Injuries and disabilities associated with the lower limbs frequently result in impairment of ambulation, and this usually necessitates the recommendation of an ambulatory assistive device (e.g., cane, crutch, and walker) in an attempt to restore locomotor function.1–3 Ambulatory assistive devices provide advantages such as stability, support of muscle action, and reduction of the weight-bearing load placed on the affected or injured limb.4
One of the most commonly prescribed ambulatory devices is the axillary crutch, which allows patients to transfer as much as 100% of body weight to the arms and axillary region during swing gait.1,5,6 It is an orthopedic device created to reduce weight bearing when typical walking is compromised by mechanical or neurological disability such that the lower limbs are incapable of withstanding the stresses imposed by the conventional walking pattern, that is, walking without assistive devices.6–11
In Nigeria, physiotherapists prescribe an axillary crutch and help with the fitting and proper use of the axillary crutch.12,13 An axillary crutch is made in different lengths, and so the patient must be measured to obtain the correct axillary crutch length (ACL).14 Although it is generally assumed that there is one correct ACL (i.e., an ideal ACL) for each axillary crutch user, most users use estimated ACL, probably because axillary crutch fitting is often done on a trial-and-error basis using different methods until patients report comfort.10,15
Axillary crutch length estimation techniques vary widely because different estimation techniques were developed to decrease or eliminate the discomforts associated with determining the correct ACL for patients who are usually unable to achieve an upright position. Thus, these estimation procedures allow bedridden or acutely injured patients to be fitted for axillary crutches while positioned supine, seated, or within a parallel bar.15 Some of the different estimation techniques used to predict ideal ACL include 77% of patient's height, 75% of patient's height, patient's height minus 40.6 cm, 77% of patient's height with footwear (FW), 75% of patient's height with FW, patient's height with FW minus 40.6 cm, 77% of arm span, 75% of arm span, arm span minus 40.6 cm, olecranon to middle finger of other hand, anterior axillary fold (AAF) to the heel of the foot, AAF to the heel of the FW, AAF to 15.2 cm lateral to heel of the foot, and AAF to 15.2 cm lateral to heel of the FW.15–19 These different estimation techniques are reflections of the methods used, which range from measurement of potential user's heights with or without FW (i.e., foot-head linear [F-HL]), arm-span (A-S), and foot-AAF (F-AAF) techniques.10,15,19 Different authors have proposed different estimations of the ideal ACL: 77% of the users' height, distance from the user's AAF to a point 15.2 cm (6 in) lateral to the heel of the foot (lateral edge of the foot), and actual height minus 40.6 cm.10,15,19 However, there is a consensus on what constitute an ideal ACL. The measurement of an ideal ACL is proposed to be taken when the potential user is in relaxed upright posture (on both lower limbs), with a distance of 3.8 to 5.1 cm (1.5–2 in) below the AAF of the shoulder to a point 10.2 to 15.2 cm (4–6 in) anterior and lateral to the fifth toe of the ipsilateral limb.10,15,19,20 Unfortunately, most potential users of an axillary crutch cannot stand on both lower limbs for axillary crutch fitting; therefore, estimation is usually required to predict the ideal ACL. According to Bauer et al.,15 clinical experience has shown that an increase in axillary distance to 6.4 cm (2.5 in) is better tolerated by most patients. Monahan21 also submitted that an axillary crutch should be adjusted for the patient so that there is a 3-fingerbreadth space between the axillary pad of the axillary crutch and the axilla when the tip of the axillary crutch is located slightly lateral and anterior to the tip of the fifth toe with the feet side by side.
The potential problems that may arise from the use of an axillary crutch are prominence in the hand, arm, and axilla.22,23 Excessive axillary weight bearing during axillary crutch use may increase axilla reaction forces 7-fold, thereby contributing to the development of neurovascular impairments, axillary artery stenosis, aneurysm formation, secondary thromboembolic disease, pain, discomfort, radial nerve compression, suprascapular neuropathy, and high ulna neuropathy with conduction block in motor and sensory fibers.9,24,25 These problems are due largely to either improper use of the crutches or use of wrong ACL.12,26
The importance of identifying a technique/method that best predicts the ideal ACL cannot be overemphasized. An incorrect adjustment of an axillary crutch may result in early fatigue, frustration, and even a fall. It has been reported that an axillary crutch that is too long decreases the user's ability to handle and use it safely, while an axillary crutch that is too short causes users (patients) to assume poor posture.19 Therefore, this study was designed to determine the method of measurement of ACL that best predict ideal ACL.
A total number of 250 apparently healthy individuals (150 male and 100 female) participated in this analytical cross-sectional study. They were students of the College of Medicine and Faculty of Pharmacy, University of Lagos, Lagos, Nigeria. The participants for this study were selected based on a sample of volunteers, where participants from the College of Medicine and Faculty of Pharmacy of University of Lagos were approached. Only those who volunteered were recruited into the study.
