Different Types Of Lower-Limb Prostheses

For lower limb amputations there are many variables and options of prostheses, there are 200 different knees and 350 different foot/ankle systems for lower limb prosthesis types. In order to get the best prosthet the amputee and prosthetist evaluate together different joint and foot components to determine which will provide optimal balance, function, safety, and way of walking efficiency.

There exist 3 general types of lower limb prostheses:

Prosthetic ankle and foot systems

Solid Ankle Cushioned Heel (SACH) The SACH is the simplest type of non-articulated foot. SACH is just a soft rubber heel wedge that compresses and mimics ankle action. This rigid keel provides midstance stability but little lateral movement.

Elastic (flexible) Keel Foot is similar to that of SACH feet, in addition, the forefoot is able to adapt to uneven terrain and remains supportive and stable during standing and walking.

Single-Axis Foot is an articulated single axis foot that contains an ankle that permits the foot to maneuver up and down. This prosthetic may be more appropriate for individuals with stability concerns, and also is more beneficial for users with amputations anywhere between the knee and hip.

Multi-Axis Foot is similar to the single-axis foot in terms of durability, weight and cost. The multi-axis foot is better on uneven surfaces than single axis. The double axis improves the absorption of the stresses of walking, this function helps protect skin and prosthesis from wear and tear.

Dynamic-Response Foot stores and releases energy during the walking cycle providing a subjective sense of push-off for the wearer. Also they provide a more normal range of motion and a more symmetric step giving a more natural feeling of walking.

Microprocessor Foot. These foot/ankle prosthesis have small computer-controlled sensors that process information received from both the individual’s limb and the surrounding environment and adjust continuously to various needs.

Prosthetic knee systems

• Single-Axis Vs. Polycentric Knees

The single-axis knee is the simplest, most economical, durable and lightest option available. The Single-axis knee usually incorporates a constant friction control and manual lock that keeps the leg from swinging forward too quickly as it swings to the next step.

Prosthetic Knee Systems have multiple axes of rotation. They can be set up to be very stable during the early stance phase, it is easy to bend to initiate the swing phase or sit down and the leg’s length shortens when a step is initiated, reducing the danger of stumbling.

• Manual Vs. Weight-Activated Locking Systems

The manual locking knee incorporates an automatic lock that can be unlocked voluntarily. This is the most stable knee available. It is possible to walk with the lock either engaged or disengaged. The manual locking knee is suggested for patients weak or unstable also as for people who frequently walk on unstable terrain.

Weight-activated stance-control knee is very stable and is often prescribed for a first prosthesis. When weight is placed on the prosthesis, the knee will lock and not bend until the weight is displaced. This knee is a common choice for less active amputees.

• Microprocessor Knees

Microprocessor knees have onboard sensors that detect movement and timing and then adjust a fluid /air control cylinder accordingly. These sorts of knees lower the quantity of effort amputees must use to regulate their timing, leading to a more natural walk.

Sport-specific prosthetic foot and knee systems

Sport-specific lower limb prosthesis helps people achieve the highest level of physical performance. Some are effective for multiple sports and recreational activities, others are designed for specific events. Socket and suspension are critical for athletes.