- Email: [email protected]
Validation of a Method to Assess Range of Motion of the Cervical Spine Using a Tape Measure
VALIDATION OF A METHOD TO ASSESS RANGE OF MOTION OF THE CERVICAL SPINE USING A TAPE MEASURE Stephen E. Asha, MBBS, MMed(Clin Epi), a, b and Richard Pryor, MD a
ABSTRACT Objective: The purposes of this study were to validate a tape measure method for measuring cervical spine range of motion compared with a universal goniometer in all planes of motion and to derive equations to convert a linear measurement to an angular distance. Methods: Participants were healthy volunteers. Measurements of flexion/extension, rotation, and lateral flexion were made with the universal goniometer and tape measure, in the neutral position, extreme of motion, and 2 positions between. Measurements from the 2 techniques were compared with Pearson correlation coefficient and simple linear regression to determine R 2, the regression coefficient and the regression equation. Reliability was assessed using the intraclass correlation coefficient. Results: There were 40 participants with a mean age of 30.5 (SD, 9.1) years. Goniometer measurements had good to excellent correlation with both absolute and percentage change in tape measurement (correlation coefficients, 0.740.94 and 0.75-0.91, respectively). Correlation was highest for flexion and extension, lowest for rotation and lateral flexion. The amount of variability in the data explained by the linear regression models (R 2) varied from 55% to 89%. Intraclass correlation coefficient ranged from 0.44 to 0.69 and 0.38 to 0.59 for intrarater and interrater reliability, respectively. Reliability was greatest for flexion and extension, lowest for rotation and lateral flexion. Conclusion: This study demonstrated that tape measurements correlated well with a universal goniometer. The tape measure may be useful for measuring cervical spine range of motion where availability, simplicity, and low cost are important considerations such as with conduct of research or patient management. (J Manipulative Physiol Ther 2013;36:538-545) Key Indexing Terms: Arthrometry, Articular; Range of Motion, Articular; Neck; Cervical; Reproducibility of Results
easuring the range of motion of the cervical spine is important for both clinical and research applications. In both these settings, an accurate and reproducible method for measuring the range of motion of the cervical spine is necessary to quantify injury/disease, the response to an intervention, or residual disability. There are various methods available to measure neck movement including visual estimation, goniometry, inclinometry, radiography, and video tracking, 1,2 with radiog-
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a Physician, Emergency Department, St George Hospital, Kogarah, NSW, Australia. b Conjoint Lecturer, Faculty of Medicine, University of New South Wales, Kensington, NSW, Australia. Submit requests for reprints to: Stephen E. Asha, MBBS, FACEM MMed(Clin Epi), c/o Emergency Department, St George Hospital, Gray St, Kogarah, NSW 2217, Australia. (e-mail: [email protected]). Paper submitted February 5, 2013; in revised form July 29, 2013; accepted July 29, 2013. 0161-4754/$36.00 Copyright © 2013 by National University of Health Sciences. http://dx.doi.org/10.1016/j.jmpt.2013.07.005
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raphy the accepted reference standard. 3 The cervical range of motion goniometer has been validated in reference to radiographic studies, 4-6 and the universal goniometer has been shown to be similarly reliable. 3 The universal goniometer consists of 2 arms connected at a point allowing rotation of the arms and incorporating a protractor so that angular distance between the arms can be measured. However, these methods are limited in their practical application in a clinical setting as they can be cumbersome, time consuming, or relatively expensive; involve exposure to radiation; or require specialist training. The use of a simple tape measure as a tool to assess cervical range of motion is attractive for its simplicity, availability, and very low cost, especially in the settings of a busy clinic, hospital ward, or emergency department (ED) where a goniometer or other measurement tool is rarely on hand for use. There have been previous studies evaluating the use of a tape measure as a means to assess cervical range of motion. 3,7,8 However, the information from these studies is limited, as they have only assessed selected cervical movements (rather than all of flexion/extension, rotation, and lateral flexion), they have used absolute distances rather
Journal of Manipulative and Physiological Therapeutics Volume 36, Number 8
than assessing a proportionate change in distance, and none have determined if a linear measurement can be converted to an angular distance. Each study also uses different landmarks from which to make linear measurements, making it difficult to compare results between studies. Using the absolute linear measurement is a potential problem because body size may be a confounder of tape measure methods 9, and the proportionate change in linear measure may be less influenced by body size. 10 Our aim was to establish a measure cervical spine range of motion where availability, simplicity, and low cost are important. Therefore, the purpose of this study was to validate a tape measure method of measuring cervical spine range of motion, using the universal goniometer as the reference standard, in all planes of motion (flexion/ extension, rotation, and lateral flexion). Secondary aims were to assess the reliability of the technique by determining the intrarater and interrater reliability and to derive equations to convert a linear measurement to an angular distance.
