Another New Prosthetic Approach for the Syme's Amputation

ROBERT WARNER, M.D. ROLAND DANIEL, CP. ALLEN L LESSWING, M.D.


The Syme's amputation is and will continue to be a very popular and satisfactory procedure. Frequently the forefoot must be sacrificed for vascular or traumatic reasons or to convert a congenital anomaly. If essentially all of the lower leg, including the heel pad, can be salvaged in such situations, the Syme's amputation remains the surgical procedure of choice. This type of amputation makes possible the most physiological use of the stump both with and without the prosthesis (i.e., getting up at night, swimming, and similar "nondressed" activities or emergency ambulation). The broad stump offers stability, the long lever gives maximum control and power, and the persistent heel pad permits total end-bearing, at least for short periods.

The popularity of the Syme's amputation accounts for the many articles on this subject, including two recent ones in the INTER-CLINIC INFORMATION BULLETIN 3,4 . Doctor Romano's article is so well done and so inclusive that we do not wish to repeat him. Doctor McCollough in August 1964 1 stressed the importance of proper surgery to avoid any possible migration of the heel pad. and of making sure that the cut was absolutely parallel to the floor for maximum stability. This surgery will then produce a wide, stable, painless, and total-end-bearing stump which will be long-lasting. The importance of correct surgical procedures as recommended by these authors cannot be overemphasized.

Once the patient is provided with an excellent Syme's stump, however, we have the problem of fitting a bulbous stump end which is wider than the leg immediately proximal to it. This problem has been approached in various ways. Until very recently the usual procedure was to make an opening with a panel (back, side, or front) to facilitate the passage of the bulky and bulbous distal stump portion past the more slender foreleg section of the socket below the maximum bulge of the calf.

These windows had many disadvantages some of which are mentioned in the article by Romano and therefore will be listed only in brief:

1. The existence of a window weakens the prosthesis and failures frequently occur at the corners in the distal socket where the panel has been cut out.

2. Pinching of stump flesh can occur, particularly at the bottom and sides of the opening. This pinching can also produce wrinkles in the stump sock thus causing further irritation to the stump.

3. The window offers an area for differential swelling and edema, particularly when the child is in the process of outgrowing the prosthesis.

4. Retention of a window requires that hardware (or, more recently, Velcro straps) be added, which increases bulk and weight, and destroys the smooth external appearance and contour of the prosthesis. This discontinuity in turn causes increased damage to clothing worn over the prosthesis.

Fig. 1

McFarlen's Procedures as Model

Like Romano and others, we have sought to create a solid plastic socket without areas of weakness and without interrupting the smooth lines of the exterior. We have used as our model the procedures described by J. M. McFarlen, CP. 2 . He recommended that an insert extending from the bulbous stump end to a proximal area of equivalent or slightly smaller diameter be constructed on the cast. This insert was formed of glued layers of 1/8in. neoprene crepe between outer skins of orthopedic horsehide. The insert is stabilized on the stump model with a cast or stump sock, a PVA bag is applied, and the socket laminated in the usual manner. However, we believe that by applying a simple insert in the form of a pad of Plastazote or other moldable or shapeable substance one can easily achieve the same purpose, i.e., fill the concave areas to come up with a cylindrical contour over which a sock may be drawn.

Preparation of Insert Pad

In preparing this pad we use sheet Plastazote of a thickness (1/4 in. to 1 in.) appropriate to the concavity to be filled. The pad extends from just above the bulbous stump end to an area of approximately equal diameter proximally.

The Plastazote sheet is cut to the proper length and is warmed with a heat gun or in the oven until it is malleable in the prosthetist's hands. It is then applied directly to the stump and shaped to the contours of the limb. After cutting appropriately for a wrap-around fit the inner edges of the pad are skived as necessary to bring the material into smooth conformity with the contours of the limb.

With the pad applied, two cast socks are pulled over the stump and a plaster-of-Paris wrap cast is made in the usual manner. We try to remove the cast with the outer sock attached. Preparation of the positive mold and lamination of the socket follow standard procedures. The bottom of the socket is finished with a simple poured pad (of Poropad or similar material used to ensure total contact). Figure 1 indicates the basic construction.

We have found that in ease of fitting, comfort, wear qualities, and lower heat production (reduction in sweating), this insert surpasses the Kemblo-rubber and Silastic-foam inner sockets suggested by Romano, et al. We believe that a complete Kemblo-rubber inner socket which holds in the heat and increases sweating, size, and weight, as we learned from experience with the old patellar-tendon-bearing below-knee sockets, is unnecessary.

In finishing the prosthesis the solid tubular plastic socket can be foamed externally to conform to the shape of the normal leg. Actually in our fittings we make the solid plastic socket partially patellar-tendon bearing for maximum stability. This type of fitting tends to eliminate any possibility that the upper edge of the socket will cut into, or otherwise traumatize, the proximal portion of the tibia, adds stability, eliminates whipping, and provides extra surface for the distribution of weight-bearing ( Fig. 2 , Fig. 3 , Fig. 4 , Fig. 5 ).

We have tried this fitting procedure with two young girls, aged three and five years, with excellent acceptance and trouble-free gait. One of us (RD) has also used this technique with more than a dozen adults with excellent results. Re-visits to the prosthetist for repairs, refitting or relief of painful stump problems have been markedly reduced.

In short, we feel that this method provides the fitting of choice for patients with Syme's amputations.

References:
McCollough, Newton C, Joseph G. Matthews, Ardis Traut, and Jack Caldwell, Early
opinions concerning the importance of bony fixation of the heel pad to the tibia in the juvenile amputee. Inter-Clin. Information Bull , 3:10:1 11, August 1964 2
McFarlen, J M , The Syme prosthesis. Orthop. & Pros Appl. J., 20 :1:29-31, March 1966.
Phelps, Marcus E , and James W Stanford, Fabricating an expandable inner-socket prosthesis. Inter-Clin Information Bull., 11 :1:7-10, October 1971.
Romano, Robert L., J. H. Zettl, and E M. Burgess, The Syme's amputation: A new prosthetic approach. Inter-Clin. Information Bull., 11 :4:1 -9, January 1972.