Transfemoral Prosthetics Flashcards
Do higher levels of amputation have a higher/lower risk of contractures
- Higher risk of contractures
How to stretch the hips flexors n prone
- Like on your stomach with your legs out straight
- Slowly troop yourself up on your elbows
- Hold for ≥10sec then lower slowly
- Repeat 3-5 times and perform 1-2x daily
Benefits of a knee disarticulation
- Bulbous distal end nachos prosthetic suspension
- Normal ADD angle of the LEE is Moree likely to be preserved
- Long lever arm of the femur facilitates control of the prosthetic knee
- Proximal component of a WBing joint, the distal femur tolerates bend-bearing pressures with the socket
What are the trade-offs of a knee disarticulation
- Knee center o prosthetic side is lower than sound side which affects gait kinematics & cosmesis when sitting
Pressure tolerant areas for a Transfemoral amputation
- Ischial tuberosity: keeps residual limb from migrating distally inn socket
- Femoral triangle: keeps pelvis from translating anterior/posterior
- Lateral shaft of the femur: provides lateral stability (frontal plane) during gait & helps maintain femoral ADD
- Soft tissue circumferences: compression & proximal distraction offer hydrostatic support that offloads the ischial tuberosity
Describe the different socket styles
- Quadrilateral: more narrow anterior/posterioir, flat self for ischial tuberosity & glutes
- Ischial containment: wider anterior/posterior (accommodate muscle contraction), more narrow medial/lateral to maintain femoral ADD
- Marlo Anatomical: lower trim lines posteriorly (more comfortable for sitting)
- Subischial: more comfortable, greater hip mobility, must be tight circumferentially
Describe prosthetic sockets and proper angle of ADD of the femur
- Prosthetic socket cannot provide enough lateral pressure to change the position of the femur
- Proper anatomical ADD is achieved only through specific surgical techniques
- An intimately contoured socket in optimal alignment enhances an individual’s gait, decrease energy expenditure, increases socket comfort, & improves overall function
Describe the position of the ischial tuberosity inn ischial containment socket
- Inside the socket
- Contained on the medial surface of the socket brim
- Pivot point to keep the pelvis from migrating laterally resulting in lateral trunk lean
What are the trade-offs of a flexible socket design
- Somewhat less durable
- More bulky to wear
- More expensive to produce than rigid sockets
What are the benefits of a flexible socket design
- Vacuum formed
- Encased in a rigid frame which provides support during WBing & helps to maintain socket shape
- Accommodates to change in muscle shape during contraction & can easily by modified after initial fabrication
- More comfortable to wear especially in sitting
- Useful if suction suspension is desired
Force couples during loading response
- Anterior/proximal
- Posterior/distal
Force couples during terminal stance
- Anterior/distal
- Posterior/proximal
Force couples during mid-stance
- Medial/proximal
- Lateral/distal
Criteria to begin fitting
- Wound closure
- Tolerant to force couple pressures
- Circumference reduction
- Sound side weight bearing ability
- Evaluate WBing regions
Describe contracture reduction to begin fitting for prosthetic
- Progresses slowly
- Measure & give patient a goal
- Passive stretching
- Active stretching when ambulating with a prothesis
- Over 25º not advised to fit
Prosthetic features that affect energy expenditure
- Weight of the prosthesis
- Socket fit
- Alignment of the prosthesis
- Functional characteristics of the prosthetic components
The energy cost of gait __________ significantly as the length of the residual limb _____________
- Increases, decreases
- Less efficient in terms of energy expended over distance (per meter)
3 variables that influence knee stability during stance
- Individual’s ability to voluntarily control the knee using muscular power (hip extensors)
- Alignment of the knee unit with respect to the weight line (trochanter knee ankle line)
- Inherent mechanical stability of the knee unit
Prosthetic alignment considerations
- Confirm flexion of prosthetic socket: match the patient flexion +5
- Check height (IT to floor)
- Foot level in the shoe
- Knee stability
What can cause an unaccommodated hip flexion contracture
- AK prosthetic socket not aligned to match patient measurements
- Most commonly results in lordosis form insufficient socket flexion
- Patient may also stand with the knee flexed
Shoes with different heel heights affect knee stability in what ways
- Most prosthetic feet are designed for a standard 3/4 inch heel
- Decreasing the heel height results in an extension moment creating an excessively stable knee
- Increasing the heel height results in a flexion moment creating instability of the prosthetic knee
Describe pelvic stability during gait with a prosthetic
- The femur without its distal attachment at the knee is susceptible to lateral displacement within the socket during WBing
- The displacement can make it difficult to maintain a horizontal pelvis & results win an apparent Trendelenburg sign & compensatory gait deviations
- Pelvis stability is especially problematic for those with short residual limbs
What intrinsic (patient) factors can cause lateral trunk bending towards the prosthetic side
- Decreased balance
- Short residual limb = shorter lever arm for pelvis to stabilize
- Weak ABD (Glute Medius)
- Painful residual limb
What extrinsic (prosthetic) factors can cause lateral trunk bending towards the prosthetic side
- Socket/lateral wall not ADD enough
- Socket/medial wall too high = pinch of soft tissue so lateral bend to avoid pressure on the pubic ramus
- Prosthesis too short = mid-stance hip drop
Describe the correct way to don the prosthesis
- It must have full distal contact
- View & palpate distal limb through the valve hole
- Note the lanyard length that exits the socket
- Check pelvis for length equality: leg will appear high if not donned correctly
- Ensure correct rotational position of socket
