Prosthetic Sockets, Knees, and Feet Flashcards
Approximately how many new amputations occur every year?
135,000
What percentage of amputations are due to vascular related disease?
70% (85%…who knows)
What percentage of amputations are due to trauma?
22%
What percentage of amputations are due to congenital birth defects?
4%
What percentage of amputations are due to tumors?
4%
When does limb shaping begin?
After sutures are removed somewhere around 2-4 weeks
When does a patient receive a temporary prosthesis which will allow them to begin prosthetic gait training?
5 weeks-4 months
When will a patient typically receive their permanent prosthesis?
Anywhere from 6 months to 1 year post-op
What 7 things are important to instruct your patient not to do post-op in regards to positioning?
- do not hang stump over bed
- do not sit in wheelchair with stump flexed
- do not place pillow under hip or knee
- do not place pillow under back curving spine
- do not lie with knees flexed
- do not place pillow between knees
- do not sit with knees crossed
60% of our patients are __ years or older
45
What 6 things determine the prosthetic prescription?
- Functional ‘K’ level
- Physical Concerns
- Vocational and Leisure Activities
- Cognitive skills
- Home environment
- Insurance Coverage
Describe a level 0 patient
Does not have the ability or potential to ambulate or transfer safely with or without assistance and a prosthesis does not enhance their quality of life or mobility
Describe a level 1 patient
Has the ability or potential to use a prosthesis for transfers or ambulation on level surfaces at fixed cadence. Typical of the limited and unlimited household ambulatory.
Describe a level 2 patient
Has the ability or potential for ambulation with the ability to traverse low-level environmental barriers such as curbs, stairs, or uneven surfaces. Typical of the limited community ambulatory.
Describe a level 3 patient
Has the ability or potential for ambulation with variable cadence. Typical of the community ambulatory who has the ability to traverse most environmental barriers and may have vocational, therapeutic, or exercise activity that demands prosthetic utilization beyond simple locomotion.
Describe a level 4 patient
Has the 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
Are functional level 0 patients typically recommended for prosthetic use?
NO
What are the prosthetic limits for functional level 1 patients?
There are no limits on socket design, however there are limits on suspension choices, and the selection of knees and feet.
Functional level 1 patient prosthetics are for ______ purposes only.
basic ambulation
What are the prosthetic limits for functional level 2 and 3 patients?
There are NO limits on socket design, suspension, or interface
Functional level 2 patient prosthetics are for ______ purposes only.
basic ambulation
The typical transtibial prosthetic costs anywhere from _____ to _____
$7,000-$14,000
The typical tranfemoral prosthetic costs anywhere from _____ to _____
$10,000-$60,000
It is typical that the patient is responsible for __% of the prosthetic cost
20%
In regards to socket design what are 2 essential components?
It must be contour in order to provide relief and support for muscle function and total contact must be maintained
What 2 things can line the socket interface?
socks and gel liners
What are 4 suspension mechanisms for sockets?
- sleeve
- suction
- pin locks
- belts
Despite the fact that patients following Symes amputation have a long lever arm from intact tibia and fibula and full weight bearing on the heel pad, problems still exist. What is the biggest problem?
There is limited space available between the distal portion of the residual limb and the floor.
What type of prosthetic foot is used in nearly all contemporary Syme prostheses? What are its advantages?
Stationary-ankle flexible-endoskeleton (SAFE) foot
It has a flexible anterior keel that allows an easier rollover and reduces the ground reaction forces on both prosthesis and residual limb
What does SACH stand for?
Solid Ankle Cushion Heel
Describe the mobility that is allowed in a SACH foot and the advantages and disadvantages
Provides plantarflexion moment at heel strike which increases stability, however does not allow for inversion/eversion movements
What patient level is a SACH foot appropriate for?
K1
What does SAFE foot stand for?
Stationary Ankle Flexible Endoskeletal
What is the difference between the SACH foot and the SAFE foot?
They both provide stability at heel strike, however the SACH foot has the ability for the sole to conform to slightly irregular surfaces (mild inversion eversion compontent of motion) which makes it easier for the amputee to walk over uneven terrain
What are SAFE feet sometimes referred to as?
