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Methods for estimating the proper length of a cane
1173
DEVICES
Methods for Estimating the Proper Length of a Cane Rajeswari Kumar, MD, Meng Cheng Roe, AID, Oscar U. Scremin, MD, PhD A B S T R A C T . Kumar R, Roe MC, Scremin OU. Methods for estimating the proper length of a cane. Arch Phys Med Rehabil 1995;76:1173-5.
Objective: To find a practical method of cane length measurement that achieves the elbow flexion of 20 ° to 30 ° . Design: Two standard methods of cane length measurements were compared. Method I: Length of the cane measured from the floor to the top of the greater trochanter. Method II: Length of the cane measured from the floor to the distal wrist crease. Using an adjustable cane, each individual was fitted according to the two methods, and elbow angle was measured after each adjustment. Cane length was also correlated with arm length and height. Participants: Fifty-two normal volunteers who were ambulatory without assistive devices. Results: Mean _+ SD of the elbow angle according to Method I and Method II was 44.8 _+ 11.8 and 25.4 + 6.1, respectively. A significant difference was found in the elbow angle between the two methods (unpaired two-tailed student t test, p = 5.910-18). O f the 52 volunteers, 4 (7.7%) measured according to method I and 49 (94.3%) measured according to method II showed the elbow angle between 20 ° and 30 ° . The ideal length of the cane (L) also can be determined by the formula L = H × .45 + .87 meters or A × .76 + .19 meters, where H is the height of the individual in meters and A is the arm length measured in meters. Conclusion: Ideally, cane length should be measured from the floor to the distal wrist crease. The length can also be determined using the above formulae. This is a US g o v e r n m e n t work. There are no restrictions on its use.
A N E S are among the most commonly prescribed ambulatory devices. They are helpful in unloading painful joints and in stabilizing the ambulation in patients with impaired balance.~'2 The degree of assistance they provide varies considerably from one patient to another. In 1967, Jebson 3 reported that a cane of ideal length should produce up to 30 ° of elbow flexion, " w h i c h allows the arm to lengthen and shorten at different phases of gait cycle." The current standard recommendation for prescription of a cane is that its ideal length should produce 20 ° to 30 ° of elbow flexion. 3'4 Although there are several guidelines for measuring the
C
From the Department of Physical Medicine and Rehabilitation, Veterans Affairs Medical Center, and Department of Medicine, University of California at Los AngeLes School of Medicine (Dr. Kumar); University of California at Los Angeles Multicampus Residency Program in Physical Medicine and Rehabilitation, Veterans Affairs Medical Center (Dr. Roe); and Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, and Department of Physiology, University of California at Los Angeles School of Medicine (Dr. Scremin). Submitted for publication January 17, 1995. Accepted in revised form May 23, 1995. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Rajeswari Kumar, MD, PM&R Service, W 117, West Los Angeles Veterans Affairs Medical Center, Wilshire and Sawtelle Boulevards, Los Angeles, CA 90073. This is a US government work. There are no restrictions on its use. 0003-9993/95/7612-338050.00/0
length of crutches in a clinical setting, the guideline for measurement of canes has been poorly defined. The elbow angle can be measured with a goniometer while the patient is being fitted with a cane; however, this is not a practical method in a clinical setting. One commonly used method for determining proper cane length is to measure the distance from the floor to the greater trochanter. 3'4 However, there is no documentation that this method provides the desired elbow flexion. The present study compared two methods of measuring cane length to determine which one produced elbow flexion of 20 ° to 30 ° and to develop guidelines for cane length measurement in a clinical setting.
