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Difference in sensibility between the dominant and nondominant index finger as tested using the semmes-weinstein monofilaments pressure aesthesiometer
Difference in Sensibility Between the Dominant and Nondominant Index Finger as Tested Using the SemmesWeinstein Monofilaments Pressure Aesthesiometer J. Joris Hage, MD, PhD, Lydia P. E. van der Steen, Peter J. M. de Groot, Amsterdam, The Netherlands In 130 active subjects aged 7 to 76 years, sensibility of both index fingers were tested using Semmes-Weinstein monofilaments. Subsequently, subjects were asked to indicate their dominant side. The gathered data was analysed statistically to try and find a possible difference in sensibility between the dominant and nondominant side. No difference was found in the majority of our series (76). The index at the nondominant side was found to have superior sensibility in 35 out of 130 subjects, while the reverse was true in the remaining subjects (19). In case there is a difference in sensibility between the two hands, the less sensitive side shows 'normal' distribution of light touch thresholds, whereas at the more sensitive side these thresholds usually scored one nylon rod marker lower. (J Hand Surg 1995;20A:227-229.)
As is true for motor functions, the sensory functions may be expected to be superior at the dominant side. Through daily testing experience, one author (PJMG) felt that the hand indicated by the patients to be nondominant, usually showed better sensibility than its dominant counterpart. In 1981, Dellon reported that no difference was found between the dominant and nondominant hand while testing sensibility of fingertips of 39 hands in 32 subjects using the moving two-point discrimination test.~ Because the Semmes-Weinstein test using monofilaments is generally accepted as the most objective and reproducible test of sensibility,Z.3 it was chosen to investiFrom the Departments of Plastic and Reconstructive Surgery and Occupational Therapy at the Academic Hospital of the Free University, Amsterdam, The Netherlands. Received for publication Nov 30, 1993; accepted in revised form May 5, 1994. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests" J. J. Hage, MD, Department of Plastic and Reconstructive Surgery, Academic Hospital of the Free University, P.O. Box 7057, NL-1007 MB Amsterdam, The Netherlands.
gate whether or not Dellon's observations could be e n d o r s e d using a more sensitive test in a larger series.
Material and Methods Subjects The Semmes-Weinstein test was performed on both index fingers in 130 volunteers (58 men, 72 women). Mean age was 41 years (range, 7 to 76 years). Possible participants with any form of disorder of hand or arm, as well as those suffering from diabetes mellitus, uremia or any other illness that might influence skin sensibility, were excluded. Testing and Analyzing of Results The S e m m e s - W e i n s t e i n Pressure Aesthesiometer (Research Designs, Inc., Houston, TX) was used to measure light pressure thresholds on the pad of the index of both hands. This way, every subject had control, thereby eliminating the influence of age, intelligence and occupation of the subject. 3 Testing was executed in accordance with the recThe Journal of Hand Surgery
227
228
Hage et al. / Difference in Hand Sensibility
ommendations given by Bell-Krotoski, 4 after individually explaining the entire procedure to each volunteer participating. The hand to be tested first, was chosen at random. All tests were performed by one of the authors (LPES), and in a standardized setting using one and the same filament set, in order to optimally eliminate differences between volunteers. 3 The tested hand was fully supported on a folded towel in the examiner's hand. After establishing the light pressure thresholds of both index fingers, the patient was asked for subjective dominance. This, and the subject's sex and age were recorded in combination with the threshold data. No recordings of callus thickness, occupation or digit temperature were made. 5 The test results were analysed statistically using dichotome methods in order to establish the 95% confidence interval of each percentage obtained. 6
Results and Comments Of the 130 volunteers, 113 (49 men, 64 women) indicated to be predominally righthanded. The remaining 17 (9 men, 8 women) claimed leftsided dominance. In 76 volunteers the light pressure threshold at the indicated dominant side equalled that found at the nondominant side. In 35 volunteers the index
on the dominant side was found to be less sensitive than that of the nondominant side while in the remaining 19 volunteers, it was found to be contrary. Based on these results, 50-67% of the population is e x p e c t e d to r e v e a l equal s e n s i b i l i t y , while in 19-35% superior sensibility will be found at the nondominant side. The dominant side is expected to have better sensibility in 9-21% of the population. Because the 95% confidence interval for 76 volunteers does not overlap that of the remaining 54 volunteers, they have in a statistically significant higher chance of the monofilament sensibility of the index on the dominant side equaling that of the nondominant side. In case there is a difference in sensibility between the two hands (n = 54), the chance that the nondominant hand is the more sensitive one (35 volunteers) is greater. Our conclusions are based on application of a 95% confidence interval for determining statistical significance. Applying 98% confidence intervals, our resuits do not reach significance. For this to happen, an even larger series is to be tested. Of the 260 tested index fingers, 148 experienced the light pressure threshold that corresponded with the 2.83 (nylon rod marker) filament. Thresholds ranged from 1.65 IOglo 0.1 mg to 3.84 lOgl0 0.1 mg
Number of fingers
1,50r
130
110
90
70
50
30
10
1.65 2.36 2.44 2.63 3.22 3.61 3.84
Nylon rod markings
Figure 1. Distribution of light pressure thresholds found in the 260 index fingers of 130 tested subjects.
