Vacuum-Formed Upper-Extremity Splints

Vacuum-Formed Upper-Extremity Splints


For a number of years upper-extremity splints of various types have been made with San Splint. They have usually been fastened with Velcro or straps and buckles. The obvious advantage in using San Splint is the ease with which it can be fabricated into a satisfactory orthosis. Its disadvantages are its tendency to "creep" in warm weather, and its deterioration in long-term applications.

With the acquisition of vacuum-forming equipment at our Centre, we decided to try the application of vacuum-forming techniques to some of the new plastic materials now becoming available. The types of splints fabricated so far have been fixed-position ones. As yet no attempt has been made to fabricate articulated splints by this method.

Materials

The materials polyethylene and polypropylene have been found to be the most suitable for these applications. A soft liner of Plastazote-a closed-cell foamed polyethylene-has been used under the splint materials whenever possible. These materials are quite inert and can be cleaned very easily. Common adhesives, however, do not work very well with them.

Methods

Since the Plastazote does not draw very well, it is heated and hand-formed over the cast. If polyethylene is used, it is formed directly over the Plastazote-covered cast. Since Plastazote is a foamed polyethylene the two materials fuse when in the molten state, forming a welded bond. If polypropylene is used, the formed liner is removed and the cast covered by two layers of thick "stockinette." (to compensate for the thickness of the liner), and the polypropylene is formed in the standard fashion. The liner is glued in after the splint is cut out. The adhesive used is 3-M, type HC-4693. The bond obtained is adequate to keep the liner in place. So far ten patients have been fitted with splints fabricated in this manner. All patients preferred their new splints, which are withstanding the rigors of their childhood activities far better than their San Splint antecedents.

Sample Splints

Different views of the same splint made of Plastazote-lined polypropylene are shown in Fig. 1 , Fig. 2 , and Fig. 3 . The patient was an 18-year-old athetoid. The excellent manner in which the material has conformed to the thumb web space can be seen in Fig. 1 .

Fig. 4 shows two splints, both Plastazote-lined; one of polypropylene, the other of polyethylene. The patient was a 2-year-old infant with a radial clubhand and no thumb. The upper ring fits around the wrist; the lower on the forearm just distal to the elbow.

Fig. 5 and Fig. 6 show an experimental thumb block splint made of polypropylene without a liner, but textured on the inside by "stockinette." A variation of this splint has been fitted to two patients with good results.

Conclusion

Vacuum-formed splints of polyethylene and polypropylene have been at least as comfortable as San Splinl devices, and in all cases they have been lighter and easier to maintain than those they replaced. The fabrication time involved is somewhat greater than with San Splint due to the need for cast-taking, but since little preparation of the plaster positive is heeded (as compared to a mould for lamination), and a better fit is obtained, overall time may well be saved.

Ontario Crippled Children's Centre Toronto 350, Ontario, Canada