METHODS Fifty-two normal volunteers who were ambulatory without assistive devices participated in this study. An adjustable cane was used for measurements. Two methods were used to determine cane length. M e t h o d 1. The person stood erect wearing comfortable, flat shoes. The length of the cane was adjusted so that the top of the cane corresponded to the top of the greater trochanter. The lower tip of the cane was placed at a point 6 inches lateral to the little toe. M e t h o d 2. The person stood with the arm hanging loosely close to the body. The cane length was adjusted so that the top of the cane was at the distal wrist crease. The lower tip of the cane was again placed at a point 6 inches lateral to the little toe. After adjustment of the cane, the person held the cane as if using it to walk, and the elbow angle was measured. To measure the angle, the center of the goniometer was placed in the lateral epicondyle. By palpating along the spine of the scapula, the acromion was localized. By palpating further laterally, the midpoint on the lateral end of the acromion was located. One arm of the goniometer was placed on the lateral aspect of the arm along the long axis of the humerus connecting this point on the acromion to the lateral epicondyle. The other arm of the goniometer was placed in the middle of the forearm. The actual length of the cane was measured after each adjustment using a tape measure. To find the relationship between arm length (A) and length of the cane (L), arm length was measured in 41 volunteers. To measure arm length, the individual stood erect with the arm in 90 ° of abduction and the elbow, wrist, and fingers in extension. The arm length was measured from the sternal notch to the tip of the middle finger. The height was measured in meters in 15 individuals. To measure the height, the person stood with comfortable, flat shoes in front of the scale. Because statistical analysis in 15 people showed no significant difference between the reported and measured height (Pearson correlation, r = .8011, p < .0001), only the reported height was recorded for the rest of the 37 individuals. Statistical analysis. An unpaired two-tailed student t test was used to compare the elbow angle between the two methods. Regression analysis was used to compare height and arm length with the cane length measured according to Method 2.
Arch Phys Med Rehabil Vol 76, December 1995
1174
ESTIMATING PROPER CANE LENGTH, Kumar
Occurrenl ;currences
20 16 12
Elbow
20 16 12 } Fig 1. The elbow angle obtained when cane length was measured according to method 1 (trochanter) and method 2 (wrist) (n = 52). Pooled value (men and women) of elbow angle with method 1 was significantly different from method 2 (unpaired two-tailed student ttest; p = 1.2 × 10 le).
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RESULTS Fifty-two volunteers with ages ranging from 22 to 78 years participated in the study. Mean age (mean ± SD) was 35.7 ± 11.12 for women and 45.04 ± 19.2 for men. There were 21 men and 31 women. Measurement of the elbow angle that resulted when cane length was determined according to method 1, ie, floor to the greater trochanter, showed that only 4 of 52 (7.7%) subjects had the elbow angle between 20 ° and 30 ° and the rest of the subjects had an elbow angle greater than 31 ° (fig 1). However, when cane length was determined according to method 2, ie, from the floor to the distal wrist crease, the resulting elbow angle was between 20 ° and 30 ° in 49 of 52 (94.3%) subjects, and only 3 of 52 (5.7%) had an elbow angle greater than 31 ° (fig 1). Regression analysis showed that age did not correlate with the resulting elbow angle (fig 2). Since there was no correlation between gender and the elbow angle 60 "~
(table 1), the data from both genders were pooled. Mean _ SD of the elbow angle according to method 1 was 44.8 + 11.8 (n = 52) and according to method 2 was 25.4 ± 6.1 (n = 52). There was a significant difference between the mean of the elbow angle between the two methods (unpaired two-tailed t test; p = 5.9 x 10 ,8) (fig 1). A significantly greater number of people achieved an appropriate elbow angle using method 2. Regression analysis showed that the length of the cane (L) can be determined from the formula L = A x .76 + .19m, where A is the a n n length measured from the sternal notch to the tip of the middle finger with the arm abducted at 90 ° and elbow, wrist, and fingers in extension (fig 3). Regression analysis also showed that the height of the individual is twice the length of the arm (Arm length [A] = .50 x H + .01m, where H is the height of the individual). Thus, a significant correlation was also found between the length of the cane and the height of the subjects. The length of the cane (L), therefore, can also be determined by the formula L = H x .45 + .087m (fig 4). DISCUSSION Canes are the most commonly prescribed walking aids. 2 They increase the base of support and reduce the fear of instability
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Table 1: Elbow Angle, Cane Length, Height, and Arm Length Measurements (n = 52)
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Fig 2. The relationship between age and elbow angle In = 52). The coefficient of the regression of the elbow angle on age, on age obtained by least squares method, was not statistically significantly different from zero.