Before the commencement of the study, ethical approval was sought and obtained (reference number ADM/DCST/HREC/221/404) from the research and ethics committee of the Lagos University Teaching Hospital, Lagos, Nigeria. Participants were informed about the procedures and purpose of the study, and their informed consent was sought before participating in the study. Participants with any musculoskeletal abnormalities such as obvious limb-length discrepancy (LLD) above 2.5 cm (1 in) caused as a result of congenital abnormality or trauma at either the upper or lower limbs that could make bilateral symmetrical fixing of axillary crutches impossible and those who did not meet the height requirement of 162 to 192 cm (i.e., 5 ft 4 in to 6 ft 4 in) for the adult axillary crutch15,19 were excluded.
Each participant's weight and height were measured using a portable weighing scale (Hana, China) and an adapted horizontal height meter that were previously calibrated. Body mass index (BMI) was calculated for each participant using the formula of weight in kilograms divided by the square of height in meters.
The measurements for the research protocol consisted of four stations: station 1 involved F-HL technique. The participants' height with and without FW (standard FW used was 1.3 cm; i.e., 0.5 in) were measured and recorded. There are six different methods of ACL estimation under the foot-head category, calculated as follows: 77% of participant's height without FW, 75% of participant's height without FW, 40.6 cm subtracted from participant's height without FW, 77% of participant's height with FW, 75% of participant's height with FW, and 40.6 cm subtracted from participant's height with FW.
Station 2 involved the A-S technique. The participants were positioned against an adapted horizontal height meter (Figure 1), and the distance from the tip of the middle finger of one hand to the tip of the middle finger of the other hand was measured. Of the four methods of ACL estimation, three were calculated using the initial measurement. These are 77% of the participant's arm span, 75% of the participant's arm span, and subtracting 40.6 cm from participant's arm span. The fourth method of ACL estimation using the A-S technique involves measurement from the olecranon of the elbow of one hand to the middle finger of the other hand.
Station 3 involved the F-AAF linear technique; the participants were requested to assume an upright standing position, and the following measurements were taken and recorded: 1) the AAF to the heel of the foot, 2) AAF to the heel of the FW, 3) AAF to 15.2 cm lateral to the heel of the foot, and 4) AAF to 15.2 cm lateral to the heel of the FW.
In station 4, ideal ACL was measured for each of the participants using a pair of adjustable axillary crutches (Figure 2) by requesting them to stand (on FW) with their feet at 10 cm distance apart and their shoulders relaxed. The crutch tip was placed 15.2 cm laterally and anteriorly from the fifth toe using a measured template and a distance of 3 fingerbreadths, which is approximately 6.4 cm (2.5 in) between the top of the foam-rubber axillary pad and the axillary fold. All measurements were recorded to the nearest 0.1 cm.
Data were analyzed using the Statistical Package for Social Sciences (SPSS) version 17.0 and summarized using descriptive statistics of mean, standard deviation, minimum, and maximum. Independent t-test was performed on baseline statistics of age and physical characteristics of the participants. Pearson product-moment correlation coefficient (r) was used to determine the degree to which each of the 14 different ACL estimates is associated with the ideal ACL and linear regression equations were developed for each technique. Level of significance was set at P < 0.01.
A total of 250 apparently healthy individuals (age range, 18–32 years) with a mean age of 21.22 years (±2.46 years) participated in this study. Independent t-test showed that there was significant difference between males and females at baseline except age and BMI (Table 1).
The mean value of ideal ACL as measured in this study is 131.52 cm (±5.79 cm) (Table 2). However, the mean values of ACL estimates obtained by the four methods of ACL estimation under the F-AAF were not as close to the ideal ACL as the values obtained under A-S techniques (Table 2). All the six different methods of ACL estimates under the F-HL technique produced mean values that were close to the mean value of the ideal ACL, with the measurement height minus 40.6 cm producing the mean estimated ACL value (131.31 cm [±7.06 cm]) nearest to the ideal ACL (Table 2). The four methods of ACL estimation under the A-S technique category produced mean values that were farthest from the mean value of the ideal ACL, with the measurement of arm span minus 40.6 cm producing an ACL estimate (140.19 cm [±9.68 cm]) farthest from the ideal ACL (Table 2).
The Pearson product-moment correlation coefficient showed that the ideal ACL strongly and significantly correlates with each of the 14 estimated ACL (P < 0.01), with the measurement “AAF 15.2 cm lateral to the heel of the FW” having the strongest correlation (r = 0.968, P = 0.00) with the ideal ACL, while the measurement “olecranon of one elbow to middle finger of other hand” had the least correlation (r = 0.835, P = 0.00) with the ideal ACL (Table 3).
Linear regression equations computed by regression of ideal ACL with height, height with FW, and arm span are y = 0.779x − 2.5 cm, y = 0.779 – 3.5 cm, and y = 0.507x + 39.9 cm, respectively (Table 4). The F-AAF linear techniques equation results produced the least amount of mean squared error (MSE), while A-S techniques equation results produced the greatest MSE (Table 4). Anterior axillary fold to 15.2 cm lateral to the heel of the FW had the least MSE (2.142 cm2) and olecranon to MF of other hand had the greatest MSE (10.196 cm2).
This study sought to determine the method of ACL estimation that best predicts ideal ACL. The study considered 14 different methods of ACL under three techniques of measurement: six F-HL techniques, four A-S techniques, and four F-AAF techniques.
