Below knee limb loss, also known as a below knee amputation (BKA), refers to the amputation or absence of the leg below the knee. This type of amputation can be a result of complications from vascular diseases, such as diabetes or peripheral arterial disease, or other conditions that affect blood flow. It can also occur due to trauma events, cancer, infection, or being born with a limb difference.
A below knee prosthetic limb is designed to help individuals who have undergone a below knee amputation regain mobility and functionality. It consists of several components, including a suspension sleeve or belt, socket, shin tube/pylon, and prosthetic foot. The suspension holds the artificial limb onto the residual limb, and there are different types of suspensions available depending on the individual’s needs and preferences.
Advantages of below the knee prostheses
Below knee prostheses offer several advantages for individuals with below knee limb loss:
1. Improved mobility: A below knee prosthesis allows individuals to walk and engage in daily activities more easily. It provides support and stability, enabling the user to maintain balance and stability while walking.
2. Natural movement: The design of below knee prostheses aims to mimic the movements of a natural leg as closely as possible. This helps individuals regain a natural gait pattern, making their walking appear more natural to others.
3. Comfort and fit: Below knee prostheses are customized to fit the individual’s residual limb correctly, ensuring optimum comfort and functionality. The socket is designed to distribute pressure evenly, reducing the risk of discomfort or skin irritation.
4. Versatility: Below knee prostheses can be adapted to accommodate various activities and terrain. Prosthetic feet with different features, such as shock absorption or specialized grips, can be used for specific activities like running or hiking.
5. Improved quality of life: By restoring mobility and independence, below knee prostheses can significantly improve the overall quality of life for individuals with below knee limb loss. They can engage in activities they enjoy and regain a sense of normalcy in their daily lives.
Conclusion
In summary, below knee prostheses are crucial in helping individuals with below knee limb loss regain mobility and functionality. They offer several advantages, including improved mobility, natural movement, comfort and fit, versatility, and an improved quality of life. With advances in prosthetic technology, individuals can expect better outcomes and increased capabilities with below knee prostheses.
Socket Designs
Different types of socket designs for below the knee prostheses
Below the knee prostheses require specific socket designs to accommodate the unique needs of individuals with symes amputations and transtibial amputations. The socket design for a symes amputation is slightly different than that of a transtibial socket. The main difference lies in the way pressure is distributed throughout the limb.
For a symes amputation, the socket design places more emphasis on the distal end or the very bottom of the prosthesis, as tolerated by the individual. The carbon fiber frame is directly connected to the prosthetic foot. This requires the use of a low-profile foot with a small build height. Examples of suitable feet include the Endolite Esprit and Ability Dynamics Rush Rover.
On the other hand, the socket design for a transtibial amputation focuses on redistributing pressure throughout the residual limb. This is done to prevent limb soreness, redness, bruising, and edema. The number of ply in the sock used can affect the thickness and provide better stability. The higher the number of ply, the thicker the sock, which can help prevent excessive movement of the limb within the socket. This can help in avoiding discomfort and complications.
Benefits of each socket design
The different socket designs offer certain benefits based on the specific needs of the individual. Here are some key benefits:
Symes Amputation Socket Design:
Places emphasis on the distal end of the prosthesis to provide better control and proprioception for individuals with a symes amputation.
Directly connects the carbon fiber frame to the prosthetic foot, ensuring a low profile and small build height for a more natural gait.
Suitable for individuals with good tolerance for weight-bearing on the foot.
Transtibial Socket Design:
Redistributes pressure throughout the residual limb, reducing the risk of soreness, redness, bruising, and edema.
Allows for adjustments in alignment through different componentry to optimize the individual’s gait.
Requires a diagnostic socket to account for residual limb volume reduction in new amputees.
In conclusion, socket designs for below the knee prostheses vary depending on the type of amputation. The symes amputation socket design focuses on the distal end of the prosthesis, while the transtibial socket design redistributes pressure throughout the residual limb. Both designs have their own benefits and are tailored to meet the specific needs of the individual.
