Prostheses are typically modular, assembled from individual components rather than purchased as complete units. These components can be selected, assembled, and adjusted to adapt to a user’s environmental and lifestyle factors, such as professional activity, temperature, humidity, culture (being able to sit cross-legged or to squat; limb covering colour or cosmesis), and affordability. Components from different suppliers are mostly interchangeable and compatible. Key components of lower limb prostheses are summarized in the below Table.
Table 40: Summary of lower-limb prostheses components
Component type and materials | Component descriptions and varieties |
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Component type: Socket Materials: Polypropylene, thermoplastic elastomer (TPE), wood, aluminium, glass-reinforced plastic (GRP), resin, carbon fibre |
Interface between the residual limb and the prosthesis. Must be individually moulded and meticulously fitted to ensure pressure is distributed and to avoid damage to skin and tissue.
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Component type and materials | Component descriptions and varieties |
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Component type: Liner, sleeves, socks Materials: Ethylene-vinyl acetate (EVA) foam, silicone, gel, urethane, thermoplastic elastomer (TPE), Pe- Lite, wool, cotton |
Soft interface materials that ensure fit, comfort, and that the prostheses stays attached to residual limb. Certain suspension systems require liners. When used properly, they provide a cushioning effect within the socket, help to minimize friction forces, and provide even pressure distribution. Socks can be used to adapt to changes in the volume of the residual limb.
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Component type: Foot prostheses Materials: Polypropylene, polyurethane, wood, rubber, carbon fibre. Description: Point of contact between prosthesis and contact surface, with different designs optimized for different functions or terrains. The foot can be differentiated by age group, gender, and weight. By its functionality, foot prostheses can be subcategorized into the following types: |
SACH (solid ankle cushion heel) Foot: Rigid foot without ankle articulation.
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Single Axis Foot contains an ankle joint that allows the foot to move up and down, enhancing knee stability. The SACH foot and the single axis foot are the most used in LMICs currently.
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Multi-Axis Foot: More advanced than s ingle-axis foot which allows a rocking motion of the foot from heel to toe as well as from side to side.
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Carbon Fibre Prosthetic Foot: More advanced prosthetic foot, are lighter and provide users the maximum energy storage and return.
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Pirogoff Foot: A half foot for patients that have experienced diabetic foot amputation.
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Component type and materials | Component descriptions and varieties |
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Energy Storing and Return Foot: Designed to store energy when weight is applied (during the stance phase) and release it as the foot lifts off the ground. This makes walking more efficient and reduces the energy needed from the user.
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Microprocessor-Controlled Foot incorporate computer chips that adjust the stiffness and angle of the foot in real-time. They respond to changes in terrain and walking speed, providing a more natural gait and increased stability.
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Component type: Knee Joint Prosthetic knees can be mechanical or pneumatic. All prosthetic knees require some stability mechanism, this can be manual or a weight-activated auto locking system. Knee joints mimic the function of a natural knee by providing safety, symmetry, and smooth movement while walking. High variations exist in activity level, functionality, technology, and materials. Materials: Stainless steel, titanium, aluminium, polypropylene, nylon, wood |
Mechanical Knee Joint (Single-axis)
Mechanical Knee Joint (Multi-axis)
Mechanical knees use a mechanical hinge to replace the knee joint. Mechanical knees could be further subdivided into single-axis (monocentric) or multi-axis (polycentric knees). Polycentric knees have multiple axes of rotation that help mimic the natural movement of the human knee, providing a more stable walk, especially for those who need enhanced stability. |
Pneumatic knees utilize air to adapt their behaviour to different walking speeds as the wearer swings the leg forward and backward.
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Hydraulic knees use fluid dynamics to control the swing and stance phases of walking, offering a smooth and natural gait at various walking speeds.
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Component type and materials | Component descriptions and varieties |
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Microprocessor-Controlled knees (MPKs) incorporate sensors and computer technology to adjust the knee’s response in real-time, improving stability and efficiency. They are particularly useful for navigating slopes, sitting down, and standing up.
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Component type: Pylon Materials: Wood, titanium, aluminium, steel, carbon fibre, glass-reinforced plastic (GRP), polypropylene |
A pylon connects the socket to the foot it is lightweight it absorbs shocks.
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Component type: Adapters Materials: Mainly metals such as stainless steel, titanium, aluminium |
A wide range of adapters is used to connect different parts of the prosthetics components. For example, there are adapter for the foot, adapter for pylon, adapter between knee joints and socket etc.
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Component type: Cosmesis Materials: Silicone, local fabrics, ethylene-vinyl acetate (EVA) foam |
Limb covering to mimic appearance of real limb. Can be readymade or custom- designed or made from locally sourced materials
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The report will primarily focus on the key components of lower limb prostheses, such as knee joints and foot, as these are more standardized and in greater demand for large-scale procurement.