Prosthetics Flashcards
Limb Prosthetics
Artificial replacement for any or all parts of upper or lower limbs
- Designed to supplement function and appearance
Provides function that otherwise wouldn’t be possible
- Functional tasks, walking sports
Stats of causes of Amputation
Disease is the #1 cause of amputation
- Diabetes accounts for 2/3 of lower limb amputations in Canada
- 3.7 million Canadians have been diagnosed
- Preceded by foot ulcers or infected wounds
43% of amputations occur in the age range of 40-64
Widely reported that 87% of leg amputations are preventable
53% of lower limb amputations are trans-tibial
32% trans-femoral
large emphasis on the conservation of tissue
- More residual musculature aids in retaining as much muscular function post-amputation
Components of a prosthetic limb
Residual Limb (Stump)
- Remaining tissue in which the prosthetic attaches
Socket
- “Tube” that will surround and support stump
Socket Liner
- Provides comfortable contact surface
- Key role in preventing injury with skin
Prosthetic System
- Cosmetic, body powered, myoelectric
Types of prosthetics
Cosmetic
- Low function
- For looks
Body-Powered
- Uses movements of other parts of body to move prosthetics
Myoelectric
- Uses electrical signals sent by muscles to control prosthetic
Considerations when choosing a prosthetic
- Amputation Level
- Career/Job
- Financial Freedom
- Cosmetics
- Functionality: of prosthetic and individual (can they learn to control it)
5 Key Steps in Manufacturing Prosthetics
- Measurement of Stump
- Measurement of Anthropometrics
- To create symmetry across body - Molding of the stump
- create negative mold by wrapping remaining limb
- Back fill mold to create positive mold
- Use thermoplastic to create molded socket - Fabrication of permanent socket and articulating parts
- Assemble and fine tune
Types of Formation
Preparatory
- Temporary limb used while the stump is still maturing
- Allows for users to “test run” a prosthetic
- Results in a better fit
Definitive
- Final prosthetic that users will use
How did early manufacturing control knee swing
Friction
- Mechanical locks were used for stance phases of gait
- these locks prevent buckling
- not ideal for sports
What units need to be considered for trans-femoral amputations
Knee unit and foot unit
Why did terry fox require an extra hop on his health leg which running
to allow more time for his prosthetic to swing through
S.A.C.H. System
Solid Ankle Cushing Heel
- Historically what was used
- No articulation of ankle
- Foot motion did resemble closely to natural walking
Flex foot
- Modern design
- Originally designed for athletic scenarios
- Used spring like design to return energy back to body (help with propulsion and breaking)
Common Problems in Lower limbs
Socket Fit
- Poor fit can result in friction or strain on tissues
- Loss of muscle in residual limb
Greater Energy Expenditure
- If limb is not balanced and weighted properly
- >2cm of leg length discrepancies have implications
Asymmetry between limbs
- muscular imbalances
- Unequal loading
Motor Learning
- Having to re-learn how to walk
Ratationplasty
- Above femur amputation
- Place foot at amputation location but backwards
- Ankle used as knee joint to move prosthetic
- requires motor relearning
Lower Limb Rehabilitation
Common hurdle to overcome is symmetry between limbs
- Traditional approach: visual gait assessment
- Modern Gait Assessment: MOCAP, IMU, Force Plates
Asymmetries can occur because of a lack of confidence or inability to control the limb
Myoelectric Prosthetics
Focus is on myoelectric control and neural control
- Muscle Activity via surface electrodes
- Neural Interfacing
Microcontrollers dictate movement
- Process signals and produce movement based on these signals
Electrodes pick up microvolts generated by muscle contractions of the residual limb
Signals are amplified and used to activate motor within
Electrodes are placed on flexors and extensors of residual stump
Agonist-Antagonist myoneural interfacing surgery
- Limb movement is controlled by muscle pairs
- Allows for greater proprioception
- AMI allows for users to feel as though they are moving a physiological limb
Continuous Neural control of bionic limbs study design
- 14 individuals 18-65, 7 AMI group and 7 Non-AMI group
- Evaluated various walking speeds, adaptations to slopes and stairs and obstacle crossing
HYPOTHESIS - AMI would produce elevated muscle afferent signaling resulting in the promotion of highly biomimetic gait
Continuous Neural control of bionic limbs study results
- AMI had 41% higher max walking speed compared to 39% in control (65% restored energy - comparable to fast walking healthy individuals
- AMI group were able to modulate bionic peak power better than control group (+202% ascent vs -163% descent)
- General improvements in traversing obstacles (54% faster than the control grou)
Current Technology of bionic legs
- Pre-defined robotic control architectures for locomotion
- Finite state machine and pattern recognition from cyclic nature of gait
- Uses current state + sensors to predict appropriate movement
Neuroprosthetic legs
- Not reliant on gait controller
- AMI links residual agonist-antagonist muscles
- Restores natural muscle dynamics
Below the knee AMI amputation control
- Lateral Gastroc linked to Tibialis Anterior for ankle control
- Peroneus longus linked to Tibialis Posterior for subtalar control
Advancements in Hand Bionics
PYSCHOIC is a pioneer myoelectrical hand bionic company
Developed the “ability hand”
- Integration of touch via haptic feedback
- Carbon Fiber construction
- Waterproof
- Variety of hand grips (5 Finger articulation)
