Silicone-Rubber Implants to Control the Overgrowth Phenomenon in the Juvenile Amputee

ALFRED B. SWANSON, M.D., F.A.C.S.


In our clinic silicone-rubber implants have been used since 1963 2,4,6 for control of the overgrowth phenomenon effecting amputated long bones in children. This work, which has been conducted with the support of the John A. Hartford Foundation, Inc., has resulted in continued improvement of implant design and surgical technique. The method now being used seems to yield excellent results. This report of our technique is being presented in the hope that it will be of interest and assistance to other professionals concerned with the careof the juvenile amputee.

Occurrence of Overgrowth

The phenomenon of overgrowth is frequently seen in transdiaphyseal amputations of children, especially those of the humerus and the tibia1. It seems to be the result of endosteal and periosteal bone production at the severed end of the bone. Hence control of this production is essential for adequate treatment. The spike constituting the overgrowth grows into a resisting soft-tissue envelope, therefore an adequate soft-tissue cover should be provided 7 . When overgrowth does occur, multiple stump revisions may be required before the child reaches maturity.

To avoid overgrowth, any elective amputation in the child should, whenever possible, be a disarticulation through a joint and not a transection through a long bone. A generous soft-tissue cover should always be provided over the end of the stump.

The intramedullary stemmed implant designed at Blodgett Memorial Hospital is a mushroom-shaped, heat-molded, flexible silicone-rubber implant with a collar. This design insures increased stability of the implant while providing an encapsulating mechanism to restrict both endosteal and periosteal bone growth 3,5,8 . The implant is manufactured in six sizes by the Dow Corning Corp., Midland, Mich., to assure proper fit ( Fig. 1 ).

Technique

The transverse incision is placed 2 or 3 cm. above the end of the stump to avoid undesirable scarring of the distal soft tissues. The bone is transected at this level and the distal portion excised in a retrograde fashion. The proximal bone should be handled gently leaving the periosteum intact to the end of the bone. Periosteal stripping is coptraindicated. The intramedullary canal is reamed minimally to accept the stem of the implant. A 2-0 to 3-0 dacron suture is passed through a small drill hole made approximately one inch from the end of the bone with the needle directed from the outside into the intramedullary canal. The curved needle is then straightened and passed through the implant in a proximodistal direction so that the suture emerges in the middle of the distal end of the head of the implant. The implant is adjusted in position and sutured in place. The suture provides early postoperative stabilization of the implant until adequate encapsulation has occurred ( Fig. 2 and Fig. 3 ). The implant stem should fit easily into the end of the bone and the cuff should not be constrictive over its end. A myofascial closure is carried out over the implant and care is exercised to assure that the skin closure remains relatively loose.

When the stump is infected or the bone end protrudes through the skin, a two-stage procedure should be done. In the first stage, the bone is simply transected. When the stump is well healed and infection-free, the secondary implant cuffing procedure can be accomplished safely.

This simple procedure not only seems to control the overgrowth problem of the juvenile amputee but also provides a pain-free stump with a mobile, distal soft-tissue cover ( Fig. 4 and Fig. 5 ). This method has been used successfully in both upper- and lower-extremity amputations.

Summary

The overgrowth phenomenon in the transdiaphyseal amputation stump of the growing child has been the subject of a research project in this department since 1962. A heat-molded, intramedullary stemmed and collared silicone implant which is sutured to the bone appears to control periosteal and endosteal bone overgrowth. The operation must be done on an infection-free stump, otherwise the procedure should be carried out as a two-stage technique. The stump end should be covered with adequate and mobile soft tissue. It is believed that this method, properly applied, can solve the difficult problem of overgrowth.

Consultant, Michigan Area Juvenile Amputee Clinic, and Chief, Orthopaedic Surgery and Orthopaedic Research, Blodgett Memorial Hospital, Grand Rapids, Mich.

References:
1.Frantz, C. H., and G. T. Aitken, Management of the child amputee. The American Academy of Orthopaedic Surgeons Instructional Course Lectures, 17:246-298. The C. V. Mosby Co., St. Louis, 1960.
2.Swanson, A. B., Improving the end-bearing characteristics of lower extremity amputation stumps-A preliminary report. Inter-Clin. Information Bull., 5:5:1-7, February 1966.
3.Swanson, A. B., A flexible implant for replacement of arthritic or destroyed joints in the hand. Inter-Clin. Information Bull. 6:3:16-19, December 1966.
4.Swanson, A. B., B. L. Hotchkiss, C. H. Frantz, and J. R. Glessner, Jr., Study of end-bearing characteristics in the lower extremity amputee. Scientific Exhibit, American Academy of Orthopaedic Surgeons, San Francisco, January 1967.
5.Swanson, A. B., Silicone rubber implants for replacement of arthritic or destroyed joints in the hand. Surg. Clin. N. Amer., 48:1113-1127, October 1968.
6.Swanson, A. B., Bone overgrowth in the juvenile amputee and its control by the use of silicone rubber implants. Inter-Clin. Information Bull., 8:5:9- 18, February 1969.
7.Swanson, A. B., Improving the end-bearing characteristics of lower extremity amputation stump by the use of silicone rubber implants. Thesis presented to the American Orthopaedic Association, 1969.
8.Swanson, A. B., Finger joint replacement by silicone rubber implants and the concept of implant fixation by encapsulation. International Workshop on Artificial Finger Joints, suppl. to Ann. of Rheum. Dis., 28:47-55, 1969 (Brit. Med. Assn.).