The Preformed (PTB) Socket for Primary Below-Knee Amputation

A. EMMERSON A. McDOUGALL, F.R.C.S.


It has been found that the most effective method of rehabilitating the amputee patient is to encourage early functional use of the stump, i.e., as soon as it can be done with safety in the postoperative period.

Clippinger 3 has stressed the advantages of early prosthetic fitting in the case of the elderly above-knee amputee. These advantages are: quicker maturation of the stump, preservation of muscle tone, prevention of contractures, and facilitation of gait training. To this end he advocated the early fitting of a temporary plaster pylon.

It was with these factors in mind that the immediate postoperative fitting of a prosthesis was developed, the technique first being used by Berlemont 1 , and later by Weiss 12 . The immediate postoperative fitting of a prosthesis (IPOFP) has been enthusiastically advocated in the United Kingdom by Vitali" and in America by Burgess 2 .

Success with this particular technique requires the services or a fully qualified prosthetist who has had extensive training in its use (Murdoch 8 ) and one who has ample access to the patients before, during, and after operation. The ideal unit with highly specialized services to which patients can be transferred for amputation and limb fitting is still the exception rather than the rule. The majority of the amputees who come to our centre, for instance, have had their operations performed by surgeons from different surgical disciplines working in hospitals located at some distance from us. Most of the amputations are for gangrene due to vascular insufficiency and our first contact with the patient is after the operation, so that it is neither practical nor desirable to recommend immediate postoperative fitting of a prosthesis.

We have tried the technique of immediate postoperative fitting in a number of selected cases, but like Macdonald 7 and Elliott 4 we felt that, with our limited resources, we could not deal successfully with the inherent difficulties in its use.

We also had in mind the work of Taylor 10 who pointed out that amputation in patients with obliterative arterial disease is known to carry a risk of gas gangrene. He recorded three cases of postoperative gangrene following amputation. Parker 9 also has reported on eleven amputees with postoperative clostridial infections-nine of whom died. The advent of the patellar-tendon-bearing limb has made it possible for any local limb-fitting centre to construct a temporary prosthesis in a short time. This temporary prosthesis is used in the interval between amputation and the fitting of a permanent prosthesis (Fulford 6 ).

The standard preparation of a temporary limb requires the routine casting of the stump in plaster, cast rectification, manufacture of the limb, and subsequent attendance of the patient for fitting and alignment. This procedure can occupy several days and any changes in the stump during this time can add a few more days to the process. To expedite fitting, the use of preformed sockets was first suggested by Foort5 in 1970. We have used this technique and found it to be most satisfactory and safe in a small but busy unit such as ours. The preformed socket can be fitted on the day the sutures are removed from the amputation wound; the leg can be completed, and the patient can leave the hospital using crutches or walking sticks within an hour or two.

Procedure

The preformed sockets are made of transparent plastic. We hold in stock ten sockets each for left and right, with diameters ranging from 3 1/4 in. to 4 3/8 in.* We have three socket lengths for each set (short, medium and long), thus giving a choice of 30 sockets each for left and right limbs ( Fig. 1 ). A socket suitable for the patient is selected and fitted to the stump. Where necessary, distal contact pads of foam rubber are used ( Fig. 2 and Fig. 3 ). After the socket is applied the patient is asked to bear weight on it. An adjustable stool is used to obtain the correct height. As the socket material is transparent it is possible to estimate and apply an appropriately sized foam-rubber contact pad.

Wedge disc alignment units are next attached to the socket and the appropriate SACH foot is selected Fig. 4 ). A metal post of predetermined length is used to connect the socket and the foot. Routine alignment procedures are carried out after the cuff suspender is applied ( Fig. 5 ). When the patient is a female we apply a cosmetic fairing to cover the post and the alignment units ( Fig. 6 ).

In our hands this has been a very safe and satisfactory procedure in dealing with the primary below-knee amputee and we have used it successfully in our last 40 patients.

The method has been accepted readily by the patients who see that the operation wound is healed and the stitches are removed. They need no persuading that the time has come for the limb to be fitted.

If the home circumstances are suitable, the patients can leave the hospital on the same day and attend subsequently as out-patients.

As indicated the procedure takes about an hour to complete, its safety is self-evident and it is a cheap method of constructing a modular limb. The alignment components and SACH feet can be used more than once; the sockets are not used again.

Summary

The use of a preformed socket for the primary below-knee amputee has been described. We believe that it is a simpler and safer technique than the immediate postoperative fitting procedure and can be carried out at any limb-fitting unit. Moreover, it is an inexpensive method of constructing the first limb for an amputee, along elementary modular lines.

* The stock sockets are formed from master positive casts. A glass stockinette is used 10 form the body of the socket with several layers of glass cloth applied at the proximal end to reinforce the base for the unit attachment. The materials are laid up on the cast and polyester resin is used in the standard manner. The sockets have sufficient transparency for us to determine the amount of end contact and the correct positioning of the stump within the socket walls. Our socket diameters correspond to knee diameters at the level of the medial tibial plateau.

References:
1. Berlemont, M., Notre Experience de l'Appareillage Precoce des Amputes des Membres Inferieurs aux Etablissements Helio-Marins de Berck Annales de Med. Phys., 4:4, Oct., Nov., Dec. 1961.
2. Burgess, E. M., J. E. Traub, and A. B. Wilson, Jr., Immediate postsurgical prosthetics in the management of lower extremity amputees. TR 10-5, Prosthetic and Sensory Aids Service, Veterans Administration, Washington, D.C., April 1967.
3. Clippinger, F. W., Use of temporary quadrilateral socket plaster pylon in the elderly amputee. Southern Med. J., 56-58, 1963.
4. Elliott, J. K., Early fitting of artificial limbs-A reply to an abstract of a paper by A. A. Macdonald that was presented at the New Zealand Orthopedics Association's 1966 Annual Meeting, Wellington, N. Z., Sept. 12-14. J. Bone and Joint Surg., 49-B:806, 1967.
5. Foort, J., Personal communication, 1970
6. Fulford, G. E., and M. J. Hall, Amputation and Prostheses: A Survey in North-West Europe and North America. John Wright & Sons Ltd., Bristol, England, 1968.
7. Macdonald, A. A., Early fitting of artificial limbs. An abstract of a paper presented at the New Zealand Orthopedics Association's 1966 Annual Meeting, Wellington, N. Z., Sept. 12-14. J. Bone and Joint Surg, 49-B:806, 1967.
8. Murdoch, G., Immediate postsurgical fitting. An editorial. Pros. International, 3:8:2-7, 1969.
9. Parker, M. T., Clostridial sepsis following amputation. Brit. Med. J., 2:698, 1967.
10. Taylor, G. W., Preventive use of antibiotics in surgery (Amputation in ischaemic disease of the leg). Brit. Med. Bull., 16:51, 1960.
11. Vitali, M., Immediate Post Operative Fitting. Progress Reports Nos. 7 & 8, Ministry of Health, Research Department, Limb Fitting Centre, Roehampton, 1966.
12. Weiss, M., Neurological implications of fitting artificial limbs immediately after amputation surgery-Report of Workshop Panel on Lower-Extremity Prosthetics Fitting; Committee on Prosthetics Research and Development, National Research Council, February 1966.