“flexible keel” feet
What patient level is a SAFE foot appropriate for?
K1 and K2
In what amputation type is the 2 single axis foot types (SACH and SAFE) beneficial to?
BK amputees with weak quad strength can benefit
What is the differences between functional level K3 feet (Seattle Litefoot, Quantum foot, etc.) and the SACH foot?
They are fabricated from lightweight flexible carbon fiber
What are the 4 advantages of level K3 feet?
- offer increased ankle motion
- reduce energy consumption
- reduce sound side loading
- store and return more energy
What is the advantage of the fenestrated heel assocaited with the Ossur Low profile Flex-Symes Foot?
It allows for greater compression and less shock.
What is the typical adjustment made that allows the bulbous distal end of the residual limb to pass the narrow shank portion of the prosthesis in a Symes amputation?
closed double-wall prosthesis with attached flexible inner walls fabricated with expandable material. Windows may need to be added
What type of prosthetic foot should K1 patients use?
Single axis foot, most commonly the SACH foot
What type of prosthetic foot should K2 patients use?
A flexible keel or multi-axial foot such as the SAFE foot
What are the advantages of multi-axial dynamic response feet?
They provide compliance to uneven ground and “release” energy at toe-off
What are 2 specialty prosthetic feet types?
- Micro-processor controlled ankle
- Those with an adjustable heel height
What does a micro-processor controlled ankle do?
Adjusts plantar and dorsiflexion during gait
Describe the functions of the pylon, both simple and dynamic
- Typical prosthetic pylons are rigid and only function as an attachment between the socket and foot to establish the correct overall height.
- Dynamic pylons allow for energy to be stored as spring tension as they flex through midstance and terminal stance.
What is an extra component that can be directly mounted under the socket to reduce amount of torque and shock that is transferred from the ground to the limb?
Vertical Shock and Torque Absorbers
What are the advantages of vertical shock and torque absorbers?
- Reduce impact at heel strike
- Reduce rotational shear forces within socket
What are the disadvantages of vertical shock and torque absorbers?
- Increased weight
- Increased maintenance and cost
- Clearance can be issue an for long residual limbs
What are the 3 socket designs for transtibial prosthetics?
- Patellar Tendon Bearing (PTB)
- Total Surface Bearing (TSB)
- Hybrid sockets : RCR Transtibial Socket
Describe the reasoning behind the development of the patellar tendon bearing socket
Load the limb in areas that are more pressure tolerant and relieve the tissue over the bony prominences like the tibial crest and head of the fibula
What are the 2 major weight-bearing areas of the PTB socket?
- patellar tendon
- medial tibial flare
What is the intent in designing a TSB socket?
to distribute uniform pressure over the entire surface of the limb
TSB sockets are typically used with what type of interface?
gel liner interface
According to the study provided in class is the PTB or TSB socket more effective in the rehab process of transtibial amputees? Why?
total surface bearing
They are lighter, provide better suspension, and weight acceptance is normalized
What is a specialized total surface bearing socket that utilizes compression chambers to achieve a uniform fit?
Hydrostatic Design Sockets
What are the advantages of a hybrid socket (ROM and rotational control socket)?
- Increases the patient’s comfortable range of motion
- Allows for a longer stride length
- Walking up slopes, ramps and stairs is much easier
- Facilitates kneeling on the prosthetic side
- Reduces gapping of socket at knee when sitting
- Improves rotational control
- Equalized pressure distribution
The material that separates the limb from the socket is referred to as what?
interface
What are the 3 types of transtibial socket interfaces?
- socks
- nylon sheaths
- gel liners
What are the advantages of using a urethane gel liner over a silicone gel liner?
Silicone does not thin out over bony prominences, whereas urethane distributes the pressure more evenly, so the patient does not feel high pressure points
What are the _ types of transtibial suspensions?
- waist belt
- joints and corset
- supracondylar/suprapatellar suspension
- sleeve
- locking liners
- active suction
A suspension sleeve provides suspension through 2 biomechanical principles, what are they?
friction and vacuum
Suspension sleeves create a ____ pressure during the swing phase
negative
Describe the progression locking liners have made
- earliest used a ring that screwed into the distal end of the liner
- strap came next
- pin-and-lock mechanism is now used
What type of liner is used most frequently with AK amputees?
