Transfemoral Delicious Knowledge® Flashcards
Which is more important… the prosthetic knee choice or the socket?
the freakin socket
PROSTHETIC GAIT CONSIDERATIONS: HIP
Stability of the femur against the socket wall (socket design)
PROSTHETIC GAIT CONSIDERATIONS: HIP
Stability of the residual limb within the socket
Stability of the femur
- Single bone surrounded by soft tissue
- More variability in contours of the socket design
than TT sockets - Hip muscle balance is impacted by the amputation (loss of adductors)
Quadrilateral socket
- Rectangular (top view)
- Relief for adductor tendon
- Pressure on Scarpa’s triangle lateral
- Posterior brim has a shelf for the ischium/gluteals to bear
- Anterior/Lateral brims are higher than medial/posterior brims
ISCHIAL CONTAINMENT SOCKET
- More oval in shape (top view)
- M/L dimension is narrower than A/P dimension
- Medial/posterior walls are higher than quad socket in order to contain the ischium
- High posterior and lateral walls hold the pelvis
- Design keeps the femur more adducted
Types of positioning that determine the STABILITY OF THE RESIDUAL LIMB WITHIN THE SOCKET
- Active positioning
- Passive positioning
ACTIVE SOCKET POSITION
Active co-contraction of quadriceps and hip extensors creates optimal pressure within the socket.
This provides support for postural alignment and stability.
PASSIVE SOCKET POSITION
User is passively in the socket (little volitional muscle activity) causing abnormal pressure and poor containment.
Lack of postural support results in weight placed on the posterior brim of the socket.
(The user is “sitting” on the socket.)
ACTIVE USER/SOCKET INTERFACE:
• Co-contraction of hip extensors and quadriceps within the prosthetic socket is important:
• Provides stability
• Additionally limits abnormal force between the
residual limb and the socket
FRONT WALL ACTIVATION:
- Active pressure of the residual limb in a forward motion against the anterior wall of the socket
- Occurs when the user is activating HIP FLEXION
BACK WALL ACTIVATION:
- Active pressure of the residual limb in a backward motion against the posterior wall of the socket
- Occurs when the user is activating
HIP EXTENSION
HIP ISSUES WITH GAIT: SWING PHASE
- Often hip flexion motion is excessive (too much “Front Wall” effort by the User)
- Excessive hip flexion moves the prosthetic knee quickly into knee extension and allows the user’s limb to descend passively to heel strike
- This can also lead to vaulting on the sound side by creating excessive forward momentum.
HIP ISSUES WITH GAIT: SWING PHASE
- Hip flexion is like a kick
- Pelvis retracts with a kick
- Gailey: work with pelvis to retrain anterior pelvic motion in the transverse plane with swing phase
HIP ISSUES WITH GAIT: STABILITY
- Lack of active socket position causes lack of stability at the hip in Stance phase
- User gets distal femur pain as bone rests on posterior socket wall and pushes distal end into the front wall of the socket (just “sits” in the “bucket”)
- Need to cue “BACK WALL” firing of hip extensors as User comes to Heel Strike and all the way to Toe Off
PROSTHETIC GAIT CONSIDERATIONS: KNEE
- Alignment (Involuntary Control)
- User effort (Voluntary Control)
Characteristics of the Knee Mechanism
- Stance Control
* Swing Control
• Voluntary prosthetic knee control
• Determined completely by muscular efforts of the prosthetic user
• Involuntary prosthetic knee control
- Created by alignment of the prosthetic components
* Created by knee component features (locking knees, weight-activated stance control knees, some hydraulic knees)
KNEE ALIGNMENT
- Knee usually aligned relative to hip axis and ankle axis
- Active Users (K4) usually set with LESS knee stability
- Low Activity Users (K1) usually set with MORE knee stability
Ankle axis directly below or behind knee axis for
LESS STABILITY (active users)
Knee will flex easily unless
muscular effort exerted to control it.
