The patient with hypersensitivity occurring after hand trauma presents the physician and the therapist with a unique challenge, both in evaluation and in treatment of the problem. The lack of an objective assessment of both the complaint and the improvement, as well as the deficiency of published formalized treatment procedures, has made hand hypersensitivity particularly thought provoking.
The purposes of this chapter are to discuss the development of and indications for a method of desensitization treatment, to describe the Downey Hand Center Hand Sensitivity Test (DHCHST), an instrument for measuring the status and improvement of hypersensitivity, and to outline the progress of 124 patients who completed the desensitization test and treatment at the Downey Hand Center (DHC).*
Methods for decreasing hypersensitivity of the injured hand are just now appearing in the literature. Several earlier approaches to the desensitization of painful scars and amputation stumps have been documented. Rubin recorded complete relief of pain and tenderness caused by phantom limb, neuroma, and scar origin, in 23 of 37 areas of hypersensitivity, with the use of ultrasound treatment. Vibration has historically been used in the treatment of hypersensitive scars. Russell and Wall theorized that the nerve fibers concerned with firing hyperpathic sensations are very easily traumatized into inactivity by a vibrator. Hochreiter, in her study of the effect of vibration of 80 Hz on tactile sensitivity, stated that vibration results in an elevated tactile threshold and that the increase lasts for at least 10 minutes but not as long as 15 minutes, a duration indicating that vibration actually reduces tactile sensitivity. Brown hypothesized that in dropping particles from a height over the involved area one can elicit a response similar to vibration. Melzak relates that vibration is also able to modify the amount of pain produced by noxious stimulation of the skin in normal subjects.
Russell theorized about the use of percussion to treat painful amputation stumps and phantom limbs. He posited that conduction in a mixed nerve is easily interrupted by repeated pressure without causing pain and that the regenerating nerve fibers, which form neuromas in an amputation stump, might well be even more vulnerable to minor trauma than normal nerves and nerve endings are. It was considered likely, therefore, that if painful neuromas are repeatedly percussed, their nerve fibers would gradually degenerate and be replaced by fibrous tissue. A survey of phantom limb treatment lists a number of approaches to the problem of painful stumps in phantom limb, only one of which is stump conditioning or desensitization.
Hardy described a sequential method of desensitizing the traumatized hand. Five levels of desensitization included use of paraffin, vibration, massage, constant touch-pressure, textures, object identification, and specific tools to simulate common job activities. Work simulation was included as a final level of the desensitization program. Brown stated that desensitization techniques aided in the physiologic and psychological change toward normalcy and advocated the use of textural stimulation and the judicious use of vibration as well as the performance of functional activities as means of desensitization.
A survey of 32 surgeons and therapists by me in 1982 indicated that desensitization is included as part of the treatment regimen of a number of therapists and physicians and that the majority of them would like to see a proved method of desensitization developed.
Hypersensitivity, as used in this chapter, is defined as a condition of extreme discomfort or irritability in response to normally nonnoxious tactile stimulation. It is important to point out that the hypersensitivity referred to throughout this chapter occurs at or near the injury site and is not to be confused with the general manifestations of pain, as seen in causalgia or the shoulder-hand syndrome.
Two relevant dictionary definitions of “desensitize” are as follows: “to lessen the sensitiveness of, to eliminate the native or acquired reactivity or sensitivity of an animal, organ, tissue, etc” to an external stimulus such as an allergen” (Random House Dictionary) and “to render less sensitive or insensitive as to light or pain” (American Heritage Dictionary).
Treatment in this chapter is defined as the use of modalities and procedures designed to diminish or reduce symptoms. Desensitization treatment as described here is specifically designed to reduce the symptom of hypersensitivity in the injured hand. Although a connection may be theorized, it is not to be confused with that used for sensibility reeducation.
Development of Treatment
After working with a significant number of patients at the Downey Hand Center, it became evident to the staff that the natural tendency for many patients was to protect the sensitive areas after injury or surgery. Use of parts of the hand commonly involved in pinch and grasp was avoided, a situation that resulted in awkward pinch patterns, such as extensor habitus. Patients found use of the hand with areas of hypersensitivity dangerous in that when they were touched inadvertently they might withdraw and drop whatever they were working on, possibly hurting themselves or others. This condition was a definite deterrent to returning to work. Part of the therapist’s role became to inform the patient that it was not only all right but actually beneficial to touch the hypersensitive areas.
In 1976, as a first step in organizing our program, a hierarchical method of treatment of the hypersensitive hand injury was begun at the Downey Hand Center. Our staff arbitrarily picked 10 different textures and 10 different particles and lined them up in what was considered a logical hierarchy of least irritating to most irritating. I published a general description of this method in 1978. Three types of modalities were used: dowel textures, with use of materials glued onto 1/2 -inch dowel sticks; contact, with use of particles such as rice and beans; and vibration, with use of battery-operated and electric plug-in vibrators ( Fig. 56-1 ). These first two modalities were then divided into 10 subcategories each, four in the case of vibration, and organized in what was considered a logical hierarchy of least irritating to most irritating.
These textures and particles were chosen on the basis of how tactilely stimulating they seemed to be, from giving very little tactile sensation to giving a significant amount. We can only speculate about whether subjects are sensitive to the textures or to the pressure exerted by the modalities employed. Another consideration was availability of the materials so that the treatment could be standardized if desired.
