used to descend stairs step over step
Can be either single axis or polycentric linkage
Hydraulic Swing Phase Knee
Functional level 3-4
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
Microprocessor Swing
Functional Level 3-4
Provides resistance to flexion/extension during swing phase
Enables variable cadence; ability to change walking speeds without hesitation
Added expense due to computer technology
Maintenance is essential
Microprocessor Swing/Stance
Functional Level 3-4
Some level 2 requiring added stability
On board computer analysis gait 50 times per 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
Microprocessor Knee
Utilize microprocessor controls to adjust resistances according to ‘real time analysis’ of gait
‘Stumble Recovery’
Typically involved authorization process
Expensive initial cost and repairs
Power Knee
Motor powered to simulate knee function without relearned motor strategies using alternative muscle groups. The knee mechanically replaces the knee function.
Specialized Adaptors/Knee
water knee
positional rotators
quick disconnects
Functional Level 1 feet:
single axis foot
SACH foot
Single axis foot
provides plantar –flexion moment at heel strike improving stability
SACH
Solid Ankle Cushion Heel foot
SACH foot is simple design, low cost lowest function
Functional Level 2 feet:
multi-axial foot
flexible keel foot
Multi-axial foot
provides plantar and dorsi-flexion as well as inversion, eversion and rotation, reducing shear forces on limb and greater stability on uneven surfaces
Flexible Keel foot-
SAFE Foot internal flexible keel permits tri-planar movement with an easy roll over
Functional Level 3 feet:
no restrictions
Dynamic response/energy storing feet
absorbs energy” during mid and terminal stance
“releases energy” at toe off
More energy efficient gait
Can incorporate pylon for increased reaction
Can incorporate inversion/eversion
Lightweight and durable
Body Mass and activity sensitive
Multi-axial dynamic response feet
Provides Multi axial compliance to uneven ground
Dynamic response at toe off for more dynamic walkers
Classified as “Energy Storing”
Split toe allows for inversion eversion
Specialty Feet
micro-processor controlled ankle (adjusts plantar and dorsiflexion) adjustable heel height special uses (running, swimming)
Vertical Shock and Torque Absorbers Advantages
Reduce impact at heel strike
Reduce rotational shear forces within socket
Vertical Shock and Torque Absorbers Disadvantages:
Increased weight
Increased maintenance and cost
Clearance an issue for long residual limbs
Syme limbs prosthetic characteristics:
Light enough to wear comfortably
Ability to supply the equivalent of foot and ankle function
Lengthening of the limb to adjust for loss of the talus and calcaneous
Distribution of the high forces developed in the ankle area
Provision of rotary stability about the long axis
Provision of shock absorption
Suspension during swing phase
Readily donned without requiring multiple non-cosmetic, difficult fasteners
Adjustability to relieve pressure along a sensitive scar line
Cosmesis
SAFE foot:
stationary-ankle-flexible-endoskeletal
makes it easier for the amputee to walk over uneven terrain
Foot has the same action as the SACH plus the ability for the sole to conform to slightly irregular surfaces (mild inversion eversion compontent of motion)
