The Rancho Syme Prosthesis with the Regnell Foot
Michael J. Quigley, C.P.O. *
Sam E. Hamontree, CP. *
The Syme amputation has been with us since 1842, when James Symes developed it for three reasons, "(1) the risk to life will be smaller, (2) a more comfortable stump will be afforded, (3) the limb will be more seemly and useful for ambulation." Since then, the major improvement in the surgical technique has been the introduction of the two stage Syme amputation, which was developed to increase the success rate in dysvascular and infected patients. Wagner further refined the technique at Rancho Los Amigos Hospital, and increased his success rate to 95% by the use of Doppler ultrasound to determine adequate blood flow. Wagner also advocates removing the flares of the tibia and fibula during the second stage to narrow the distal end and provide better cos-mesis.
The advantages of the Syme level of amputation are many (Fig. 1), but the design of the prosthesis has been a constant challenge for prosthetists (Fig. 2). The Syme level amputee is typically more active, walks at a faster pace, and expends less energy than the below-knee amputee; for these reasons the demands on the prosthesis are greater. Breakage of Syme prostheses has been a constant problem, especially with prosthetic designs that have openings (medial opening, posterior opening, etc.). Syme prostheses that have no openings must allow enough room for the bulbous end of the leg to pass through, giving a "stovepipe" appearance to the leg. In addition, the "no opening" designs had other advantages, i.e., the silastic bladder expandable wall design was not durable and tended to delaminate, the full insert type added additional bulk to the prosthesis, and the removable pad design needed constant adjustment.
The Rancho expandable wall prosthesis eliminates many of the problems inherent in other designs. This prosthesis was first described in the AAOS Atlas of Limb Prosthetics although fabrication was not detailed at that time. The Rancho expandable wall prosthesis incorporates the following features:
Strength—The "no opening" design laminated to the Regnell foot provides maximum strength and durability.
Expandable liner—A durable elastic window sewn in a thin flexible inner liner eliminates problems with silastic or Pe-lite™ inserts, which will tear or add excess bulk.
Cosmesis—No buckles or straps are required. No line or seam at ankle joint. Bulk is kept to a minimum with thin wall thickness.
Ease of adjustment—Although the expandable inner is bonded in place permanently, it can be left unbonded for the first month of wear to allow for adjustments.
Can accommodate large distal ends—Two expandable windows can be made in the flexible liner to allow for large distal ends.
Negative Impression Procedure and Measurements
The plaster negative impression is taken in the conventional manner. Reliefs are made over the bony prominences by the use of 1/8" padding before the impression is taken. The circumferences of the distal end and the narrowest part of the ankle should be compared. Maximum cosmesis is attained when the malleoli have been trimmed and the largest circumference at the distal end is about 3/4" greater than the smallest ankle circumference.
After the necessary modifications are made to the positive model, measure the M-L at the distal end, then move the calipers proximally until the model has the same M-L. This will determine the length of the elastic panel (Fig. 3). If the circumference of the distal end is 1 1/4" or greater than the narrowest part of the model, two elastic panels will be necessary.
To allow space for the elastic panel, polyethylene "inserts" (Fig. 4) are cut to the length determined above, and are inserted between two nylon stockinettes for the expandable liner. The polyethylene inserts are laminated into the nylon using a 80% flexible, 20% rigid resin.
The PVA bag is left on the lamination and a polyurethene foam buildup is made over the lamination (Fig. 5); this is then measured and shaped down to 1/4" less than the circumference of the distal end. A PVA bag is pulled over the foam and an outer shell of 6 nylon is laminated using rigid (90-10) resin (Fig. 6). After the resin sets, a hole is drilled in the distal end and the outer lamination is forced off the model using compressed air (Fig. 7). The polyurethene foam buildup and PVA bag are then removed from the inner lamination.
Remove the polyethylene inserts by drilling small holes in the center of each end and slitting the outer nylon with a razor (Fig. 8 and Fig. 9). Most of the laminated nylon covering the outside of the polyethylene sleeve is removed, leaving a 1/4" overlap to hold the stitching for the elastic panel. A single vertical razor slit is made on the inside of the liner to allow expansion. Use the polyethylene sleeves as patterns to cut out one-way stretch elastic. The proper elastic for this procedure, called grip-net, is difficult to find, as it must have a heavy durable weave and comes in a wide roll (8" or greater).
The elastic panels are temporarily taped in place and then sewn in place in a long arm patcher sewing machine (Fig. 10). The liner may have to be folded and/or lubricated with silicone to allow the machine to reach the end of the insert. The prosthesis is now ready for static alignment on the Regnell foot (Fig. 11).
The Regnell foot is an external keel design specifically suited for Syme prostheses because the distal end of the socket can be placed very close to the floor: a thin sole and heel cushion take little space under the prosthesis. No ankle bolt is needed, and the finished laminated external keel provides good cosmesis. The toe break is located and designed to allow for more optimum A-P alignment of the socket, resulting in smoother functional rollover and more cosmetic shaping.
Static alignment can be set up by either sinking the socket into the keel of the foot, or by cutting off the top of the foot with a bandsaw, leaving only the amount equal to the leg length discrepancy (Fig. 12). The socket is then sunk into the block cut-off of the foot and tack glued to the prosthesis (Fig. 13). The second method allows the prosthetist easier M-L and A-P and toe-out adjustments by simply moving the block on the prosthesis and regluing. Dynamic alignment is achieved in the usual manner.
Following dynamic alignment, the socket is shaped to blend into the foot and roughed up. All soft parts of the foot are taped off and the final lamination of 2 nylon is made. The sole of the foot is not removed during lamination (Fig. 14). The lamination is then trimmed away, leaving the sole and toe break free (Fig. 15).
The expandable liner is inserted into the outer shell. If no adjustments are anticipated, the liner is bonded to the outer shell at the proximal border with sealing resin.
The Rancho expandable wall Syme prosthesis, when used with a Regnell foot, provides a very practical solution to the problems existing in other Syme prostheses. Many of the durability and cosmesis problems have been eliminated. Whenever possible, prosthetists should encourage physicians to perform more Syme level amputations, and to try to achieve less bulky distal ends when these amputations are performed.
The prosthesis described here was developed in response to the needs of Richard Voner, CP., of Orthomedics and William Wagner, M.D., of Rancho Los Amigos Hospital, Downey, CA.
The fabrication procedure was developed by Ortho-medics Central Fabrication, which also provided the fabrication photos.
- Syme, J. "Amputation at the Ankle Joint," London Edinburgh Monthly J. Medical Science, 2, 1843, p. 93
- Harris, R.I. "Syme Amputation," J. Bone and Joint Surgery, 38B, 1956, p. 614.
- Spitther, A.W., J.J. Brennen, and J.W. Payne, "Syme Amputation Performed in Two Stages," J. Bone and Joint Surgery, 55A, 1973, p. 568
- Wagner W., "The Syme Amputation," AAOS Atlas of Limb Prosthetics.
- Waters, R.L., J. Perry, D. Antonelli, and H. Hislep, Energy Costs of Walking of Amputees, The Influence of Level of Amputations.
- Voner, R,, "The Syme Amputate: Prosthetic Management," AAOS Atlas of Limb Prosthetics, pp. 334-340.