Seal-in-liner/Pull in liner or suction seal liner with one way valve
What is a major advantage to sockets that utilize suction suspension?
pistoning is reduced which makes for better gait and improved proprioception
What are the 3 types of transfemoral socket designs?
- Quadrilateral
- Ischial Containment
- Marlo Anatomical Socket (MAS)
Describe the shape if the quadrilateral socket
4 distinct walls
- wider M/L
- narrower A/P
What surface provides weight-bearing in the quadrilateral socket?
ischium and gluteal muscles
What type of patients utilize the quadrilateral socket?
healthy, muscular individuals
Why did Long develop the ischial containment socket?
He wanted to align the distal femur over the center of the knee and through the center of the foot in order to retain normal anatomical positioning.
Describe the shape if the ischial containment socket
4 distinct walls
- narrower M/L
- wider A/P
What is the significance of widening the anteroposterior dimension and narrowing the mediolateral one?
Supports the femur better which prevents lateral shifting of the socket during weight bearing.
Also enhances muscle function by providing more room
What 2 things does transfemoral suspension enhance?
proprioception and control
What are the advantages of belt suspension?
- Can be simply applied
- Rotational control for shorter limb length
- Positive point of attachment over contra-lateral pelvic crest
What are the disadvantages of belt suspension?
- Can cause skin irritation
- Silesian Belt can not be removed for laundering
- Removable belts are bulky and retain body heat
What are the advantages of suction suspension?
- Increased Proprioception
- Less vertical displacement of prosthesis during ambulation
What are the disadvantages of suction suspension?
- limb volumes must be stable
- Less effective on limbs with irregular contours or scars
- Short residual limbs may require secondary suspension
- Perspiration can be a problem
- Adductor roll can develop
What are the 4 functions 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
What are the 2 advantages of single axis prosthetic knees?
- Less moving parts and simple design
- Lower fabrication costs
What are the 2 disadvantages of single axis prosthetic knees?
- No inherent mechanical stability (decreased stability at heel strike)
- Knee extension occurs at fixed rate
What type of patient is a single axis-knee not appropriate for?
individuals with relatively short residual limbs who lack the mechanical advantage of a long femoral lever for muscular control of the knee
The single-axis knee has a ____ center of rotation, whereas the polycentric knee has a _____ center of rotation
fixed
moving (similar to human knee)
What are the 2 advantages of polycentric prosthetic knees?
- have inherent stability at heel strike
- it is easy to initiate the swing phase
What are the 2 disadvantages of polycentric prosthetic knees?
- Tend to be heavier
- Increased maintenance
What type of patient is a polycentric knee appropriate for?
Individuals with long residual limbs or knee disarticulation.
Also good option for individuals with short residual limbs or significant weakness of hip extensors
What functional levels utilize a manual locking knee?
K1 and K2 (lower functioning)
What functional levels utilize a friction knee?
K1 and K2 (lower functioning)
How does a friction knee work?
Functionally acts like a simple door hinge in which the swing phase of gait is controlled by how tight the hinges are
What knees are preferred in K2 level patients?
- stance flexion
- stance control
What is the significance of adding a stance flexion feature?
Slight knee flexion moment at heel strike mimics the sound side
What is the most popular knee fit in the US? Explain why….
The stance control knee because the majority of amputees are decrepit versus athletic and this knee allows for added stability during missteps on uneven terrain
How does the stance control knee increase stability?
A breaking mechanism locks the knee during the stance phase
What knees are preferred in K3 level patients?
All fluid and pneumatic swing and stance control, including microprocessor knees
What level patient can use a hydraulic swing phase knee?
K3 and K4
Describe the Hydraulic Swing Phase Knee
Its hydraulic mechanism provides resistance to flexion/extension during swing phase which allows for variable cadence
What level patient can use a microprocessor knee?
K3 and K4
Like the hydraulic swing phase knee the microprocessor knee provides resistance to flexion and extension during the swing phase of gait. The difference is that this knee has higher resistance during ____ phase and lower resistance during ____ phase
stance
swing