Ankle axis ahead of knee axis for
STABILITY
User exerts little effort to keep knee
straight
MECHANICAL KNEE: STANCE VOLUNTARY CONTROL
- Need to have stability in WB
- Safely transition weight from heel to toe of the prosthetic foot without knee buckling
- Active hip extension maintains foot on the ground and gets weight over the prosthetic foot
PROSTHETIC KNEE COMPONENTS
- Outside Hinges
- Single Axis
- Single Axis Weight Activated Stance Control
- Polycentric
- Manual Locking
List prosthetic knee components from least to most inherent stability
- Outside Hinges
- Single Axis
- Single Axis Weight Activated Stance Control
- Polycentric
- Manual Locking
List prosthetic knee components from most to least voluntary control
- Outside Hinges
- Single Axis
- Single Axis Weight Activated Stance Control
- Polycentric
- Manual Locking
MECHANICAL KNEE: STANCE
Remember: If there is not active effort by the user, the prosthetic knee mechanism can BUCKLE in standing/Stance phase
• Knee component choice can help control this by providing stability if certain conditions are met
STABILIZERS
Resist knee flexion during early Stance and Midstance
• Manual Lock: User walks with a stiff knee
• Brake: Wedge that lodges in a groove and holds when User initiates Stance phase with the prosthetic knee fully extended or flexed no greater than 25 degrees. Does not work beyond Midstance.
STABILIZERS: HYDRAULIC KNEE
• Brake mechanism for Stance control
• Usually also has a manual lock mode or
deactivation mode
• Mauch SNS (Swing N Stance) is an example of this
True/False: All amputees are veterans
This is actually false
WEIGHT-ACTIVATED STANCE CONTROL (SAFETY KNEE)
• Provides resistance to the prosthetic knee flexing (buckling)
• Acts like a brake
• User must unweight the prosthesis to release the
knee for sitting or stepping
• Not a smooth movement
POLYCENTRIC KNEES
- 2 or more pairs of bars that pivot proximally and distally
- Changing axis of knee rotation
- Stable at Midstance
- Releases with Toe-off to initiate flexion for Swing
MECHANICAL KNEE: STANCE
- Most knee mechanisms release when the prosthetic knee is in full extension and the weight has transitioned onto the toe of the prosthetic foot. (Terminal Stance to Toe-Off)
- This initiates Swing Phase
SWING CONTROL: FRICTION MECHANISMS
- Constant Friction (resists motion of shank through swing phase)
- Variable Friction (imitates action of sound knee, works in early and late swing phase)
- Heel Rise
- Terminal Impact
CONSTANT FRICTION MECHANISMS
- Clamps on the knee bolt (hinge)
- Tighten the clamps to increase the resistance
- Used with users who do not change walking velocity
What is Tyler’s favorite aspect of marriage?
se………………….tting the table for dinner
HOW DO VARIABLE FRICTION MECHANISMS WORK?
- Fluid, Hydraulic (oil) or pneumatic (air) unit has a piston moving up and down in a cylinder
- Amount of resistance is determined by walking speed
- Mimics the dampening effects of quadriceps and hamstrings in the normal limb
- For users with variable cadence/high activity levels
EXTENSION AIDS
• Provide a little extra help with Terminal Swing
• Assists to get the knee to extension for
Stance phase
• K1, K2 users need this because gait speed is so slow that knee may not fully extend at the end of Swing phase
PROSTHETIC GAIT CONSIDERATIONS: FOOT
- Any foot/ankle can be used with most transfemoral prostheses
- Energy-storing feet help to walk a little faster than nondynamic feet
- Some knee units must be used with a particular prosthetic foot
- C-leg® must use Otto Bock foot or void warranty
TEACHING TRANSFEMORAL GAIT: Know and understand your patient:
- Cognitive level
- FEAR level
- Prior level of function
- Co-morbidities
TEACHING TRANSFEMORAL GAIT:
- Know your prosthetic components!
- Understand the biomechanics of the components; ask your prosthetist to explain the features.
- Help your patient to understand how the prosthesis works.
UNDERSTAND THE TECHNOLOGY
• Go to the product website
• Contact the sales representative for
information
• If you don’t understand how it works, then how can you expect your patient to understand it?
