Socket Materials

Advancements in types of sockets materials have also ocurred in the last ten years. Rock hard laminated sockets have been replaced by more flexible materials. These new semi-flexible plastics, silicone and rubber, and easier to mold to your shape. They are lighter in weight. They hold on to the skin more comfortably with less skin irritation. We no longer have to move or "slosh around" in a bucket.

A socket MUST have some degree of rigidity and strength in order to attach components and bear weight. How they attach to the body (called suspension) varies, and one size does NOT fit all. The amount of rigidity and the trim lines will vary with each persons body shape and whether you're a hip-disartic or a hemi. There are infinite variations, but for convenience sake I've broken them down into 3 types of sockets.

In the distant past these were made from reinforced leather. Laminated or reinforced plastic materials were introduced in the 50's and 60's are still used today. However, the completely rigid plastic sockets are generally no longer in use. The newer reinforced plastics can be made softer in certain areas for comfort according to the clients needs. As long as the contoured socket concept is followed, and the bones or soft tissues are cupped and held in place, this is perfectly acceptable. Although somewhat heavy, weight can be controlled by thinning the socket in non weight bearing areas. These sockets are less expensive, relatively easy to manufacture, and are very durable.

	SINGLE LAYER SOCKET (HEMIPELVECTOMY) This socket is made of the newer plastic laminates. Note the contouring and cupping of the soft tissues below (A) and relief over the coccyx (tail bone) (B). Thinning and relief over the ribs (C) and flaring out at the top (D).
2. DOUBLE LAYER SOCKET This type consists of a supportive layer of rigid material, usually carbon fiber which is strong and light weight. (They make airplane parts out of this stuff). Sometimes it's left in it's original color which is black, but can be painted a flesh color. Inside is a separate layer of various types plastic materials referred to as "bioelastic" or "thermoplastic", which are flexible. The two layers are held together by screws or bolts. The exact trim lines of each layer will depend on body shape and individual needs. The main advantage to this type of socket is the ability to adjust, reshape, thin out, or even replace the inner liner as needed. The inner liner can be carefully molded to your anatomy making for a comfortable, intimate fit, and can be used for hip's, hemi's and high AK's with extra bits of bone to accommodate. The flexible plastic is quite comfortable and durable. Weight depends on the amount of supportive material vs. flexible liner; the bigger you are, the more you'll need. They are moderately easy to manufacture for most prosthetists.
	DOUBLE LAYER SOCKET (HIP-DISARTICULATION) The rigid material is flesh colored and provides the support. The inner liner is cut to a minimum yet provides a close, intimate fit to the remaining bones and soft tissues.
Photo courtesy of Tom Guth C.P., RGP Prosthetics
	DOUBLE LAYER SOCKET (HEMIPELVECTOMY) Note that the inner layer is molded and countoured to hold the soft tissues below (A). It extends high over the ribs to support the back and prevent twisting, turning, and pistoning. There is no pressure or weight-bearing in the ribcage (B). The firm support (carbon fiber) extends around the sound side and below (C). Foam padding for cosmesis (D).

In this type the rigid support system is hidden or buried inside the socket. Either silicone or synthetic rubber materials are incorporated around the rigid support, both inside and outside the socket. Fabrication is more complex and few prosthetists have the technological skill or equipment necessary. With this type, it is extremely important to have at least one or 2 check sockets done first to assure for a correct fit since it is more difficult to make changes or adjustments once the socket is manufactured. Although these can be the most flexible of all, some prosthetists feel that the materials are less durable. Some people love the softness and flexibility, while others dislike the feel of the material against the skin. Weight will vary with your size and shape but rubber and silicone is slightly heavier than the thermoplastics . They are usually more expensive for the technical reasons of fabrication and fewer prosthetists have experience in dealing with these materials.

WHICH TYPE IS BEST? Most often it depends on the experience of the prosthetist, specifically which materials he feels most comfortable in working with. He also may be limited by the manufacturing and technical support of his facility. Not each prosthetic facility will have the technical capabilities to work with all materials. One size or style does NOT fit all. The degree of softness vs. support depends on your body shape, comfort level and trim lines, how high or low, and how the material feels against your skin, as well as the ability to make changes and cost. The trick is finding a CP who can give you not only what you want, but what you need to walk.

There are infinite variations to the exact size and shape of a socket. For hip-disarticulations sockets can be made quite low, sometimes called a Bikini cut. Sometimes the gluteal muscles have been left fairly intact and when these are powered up and contract, they can force you out of the socket, loosing suspension. By cutting out areas, using a diagonal support, or straps over the iliac crests, suspension can be maintained while keeping the actual socket quite small. Some HD's and high AKs may even be held in place with a suction socket.

For hemipelvectomies, most of our sockets must extend above the waist or higher for support and containing soft tissue. The ribs should NOT be used for weight bearing, but some flexible support coming up over the ribs can be very useful in preventing twisting and turning and provide back support. This is especially important to those of us who have developed a functional scoliosis. Each individual must find the balance between stability and comfort. My personal opinion is that making a hemipelvectomy socket too soft or cut too low defeats the purpose. Something has to hold you up, so I suggest that you start out with as much support as possible. It can always be cut down later.

"My first two prosthetics had a socket of soft silicone, very comfortable material, but not enough support. I've also found that a semi-hard socket with high support around the ribs provides more stability and comfort over pressure points" Coreen, HP

"I personally feel that it's a mistake to make the socket too soft or cut too low, you'll loose your support. I prefer 3 straps. We hemi's need firm stability to power the leg forward" Mary, Physical Therapist and HP

For both hips and hemi's, the opening may be placed in the front, side, or back. Usually 2 or 3 straps are used, and various types of strap materials are available such as Velcro, leather, or reinforced Dacron. Some people have used a lace-up type opening.

CONTRA-LATERAL ISCHEAL GLUTEAL WEIGHT BEARING is a fancy term for a small extension on the bottom of the socket which crosses over to the sound side. It provides a ledge or shelf for weight bearing underneath the sound buttock. This concept is commonly used in the UK. Prosthetists are in disagreement as to how helpful this can be. Some people have this extension and like it, others have tried it and rejected it as useless. It's a matter of personal preference. It's your call.