A central resource for individuals with congenital or aquired limb loss, their families, carers and healthcare professionals
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Types of Socket

The socket configuration will generally reflect the methodology used by the prosthetist.

Above knee sockets

Above knee sockets are either Ischial bearing or Ischial containment sockets. Through the years, there has been a transition in socket design for transfemoral amputees from the plug fitting, pre quad, quadrilateral and the latest Ischial containment.

Ischial tuberosity, a term you will frequently hear used in relation to an above knee socket, is the roughened area at the base of the ischium bone for the hamstring’s attachment. When seated, with your fingers placed between the seat surface and either side of the buttocks, you will easily locate this bony prominence.

The Ischial Weight Bearing Socket, also called the Quadrilateral Socket, is generally an early fitting prosthesis. It enables full weight bearing on the ischial tuberosity and thigh area while bypassing the weight around the amputation during walking. The design incorporates a quadrilateral socket which is adjustable in both the anterior to posterior and medial to lateral directions. This socket was first introduced in the 1950s. The main features are:

  • Four-sided shape of the socket when viewed transversely.
  • Strong emphasis on individual anatomy of soft tissues and underlying bony structures.
  • Direct ischial bearing on a brim or shelf.

The Ischial Containment Socket is thought to be more stable because it locks the ischial tuberosity in the socket. This also helps to stabilise the femur from abducting and improves gait. The Ischial Containment Socket was introduced in the 1980s. The main features are:

  • Narrower in the M-L dimension to gain better control of femur and maintain its normal alignment.
  • Ischium contained within socket using bony lock.
  • Goals include increased comfort for user, and improved control of pelvis and trunk.

The M.A.S.® Socket design is based on the Ischael containment type socket. This new design provides several clinical benefits: patients can sit more comfortably; there is no plastic beneath the gluteus; the prosthesis is easier to don; patients enjoy full range of motion, better functional gait and, important to patients and family members too,  much better cosmesis. Created in 1999 by Marlo Ortiz. You can read more on the Dorset Orthopaedic website http://www.dorset-ortho.com/

Below Knee Sockets

Patella Tendon Bearing (PTB)
This socket is the most commonly used for below knee amputees. The PTB socket completely encloses the stump. It allows you to put weight on areas of the limb that can tolerate pressure, such as at the patella tendon (directly below the knee cap), and keeps the limb from bearing weight on areas which can cause problems such as on the very bottom of the limb. To keep the PTB socket on the residual limb a form of suspension must be used.

Silicone Suction Suspension (3S)
Silicone suction suspension can be used with patella tendon bearing (PTB), total surface bearing, or hydrostatic socket designs. Total surface bearing is a general loading of the entire residual limb and hydrostatic designs elongate the tissue to eliminate movement within the socket.With silicone suction suspension, the user rolls a silicone suspension sleeve onto the residual limb creating a seal. The suspension sleeve has a pin on the end that locks into the bottom of the prosthetic socket. A prosthetic sock must be worn over the silicone insert in order to allow for volume fluctuation. Silicone suction suspension is best fit with cylindrical shaped residual limbs.

Vacuum Assisted Socket System (VASS)
Is a specialist product developed by Total Environmental Control (TEC). It is used to manage residual limb volume fluctuation. The system consists of a TEC liner, suspension sleeve and air evacuation pump to create an elevated vacuum between the liner and the socket wall. This elevated vacuum regulates volume fluctuation in the residual limb, reducing forces exerted on the residual limb.

Upper limb sockets

Upper-limb socket design has improved over the last 10 years using technology from lower limb socket design. The advances in material technology have allowed for the development of these modern sockets. Flexible inner socket materials enable a better socket fit as well as maintaining comfort. They are easier to adjust once the prosthesis is fabricated. New materials have also simplified the process of donning “pull-in” sockets.

  • The Anatomically Contoured and Controlled Interface (ACCI) socket was designed for the transradial (below-elbow) amputee.
  • The Advanced Humeral Interface (AHI) socket was developed for transhumeral (above-elbow) amputees.
  • The X-Frame Interface was developed for shoulder disarticulation, forequarter, and some “humeral neck amputees.