Suspension Methods
Various suspension methods used for below the knee prostheses
There are different suspension methods used in below the knee prostheses to secure the artificial limb onto the residual limb. The choice of suspension method depends on the individual’s residual limb shape, size, activity level, and preference. Here are some common suspension methods used:
1. Passive suction suspension: This method uses a silicone liner that creates a vacuum seal between the liner and the socket, holding the prosthesis in place. It provides good suspension and stability but may require some manual adjustment throughout the day.
2. Active vacuum suspension: This method incorporates a mechanical pump that actively maintains the vacuum seal, providing consistent suspension throughout the day. It offers excellent comfort and reduces the need for manual adjustments.
3. Strap and buckle suspension: This method uses straps and buckles to secure the prosthesis onto the residual limb. It allows for easy adjustment and can accommodate changes in limb volume. However, it may not provide as secure suspension as other methods.
4. Sleeve suspension: This method uses a sleeve made of neoprene or silicone material to hold the prosthesis in place. It provides good suspension and allows for easy donning and doffing. However, it may require regular replacement as the material can stretch over time.
5. Pin/lock suspension: This method utilizes a pin that locks into a corresponding receptor on the socket, providing secure suspension. It is commonly used for individuals with high activity levels or those who require a high degree of stability.
Advantages and disadvantages of each suspension method
Each suspension method has its own advantages and disadvantages. Here is a comparison of the different suspension methods:
Passive suction suspension:
Advantages: Provides good suspension and stability, relatively comfortable.
Disadvantages: May require occasional manual adjustment, may not be suitable for all residual limb shapes.
Active vacuum suspension:
Advantages: Provides consistent suspension throughout the day, excellent comfort.
Disadvantages: Requires maintenance of the mechanical pump, may be more expensive.
Strap and buckle suspension:
Advantages: Easy adjustment, accommodates changes in limb volume.
Disadvantages: May not provide as secure suspension as other methods, may require frequent adjustment.
Sleeve suspension:
Advantages: Good suspension, easy donning and doffing.
Disadvantages: Material may stretch over time, requiring replacement.
Pin/lock suspension:
Advantages: Provides secure suspension, suitable for high activity levels.
Disadvantages: Requires precise alignment, may limit range of motion.
In conclusion, there are various suspension methods available for below the knee prostheses, each with its own advantages and disadvantages. The choice of suspension method should be based on the individual’s specific needs and preferences, as well as the recommendation of the prosthetist. It is important to have a well-fitting and properly suspended prosthesis to ensure optimal comfort and function.
Components and Materials
Components used in below the knee prostheses
Below the knee prostheses consist of various components that work together to provide functionality and support to individuals with amputations. These components include:
1. Socket: The socket is the part of the artificial limb that the residual limb fits into. It can be made of thermoplastic, metal, or laminated material. The socket design varies depending on the type of amputation and aims to distribute pressure and provide a secure fit.
2. Liner: The liner is a removable inner socket made of flexible material. It helps to improve comfort, reduce friction, and provide cushioning between the residual limb and the socket.
3. Pylon: The pylon is a rod-like component that connects the socket to the foot. It provides stability and support during weight-bearing activities.
4. Foot: The foot component simulates the function and movement of a natural foot. Various types of feet are available, including energy-storing feet, dynamic response feet, and multi-axial feet. The choice of foot depends on the individual’s activity level and lifestyle.
5. Prosthetic Knee: For individuals with a below the knee amputation, a prosthetic knee is not always necessary. However, in cases where knee motion is required, a prosthetic knee component can be added. Prosthetic knees vary in terms of their range of motion, stability, and control.
Different materials used and their benefits
The materials used in below the knee prostheses play a crucial role in providing durability, flexibility, and comfort. Here are some common materials used and their benefits:
1. Carbon Fiber: Carbon fiber is lightweight yet strong, making it an ideal material for the frame of the prosthesis. It allows for better energy transfer and reduces strain on the residual limb. Carbon fiber also provides natural shock absorption, enhancing the individual’s gait.
2. Thermoplastic: Thermoplastic materials such as polyethylene are commonly used in the socket construction. These materials can be molded and shaped to create customized sockets that fit the individual’s residual limb comfortably. Thermoplastic sockets are lightweight and durable, providing a good balance between flexibility and support.
3. Silicone: Silicone is used in the fabrication of liners and provides excellent cushioning and shock absorption. It conforms to the shape of the residual limb, reducing pressure points and enhancing comfort. Silicone liners also offer moisture-wicking properties, helping to keep the residual limb dry.