The Journal of Hand Surgery / Vol. 20A No. 2 March 1995 and showed a normal distribution (Fig. 1). This distribution indicates that, as in most biological measurements, the upper limit of 'normality' is quite imprecise. Although the 2.83 loglo 0.1 mg threshold is used as the general cutoff, it should not be concluded that pressure thresholds above this limits are to be judged 'abnormal'. The same applies to the 'supernormal' sensibility scored in some of the volunteers in this study. In the 54 volunteers that experienced a difference of threshold between the two index fingers, this difference corresponded with only one nylon rod marker in 47. A difference of two nylon rod markers was found in 4. In the remaining 3 volunteers, a difference of three nylon rod markers was observed. In cases where the dominant index had superior sensibility (n = 19) the distribution of light touch t h r e s h o l d s was n o r m a l at the n o n d o m i n a n t side, while the dominant index showed better than normal sensibility. In cases where the nondominant hand was found to be more sensitive (n = 35), the dominant side scored 'normal' while the distribution of t h r e s h o l d s at the n o n d o m i n a n t side m o v e d o n e nylon rod marker downward. Hence, in the cases where there was a difference in sensibility between the t w o h a n d s (n = 54), the less s e n s i t i v e side showed a normal distribution of light touch thresh-
229
o l d s , w h e r e a s at the m o r e s e n s i t i v e side t h e s e t h r e s h o l d s usually s c o r e d o n e n y l o n r o d m a r k e r lower. Like Dellon, 1 but opposing the results found b y T h o r n b u r y and Mistretta, 5 we did not find variations related to the subject's sex or age.
References 1. Dellon AL. The moving two-point discrimination test: Clinical evaluation of the quickly-adapting fiber receptor system. J Hand Surg 1978;3:474-81. 2. Bell-Krotoski J, Tomancik E. The repeatability of testing with Semmes-Weinstein monofilaments. J Hand Surg 1987;12A: 155-61. 3. Ewing-Fess E. Documentation: essential elements of an upper extremity assessment battery. In: Hunter JM, Schneider LH, Mackin EJ, Callahan AD, eds. Rehabilitation of the hand. 2nd ed. St. Louis: Mosby, 1984: 49-78. 4. Bell-Krotoski JA. Light touch-deep pressure testing using Semmes-Weinstein monofilaments. In: Hunter JM, Schneider LH, Mackin EJ, Callahan AD, eds. Rehabilitation of the hand: surgery and therapy. 3rd ed. St. Louis: Mosby, 1990:585-93. 5. Thornbury JM, Mistretta CM. Tactile sensitivity as a function of age. J Gerontology 1981;36:34-9. 6. Jonge H de. Inleiding tot de medische statistiek, volume I. Groningen: Wolters-Noordhoff, 1963:218.
As is true for motor functions, the sensory functions may be expected to be superior at the dominant side. Through daily testing experience, one author (PJMG) felt that the hand indicated by the patients to be nondominant, usually showed better sensibility than its dominant counterpart. In 1981, Dellon reported that no difference was found between the dominant and nondominant hand while testing sensibility of fingertips of 39 hands in 32 subjects using the moving two-point discrimination test.~ Because the Semmes-Weinstein test using monofilaments is generally accepted as the most objective and reproducible test of sensibility,Z.3 it was chosen to investiFrom the Departments of Plastic and Reconstructive Surgery and Occupational Therapy at the Academic Hospital of the Free University, Amsterdam, The Netherlands. Received for publication Nov 30, 1993; accepted in revised form May 5, 1994. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests" J. J. Hage, MD, Department of Plastic and Reconstructive Surgery, Academic Hospital of the Free University, P.O. Box 7057, NL-1007 MB Amsterdam, The Netherlands.
gate whether or not Dellon's observations could be e n d o r s e d using a more sensitive test in a larger series.