METHODS Study Setting and Population The study was conducted in the ED of a tertiary referral hospital located in Sydney, New South Wales, Australia, during November 2012. Participants were a convenience sample of healthy volunteers sourced from among the staff employed in the ED. Permission for the study was granted by the human research ethics committee of South Eastern Sydney Local Health District (Northern Sector). Written informed consent was obtained from all participants.
Study Protocol Measurements of all 6 neck movements (flexion/extension in the sagittal plane, rotation left and right, lateral flexion left and right) were made with each technique (universal goniometer and tape measure). For each movement, a measurement was first made in the neutral position, at the extreme of motion, and 2 positions in between chosen arbitrarily by the participant. The purpose of the additional “in between” measurements was to obtain data points across the full spectrum of the range of motion to demonstrate the linear (or otherwise) nature of the relation between the 2 variables. This would allow the results to be applied to people with limited range of motion, only able to move a fraction of the range of motion achieved by healthy volunteers. At each position, a measurement was taken using both methods, and the method of measurement to be used first was randomly assigned for each participant. The randomization sequence was generated using a random number table. All measurements were made by a single examiner. To determine the intrarater and interrater reliability, the primary examiner repeated measurements at the extreme of
Asha and Pryor Tape Measure Range of Motion
the range of motion for each movement on half the participants, and a second examiner took measurements at the extreme of the range of motion for each movement on the remaining participants, respectively.
Measurements Participants were instructed to sit in a straight back chair looking forward, arms relaxed and resting on the thighs, their back resting against the chair, and their teeth gently clenched. Participants were asked to keep their shoulders still during all the measurements. For measurements using the tape measure, we used a previously described method. 11 Flexion and extension were measured from sternal notch to tip of chin. Rotation was measured from the tip of the chin to the most lateral palpable bony point on the tip of the shoulder opposite to the direction of neck movement (ie, if measuring rotation to left, measurements were made from the tip of the right shoulder). Lateral flexion was measured from the tragus of the ear to the tip of the shoulder both on the same side as the direction of neck movement (ie, if measuring left lateral flexion measurements were made from the tip of the left shoulder to the left tragus). For measurements using the universal goniometer, we used a previously described method. 12 For flexion and extension measurements, the examiner stood to the side of the participant, the axis of the goniometer was centered over the external acoustic meatus, the fixed arm was held vertical, while the movable arm was aligned with the base of the nares. Lateral rotation was measured with the examiner standing behind and looking down at the top of the participants head. The goniometer's axis was centered on the vertex of the participant's head, the fixed arm aligned parallel to an imaginary line between the participant's acromion processes, and the movable arm aligned with tip of the participant's nose. Lateral flexion was measured with the examiner in front of the participant, the axis of the goniometer positioned over the center of the participant's sternal notch, the fixed arm aligned parallel to an imaginary line between the participant's acromion process, and the movable arm aligned with the tip of the subject's nose. These measurement methods are illustrated in Figure 1.
