A New Plastic Orthosis For The Rheumatoid Hand
Richard D. Koch, C.O. *
For years orthotists have been splinting the rheumatoid patient with a variety of hand orthoses to provide relief from pain and therefore function. Few have been successful.
In 1963 we, at the University of Michigan  focused our attention on the development of an orthosis that would be simple, light in weight, inexpensive, but one that would give the rheumatoid patient the control forces that are needed to relieve the pain, yet permit function. Many different models were designed and tried before we arrived at our present metacarpophalangeal-type orthosis (MCP) (Fig. 1 ).
The material* used is a parent polyvinyl chloride that can be molded at a relative low temperature and has a high resistance to impact forces. This material in 1/8 inch thickness sheet requires a temperature of only 170 degrees F. to make it moldable. At this temperature it can be molded directly over the patient's limb when a piece of chamois leather is used to dissipate the heat. The orthotist does not need gloves because his hands are moving constantly while molding the orthosis. The 170 degree heat dissipates quite rapidly, so one does not have to hold it for more than 10-15 seconds. Polyvinyl chloride in this form can also be heated without damaging the plastic as many times as needed to make adjustments. Because the material is transparent, the areas where total contact is needed can be observed. Because PVC does not breathe, ventilation holes are needed.
Design Principles
Two three-point force systems are used to control ulnar deviation, and two to control volar subluxation. The system for control of ulnar deviation at the metacarpophalangeal joints is shown in Fig. 2; the one for control of ulnar deviation about the wrist is shown in Fig. 3. The system for control of volar subluxation at the wrist is shown in Fig. 4; the one for control of volar subluxation at the MCP joints is shown in Fig. 5. To acquire these corrections the three straps must be secured tightly.
Application
One of the major advantages we noted was the reduction of pain at the wrist while wearing these orthoses. This is achieved by molding the plastic over the pisiform and using the middle dorsal strap to provide a counter force pushing downward over the heads of the ulna and radius. At first we didn't think we could place the middle strap over the head of the ulna because it is a point that cannot tolerate pressure in the case of most hand orthoses, but with the rheumatoid we found it was the major factor in the reduction of pain at the wrist. Only about 5% of our patients object to the location of this strap. For those who do complain, a soft form pad is added to the strap (Fig. 6 ). The distal strap should be allowed to pivot so that it can be wrapped around "proximal" to the MCP joints, and thus provide a counter force to MP volar subluxation, as the wrist strap provides in the case of volar subluxation of the wrist.
Orthoses for the rheumatoid hand usually were applied only when the hand was at rest . We know now that damage occurs during activity, and this has led us to believe that the functions provided by these new orthoses are also beneficial during use of the hand . Originally the orthosis was used only at night. However, many patients reported wearing their orthosis for performing some activities during the day that normally caused them pain. It is possible to perform many activities while wearing the orthosis because one has total use of the distal eight interphalangeal joints (Fig. 7). The thumb web space is free from any plastic material when the orthosis is fitted properly, giving the patient full use of his thumb (Fig. 9 ).
If the disease is confined to the wrist only, we apply a simple wrist cock-up type of orthosis (Fig. 8 ). This is done easily by removing the distal portion of the standard MCP orthosis. This arrangement allows the patient to flex fully his MCP joints to give him much more hand function. However, the distal portion is needed when volar subluxation is present in order to limit MCP flexion.
Special Points In Fitting
The degree of wrist dorsiflexion needed varies between 5 degrees and 20 degrees, depending on how tight the wrist flexors are. Patients wearing these orthoses also carry on an exercise program designed to maintain hand and wrist motion.
The most important factors to keep in mind when fitting the MCP orthosis are the location of the distal volar hand portion and the location of the three retaining straps. The distal edge of the orthosis should be located mid-way between the MP joints and the PIP joints, which will form an arc along all four fingers (Fig. 9 ). This limits MP flexion, but allows total use of the PIP and DIP joints. We usually fit the most severely involved hand first, and almost always the patient requests one for the other hand. Follow-up indicates that the majority of our patients have continued to wear their orthoses.
*Available from Almac Plastic Co., 26400 Grose-beck Highway, Warren, Michigan.
References:
- Smith, E., R. Juvinall, L. Bender, R. Pearson: "Flexor forces and rheumatoid metacarpophalangeal deformity." JAMA 98:130-134,1966.
- Koch, R., E. Smith, R. Juvinall, R. Pearson: "Dynamic ulnar-deviation splint." Technical Report #7, ORA Project 07915. Vocational Rehabilitation Administration, Department of Health, Education, and Welfare, VRA Grant #RD-1527-M-66-C2. January, 1967.
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