TEACHING TRANSFEMORAL GAIT: KEY COMPONENTS
- Hip stability (Back Wall Firing)
- Pelvic motion forward (Transverse Plane)
- Swing to Heel Strike (Accurate movement without excessive Front Wall Firing)
- Balance
GAIT TRAINING LEARNING CURVE
New amputee:
- Doesn’t know what things are supposed to feel like
- Everything is new
- Doesn’t understand what is wrong or even IF something is wrong
- Doesn’t always understand what is right
THE C-LEG®
The World’s First Prosthetic Knee System with:
Microprocessor Controlled
• Hydraulic Stance and
• Hydraulic Swing Phase
HERITAGE: FIRST GENERATION
- No wireless remote
- Offered two Modes
- Second Mode accessed through loading the toe of the prosthesis in a specific manner
COMPACT
- Introduced in 2004
- Designed for K2 and K3 Functional Level
- Does not have variable cadence
- Offers stumble recovery/stability
SECOND GENERATION OF THE C-LEG®
This came after the first generation
C-LEG® CONCEPT
• Integrated knee-shin-ankle + foot assembly
• Real-time gait analysis (now including
accelerometer and gyroscope in Genium)
• On-board computer + software rules
• Improved stance and swing phase control
• Easy for amputee and prosthetist
C-LEG® FUNCTION
- Microprocessor Stance phase control
- Microprocessor Swing phase control
- “Default stance” / stumble recovery
- Hydraulic-yielding stance control
- Microprocessor-controlled switching from stance to swing phase and vice versa
ANKLE MOMENT SENSOR PYLON
- Pylon is a sensor
- Pylon is FLEXING during gait
- NEVER CUT THE TUBE ADAPTER of the C-leg to make height changes: It will affect the distal strain gauges.
How does it work?
Input -> Processing -> Output
C-LEG® VS. NON-MICROPROCESSOR KNEE MECHANISM
- Non-Microprocessor Knee Mechanism: the patient has to respond to the pre-set parameters of the knee
- C-leg®: the patient moves and the knee responds to the movement
DYNAMIC MAXIMUM TOE LOAD
- Prosthetist determines 100% (Maximum Toe Load)
* Microprocessor calculates 70% Toe Load
Stance flexion dampening is turned OFF only if:
1) The knee is in extension
AND
2) Toe load is >70%
STANCE DISENGAGEMENT RULES
- Dorsiflexion moment at terminal stance [toe loading] >70% of Maximum Toe Load
- Knee is fully extended
Stance disengagement occurs ONLY if BOTH criteria are met!
STANCE CONTROL
• This is the “default” setting • The C-leg® knee’s resistance to stance flexion is
turned off ONLY if certain criteria is met • Stumble recovery feature
• Unique to the C-leg® and Genium®
THE 4 “S” OF THE C-LEG® STANCE CONTROL
- Stumble recovery
- Stairs
- Sitting
- Shock absorption at Loading Response (Stance flexion)
BENEFITS OF STANCE CONTROL
- Descending Stairs in a reciprocal pattern
- Controlled descent of ramps and decline surfaces
- Controlled sitting and kneeling movements
- Ability to move on rough terrain
- Stability on uneven surfaces
- Energy efficient gait
BENEFITS OF MICROPROCESSOR SWING CONTROL
• Widest range of variable cadence
• Efficient and effective heel rise and terminal impact
control
• Dynamic cosmesis
• It functionally looks like the sound limb
• Anticipatory Control
• Resistance is adjusted for the
NEXT STEP
This is important to remember when gait training!
SECOND MODE
- Set by the prosthetist
- Accessed by: Wireless remote control, User loading the toe in rapid succession
- Can be set with more or less stability, depending on the desired function (e.g. Sports, Sustained standing)
WIRELESS REMOTE ALLOWS USER TO:
- Switch between 1st and 2nd modes
- Enable standing mode
- Modify swing phase settings
THE BENEFITS OF 2ND MODE:
- Knee can be set to specific range of motion and resistance parameters by the prosthetist
- Used for endurance and coordination enhancing leisure activities such as Biking, Inline skating, Cross country skiing, Dancing
ADDITIONAL BENEFITS OF WIRELESS REMOTE:
- Support for standing in a comfortable and secure position
- User selects and adjusts knee position:
- Doctors while operating (high precision needed!)