Statistical Methods The distance measured with a tape measure is likely dependent not only on the range of motion but also on the overall size of the person, and so, the proportional change in distance may be more useful than the absolute measurement. To determine which linear measurement (absolute or proportionate) correlated best with the universal goniometer, comparisons were conducted using the change in linear measurement from the neutral position and the change in
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Fig 1. Positioning of the tape measure and universal goniometer for measurement of cervical range of motion. linear measurement as a percentage of the neutral measurement. For the purposes of the analysis, the data for rotation to the left and right sides were combined and analyzed as a single data set, as were the data for lateral flexion to the left and right side. The data were analyzed in a correlation matrix to determine Pearson correlation coefficient. Where the relationship between the 2 variables was demonstrated to be linear, simple linear regression was used to obtain R 2, the regression coefficient with 95% confidence intervals (CI), and the regression equation to enable the conversion of a linear measurement into an angular measurement. R 2 can be interpreted as the proportion of the total variation that can be accounted for by linear regression. The regression coefficient is an estimate of the average increase in angular measurement for a 1-unit increase in the linear measurement. This analysis was conducted using SAS statistical software version 9.2 (SAS Institute, Cary, NC).
Interrater and intrarater reliability of the linear measurements was calculated using the intraclass correlation coefficient (ICC). This analysis was conducted using IBM SPSS statistics version 20 (IBM Corp, Armonk, NY). The ICC can be interpreted as follows: 0 to 0.3 indicates poor agreement; 0.3 to 0.5, fair agreement; 0.5 to 0.7, moderate agreement; 0.7 to 0.8, strong agreement; and N 0.8, almost perfect agreement. 13 To estimate the number of participants required for this study where we planned to regress the values of the goniometer against the linear measurements, we first obtained estimates from the literature for the following measurements: • Mean and SD of linear measurements for lateral rotation expressed as a proportion of the measurement in the neutral position. This was 0.39 and 0.10, respectively. 10 • Mean and SD for angular measurements of lateral rotation. This was 56.44° and 19.85°, respectively. 7 • An estimate of the slope of the regression line, calculated from the above values to be 144.7.
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Asha and Pryor Tape Measure Range of Motion
Fig 2. Plots of goniometer measurements against percentage change in tape measurements. (Color version of figure is available online.) The sample size calculation also required a value for the correlation coefficient that would be acceptable to validate the tape measure method. A correlation coefficient between 0.25 and 0.50 suggests a fair relationship, values from 0.50 to 0.75 suggest a good relationship, while a correlations of 0.75 or greater suggests an excellent relationship between the 2 variables. 14 We prespecified that the minimum acceptable correlation coefficient would need to be 0.5 or greater. Based on these estimates and using an α level of 0.05, a minimum of 34 subjects would be required to reject the null hypothesis that there is no correlation between the 2 variables with a power of 90%. This analysis was conducted using PS power and sample size calculations version 3 (http://biostat.mc.vanderbilt.edu/wiki/Main/ PowerSampleSize).
RESULTS We enrolled 40 participants in the study. A complete set of data was available for all participants. Sixteen participants (40%) were male, the mean age was 30.5 years (SD, 9.1 years), and the mean body mass index (BMI) was 23.8 (SD, 3.6).
Figures 2 and 3 are scatter plots of cervical range of motion in angular distance plotted against the linear measurements. These demonstrate a linear relationship between these variables. Goniometer measurements of flexion, extension, rotation, and lateral flexion had good to excellent correlation with both the absolute change and the percentage change in tape measurement, with correlation coefficients ranging from 0.74 to 0.94 and 0.75 to 0.91, respectively (Tables 1 and 2). Correlation was highest for flexion and extension and lowest for rotation and lateral flexion. The amount of variability in the data that can be explained by the linear regression models, as described by the value of R 2, varied from 55% to 89% (Table 1 and 2). The regression coefficients for the simple linear regression models and their 95% CI are also presented in Tables 1 and 2. Using the values of the intercept and the regression coefficients from regression models, equations were derived to enable conversion of a tape measurement to an angular distance for each of flexion, extension, rotation, and lateral flexion. These are presented in Table 3. Twenty participants had repeat measurements for testing intrarater reliability, and the remaining 20 participants had repeat measurements for testing interrater reliability. This
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Fig 3. Plots of goniometer measurements against absolute change in tape measurements. (Color version of figure is available online.) Table 1. Correlation of goniometer measurements to percentage change in tape measurement
Flexion Extension Rotation Lateral flexion
Correlation coefficient
P
0.91 0.82 0.78 0.75
b.001 b.001 b.001 b.001
R2 (%)
Regression coefficient (95% CI)
P
83 68 61 56
0.66 (0.61-0.71) 0.66 (0.58-0.74) 1.55 (1.39-1.70) 0.80 (0.71-0.90)
b .001 b .001 b .001 b .001
ranged from fair to moderate with values for the ICC varying from 0.44 to 0.69 and 0.38 to 0.59 for intrarater and interrater reliability, respectively (Table 4). Reliability was greatest for flexion and extension and lowest for rotation and lateral flexion.