4. Metal: Metal materials such as titanium or aluminum alloy are used in the construction of various components like pylons. These materials provide strength and stability while being lightweight. Metal components are adjustable, allowing for fine-tuning and alignment adjustments.
5. Rubber and Foam: Rubber and foam materials are used in the foot component of the prosthesis to simulate natural foot movement. These materials offer shock absorption and flexibility, allowing for a more natural gait and reducing impact on the residual limb.
In conclusion, below the knee prostheses utilize various components and materials to provide functionality and comfort to individuals with amputations. The socket, liner, pylon, foot, and prosthetic knee work together to create a prosthetic limb that meets the specific needs of the individual. The choice of materials, such as carbon fiber, thermoplastic, silicone, metal, rubber, and foam, ensures durability, flexibility, and optimal performance.
Hydraulic and Microprocessor-controlled Systems
Explanation of hydraulic and microprocessor-controlled systems in below the knee prostheses
Hydraulic systems in below the knee prostheses utilize fluid to provide controlled movement and support. The hydraulic ankle/foot design incorporates a hydraulic cylinder and valves that regulate the flow of fluid, allowing for adjustable resistance and enhanced movement. This system mimics the natural motion of the ankle and foot, providing a more natural gait and improving stability.
Microprocessor-controlled systems utilize sensors and a microprocessor to analyze data and adjust the prosthesis in real-time. These systems can detect changes in terrain and adjust the resistance and flexibility of the foot accordingly. This technology allows for smoother transitions and better shock absorption, reducing the risk of falls and improving overall comfort and mobility.
Benefits and advancements of these systems
Both hydraulic and microprocessor-controlled systems offer several benefits and advancements in below the knee prostheses:
1. Improved stability: Hydraulic systems provide better stability and control, especially on uneven surfaces. The adjustable resistance allows users to adapt to various terrains and activities, enhancing their overall stability and confidence.
2. Natural movement: These systems mimic the natural movement of the ankle and foot, allowing for a more natural gait pattern. This improves overall comfort and reduces the strain on the residual limb, promoting better long-term mobility.
3. Enhanced shock absorption: Hydraulic and microprocessor-controlled systems provide enhanced shock absorption, reducing the impact on the residual limb and improving comfort during walking or running. This technology allows for a smoother and more comfortable gait.
4. Real-time adjustments: Microprocessor-controlled systems can adjust the resistance and flexibility of the foot in real-time, based on the sensor data. This ensures that the prosthesis adapts to changing terrains and activities, providing optimal support and functionality.
5. Better energy efficiency: Hydraulic and microprocessor-controlled systems optimize energy transfer, allowing users to walk longer distances and engage in higher impact activities with less fatigue. This promotes a more active and independent lifestyle.
6. Customizable settings: These systems offer customizable settings that can be adjusted based on the individual’s preferences and needs. This allows for fine-tuning and personalized adjustments that optimize comfort and performance.
7. Continual advancements: The technology behind hydraulic and microprocessor-controlled systems is continually advancing. With ongoing research and development, these systems are becoming more sophisticated, offering even greater functionality and comfort.
In conclusion, hydraulic and microprocessor-controlled systems have revolutionized below the knee prostheses. These systems provide improved stability, natural movement, enhanced shock absorption, real-time adjustments, better energy efficiency, customizable settings, and continual advancements. With the use of these systems, individuals with below knee amputations can experience improved mobility, comfort, and quality of life.
Energy-Storing/Returning Systems
Overview of energy-storing/returning systems in below the knee prostheses
Energy-storing and returning systems are innovative technologies used in below the knee prostheses to improve gait efficiency and reduce energy expenditure. These systems are designed to simulate the natural biomechanics of the ankle joint and enhance the user’s overall mobility.
One example of an energy-storing/returning system is the PROPRIO FOOT, which utilizes powered ankle motion, intelligent terrain adaptation, and natural function. The PROPRIO FOOT is considered the most life-like prosthetic foot available, as it allows users to overcome a wide range of obstacles in their daily activities.