Arch Phys Med Rehabil Vol 76, December 1996
Elbow angle (°) M1 (M) Elbow angle (°) M1 (F) Elbow angle (°) M2 (M) Elbow angle (°) M2 (F) Cane length (m) M1 (M) Cane length (m) M1 (F) Cane length (m) M2 (M) Cane length (m) M2 (F) Height (m) (M) Height (m) (F) Arm length (m) (M) Arm length (m) (F) Age (yr) (M) Age (yr) (F)
Mean
SD
Cl(U)
CI(L)
43,86 45.70 25.10 25.13 .94 .78 .87 .81 1.7 1.63 39 .83 35.71 45.05
10.10 12.51 4.71 6.39 .04 .05 .05 .05 .08 .08 .05 .04 11.12 19.26
48.45 50.33 28.10 27.47 .96 .90 .89 .83 1.78 1.66 .92 .81 40.03 53.82
39.26 41.15 23,80 22.78 .92 .87 .85 .79 1.70 1.60 .86 .81 31.40 36.28
There was no significant difference in any of the variables measured between genders. Abbreviations: CI(U), upper 95% confidence interval; CI(L), lower 95% confidence interval; M, men; F, women; M1, method 1; M2, method 2.
ESTIMATING PROPER CANE LENGTH, Kumar
in elderly people. 2 By using canes properly during ambulation, the weight-bearing forces in the lower extremity can be reduced. 1'2 Some patients, however, receive canes from friends or relatives, or choose them on their own. These canes may not provide proper support or unload a painful joint in the lower extremity. Many studies have determined force transmission t h r o u g h canes. 5-7 However, methods for proper determination of a cane's length have not been reported. One previous study showed that two thirds of elderly people used a cane that was too long. 8 Canes that are too long raise the shoulder and cause an increase in flexion of the elbow. Canes that are too short cause the user to lean toward the cane while standing, and lean forward while placing the cane forward when walking. 8 It is controversial whether walking devices that are not properly measured might contribute to falls in the elderly, s'9 With the application of instrumented crutches, canes, force platform, and special camera system, Opila and colleagues j° recorded the axial and shear forces on walking aids and limbs. The values were plotted as histograms. Recording of such forces with different walking aids in patients with different disabilities was reported to be beneficial in gait training and proper prescription of walking aidsJ ° However, expensive equipment, such as a force platform and a special camera system, was required. Jebsen 3 initially made the assumption that canes may be used to support 20% to 25% of body weight and canes of ideal length produce 20 ° to 30 ° of elbow flexion, in which case elbow extensors act as shock absorbers. Later studies using an instrumented cane proved that axial loading on the cane varies between 15% to 40% of body weight. 7'~° Static analysis of upper limb loading while using a cane showed that elbow joint force and muscle moment force at the elbow depend on the amount of flexion at the elbow. Muscle moment force at the elbow is provided by elbow extensors, which help to counteract the tendency of cane forces to induce elbow flexion. 2 If the cane is fitted with the arm in full extension, the muscle moment force at the elbow is negligible. This appears ideal for reducing the muscle moment force at the elbow. However, the patient who is fitted with the arm in full extension will lean forward to advance the cane while walking. Longer
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Fig 3. The relationship between arm length and cane length (n = 41). The parameters of regression equation of wrist to floor distance on arm length estimated by the least squares method were coefficient .76X + .17 (intercept = .19, • = .85).
1175
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HEIGHT
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Fig 4, The relationship between height and cane length (n - 52) as measured by wrist to floor (method 2). Parameters of regression equation of cane length by method 2 on height estimated by the least squares method were coefficient .45X + .087 (intercept = .087, • = .086).
