L21 Lower Limb Prosthetics Flashcards
(26 cards)
Epidemiology and Cost of Prosthetics
- Each year there are 185,000 amputations that have a cost of over 8.3 billion dollars
- Main causes for these amputations are vascular diseases that take up 54 percent of the amputee
population and 45 percent of the causes are due to trauma. - # of amputations due to diabetes increased by 24% from 1988 to 2009
- Traditional lower limb prostheses: $5,000 to $50,000
- Traditional upper limb prosthesis: $3,000 to $30,000 dollars.
Leading Causes of Lower Extremity Amputations
- Peripheral Vascular Disease – infection, foot ulcer
- Diabetes – infection, foot ulcer
- Trauma
- Tumor/Cancer - osteosarcoma
- Congenital Deficiency
Amputation Levels
- Transtibial amputation: below the knee (BK)
- Transfemoral amputation: above the knee (AK)
- Hip, knee, or ankle disarticulation
- Partial foot, or toe
Components of a Lower Limb
Prosthesis
- Suspension
- Socket Design
- Alignment
- Pylon
- Prosthetic knees
- Prosthetic feet
Component Selection
- Patient’s Limb: skin, muscle function, tolerance
- Amputation level
- Type of trauma or injury: frostbite, land mines,
congenital - Gender, age
- Developed or developing countries
- Occupation
- Leisure activities
- Cost/Reimbursement
Fitting process
- Assess Individual Needs (Active, Weight, Occupation, Health)
- Cast/Scan of the Limb for Model
- Check Socket made from Model (2-3 weeks of use and appropriate changes)
- Definitive Prosthesis (After completing physical therapy)
Socket Suspension and Fit
- Stump socks: protection, comfort, absorb
sweat - Vacuum (negative pressure by drawing skin and soft tissues to walls of socket)
- More constant socket pressure
- High fidelity socket (Biodesigns)
Recent Innovations:
Lower Limb Prosthetics
- Bluetooth technology
- Microprocessor knees
- Prosthetic Materials
- Osseointegration
- CAD/CAM technology
Modern Prosthetic Materials
Plastic Polymer Laminates (Thermosets):
- Fabrication of prosthetic sockets
- Lightweight and strong
- Acrylic, epoxy, polyester
- Prosthetist has control over:
strength, thickness and stiffness
- Reinforcement fibers: Fiberglass, nylon, Dacron, carbon, Kevlar
Carbon fiber
- Used for prosthetic feet
- More life-like material
- Oscar Pistorius – Bilateral Amputee – carbon fiber-composite legs
Titanium
- Osseointegration – titanium bolt inserted into bone at the end of the stump prosthetics knees, feet, component
Bluetooth technology
Sensors on the sound limb can help control prosthetic device
Important for bilateral amputees – two prosthetic legs can commute with each other
Microprocessor Knees
Use sensors (force, accelerometer, gyroscope) and a microprocessor (on board computer) to adjust the knee.
- Swing control or
- Stance and Swing control
- Active - Motor powered: aids with flexion or extension or both; provides a knee torque
- Semi Active - No motors: adjusts the flow of hydraulic fluid in the knee to change the joint resistance
OttoBock Genium
Semi-Active (No motors)
Adjusts the flow of hydraulic fluid within the leg from sensory data through the microprocessor
Swing phase: hydraulically controlled
Stance phase: dampening
Complex sensory system :
* Gyroscope
* Accelerometer
* Knee Angle
* Force Sensors – any loading of foot and ankle
Sophisticated Control for:
* Stairs
* Ramps
* Obstacles
* Speed Changes
* Backwards Walking
Ossur Power Knee
Active (motor-powered)
First Commercial Active Knee:
* Active Flexion / Extension
* Accelerometer
* Gyroscopes
* Force Sensors
Sophisticated Control for:
* Maintains walking speeds.
* Assists with the upward motion required for stairs and inclines.
* Learns unique patterns of
gait for natural, efficient motion.
Microprocessor Controlled Active Ankle Units
Ossur: PROPRIO FOOT
* Advanced sensors with complex control
* Powered ankle motion
* Intelligent terrain adaptation
* Natural function
* High precision linear actuator receives commands via a control board
iWalk: BiOM - Hugh Herr – MIT Media Lab
* Power Plantar Flexion reduces common aches
* Power added to the toe-off to reduce amount of energy required during gait
* BiOM absorbs impact and reduces unnatural forces on the body
Prosthetic Feet
*Rigid keel
*Single-axis foot
*Multiaxis foot
*Flexible keel
*Energy-storing foot/dynamic response
Osseointegration
- Integrates titanium implants ->medullary cavity of the bone
Benefits:
* Extend from bone through the skin to create an anchor for prosthesis
* Bypasses skin contact with skin -> reducing pain and tissue damage
* Improved perception of prosthesis
Risks:
* Remove barrier function of skin -> possible contamination
* May lead to infection and metal corrosion
* More surgery
CAD/CAM
- Computer Aided Design and Manufacturing
- Generate quantitative mathematical model of the residual limb
- More robust systems use CT scans or MRI
- Increased repeatability of socket deign
- Extended prosthetic service for the developing world
Tools to Evaluate K-Levels
- Amputee Mobility Predictor
(AMP) - Patient Assessment Validation Evaluation Test
(PAVET) - Prosthesis Evaluation
Questionnaire (PEQ) - Timed Up and Go (TUG)
- Timed Walk Test
- Distance Walk Test
Outcome Measures in Clinic
Benefits:
* Justify selection of interventions
* Helps focus the intervention
* Help direct the plan of care
* Determine and predict progress/outcomes
* Improve patient outcomes
* Enhance communication with patients
* Helps to motivate the patient
* Document patient status
* Help decrease insurance denials
Limitations:
* Takes too much time for
patients/clinicians to complete
* Too much time to analyze, calculate or score
* Are difficult to interpret
* Provide information that is too subjective
* Do not help direct the plan of care
* Require more effort than they are worth
* Lack applicability to LLAs
Lower Limb Prosthetic Research
- Sit to Stand: Comparing Various Knees
- C-leg vs. Genium Comparison
- Prosthetic Feet Comparison
-> Return to Duty - Monitoring Prosthetic and
Orthotic Function in the Community
Sitting and Standing in
Transfemoral Amputees
- Side by side comparison of healthy control subjects and subjects with difference prosthetic knees
- Determine the ability of different prosthetic knees to assist with sitting and standing
- 3 types of prosthetic knees were evaluated :
- The Ossur Power Knee
- The Otto Bock C-Leg
- The Mauch Swing and Stance
Sitting and Standing in Transfemoral Amputees
Despite advances in prosthetic knees in gait, support during standing and sitting were found to be performed primarily by the intact leg.
Current generation prosthetic knees have the capability to provide kinetic
symmetry, but limitations in control, training, or confidence impede their capability.
Gait Biomechanics:
- Overground walking (VS, S, N, F)
- Weighted Walking (VS, S, N, F)
- 5° Ramp Ascent and Descent (S, N, F)
- 10° Ramp Ascent and Descent (S, N, F)
- Walking on Un-Even Terrain (Gravel)
- Walking Backwards
- Stair Ascent and Descent
Prosthetic Research with Wounded Warriors
- 14 Highly active transtibial amputees
- Heart rate and speed on SWAT Obstacle course.
- VO2 , Heart Rate, and Lower body motion tracking used in walking and running in Physical Therapy biomechanics lab.
- 14 Highly active transtibial amputees
- Heart rate and speed on SWAT
Obstacle course. - VO2 , Heart Rate, and Lower body motion tracking used in walking and running in Physical Therapy biomechanics lab.