DISCUSSION This study demonstrated that the tape measure as a tool to measure cervical spine range of motion has good to excellent correlation when compared with a universal
goniometer. This correlation was best for the movements of flexion and extension, and the high correlation was true for both the absolute change in linear measurements as well as the proportionate change in linear measurement. As the relationship between the 2 methods of measurement was linear, equations were derived that enabled linear measurements to be converted into angular units. As a linear measurement is difficult to conceptualize as a descriptor for cervical spine motion, these equations may be of use to researchers who have conducted research using the tape measure, allowing presentation of results in angular units, which is more straightforward for readers to understand. This ability to make conversions will also allow comparisons to be made with other research conducted using angular measurement instruments. The reproducibility of measuring at the extreme of the range of cervical spine motion when repeated by the same observer or a different observer using the tape measure demonstrated variability in these measurements. The ICC, which was used to assess this reproducibility, was best for the movements of flexion and extension, where it was rated as moderate and fair for the movements of rotation and
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Asha and Pryor Tape Measure Range of Motion
Table 2. Correlation of goniometer measurements to absolute change in tape measurement
Flexion Extension Rotation Lateral flexion
Correlation coefficient
P
0.94 0.86 0.79 0.74
b .001 b .001 b .001 b .001
Table 3. Equations to convert tape measurements to range of motion in degrees Flexion
R2 (%)
Regression coefficient (95% CI)
P
89 73 62 55
0.52 (0.49-0.56) 0.60 (0.53-0.66) 0.63 (0.57-0.70) 0.38 (0.34-0.43)
b.001 b.001 b.001 b.001
lateral flexion. An important factor that probably contributed to the relatively low scores for reproducibility was participant compliance. An observation made by the investigators during the study was that holding the head at the extreme of motion was frequently uncomfortable for participants. As a result of this experience, participants tended to choose a slightly reduced position for the extreme of the range of motion for the repeated measure resulting in the observed variability in these measurements. This research is a valuable addition to existing knowledge in this area, as it provides a thorough validation of the tape measure in all 3 planes of motion for the cervical spine and over the full range of these movements (not just the extremes of movement), in contrast to previous research where only selected movements have been studied. 3,7,8 We also found much better agreement with the reference standard than was found in some of these studies. 3,8 In contrast, other studies have found the interrater reliability of the tape measure method to be better than that suggested by our investigations. 7 Although the cervical range of motion goniometer or the universal goniometer would provide the most reliable measurements, our results indicate that the tape measure is a useful tool to measure cervical spine range of motion and provides a good compromise in the ED or outpatient clinic setting where the principals of simplicity, ease of use, and cost are important considerations for the successful conduct of research. The performance of the tape measure is best for the movements of flexion and extension for both correlations to the universal goniometer and the reproducibility of the measurements. An important question to ask is: why not use the universal goniometer, which also satisfies these requirements? It is the experience of the researchers and physiotherapists at this institution that the major drawback to the universal goniometer is the ease with which it is misplaced or purloined, in contrast to the availability of disposable paper tape measures. An additional benefit of disposable paper tape measures is from an infection-control perspective. The nondisposable nature of the goniometer renders it a potential fomite for the transmission of infections between patients. It was an unexpected finding that the correlation of the tape measure with the universal goniometer was virtually the same for absolute changes and proportionate changes in
Extension
Rotation
Lateral flexion