Material and Methods Subjects The Semmes-Weinstein test was performed on both index fingers in 130 volunteers (58 men, 72 women). Mean age was 41 years (range, 7 to 76 years). Possible participants with any form of disorder of hand or arm, as well as those suffering from diabetes mellitus, uremia or any other illness that might influence skin sensibility, were excluded. Testing and Analyzing of Results The S e m m e s - W e i n s t e i n Pressure Aesthesiometer (Research Designs, Inc., Houston, TX) was used to measure light pressure thresholds on the pad of the index of both hands. This way, every subject had control, thereby eliminating the influence of age, intelligence and occupation of the subject. 3 Testing was executed in accordance with the recThe Journal of Hand Surgery
227
228
Hage et al. / Difference in Hand Sensibility
ommendations given by Bell-Krotoski, 4 after individually explaining the entire procedure to each volunteer participating. The hand to be tested first, was chosen at random. All tests were performed by one of the authors (LPES), and in a standardized setting using one and the same filament set, in order to optimally eliminate differences between volunteers. 3 The tested hand was fully supported on a folded towel in the examiner's hand. After establishing the light pressure thresholds of both index fingers, the patient was asked for subjective dominance. This, and the subject's sex and age were recorded in combination with the threshold data. No recordings of callus thickness, occupation or digit temperature were made. 5 The test results were analysed statistically using dichotome methods in order to establish the 95% confidence interval of each percentage obtained. 6
Results and Comments Of the 130 volunteers, 113 (49 men, 64 women) indicated to be predominally righthanded. The remaining 17 (9 men, 8 women) claimed leftsided dominance. In 76 volunteers the light pressure threshold at the indicated dominant side equalled that found at the nondominant side. In 35 volunteers the index
on the dominant side was found to be less sensitive than that of the nondominant side while in the remaining 19 volunteers, it was found to be contrary. Based on these results, 50-67% of the population is e x p e c t e d to r e v e a l equal s e n s i b i l i t y , while in 19-35% superior sensibility will be found at the nondominant side. The dominant side is expected to have better sensibility in 9-21% of the population. Because the 95% confidence interval for 76 volunteers does not overlap that of the remaining 54 volunteers, they have in a statistically significant higher chance of the monofilament sensibility of the index on the dominant side equaling that of the nondominant side. In case there is a difference in sensibility between the two hands (n = 54), the chance that the nondominant hand is the more sensitive one (35 volunteers) is greater. Our conclusions are based on application of a 95% confidence interval for determining statistical significance. Applying 98% confidence intervals, our resuits do not reach significance. For this to happen, an even larger series is to be tested. Of the 260 tested index fingers, 148 experienced the light pressure threshold that corresponded with the 2.83 (nylon rod marker) filament. Thresholds ranged from 1.65 IOglo 0.1 mg to 3.84 lOgl0 0.1 mg
Number of fingers
1,50r
130
110
90
70
50
30
10
1.65 2.36 2.44 2.63 3.22 3.61 3.84
Nylon rod markings
Figure 1. Distribution of light pressure thresholds found in the 260 index fingers of 130 tested subjects.
The Journal of Hand Surgery / Vol. 20A No. 2 March 1995 and showed a normal distribution (Fig. 1). This distribution indicates that, as in most biological measurements, the upper limit of 'normality' is quite imprecise. Although the 2.83 loglo 0.1 mg threshold is used as the general cutoff, it should not be concluded that pressure thresholds above this limits are to be judged 'abnormal'. The same applies to the 'supernormal' sensibility scored in some of the volunteers in this study. In the 54 volunteers that experienced a difference of threshold between the two index fingers, this difference corresponded with only one nylon rod marker in 47. A difference of two nylon rod markers was found in 4. In the remaining 3 volunteers, a difference of three nylon rod markers was observed. In cases where the dominant index had superior sensibility (n = 19) the distribution of light touch t h r e s h o l d s was n o r m a l at the n o n d o m i n a n t side, while the dominant index showed better than normal sensibility. In cases where the nondominant hand was found to be more sensitive (n = 35), the dominant side scored 'normal' while the distribution of t h r e s h o l d s at the n o n d o m i n a n t side m o v e d o n e nylon rod marker downward. Hence, in the cases where there was a difference in sensibility between the t w o h a n d s (n = 54), the less s e n s i t i v e side showed a normal distribution of light touch thresh-
229
o l d s , w h e r e a s at the m o r e s e n s i t i v e side t h e s e t h r e s h o l d s usually s c o r e d o n e n y l o n r o d m a r k e r lower. Like Dellon, 1 but opposing the results found b y T h o r n b u r y and Mistretta, 5 we did not find variations related to the subject's sex or age.
References 1. Dellon AL. The moving two-point discrimination test: Clinical evaluation of the quickly-adapting fiber receptor system. J Hand Surg 1978;3:474-81. 2. Bell-Krotoski J, Tomancik E. The repeatability of testing with Semmes-Weinstein monofilaments. J Hand Surg 1987;12A: 155-61. 3. Ewing-Fess E. Documentation: essential elements of an upper extremity assessment battery. In: Hunter JM, Schneider LH, Mackin EJ, Callahan AD, eds. Rehabilitation of the hand. 2nd ed. St. Louis: Mosby, 1984: 49-78. 4. Bell-Krotoski JA. Light touch-deep pressure testing using Semmes-Weinstein monofilaments. In: Hunter JM, Schneider LH, Mackin EJ, Callahan AD, eds. Rehabilitation of the hand: surgery and therapy. 3rd ed. St. Louis: Mosby, 1990:585-93. 5. Thornbury JM, Mistretta CM. Tactile sensitivity as a function of age. J Gerontology 1981;36:34-9. 6. Jonge H de. Inleiding tot de medische statistiek, volume I. Groningen: Wolters-Noordhoff, 1963:218.