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The Garden State Tri-Wall Expansion Socket System (TESS)

Louis J. Haberman, C.P.O.

Introduction

In many instances, the prosthetist is asked to provide a prosthesis for the "hard to fit" patient. The patient expects to receive a comfortable, functional, lightweight, and cosmetic device within the parameters of the prescription, despite the complications associated with his case. Sometimes, however, the expectations of the patient are not met due to the complexities involved. Despite the best efforts of the prosthetist, the patient rejects the prosthesis due to the inability of the residual limb to tolerate normal and appropriate socket pressures associated with traditional PTB below-knee prosthetic de sign.²
The Garden State Tri-Wall Expansion Socket System (TESS) was originally designed to enhance the level of comfort for the uneventful "run of the mill" below-knee amputee. However, the design also offers solutions for fitting the, heretofore, troublesome residual limb. Indications for Application of the TESS

• the very active patient
• poor pressure tolerance
• prominent bony structures, spurs
• invaginated scars
• adhesions
• localized bursal enlargement
• short residual limb with limited pressure distribution

Traditional PTB and S/C PTB Socket designs consist of a Pelite ? insert and an unyielding hard laminated socket. The TESS Technique includes a thin-walled, completely flexible laminated shell over the Pelite? inserts (Figure 1 and Figure 2 ). Areas of the flexible laminate are cut away. These areas mate with relief chambers in the wall of the socket. Thus, a soft, yielding total-contact fit is maintained by the Pelite? insert. A soft, yielding socket is provided via the expansion chambers within the socket itself

New Trends

Many advances have been made in the treatment of the below-knee amputee. A vast array of new materials such as SurlynŽ, Ethylux PolyethyleneŽ, and IpoconŽ, can be used to offer the patient a lighter, more functional, but more expensive prosthesis.

flexibole, thin-walled ³ total surface-bearing socket designs,⁴ and atmospheric suspension systems,¹ have been successfully introduced.

Disadvantages associated with these "high tech" prostheses are:

• cost
• time required by patient
• appropriate reimbursement by third party payers
• high level of prosthetic proficiency required
• questionable longterm durability of materials
• slight residual limb changes can negatively impact prosthetic fit, function and performance.

It is certain that these exotic designs will continue to evolve and become more cost effective, more easily fabricated and consequently, available to a greater percentage of the patient population. For now, however, a great majority of below-knee amputees can benefit by utilizing the TESS Technique. The TESS Technique does not require special equipment, materials or training, and can thus be offered to patients now.

Advantages of the TESS

Clearly, the TESS offers substantial benefits not realized in conventional or even various exotic designs. These are:

• a greater level of comfort for the uncomplicated residual limb
• a yielding, total-contact socket for the "difficult to fit" or active patient
• extreme ease of adjustment, if required
• ease of fabrication utilizing conventional materials and techniques
• low cost
• minimized femoral condyle discomfort when donning a well-fitting supra-condylar below-knee prosthesis.

Fabrication

A thorough evaluation and patient-prosthetist discussion are invaluable. If possible, obtain Xeroradiographs prior to casting for enhanced assessment of the patient's anatomical peculiarities.

The residual limb is cast in the same manner currently employed by the prosthetist. Cast modification is essentially unchanged. However, substantial plaster build-ups for bony (or other) areas should be avoided. The prosthetist should generally reduce the size of plaster build-ups by approximately 30%. The distal end of the positive model should be extended about 3/8". This can minimize the possibility of end-bearing for more active patients. A soft distal end pad can be employed for maintenance of a total-contact socket fit.

The use of a diagnostic SurlynŽ check socket is advocated. For later reference, locate areas on the check socket that require expansion chambers (Figure 3) . Good judgement by the prosthetist is essential when designing the hard socket expansion chambers. Too many chambers, particularly in weight supporting areas, will result in end-bearing problems. It is recommended that a one-ply sock fit be achieved during the check socket phase.

