Individually Molded Seat-Shells for Severely Handicapped Persons

G. G. Kuhn

Conforming to the Anatomy

Over the past year or so it has been evident that a number of institutions are providing their handicapped patients with chair seals which conform to the individual's anatomical configuration An article in the July 197} issue of the Inter-Clinic Information Bulletin (Vacuum-Formed Plastic Insert Seat for Neurologically Handicapped Wheelchair Patients, by John H. Bowker, M.D., and B. A. Reed, pp. 7-12) described one technique used in the fabrication of these seats The article by Dr. Kuhn, which follows, is a modification of one which originally appeared in Acta Orlhop. Scand., 44:366-371, 1973. It describes another method of preparing "seal-shells" and is reproduced by kind permission of the author

The physically handicapped person who spends the greater part of his day in a chair is dependent, even more than a healthy person, on a well-fitted seat. Often it is not possible for him to shift his weight to distribute pressure and increase blood circulation.

For these reasons it is essential that the severely handicapped person be supplied with a seat which conforms to his anatomical requirements. It cannot be obtained in the available, mass-produced wheelchairs and their accessories. We therefore decided to build individually molded seat-shells (Fig. 1 ).


The main problem has always been, and still is, taking a mold for making the seat-shell in such a way that 1) as much as possible the deformities present are corrected; and 2) areas of pressure concentration are avoided. For several months now we have been using a plaster-of-Paris technique which is considerably simpler and, best of all, fraught with less problems than anything we have used before.

The Method

From Otto Bock KG in Duderstadt, we obtained a 60 x 80 x 20 cm block of especially soft and deeply impressionable polyether foam. This foam-rubber block is covered with a sheet of Polyvinylchloride (PVC) to protect it from water and plaster. A layer of cellulose is placed over this sheet to prevent slipping of the plaster strips or splints which are placed on top, and also to collect excess water (Fig. 2 ).

To take the seat portion of the cast the patient is placed on the prepared materials (Fig. 3 ). He sinks deeply into the foam rubber and the plaster strips are pulled up lightly on the sides and perhaps turned in a little (Fig. 4 ). The result after the plaster has hardened is shown in Fig. 5 .

The process is much the same for making the plaster mold of the back. A new cellulose and plaster-strip preparation is made and again placed on the foam block. The patient, with his legs at right angles, is placed on his back on the splints. The alignment of his back and pelvis presents no problems. Again the plaster strips are drawn up around the sides of his body as he sinks deeply into the foam block (Fig. 6 ). The resulting impression is shown in Fig. 7 .

Later the two parts (seat and back) of the seat-shell are connected. The cast, which at this point can already be called a molded seat-shell, is installed on a baseplate which can be adjusted electrically in all planes. With the aid of this baseplate it is possible for the patient himself, as well as for the orthotist, to obtain optimal alignment of the shell (Fig. 8 ). In this position the shell is transferred into the patient's wheelchair, where he tests it for a period of lime.

During the trial the patient is dressed as lightly as possible to give him a better feeling of pressure areas. When the patient and the orthotist are satisfied that no more adjustments are necessary and everything is as comfortable as possible, a positive mold of the shell is taken. It is enlarged on both sides by about 1 cm to allow for clothes. If indicated. Plastazote is placed on the seat, and the mold will then be laminated with polyester resin in the usual manner (Fig. 9 ).

The brims of the shell can be finished after the resin has set and the shell is ready to be placed into the wheelchair.

In all cases the shell is mounted on a baseplate so that it can also be placed on an ordinary chair or into a car, for example. It also enables us to place the patient in a resting position, if indicated.

Arm- and footrests are fastened directly onto the laminated shell to avoid distortion of the angle when the inclination of the shell is changed. Both foot- and armrests are fitted exactly to the patient's requirements (Fig. 10 ). Other aids such as seat belts or head rests can be added if necessary.

Individually molded seat-shells have been fitted in our clinic for such disabilities as: tetraplegia, progressive muscle dystrophy, neural muscle atrophy, meningocele, osteogenesis imperfecta, primary chronic rheumatism, arthrogryposis multiplex, and scoliosis of different origins and varying degrees of severity (Fig. 11 ).

Seat-shells which are individually molded by our method have become valuable orthopedic aids. They are often indicated, have been tested extensively, and are now used with a large degree of reliability by the disabled.

Abteilung für Technische Orthopädie und Rehabilitation der Orthopädischen Universitätsklinik Münster, Münster (Westfalen), Germany

Demoll, G., Sitzschalen und Spastiker-Stuhl nach Demoll. Orthopädie Technik, p. 298, 1972.