canes cause an increase in elbow flexion, an increased demand on triceps, and an increase in muscle moment force at the elbow. The current recommendation agrees with the previous suggestion that the cane should provide 20 ° to 30 ° of elbow flexion. ~'2'4 The commonly used method for cane length measurement, however, has not been documented to provide 20 ° to 30 ° of elbow flexion. One previous study showed that there are discrepancies in the length of the cane measured when the cane is measured from the floor to the greater trochanter and when the cane is measured from the floor to the ulnar styloid process) Our study clearly shows that the conventional method of measuring the cane from the floor to the greater trochanter is not an effective method. The cane should be measured from the floor to the distal wrist crease to provide the expected elbow angle. W e have also developed other formulae for measurement of a cane in a clinical setting. The length of the cane can be calculated if a person's height or arm length is known, using the formula given above. References 1. Blount WP. Don't throw away the cane. J Bone Joint Surg Am 1956; 38A:695-708. 2. Deathe AB, Hayes KC, Winter DA. The biomechanics of canes, crutches, and walkers. Crit Rev Phys Rehabil Med 1993;5:15-29. 3. Jebsen RH. Use and abuse of ambulation aids. JAMA 1967; 199:63. 4. Ragnarson K. Orthotics and shoes. In: DeLisa JA, editor. Rehabilitation medicine: principles and practice. Philadelphia: Lippincott, 1988:310. 5. Murray MP, Seireg AH, Scholz RC. A survey of the time, magnitude and orientation of forces applied to walking sticks by disabled men. Am J Phys Med Rehabil 1969;48:1-13. 6. Edwards BG. Contralateral and ipsilateral cane usage by patients with total knee or hip replacements. Arch Phys Med Rehabil 1986;67:734-40. 7. Ely DD, Smidt GL. Effect of cane on variables of gait for patients with hip disorders. Phys Ther 1977;57:507-12. 8. Mully GP. Walking sticks. BMJ 1988;296:475-6. 9. Sainsbury R, Mulley GP. Walking sticks used by the elderly. BMJ 1982; 284:1751. 10. Opila KA, Nicol AC, Paul P. Forces and impulses during aided gait. Arch Phys Med Rehabil 1986;68:715-22.
Arch Phys Med Rehabil Vol 76, December 1995
DEVICES
Methods for Estimating the Proper Length of a Cane Rajeswari Kumar, MD, Meng Cheng Roe, AID, Oscar U. Scremin, MD, PhD A B S T R A C T . Kumar R, Roe MC, Scremin OU. Methods for estimating the proper length of a cane. Arch Phys Med Rehabil 1995;76:1173-5.
Objective: To find a practical method of cane length measurement that achieves the elbow flexion of 20 ° to 30 ° . Design: Two standard methods of cane length measurements were compared. Method I: Length of the cane measured from the floor to the top of the greater trochanter. Method II: Length of the cane measured from the floor to the distal wrist crease. Using an adjustable cane, each individual was fitted according to the two methods, and elbow angle was measured after each adjustment. Cane length was also correlated with arm length and height. Participants: Fifty-two normal volunteers who were ambulatory without assistive devices. Results: Mean _+ SD of the elbow angle according to Method I and Method II was 44.8 _+ 11.8 and 25.4 + 6.1, respectively. A significant difference was found in the elbow angle between the two methods (unpaired two-tailed student t test, p = 5.910-18). O f the 52 volunteers, 4 (7.7%) measured according to method I and 49 (94.3%) measured according to method II showed the elbow angle between 20 ° and 30 ° . The ideal length of the cane (L) also can be determined by the formula L = H × .45 + .87 meters or A × .76 + .19 meters, where H is the height of the individual in meters and A is the arm length measured in meters. Conclusion: Ideally, cane length should be measured from the floor to the distal wrist crease. The length can also be determined using the above formulae. This is a US g o v e r n m e n t work. There are no restrictions on its use.
