A Method For Lengthening The Prosthesis Of A Growing Child

Howard V. Mooney, CP.

Reprinted with permission from the Orthopedic and Prosthetic Appliance Journal, March 1967.

It is a general practice, at least in the New England area, to fit a growing child with a prosthesis which is 1/4 inch to 3/8 inch too long. A lift corresponding to the extra length is added to the shoe on the sound side. As the child grows, the lift is removed from the shoe on the sound side and added to the shoe on the prosthetic side. This obviously allows for growth amounting to 1/2 inch to 3/4 inch without the need for lengthening the prosthesis.

This procedure has several disadvantages, in my opinion. In the first place the lifts are generally attached by a cobbler who gets his instructions secondhand from the child's parent. Secondly, even if the correct amount is properly added to the shoe, the resulting appearance of the shoe is not normal. Then, as the child grows, the removal and interchanging of lifts on the shoes is dependent on the parent, who should take the shoes to a cobbler, who once again must depend on the parent for the correct instructions.

At a recent amputee clinic Dr. Kathleen Robinson, a New Hampshire orthopedist, asked me to try to come up with a method whereby prostheses for children could be easily lengthened at home by the child's parent. This request was motivated by a desire to keep a more constant pace with the child's growth and to avoid frequent and costly trips to a prosthetic facility for lengthenings.

In view of all this I have devised a simple lengthening procedure which even an intelligent child amputee could perform. This procedure is based on the assumption that a SACH foot is used. After the prosthesis is completed, with the exception of the customary cementing of the SACH foot to the shank section, make a template of the proximal surface of the SACH foot. Make two 3/16-inch holes in the anterior template centered about 3/4 inch apart. Place the template back on the proximal surface of the SACH foot and mark the location of these holes. Repeat this marking procedure on the distal shank section. Bore two 3/16-inch holes 1-1/8 inches deep where marked in the proximal SACH foot. Bore two 3/16-inch holes 1/2 inch deep where marked in the distal shank. Insert and secure two 3/16-inch metal pins, 1-1/2 inches long, in the distal shank. These pins will serve to properly align the foot with the shin and will also prevent rotation of the foot.

Using the same template, mark and cut out three 1/4-inch-thick inserts of tempered masonite, lucite, or other suitably strong material, and drill 3/16-inch holes where indicated by the template. An additional hole of the proper size and location should be drilled in each insert to allow passage of the SACH-foot holding bolt. The edges of the inserts may be painted to blend favorably with the shank section of the prosthesis. These inserts can now be used to lengthen the prosthesis in 1/4-inch increments to a total of 3/4 inch.

This method has several advantages over adding lifts to shoes. The child starts off with his prosthesis the correct length without the need for a lift. The prosthesis may be lengthened in 1/4-inch increments in minutes by the child's parent. With this convenience available there should be no delay in keeping constant pace with the child's growth up to at least 3/4 inch. The child's shoes retain a look of normalcy without the need of exterior lifts.

I can only foresee two disadvantages in this method of lengthening: first, the possibility of the 1/4-inch lengthening pieces being lost or misplaced before they are needed. However, if the prosthetist keeps a template of each child's insert, replacements can easily be made available by mail. Secondly, as the inserts are added, the shape just above the ankle deteriorates slightly. This, however, will rarely be of concern to the growing child.

The accompanying pictures should help to make the suggested procedure very clear. A SACH-foot holding-bolt wrench should, of course, be furnished whenever this lengthening method is used.Image 1

Howard V. Mooney, CP. is from Burlington, Massachusetts