After this method was used over a period of several months, it was determined that the predetermined hierarchy was not a sound basis for treatment. Many patients found some particles and textures irritating that were not irritating to the normal, and vice versa. It was therefore decided to have the patient determine his own hierarchy of hypersensitivity for the contact and immersion textures and base his treatment on this. This method of treatment proved effective, in that most patients improved and progressed in their treatment hierarchy. In many cases, for comparison, we also recorded the patient’s hierarchy on the normal side, the results of which will be the subject of a future article.
In the process of researching the subject, it was noted that a type of hierarchical desensitization was also used with phobias and in the art of karate. Anxiety hierarchies consisting of sequentially more threatening situations were introduced in the late 1950s to treat phobias. The therapy was terminated when the final item on the hierarchy could be tolerated by the patient. The rationale of having a patient touch progressively irritating textures, in theory, is not unlike any progressive exercises that we do from gross to fine and from light to heavy. Progressing from nonirritating to irritating seemed the logical way to proceed. This process is also based on a fundamental tenet of occupational therapy, in that it is “given in increasing doses as the patient’s condition improves.”
Downey Hand Center Hand Sensitivity Test
The staff was gratified by the patients’ improvement with this method and felt a need to validate the procedure so that it could be more confidently used and shared with others. Therefore, in 1980, a new instrument, the Downey Hand Center Hand Sensitivity Test, was developed to measure the effects of desensitization treatment. First, detailed instructions were written for administration of the test so that use of the tool could be consistent. In the case of the dowel textures, the tester randomly selected one of the 10, instructing the patient to rub, roll, or tap the texture over the hypersensitive area. Then a random dowel was selected and the patient was asked, “Which of these is the most irritating?” Dowel textures ranged from moleskin to Velcro hooks, as follows:
Velcro loops 1
Rug back 10. Velcro hooks
1 Velcro USA, Inc., New York, NY.The contact or immersion particles were contained in 3- pound coffee cans into which the patient was instructed to immerse the hand. The 10 particles ranged from cotton to plastic squares and were numbered for recording purposes as follows:
Terry cloth pieces
Plastic wire insulation pieces
Small beebees or buckshot
Large beebees or buckshot
The tester randomly selected one of the 10, instructing the patient to repeatedly immerse his hand in it. Then another random texture was selected and the patient was asked, “Which of these is the most irritating?” This procedure was repeated until a sequence was established of all 10, ranging from the least irritating to the most.
To keep a consistent number of 10 with all three modalities, a hierarchy of 10 was also established for vibration, based both on speed of vibration and on amount of contact. The 83- and 100-cycle vibrator was used only in the clinic, and the 23- and 53-cycle vibrator was used at home. The patient continued the vibration step for 10 minutes a session. The hierarchy is as follows:
83 cycles, near but no actual contact on the area
83 cycles, near but no actual contact; 23 cycles, near but no actual contact
83 cycles, no contact; 23 cycles, intermittent contact
83 cycles, intermittent contact; 23 cycles, intermittent contact
83 cycles, intermittent contact; 23 cycles, continuous contact
83 cycles, continuous contact; 23 cycles, intermittent contact
100 cycles, intermittent contact; 53 cycles, intermittent contact
100 cycles, intermittent contact; 53 cycles, continuous contact
100 cycles, continuous contact; 53 cycles, continuous contact
No problem with vibration The method was the same as that used for the dowel and contact modalities.
To determine how reliable the tool was for normal persons and whether differences in reliability existed because of ethnicity, sex, or the hand being tested, a standardization sample of 40 volunteers with normal hands, 20 to 40 years of age, consisting of 10 male and 10 female Anglo-Americans and 10 male and 10 female Mexican-Americans were selected. A normal hand was defined as a hand presenting without pain, neurologic deficit, or skin abnormality. Each subject’s hierarchy of sensitivity of both hands was determined as described above. The subjects were retested in 2 weeks. The test-retest reliability figures were as follows: dowel textures—right hand .77, left hand, .79; contact particles—right hand .74, left hand, .80; vibration—right hand .82, left hand .82. There were no statistically significant differences in reliability because of sex, ethnicity, or which hand was being tested. Therefore it was concluded that the HCHST could be used as both a research and a clinical tool.
Because the same modalities were used in both testing and clinical practice, which might be confusing, it was important to differentiate the use of the DHCHST, the actual testing tool, from the desensitization treatment, which is described next. Because its function is to measure change, the DHCHST could be used to test the effectiveness of other forms of treatment in addition to the regimen described in this paper. Despite the fact that the DHCHST was validated on normal hands, the experience gained using the instrument in the study described in this paper demonstrated its value as a tool in assessing change in the injured hand.
Desensitization Treatment and Documentation
Any patient referred to the Downey Hand Center who had an area of hypersensitivity on the hand that exhibited extreme irritability to the touch was a candidate for desensitization treatment. How disabling the hypersensitivity was to him was determined by administration of the DHCHST and observation of the patient’s use of the hand. Before initiation of treatment, the results of the DHCHST and other information were recorded on the desensitization treatment form ( Fig. 56-2 ).