A N E S are among the most commonly prescribed ambulatory devices. They are helpful in unloading painful joints and in stabilizing the ambulation in patients with impaired balance.~'2 The degree of assistance they provide varies considerably from one patient to another. In 1967, Jebson 3 reported that a cane of ideal length should produce up to 30 ° of elbow flexion, " w h i c h allows the arm to lengthen and shorten at different phases of gait cycle." The current standard recommendation for prescription of a cane is that its ideal length should produce 20 ° to 30 ° of elbow flexion. 3'4 Although there are several guidelines for measuring the
C
From the Department of Physical Medicine and Rehabilitation, Veterans Affairs Medical Center, and Department of Medicine, University of California at Los AngeLes School of Medicine (Dr. Kumar); University of California at Los Angeles Multicampus Residency Program in Physical Medicine and Rehabilitation, Veterans Affairs Medical Center (Dr. Roe); and Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, and Department of Physiology, University of California at Los Angeles School of Medicine (Dr. Scremin). Submitted for publication January 17, 1995. Accepted in revised form May 23, 1995. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Rajeswari Kumar, MD, PM&R Service, W 117, West Los Angeles Veterans Affairs Medical Center, Wilshire and Sawtelle Boulevards, Los Angeles, CA 90073. This is a US government work. There are no restrictions on its use. 0003-9993/95/7612-338050.00/0
length of crutches in a clinical setting, the guideline for measurement of canes has been poorly defined. The elbow angle can be measured with a goniometer while the patient is being fitted with a cane; however, this is not a practical method in a clinical setting. One commonly used method for determining proper cane length is to measure the distance from the floor to the greater trochanter. 3'4 However, there is no documentation that this method provides the desired elbow flexion. The present study compared two methods of measuring cane length to determine which one produced elbow flexion of 20 ° to 30 ° and to develop guidelines for cane length measurement in a clinical setting.
METHODS Fifty-two normal volunteers who were ambulatory without assistive devices participated in this study. An adjustable cane was used for measurements. Two methods were used to determine cane length. M e t h o d 1. The person stood erect wearing comfortable, flat shoes. The length of the cane was adjusted so that the top of the cane corresponded to the top of the greater trochanter. The lower tip of the cane was placed at a point 6 inches lateral to the little toe. M e t h o d 2. The person stood with the arm hanging loosely close to the body. The cane length was adjusted so that the top of the cane was at the distal wrist crease. The lower tip of the cane was again placed at a point 6 inches lateral to the little toe. After adjustment of the cane, the person held the cane as if using it to walk, and the elbow angle was measured. To measure the angle, the center of the goniometer was placed in the lateral epicondyle. By palpating along the spine of the scapula, the acromion was localized. By palpating further laterally, the midpoint on the lateral end of the acromion was located. One arm of the goniometer was placed on the lateral aspect of the arm along the long axis of the humerus connecting this point on the acromion to the lateral epicondyle. The other arm of the goniometer was placed in the middle of the forearm. The actual length of the cane was measured after each adjustment using a tape measure. To find the relationship between arm length (A) and length of the cane (L), arm length was measured in 41 volunteers. To measure arm length, the individual stood erect with the arm in 90 ° of abduction and the elbow, wrist, and fingers in extension. The arm length was measured from the sternal notch to the tip of the middle finger. The height was measured in meters in 15 individuals. To measure the height, the person stood with comfortable, flat shoes in front of the scale. Because statistical analysis in 15 people showed no significant difference between the reported and measured height (Pearson correlation, r = .8011, p < .0001), only the reported height was recorded for the rest of the 37 individuals. Statistical analysis. An unpaired two-tailed student t test was used to compare the elbow angle between the two methods. Regression analysis was used to compare height and arm length with the cane length measured according to Method 2.
Arch Phys Med Rehabil Vol 76, December 1995
1174
ESTIMATING PROPER CANE LENGTH, Kumar
Occurrenl ;currences
20 16 12
Elbow
20 16 12 } Fig 1. The elbow angle obtained when cane length was measured according to method 1 (trochanter) and method 2 (wrist) (n = 52). Pooled value (men and women) of elbow angle with method 1 was significantly different from method 2 (unpaired two-tailed student ttest; p = 1.2 × 10 le).