Range of motion in degrees = − 0.54 + 0.66 × (percent change in linear measure) Range of motion in degrees = − 0.37 + 0.52 × (absolute change in linear measure) Range of motion in degrees = 5.21 + 0.66 × (percent change in linear measure) Range of motion in degrees = 3.69 + 0.60 × (absolute change in linear measure) Range of motion in degrees = 12.8 + 1.55 × (percent change in linear measure) Range of motion in degrees = 12.5 + 0.63 × (absolute change in linear measure) Range of motion in degrees = 7.31 + 0.80 × (percent change in linear measure) Range of motion in degrees = 7.37 + 0.38 × (absolute change in linear measure)
linear measurements. We had predicted that correlation with the proportionate change in linear measurements would be better based on the results of a previous study, which found that differences in body size had an important influence on absolute linear measurements. 10 A possible explanation for this is that discrepancies in absolute linear measurement may only arise at extremes of height or weight, which was not captured in our sample that had a relatively small SD in the BMI. Our results, therefore, may not be applicable to people with very high or very low BMIs. Although our results are promising for the use of the tape measure, our study was carried out among healthy participants. It is possible that the disease of the cervical spine may alter the mechanics of cervical spine motion. We recommend that further research into the tape measure should focus on similar validation methodology among a patient population with diseases affecting cervical spine mobility.
LIMITATIONS There were several other limitations to our study. It would have been optimal to validate the tape measure against the ideal criterion standard of radiography; however, we chose not to use this due to funding limitations and ethical concerns regarding the exposure of healthy volunteers to radiation. The applicability of these results to the extremes of age may be limited as the sample consisted largely of adults younger than 50 years, and no children were enrolled in the study. The study population consisted of healthy and cooperative volunteers sourced from ED staff, which may also affect the generalizablity to the population as a whole. Accurate measurement depended on participant compliance in remaining still during the arbitrary positions between neutral and full range of motion and avoiding shoulder movement when measuring lateral flexion, and this may have affected our measurements of correlation. The measurements of intrarater and interrater
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Table 4. Intrarater and interrater reliability of tape measurements Intrarater reliability Flexion Extension Rotation Lateral flexion Interrater reliability Flexion Extension Rotation Lateral flexion
ICC
95% CI
P
0.56 0.69 0.44 0.56
0.18-0.80 0.38-0.87 0.15-0.66 0.31-0.74
.004 b.001 .002 b.001
0.59 0.58 0.38 0.44
0.22-0.82 0.21-0.81 0.08-0.61 0.16-0.66
.002 .002 .007 .002
ICC, intraclass correlation coefficient.
reliability may be underpowered given that only half the participants were used for each of these calculations.
CONCLUSION Measurements made with a tape measure correlated well with the universal goniometer, and this correlation was best for the movements of flexion and extension. The high correlation was true for both the absolute change in linear measurements as well as the proportionate change in linear measurement. The tape measure may be a useful tool for measuring cervical spine range of motion in the setting where the principals of simplicity, ease of use, and cost are important considerations such as in the conduct of research and patient management.
Practical Applications • Measurements of cervical range of motion made with a tape measure correlated well with the universal goniometer, and this correlation was best for the movements of flexion and extension. • The high correlation was true for both the absolute change in linear measurements as well as the proportionate change in linear measurement. • The tape measure is a useful tool for measuring cervical spine range of motion in settings where ready availability, simplicity, and low cost of a measurement tool are important considerations for the conduct of research or patient management.
FUNDING SOURCES AND POTENTIAL CONFLICTS OF INTEREST No funding sources or conflicts of interest were reported for this study.