Another energy-storing/returning system is the EMPOWER FOOT, which provides natural bionic propulsion. The EMPOWER FOOT System is the only commercially-available device that enables amputees to achieve a normalized biomimetic response across all level-ground walking speeds. This system enhances the user’s walking efficiency and helps reduce the energy required for prosthetic ambulation.
How they improve gait and reduce energy expenditure
Energy-storing/returning systems in below the knee prostheses work by storing and releasing energy during the gait cycle, similar to the function of a natural ankle joint. When the user applies weight to the prosthetic foot, the energy-storing component compresses, storing potential energy. As the user progresses through the gait cycle, the stored energy is then released, propelling the user forward and reducing the effort required for walking.
The benefits of energy-storing/returning systems include:
1. Improved gait efficiency: These systems mimic the natural function of the ankle joint, allowing for a more natural and fluid gait pattern. This improvement in gait mechanics helps reduce the risk of developing gait deviations and associated musculoskeletal issues.
2. Reduced energy expenditure: By storing and returning energy during the walking cycle, these systems reduce the amount of energy required for prosthetic ambulation. As a result, users experience less fatigue and are able to walk for longer distances with less effort.
3. Enhanced stability and balance: Energy-storing/returning systems provide increased stability and balance during walking by mimicking the function of the natural ankle joint. This improved stability reduces the risk of falls and promotes a greater sense of confidence and independence.
4. Enhanced shock absorption: The ability of these systems to absorb and dissipate impact forces reduces stress on the residual limb and other joints. This feature is particularly beneficial for individuals with amputations who engage in activities that involve high-impact movements, such as running or jumping.
In conclusion, energy-storing/returning systems in below the knee prostheses offer several advantages in terms of gait improvement, reduced energy expenditure, enhanced stability, and shock absorption. These systems replicate the natural function of the ankle joint, providing users with a more efficient and comfortable walking experience. The PROPRIO FOOT and EMPOWER FOOT are examples of advanced energy-storing/returning systems that are revolutionizing the field of prosthetics and helping individuals with below the knee limb loss regain their mobility and independence.
Prosthetic Feet Options
Different types of prosthetic feet available for below the knee prostheses
Below the knee prostheses can be customized with different types of prosthetic feet, depending on the individual’s specific needs and activity level. The choice of prosthetic foot can greatly impact the user’s mobility, stability, and overall comfort. Some common types of prosthetic feet include:
1. Solid Ankle Cushion Heel (SACH) Foot: This is a basic and durable option that provides good shock absorption and stability. It is often recommended for individuals with lower activity levels or those who require additional support.
2. Dynamic Response Foot: This type of foot incorporates a carbon fiber design that provides energy return and a more natural walking experience. It is suitable for individuals who are active and require a higher level of responsiveness.
3. Flex-Foot: The Flex-Foot design utilizes a curved carbon fiber footplate, which allows for smooth roll-over and improved propulsion. It is commonly used by individuals who engage in running or other high-impact activities.
4. Energy-Storing Feet: As mentioned in a previous section, energy-storing/returning systems such as the PROPRIO FOOT and EMPOWER FOOT are advanced options that provide energy return and enhance mobility. These feet are suitable for individuals who have higher activity levels and want to achieve a more natural gait pattern.
Advantages and considerations for each type
Solid Ankle Cushion Heel (SACH) Foot:
Advantages:
Durable and long-lasting
Good shock absorption
Provides stability and support
Considerations:
Limited energy return
May not replicate natural ankle movement
Dynamic Response Foot:
Advantages:
Provides energy return and a more natural walking experience
Suitable for active individuals
Promotes a fluid gait pattern
Considerations:
Higher cost compared to basic options
May require adjustment period for users
Flex-Foot:
Advantages:
Smooth roll-over and improved propulsion
Ideal for high-impact activities
Enhances running efficiency
Considerations:
May not be suitable for individuals with lower activity levels
Requires proper alignment and fitting
Energy-Storing Feet:
Advantages:
Mimic natural ankle movement
Improve gait efficiency and reduce energy expenditure
Enhance stability and balance
Considerations:
Higher cost compared to basic options
May require additional training or adjustment period
It is important for individuals with below the knee limb loss to consult with their prosthetist to determine the most suitable prosthetic foot for their specific needs and goals. Factors such as activity level, budget, and lifestyle should be taken into consideration when selecting a prosthetic foot. By choosing the right prosthetic foot, individuals can experience improved mobility, comfort, and overall quality of life.