A
[u
RESULTS Fifty-two volunteers with ages ranging from 22 to 78 years participated in the study. Mean age (mean ± SD) was 35.7 ± 11.12 for women and 45.04 ± 19.2 for men. There were 21 men and 31 women. Measurement of the elbow angle that resulted when cane length was determined according to method 1, ie, floor to the greater trochanter, showed that only 4 of 52 (7.7%) subjects had the elbow angle between 20 ° and 30 ° and the rest of the subjects had an elbow angle greater than 31 ° (fig 1). However, when cane length was determined according to method 2, ie, from the floor to the distal wrist crease, the resulting elbow angle was between 20 ° and 30 ° in 49 of 52 (94.3%) subjects, and only 3 of 52 (5.7%) had an elbow angle greater than 31 ° (fig 1). Regression analysis showed that age did not correlate with the resulting elbow angle (fig 2). Since there was no correlation between gender and the elbow angle 60 "~
(table 1), the data from both genders were pooled. Mean _ SD of the elbow angle according to method 1 was 44.8 + 11.8 (n = 52) and according to method 2 was 25.4 ± 6.1 (n = 52). There was a significant difference between the mean of the elbow angle between the two methods (unpaired two-tailed t test; p = 5.9 x 10 ,8) (fig 1). A significantly greater number of people achieved an appropriate elbow angle using method 2. Regression analysis showed that the length of the cane (L) can be determined from the formula L = A x .76 + .19m, where A is the a n n length measured from the sternal notch to the tip of the middle finger with the arm abducted at 90 ° and elbow, wrist, and fingers in extension (fig 3). Regression analysis also showed that the height of the individual is twice the length of the arm (Arm length [A] = .50 x H + .01m, where H is the height of the individual). Thus, a significant correlation was also found between the length of the cane and the height of the subjects. The length of the cane (L), therefore, can also be determined by the formula L = H x .45 + .087m (fig 4). DISCUSSION Canes are the most commonly prescribed walking aids. 2 They increase the base of support and reduce the fear of instability
50
q)
40
.... ~ ...................... o ooo o o o ~ % o 0 O0 ~
~ 30 e< 20
~OoooOo
o
w
Table 1: Elbow Angle, Cane Length, Height, and Arm Length Measurements (n = 52)
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.
.
.
.
.
.
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10
I
20
40 Age
I
I
60
80
(years)
Fig 2. The relationship between age and elbow angle In = 52). The coefficient of the regression of the elbow angle on age, on age obtained by least squares method, was not statistically significantly different from zero.
Arch Phys Med Rehabil Vol 76, December 1996
Elbow angle (°) M1 (M) Elbow angle (°) M1 (F) Elbow angle (°) M2 (M) Elbow angle (°) M2 (F) Cane length (m) M1 (M) Cane length (m) M1 (F) Cane length (m) M2 (M) Cane length (m) M2 (F) Height (m) (M) Height (m) (F) Arm length (m) (M) Arm length (m) (F) Age (yr) (M) Age (yr) (F)
Mean
SD
Cl(U)
CI(L)
43,86 45.70 25.10 25.13 .94 .78 .87 .81 1.7 1.63 39 .83 35.71 45.05
10.10 12.51 4.71 6.39 .04 .05 .05 .05 .08 .08 .05 .04 11.12 19.26
48.45 50.33 28.10 27.47 .96 .90 .89 .83 1.78 1.66 .92 .81 40.03 53.82
39.26 41.15 23,80 22.78 .92 .87 .85 .79 1.70 1.60 .86 .81 31.40 36.28
There was no significant difference in any of the variables measured between genders. Abbreviations: CI(U), upper 95% confidence interval; CI(L), lower 95% confidence interval; M, men; F, women; M1, method 1; M2, method 2.