It has been customary to locate the expansion chambers over the apex of the medial condyle, and/or, tibial crest, and/or, fibula head and occasionally, the fibula shaft. In the instance of the socket photographed for this article, expansion chambers were created over the medial tibial flair and the medial hamstring areas. This was later deemed to be inappropriate. There was some loss of support which resulted in increased distal loading. It was necessary to fill the medial tibial flair expansion chamber with Pelite? to correct this. The double thickness Pelite? in this area effectively guards against impact loading during very active periods, and the distal end loading problem was eliminated.

Return to the positive model and incorporate any changes. Dry the positive model thoroughly. Fabricate the Pelite? insert in the usual manner. Pull a PVA Sheet over the Pelite? and insert and evacuate at full vacuum. Generally, a lay-up of three layers of nyglass stockinette is applied over the PVA Sheet. Laminate in the usual manner with 100% polyester 4134 flexible resin (Figure 4) . After curing, remove PVA bag and smooth the distal end of the flexible liner. Spray the sanded distal end with clear acrylic spray.

Refer to the SurlynŽ check socket and cut out 3/16" or 1/8" firm Pelite? pad(s) to the previously determined shapes (Figure 5) . Glue the Pelite? pad(s) directly onto the flexible laminated shell with contact cement. All pad edges should be sharp and crisp and perpendicular to the broad surface of pad.

Pull a PVA Sheet over the hybrid liner and evacuate at full vacuum (Figure 6) . Be certain that the PVA Sheet closely conforms to the pads and does not bridge the edges.

Add a lay-up of one layer dacron felt; carbon fiber and/or fiberglass matting; and eight to 10 layers of nyglas-tricot stockinette. Laminate with acrylic or carbon-acrylic resin with full vacuum (Figure 7) .

Acrylics are routinely used for all permanent prostheses. Acrylics must be used for supra-condylar socket designs for maintenance of the proximal socket medjo-lateral dimension. Polyester laminations may be employed for traditional PTB designs as well as temporary prostheses.

After curing, remove the plaster model and separate the components of the Tn-Wall Socket (Figure 8) . Use a cast saw or sharp knife and cut away Pelite? pads and flexible laminate of the flexible laminated portion (Figure 9) . Bevel all cut-out areas from the inside-out. Return the Pelite? liner to the flexible shell and slide a one-ply sock over it.

Bench align the socket and foot in the usual manner for dynamic fitting. The patient should wear a one-ply sock over the hybrid liner at all times. This facilitates donning and doffing and permits the femoral condyle to easily pass the narrow medio-lateral diameter of the proximal socket. If uncomfortable contact pressures are present, heat the Pelite ? insert in the sensitive areas and push out the liner. This creates relief and requires no grinding of the socket as the stretched liner is accommodated in the pre-determined expansion chamber. Proceed with customary finishing techniques after fitting (Figure 10) .

Experience and Results

As of this writing, 176 patients have been fitted with the Garden State Tn-Wall Expansion Socket System. Many of the earliest TESS prostheses are still utilized today.

The life of the Pelite? insert is substantially prolonged due to the protection afforded to it by the laminated flexible shell. The crinkling effect that normally occurs at the hamstring channels and distal end of the Pelite? liner is virtually eliminated.

Over time, some outward bulging of the Pelite? occurs in the expansion areas. This has not been a problem. Quite the contrary, it seems that the stump has created its own additional relief as needed.

Edge pressure can develop from the laminated shell if the interior cut-out edges are not finely beveled. If the expansion chambers are inappropriately located with respect to the cut-out areas in the flexible shell, the edge(s) of the acrylic socket may have to be ground to reduce the unwanted pressure (Figure 11) .

There have been occasions when the flexible laminated sleeve without expansion chambers was used with the Pelite? liner. This was done to facilitate donning a supracondylar prosthesis and to maintain the integrity of the liner.

Summary

A yielding, expandable, total-contact socket design for use by virtually all below-knee amputees has been presented. The Garden State Tri-Wall Expansion Socket System can offer the below-knee amputee a level of comfort and built-in adjustability not realized before. The technique can be reproduced by any prosthetic facility without additional equipment or training. The information offered can provide the prosthetist with another means of problem solving for the average, more difficult, or the more active below-knee amputee.