- Hair-dresser while cutting hair
- Sales people
ADDITIONAL BENEFITS OF WIRELESS REMOTE:
- Allows user to vary cadence settings
- Comfort: Casual walking
- Standard: Normal walking
- Dynamic: Fast walking
WHAT IS C-SOFT?
C-Soft is the state-of-the-art software solution to adjust C- Leg® and Compact.
SAFETY
- All microprocessor adjustments are done in standing position (static)
- NEVER make adjustments to the C-leg® microprocessor settings while the person is walking; always have them stop and pause while the adjustment is made
- Guard the patient closely when new adjustments are made to the C-leg® settings
C-LEG®
Setup C-leg® Settings
- Zero Setting
- Maximum Toe Load- Static
- Stance Flexion Damping – Static (sit to/from stand)
- Maximum Toe Load – Dynamic
UNDERSTANDING C-LEG® TERMINOLOGY
- Static: Adjustment is related to STANDING (Stance Flexion Damping – Static is for Stand to Sit)
- Dynamic: Adjustment is related to WALKING/ MOVING (Stance Flexion Damping – Dynamic is for Stairs and Ramps)
ZERO SETTING
- Used to calibrate the sensors
- Performed at the start of any adjustment session
- Mandatory before any programming can be done
- Person stands with leg behind them (All weight off of the toe, Knee in full extension)
MAXIMUM TOE LOAD - STATIC
- Enter prosthetic foot length
- Enter user body weight
- Computer will generate a number that is 100% Maximum Toe Load
STANCE FLEXION DAMPING - STATIC
• Person asked to stand up and sit down several times
• Emphasize equal weight on both legs
• “Nose over toes”; can put hands on thighs to facilitate body mechanics
• Observation and patient feedback are used to adjust this setting
• Time it to ride the resistance down for smooth transition
• NOTE: This setting can be used as a tool to encourage prosthetic weightbearing during transfers
• New users may benefit from increasing this setting to • improve confidence that the limb will support them.
• Increase=more resistance Decrease=less resistance
• Adjust setting based on observation and
patient feedback
MAXIMUM TOE LOAD – DYNAMIC
- Measures toe load while the person is walking
- Need to get 10 good walking steps
- Computer calculates 100% Maximum Toe Load
- Prosthetist can also manually adjust Maximum Toe Load – Dynamic
- This setting adjustment can be helpful when the person is having trouble meeting the toe load consistently.
MAXIMUM TOE LOAD – DYNAMIC AUTOMATIC ADJUSTMENT (10 STEPS)
Maximum Toe Load value will automatically be generated when ten good steps have been recognized.
MAXIMUM TOE LOAD – DYNAMIC MANUAL ADJUSTMENT
- Observe while walking
- Adjust as necessary so that the Blue line stays at the black bar
- Recheck outside parallel bars, or with other devices.
TOE LOAD
• Maximum Toe Load is 100%
• Microprocessor calculates when 70% of this
Maximum Toe Load is achieved during gait
• The knee releases to FREE SWING once the prosthetic knee is in FULL EXTENSION and >70% of Maximum Toe Load is reached
TOE LOAD SETTING – TOO HIGH
A setting that is too high may have the consequence that swing phase is not initiated and the knee joint remains in stance phase resistance. Time RISK: The amputee will most likely stumble.
TOE LOAD SETTING – TOO LOW
A setting that is too low will have the consequence that swing phase is initiated too early and the knee joint will no longer provide stability Time when necessary.
RISK: The amputee might collapse.