ESTIMATING PROPER CANE LENGTH, Kumar
in elderly people. 2 By using canes properly during ambulation, the weight-bearing forces in the lower extremity can be reduced. 1'2 Some patients, however, receive canes from friends or relatives, or choose them on their own. These canes may not provide proper support or unload a painful joint in the lower extremity. Many studies have determined force transmission t h r o u g h canes. 5-7 However, methods for proper determination of a cane's length have not been reported. One previous study showed that two thirds of elderly people used a cane that was too long. 8 Canes that are too long raise the shoulder and cause an increase in flexion of the elbow. Canes that are too short cause the user to lean toward the cane while standing, and lean forward while placing the cane forward when walking. 8 It is controversial whether walking devices that are not properly measured might contribute to falls in the elderly, s'9 With the application of instrumented crutches, canes, force platform, and special camera system, Opila and colleagues j° recorded the axial and shear forces on walking aids and limbs. The values were plotted as histograms. Recording of such forces with different walking aids in patients with different disabilities was reported to be beneficial in gait training and proper prescription of walking aidsJ ° However, expensive equipment, such as a force platform and a special camera system, was required. Jebsen 3 initially made the assumption that canes may be used to support 20% to 25% of body weight and canes of ideal length produce 20 ° to 30 ° of elbow flexion, in which case elbow extensors act as shock absorbers. Later studies using an instrumented cane proved that axial loading on the cane varies between 15% to 40% of body weight. 7'~° Static analysis of upper limb loading while using a cane showed that elbow joint force and muscle moment force at the elbow depend on the amount of flexion at the elbow. Muscle moment force at the elbow is provided by elbow extensors, which help to counteract the tendency of cane forces to induce elbow flexion. 2 If the cane is fitted with the arm in full extension, the muscle moment force at the elbow is negligible. This appears ideal for reducing the muscle moment force at the elbow. However, the patient who is fitted with the arm in full extension will lean forward to advance the cane while walking. Longer
1.2 "~ 1,1 q) E 1.0 •
o 0.9 IJ_
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0.6 .7
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Length ( m e t e r s )
Fig 3. The relationship between arm length and cane length (n = 41). The parameters of regression equation of wrist to floor distance on arm length estimated by the least squares method were coefficient .76X + .17 (intercept = .19, • = .85).
1175
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1.1 1.0
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,m
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1.6
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1.8
1.9
HEIGHT
(meters}
Fig 4, The relationship between height and cane length (n - 52) as measured by wrist to floor (method 2). Parameters of regression equation of cane length by method 2 on height estimated by the least squares method were coefficient .45X + .087 (intercept = .087, • = .086).
canes cause an increase in elbow flexion, an increased demand on triceps, and an increase in muscle moment force at the elbow. The current recommendation agrees with the previous suggestion that the cane should provide 20 ° to 30 ° of elbow flexion. ~'2'4 The commonly used method for cane length measurement, however, has not been documented to provide 20 ° to 30 ° of elbow flexion. One previous study showed that there are discrepancies in the length of the cane measured when the cane is measured from the floor to the greater trochanter and when the cane is measured from the floor to the ulnar styloid process) Our study clearly shows that the conventional method of measuring the cane from the floor to the greater trochanter is not an effective method. The cane should be measured from the floor to the distal wrist crease to provide the expected elbow angle. W e have also developed other formulae for measurement of a cane in a clinical setting. The length of the cane can be calculated if a person's height or arm length is known, using the formula given above. References 1. Blount WP. Don't throw away the cane. J Bone Joint Surg Am 1956; 38A:695-708. 2. Deathe AB, Hayes KC, Winter DA. The biomechanics of canes, crutches, and walkers. Crit Rev Phys Rehabil Med 1993;5:15-29. 3. Jebsen RH. Use and abuse of ambulation aids. JAMA 1967; 199:63. 4. Ragnarson K. Orthotics and shoes. In: DeLisa JA, editor. Rehabilitation medicine: principles and practice. Philadelphia: Lippincott, 1988:310. 5. Murray MP, Seireg AH, Scholz RC. A survey of the time, magnitude and orientation of forces applied to walking sticks by disabled men. Am J Phys Med Rehabil 1969;48:1-13. 6. Edwards BG. Contralateral and ipsilateral cane usage by patients with total knee or hip replacements. Arch Phys Med Rehabil 1986;67:734-40. 7. Ely DD, Smidt GL. Effect of cane on variables of gait for patients with hip disorders. Phys Ther 1977;57:507-12. 8. Mully GP. Walking sticks. BMJ 1988;296:475-6. 9. Sainsbury R, Mulley GP. Walking sticks used by the elderly. BMJ 1982; 284:1751. 10. Opila KA, Nicol AC, Paul P. Forces and impulses during aided gait. Arch Phys Med Rehabil 1986;68:715-22.
Arch Phys Med Rehabil Vol 76, December 1995