Prosthetic Knee Options
Overview of prosthetic knee options for below the knee prostheses
Below the knee prostheses often include a prosthetic knee to restore mobility and provide stability during walking. There are several types of prosthetic knee options available, each with its own advancements and benefits. These options are designed to meet the specific needs and preferences of individuals with below the knee limb loss.
Advancements and benefits of each knee type
1. Mechanical Knees: Mechanical knees are the most basic type of prosthetic knees. They rely on manual control by the user to provide stability during walking. While these knees may not offer the same level of functionality as more advanced options, they are often a cost-effective choice for individuals who require a simple and reliable solution.
2. Single-Axis Knees: Single-axis knees are designed to provide stability and control by allowing movement in only one plane. These knees are ideal for individuals who have a more predictable gait pattern and do not require advanced features. Single-axis knees offer simplicity, durability, and improved stability during walking.
3. Polycentric (Four-Bar) Knees: Polycentric knees, also known as four-bar knees, utilize a four-bar linkage system to provide a more natural walking motion. These knees have multiple pivot points, allowing for a smoother and more controlled gait. The polycentric design enhances stability, shock absorption, and adaptability to different walking terrains.
4. Microprocessor-controlled Knees: Microprocessor-controlled knees are a highly advanced option that utilizes sensors and microprocessors to analyze and adjust the knee’s function in real time. These knees offer a more dynamic and natural gait pattern by continuously adapting to the user’s movements and providing appropriate resistance and support. Microprocessor-controlled knees can significantly improve the user’s walking efficiency, stability, and overall comfort.
5. Hydraulic/Pneumatic Knees: Hydraulic and pneumatic knees use fluid or air pressure to control the knee’s movement and provide stability. These knees offer adjustable resistance to better mimic the function of a natural knee joint. Hydraulic and pneumatic knees provide smoother and more controlled movements, improved shock absorption, and enhanced stability during different activities and terrains.
In conclusion, the choice of prosthetic knee for individuals with below the knee limb loss depends on factors such as level of activity, gait pattern, and personal preference. Mechanical knees are a basic and cost-effective option, while single-axis, polycentric, microprocessor-controlled, and hydraulic/pneumatic knees offer varying degrees of functionality and advanced features. Consultation with a prosthetist is essential to determine the most suitable knee option that will optimize mobility, stability, and overall quality of life for individuals with below the knee limb loss.
Conclusion
Importance of selecting the right below the knee prosthesis
Selecting the right below the knee prosthesis is crucial for individuals with limb loss to regain mobility and improve their quality of life. The choice of prosthetic knee plays a significant role in providing stability, control, and functionality during walking. Different prosthetic knee options offer various advancements and benefits, allowing individuals to find the most suitable solution that meets their specific needs and preferences.
Considerations for choosing the most suitable prosthesis
When choosing a below the knee prosthesis, several factors need to be considered:
1. Level of activity: Individuals with a more active lifestyle may require a prosthetic knee that can withstand higher levels of impact and provide enhanced functionality. Microprocessor-controlled knees or hydraulic/pneumatic knees may be more suitable for those engaged in sports or physically demanding activities.
2. Gait pattern: Individuals with a more predictable gait pattern may opt for a single-axis knee or polycentric knee, which provide improved stability and control. For those with a less predictable gait pattern, a microprocessor-controlled knee may be beneficial in adapting to changes in walking speed and terrain.
3. Personal preference: Each prosthetic knee option has its own advantages and features. Personal preference plays a significant role in determining the most suitable knee type. Consulting with a prosthetist and trying out different knee options can help individuals make an informed decision.
It is important to note that prosthetic technology continues to advance, and new options may become available over time. Regular follow-up with a prosthetist is necessary to ensure the prosthesis continues to meet the individual’s needs and to explore any advancements that may improve mobility and comfort.
By selecting the right below the knee prosthesis, individuals can regain the ability to walk with confidence and independence. It is a personalized process that requires careful consideration of individual needs, activity level, and personal preference. Working with a prosthetist is essential in finding the most suitable prosthetic knee that enhances mobility, stability, and overall quality of life.