C-LEG® GAIT SETTINGS:
• Swing Phase -Swing Flexion -Dynamic Factor -Knee Angle Threshold -Swing Extension Damping • Stance Flexion -Stance Flexion Damping – Dynamic -Stance Extension Damping - Dynamic
SWING PHASE SETTINGS
• Swing Flexion
-Dynamic Factor
-Knee Angle Threshold
• Swing Extension Damping
DYNAMIC FACTOR (HOW MUCH)
- This is the “dynamic” closing of the flexion valve to control heel rise.
- Start at “2”.
- If there is too much heel rise, increase 2 the dynamic factor.
- Use this setting to control heel rise at all cadences, so it is important to have patient walk fast.
KNEE ANGLE THRESHOLD (WHEN)
- Knee Angle Threshold is an optional setting.
- Only used with advanced ambulators.
- It determines the amount of “free” knee flexion.
- This is WHEN flexion resistance will engage to control heel rise.
- Start at 40 degrees. Leave high for efficiency.
SWING EXTENSION DAMPING (RESISTANCE)
- This adjustment is used to control impact during terminal swing
- Controls OPEN CHAIN knee extension
- Adjust this setting for smooth deceleration at all cadences
EXCESSIVE “KICK” DURING SWING: PROSTHETIST ADJUSTMENTS
- Prosthetist can adjust Swing Extension Damping to control terminal impact and deceleration
- Can work with the patient to become more comfortable with a smooth swing phase
STANCE EXTENSION DAMPING - DYNAMIC
- This is only adjusted in the advanced user.
- This controls CLOSED CHAIN knee extension
- Observe amputee while walking to determine if he/she is walking with stance phase knee flexion.
- Stance Extension Damping - Dynamic only engages if the amputee is walking with stance phase knee flexion.
STANCE EXTENSION DAMPING - DYNAMIC
- Most amputees will be at or near the maximum value (115-120).
- Adjust to see a smooth transition from knee flexion in loading response to complete knee extension in terminal stance.
INITIAL CONTACT
- Cue the user to engage active hip extension (BACK WALL firing)
- Active position in the socket creates stability as the user transitions to Mid Stance
LOADING RESPONSE
- Cue the user to engage active hip extension (BACK WALL firing)
- Stance knee flexion will occur in the advanced user (shock absorption at initial loading)
MID STANCE
Cue the user to engage active hip extension (BACK WALL firing)
TERMINAL STANCE
- Cue the user to engage active hip extension (BACK WALL firing)
- At this point, toe load criteria will be met and the knee will release into swing phase
PRE SWING
• Cue amputee to keep pelvis moving forward
• There is little to no active hip flexion required to
advance the limb due to the dynamics of the microprocessor system
INITIAL SWING
Monitor closely for gait deviations, cue as needed: • Trunk stability • Pelvic rotation ****** • Foot clearance • Linear forward progression of limb
MID SWING
Monitor closely for gait deviations, cue as needed: • Trunk stability • Pelvic rotation ****** • Foot clearance • Linear forward progression of limb
TERMINAL SWING
- Cue amputee to re-engage active hip extension
* Encourage heel strike
CUES DURING GAIT:
• Verbal: -"Back Wall" -"Push" then "relax" -Heel strike • Tactile: -Therapist directs anterior force against the posterior socket -Pelvic Cues (Gailey) -Trunk-upright positioning
ASSISTIVE DEVICES: Previous prosthetic users:
• May need to use a device temporarily as a tool to achieve
optimal gait
• Usually can wean from device quickly
ASSISTIVE DEVICES: New amputees:
- Start with bilateral device
- Progress to unilateral device
- Goal is ambulation without a device (but it is ok to use one if needed)
TOE LOAD
• Monitor Toe Load with gait activities
-If difficulty getting knee to break for swing phase, may need to decrease Maximum Toe Load to make it easier for the patient to meet the criteria.
-If knee is breaking easily, may need to increase Maximum Toe Load
• Toe Load will change with different assistive devices
-Higher with walker
-Lower with cane initially
-Progresses with patient comfort loading the
prosthetic limb during gait
• Always set the Toe Load for the device the patient will be using at HOME
What is not fun to do?
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