A Method Of Determining Total Contact In Prostheses

Newton C. McCollough, M.D. Raymond E. Gilmer, Jr., M.D.

The necessity for achieving total contact with the stump in below- and above-knee prostheses is well recognized. Its absence leads to edema, hyperemia, and sometimes skin breakdown. Conventional methods for assessing the attainment of total contact are not always reliable. At the Orlando clinic we have for some years routinely X-rayed the stump in the socket under weight-bearing conditions (Fig. 1A/1B and Fig. 3A/3B ). However, the films obtained did not always demonstrate a clear demarcation between the soft tissues and the socket. As a refinement, we have developed a method by which the stump is painted with a contrast material which clearly outlines the periphery of the stump in the prosthesis on X-ray study (Fig. 2A/2B ).

The method is as follows: Two or three coats of a saturated solution of sodium iodide in absolute alcohol are applied over the stump with a sponge and allowed to dry. The solubility of the salt in absolute alcohol is considerably less than in water, but the rapidity with which the alcohol dries makes it extremely convenient for use in the clinic. The usual number of stump socks is applied. The stump is inserted into the prosthesis, and weight-bearing films are made in the anteroposterior and lateral projections.

On X-ray, the periphery of the stump is clearly outlined by a fine radiopaque border. Lack of total contact is easily recognized (Fig. 4A/4B and Fig. 5 ). Compression of the skin-such as over the patellar tendon-is indicated by an increased density of the contrast material (Fig. 2A/2B ). Even the pressure marks made by the mesh of the sock against the skin are clearly defined. We do not completely understand the cause of this increased density, but believe that compression of skin probably results in a slightly increased concentration of sodium iodide.

To date no skin problems have developed from the application of the sodium iodide solution. Other solvents have been tried, but alcohol seems to be the most effective vehicle to date. The solution can be obtained from any pharmacist at little expense. The method has been used with both our "hard" and "soft" sockets, being helpful in determining total contact in each type. Although the method has been used on only a few cases to date, it appears to be much superior to conventional methods of determining total contact. Further study is necessary to fully establish its role in routine prosthetic clinic use.

Newton C. McCollough, M.D. and Raymond E. Gilmer, Jr., M.D. are associated with the Child Amputee Clinic Florida Crippled Children's Commission Orlando, Florida