Above-knee prosthetic management is particularly challenging due to the loss of both knee and ankle joints. However, recent advances in socket design are enabling transfemoral amputees to make great strides in regaining mobility.
    An estimated 20-30% of all lower-limb amputations occur at knee level or above. Of these, more than 80% result from vascular insufficiency, so the population tends to be older and not particularly robust.
    For this group, optimal socket fit, comfort and ease of use are essential to a positive functional outcome. Comfort proceeds from a proper fit. If an amputee is uncomfortable wearing his or her prosthesis, a less-than-optimal socket fit is a likely culprit, and a lightweight flexible design fabricated with the aid of a test socket offers a primary solution.
    With increased understanding of residual limb anatomy and taking advantage of the desirable properties of flexible sheet plastics, prosthetists today are able to give above-knee amputees a new level of comfort and control, which significantly improves their opportunity to regain effective mobility.
    These designs, variously known as dynamic or flexible sockets, are closely contoured to the wearer’s residual limb anatomy and feature a lightweight, flexible plastic interface capable of expanding and contracting with action of the residual limb muscles. This inner socket typically fits within a sturdy, but lightweight, laminated outer frame for strength and stability. Sometimes anterior and/or posterior windows are cut into the outer socket to allow for increased quadricep and hamstring activity and improved wearer comfort.
    The majority of today’s above-knee sockets are derivations of what has come to be classified generically as the ischial containment (I. C.) total contact design.
    Advantages of this shape include enhanced amputee comfort, greater rotational stability and a more-normal gait, yielding greater velocity with less energy and oxygen expenditure.
    Improved methods of suspension contribute to comfort and function of today’s transfemoral sockets – notably gel liners and direct contact suction.
    Gel liners are probably the most popular method of above-knee suspension. They are rolled on like a sock and maintain suction with the residual limb. Some gel liners maintain suction with the socket wall as well. Others incorporate a distal pin that fits into a mechanical lock in the socket. These liners protect residual limb tissue both by absorbing impact stress and reducing surface friction.
    Drawbacks of gel liners include difficulty mastering how to insert a locking pin into the shuttle lock, particularly among older wearers; durability issues requiring frequent replacement; and hygiene issues resulting from insufficient cleaning after use. Nevertheless, gel liners tend to provide the highest level of overall wearer satisfaction.
    When neither suction nor locking liner suspension will work, a hip joint and pelvic band provides a less-rigorous alternative, particularly for geriatric patients and when stability is an issue.
    Socket design is highly individualized. The socket must intimately reflect the wearer’s residual limb shape, musculature and sensitivity as well as his/her overall health, lifestyle and activity level. Every prosthetist has a unique approach to socket engineering and will often incorporate elements of different socket shapes into a hybrid design that will meet the patient’s unique needs.