How too ensure correct rotational position of socket
- Adductor longus should be in anterior medial corner
- Ischial tuberosity: have pt flex forward at the hip & palpate IT and see that ti matches the seat on the socket
What muscles are needed to prevent lateral trunk bend during mid-stance in the coronal plane
- Hip abductor strength & femoral adduction in socket is needed
What can cause an unstable knee (AK)
- Hip flexion not accommodated in the socket position over the knee
- Knee center too far anterior
- Heel too high
- Prosthesis too long
What are the more common types of transfemoral suspension
- Traditional pull in suction
- Roll on liners: pink lock, lanyard, one-way valve suction (seal inn liner)
- Elevated vacuum
What are the less common types of transfemoral suspension
- Silesiian belt suspension
- Total elastic suspension belt
- Pelvic belt and hip joint
Describe a traditional suction socket
- Uses negative air pressure, skin to socket contact, & muscle tension to hold the socket onto the limb
- Intimate fit is essential
- High shearing forces associated with donning a suction socket
- Inappropriate for patients with recent amputation who will continue to lose limb volume or those with Hx oof fluctuating edema or unstable weight
Describe an elevated vacuum suspension
- Lower trim lines in comparison to other transfemoral socket designs leading to increased pt comfort & ROM
- By utilizing elevated negative pressure around the distal 2/3 of the residual limb, the socket no longer requires compression of the proximal residual limb to provide WBing & stabilization
Who designed a hydraulic prosthetic knee for veterans with amputations after the war
- Henschke Mauch
List the prosthetic knee types
- Manual locking knee
- Single axis knee
- Weight activated stance control knee
- Polycetric knee
- Hydraulic knee
- Microprocessor knee
- Power knee
- Sport specific knees
Describe a single axis knee
- Most economical, durable, & lightest option available
- Pt must use heir own muscle power to keep them stable when standing
- To compensate the knee often incorporates a constant friction control & a manual lock
- Friction keeps the leg from swinging forward too quickly as it swings through to the next step
Describe a state control knee
- Very stable & often prescribed for a first prosthesis
- If weighted the knee will not bend until the weight is displaced
- Functions as a constant friction knee during leg swing but held in extension when weighted
- If initial contact is made when the knee is not fully extended the braking mechanism provides additional mechanical stability to knee the knee from rapidly buckling
Describe a hydraulic knee
- Cadence responsive, fwd progression of the prosthetic shin changes as gait speed changes
- Provides the closest thing to normal knee function for active amputees
- Although they provide smoother gait they are heavier, require more maintenance, & a higher initial cost
What happens if the patient takes too big of a step
- Ground reaction force will go posterior to the knee causing a flexion moment leading to knee buckling at initial contact
How do you counter-act the knee flexion moment without quads?
- Use hip extension
How is mid-stance affected by going up or down a ramp?
- While going up a hill you tend to lean forward meaning the hip extensors are working more but it makes it harder for them to flex the knee
Describe medial and lateral whips
- Name for the direction the heel goes
- Medial whip: heel is faced radially and the knee is face out laterally
Evidence for hydraulic knees when using swing control
- Leads to increased confront & improved walking speed in a active pts
- Leads t improved gait symmetry & speed
- Reduces stride time & improves the symmetry of swing phase duration
- Indicated for active walkers, permitting increased walking comfort, speed, & symmetry
Evidence of microprocessor knees (MPK)
- Decrease O2 rate at self selected speed
- Reduce energy requirements of walking
- Increased walking speed on uneven terrain
- Improved gait pattern during stair descent
- Decreased number of subject reported stumbles & falls
- Reduced wear & tear of the contralateral limb
Describe the microprocessor knee and K2 functional level
- Amount limited community ambulatory, MPK use may significantly reduce uncontrolled falls by up to 80%
- Persons with a lower functional level might also benefit from using a prosthesis featuring an MPK
Parameters that are NOT primary indications in prosthetic knee joint selection
- Daily step counts
- Temporal and spatial gait symmetry
- Self reported general health
- Total costs of prosthetic rehabilitation
How to educate amputees on how to negotiate ramps and hills
- Instruct pt to lean back when going downhill to align with the ground reaction force at initial contact/loading response & ‘ride’ the friction of the knee mechanism down the hill
- Instruct pt to lean forward into the hill bc the only muscles available to pull them uphill are the hip extensors which have a better mechanical advantage in a flexed posture (fwd lean creates extension moment at knee making it difficult to unlock which is achieved through loading the prosthesis through terminal stance once toe load is achieved
Foot selection for stability
- A foot that can reach flat foot quickly is preferable bc it enhances stance phase knee stability
- Reaching foot flat quickly is especially important for individuals who have a short residual limb or weak hip extensors
Foot selection for active individuals
- Energy storing capabilities of these prosthetic feet at push-off promote rapid advancement of the shin section during swing phase. This enhances the ability of the individual who is using a transfemoral prosthesis to walk at faster speeds.
- Most of these feet are much lighter in weight than the articulating feet.
Benefits of a hip disarticulation
- More advanced options such as the Ottobock Helix system
- Provides dynamic stability & triplanes motion control
- Makes it easier to extend the leg & clear the toe during gait