The findings of this study showed that there was a strong correlation between the ideal ACL and each of the 14 different methods of ACL estimates. This implies that any of the 14 methods may be used to estimate ACL. This finding is in agreement with the findings of previous studies: Bauer et al. 15 compared nine different methods of estimating ACL against the ideal ACL and found a correlation between each of them and the ideal ACL; Adegoke and Maruf19 compared eight different methods of estimating ACL against the ideal ACL and found a correlation between the ideal ACL and each of the methods; and Amaeze and Okoye10 compared three different methods of estimating ACL against the ideal ACL and found a correlation between the ideal ACL and each of these methods.
The outcomes of this study demonstrated that the six different methods under F-HL technique category produced a mean ACL value, which is close to the mean ideal ACL value, while the four different methods under A-S techniques produced a mean ACL value, which is far from the ideal ACL mean value. This finding is corroborated by Adegoke and Maruf,19 who in their study on the predictive ability of crutch-length-estimation techniques in apparently healthy university undergraduates reported that the F-HL techniques had mean values close to the ideal ACL mean value while the A-S techniques produced mean ACL values that were far from the ideal ACL mean value.
The Pearson product-moment correlation coefficient and linear regression further revealed that the different methods of ACL estimation under the A-S techniques poorly predicted the ideal ACL, with the measurement from the olecranon of one elbow to middle finger of other hand having the least predictive value and greatest MSE for ideal ACL. This finding is in line with the trend in the literature and agrees with the findings of Adegoke and Maruf16 and Bauer et al.,15 who also reported that measurement from olecranon of one elbow to middle finger of other hand poorly predicted the ideal ACL.
Interestingly, anecdotal evidence suggests that the A-S technique methods of ACL estimate is a commonly used method in Nigeria. The finding of this study supports the use of the F-HL technique of ACL estimation, particularly 77% of height. The finding that the F-HL technique is closest to the ideal ACL value implies that patient's height can be considered when prescribing axillary crutches. Thus, the measurement of patient's height can be considered when prescribing axillary crutches for rehabilitation purposes.
Pearson product-moment correlation coefficient also revealed that measurement from AAF to a point 15.2 cm lateral to the heel of the FW best predicts the ideal ACL as this had the highest correlation with the ideal ACL (r = 0.967) and this accounted for 93.7% of the percentage variation between the two variables (i.e., the measurement from AAF to 15.2 cm lateral to the heel of FW and ideal ACL). Thus, the measurement of AAF to 15.2 cm lateral to the heel of the FW had the least difference from the ideal ACL (MSE = 2.142). This finding agrees with the finding of Adegoke and Maruf,19 who also reported that measurement from AAF to a point 15.2 cm lateral to the heel of the foot best predicts the ideal ACL, but the percentage variation recorded in this present study was less when compared with the 86% variation obtained by Adegoke and Maruf.19 The difference may be due to the slight difference in the methodology. Participants in the present study were measured with a tape measure from AAF to a point 15.2 cm lateral to the heel of the FW to get their ACL estimates, while Adegoke and Maruf19 carried out their measurements by adjusting the axillary crutch from the AAF to the heel of the foot. However, the finding of this study disagrees with the finding of the studies by Bauer et al.15 and Amaeze and Okoye,10 who in their study reported that 77% of height was the best predictor of ideal ACL, accounting for 91% and 89% variations, respectively. In these two studies, participants were measured in supine position for F-AAF technique, while in this present study, measurement was done with the participants in standing posture with FW. This may be responsible for the observed differences between the findings of the present study and those of Bauer et al.15 and Amaeze and Okoye.10
Regression analysis was used to derive equations for ACL: F-AAF technique had the least MSE, supporting our findings that F-AAF best predicts ACL. In addition, the finding that the A-S techniques had the most MSE also support our findings that A-S techniques is a predictor of ideal ACL. Regression analysis was also used for the height of the subjects and the outcome revealed that height with the FW had the least MSE with equation being 77.9% and subtracting 3.5 cm (MSE = 3.223 cm2). The MSE finding for height from this study was in agreement with the findings of the studies by Bauer et al.15 who reported an MSE of 3.23 cm2 for self-reported height.
All the six methods of measurement of ACL under F-HL techniques did well in predicting the ideal ACL. Of the four AAF techniques, measurement from AAF to a point 15.2 cm lateral to the heel of the FW was the best predictor of the ideal ACL (the type of FW used by the patient should be considered in predicting ACL). However, all four methods of measurement of ACL under the A-S technique poorly predicted the ideal ACL. Of the methods of measurement under A-S technique, measurement from olecranon of one elbow to middle finger of other hand was the poorest predictor of the ideal ACL. It is therefore recommended that measurement from AAF to a point 15.2 cm lateral to the heel of the FW should be used to predict ideal ACL rather than measurement from olecranon of one elbow to middle finger of other hand, which seems to be commonly used in physiotherapy and other health care clinics across Nigeria.
The authors wish to thank the participants—students from the College of Medicine of the University of Lagos—for consenting to participate in this study.
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