CONTRIBUTORSHIP INFORMATION Concept development (provided idea for the research): SEA, RP Design (planned the methods to generate the results): SEA, RP Supervision (provided oversight, responsible for organization and implementation, writing of the manuscript): SEA, RP Data collection/processing (responsible for experiments, patient management, organization, or reporting data): SEA, RP Analysis/interpretation (responsible for statistical analysis, evaluation, and presentation of the results): SEA, RP Literature search (performed the literature search): SEA, RP Writing (responsible for writing a substantive part of the manuscript): SEA, RP Critical review (revised manuscript for intellectual content, this does not relate to spelling and grammar checking): SEA, RP
REFERENCES 1. Antonaci F, Ghirmai S, Bono G, Nappi G. Current methods for cervical spine movement evaluation: a review. Clin Exp Rheumatol 2000;18:S45-52. 2. Williams MA, McCarthy CJ, Chorti A, Cooke MW, Gates S. A systematic review of reliability and validity studies of methods for measuring active and passive cervical range of motion. J Manipulative Physiol Ther 2010;33: 138-55. 3. Whitcroft KL, Massouh L, Amirfeyz R, Bannister G. Comparison of methods of measuring active cervical range of motion. Spine 2010;35:E976-80. 4. Tousignant M, Duclos E, Lafleche S, et al. Validity study for the cervical range of motion device used for lateral flexion in patients with neck pain. Spine 2002;27:812-7. 5. Tousignant M, de Bellefeuille L, O’Donoughue S, Grahovac S. Criterion validity of the cervical range of motion (CROM) goniometer for cervical flexion and extension. Spine 2000;25: 324-30. 6. Ordway NR, Seymour R, Donelson RG, Hojnowski L, Lee E, Edwards WT. Cervical sagittal range-of-motion analysis using three methods. Cervical range-of-motion device, 3space, and radiography. Spine 1997;22:501-8. 7. Maksymowych WP, Mallon C, Richardson R, et al. Development and validation of a simple tape-based measurement tool for recording cervical rotation in patients with ankylosing spondylitis: comparison with a goniometer-based approach. J Rheumatol 2006;33:2242-9. 8. Wolfenberger VA, Bui Q, Batenchuk GB. A comparison of methods of evaluating cervical range of motion. J Manipulative Physiol Ther 2002;25:154-60. 9. Prushansky T, Dvir Z. Cervical motion testing: methodology and clinical implications. J Manipulative Physiol Ther 2008; 31:503-8. 10. Chibnall JT, Duckro PN, Baumer K. The influence of body sizes on linear measurements used to reflect cervical range of motion. Phys Ther 1994;74:1134-7.
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11. Hsieh C, Yeung BW. Active neck motion measurements with a tape measure. J Orthop Sports Phys Ther 1986;8:88-92. 12. Youdas JW, Carey JR, Garrett TR. Reliability of measurements of cervical spine range of motion—comparison of three methods. Phys Ther 1991;71:98-104.
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13. Stattools.net, 2010 [accessed December 2012] Available from: http://www.stattools.net/ICC_Exp.php. 14. Dawson-Saunders B, Trapp RG. Basic and clinical biostatistics. 2nd ed. Norwalk (Conn): Appleton and Lange; 1994. p. 54.
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ABSTRACT Objective: The purposes of this study were to validate a tape measure method for measuring cervical spine range of motion compared with a universal goniometer in all planes of motion and to derive equations to convert a linear measurement to an angular distance. Methods: Participants were healthy volunteers. Measurements of flexion/extension, rotation, and lateral flexion were made with the universal goniometer and tape measure, in the neutral position, extreme of motion, and 2 positions between. Measurements from the 2 techniques were compared with Pearson correlation coefficient and simple linear regression to determine R 2, the regression coefficient and the regression equation. Reliability was assessed using the intraclass correlation coefficient. Results: There were 40 participants with a mean age of 30.5 (SD, 9.1) years. Goniometer measurements had good to excellent correlation with both absolute and percentage change in tape measurement (correlation coefficients, 0.740.94 and 0.75-0.91, respectively). Correlation was highest for flexion and extension, lowest for rotation and lateral flexion. The amount of variability in the data explained by the linear regression models (R 2) varied from 55% to 89%. Intraclass correlation coefficient ranged from 0.44 to 0.69 and 0.38 to 0.59 for intrarater and interrater reliability, respectively. Reliability was greatest for flexion and extension, lowest for rotation and lateral flexion. Conclusion: This study demonstrated that tape measurements correlated well with a universal goniometer. The tape measure may be useful for measuring cervical spine range of motion where availability, simplicity, and low cost are important considerations such as with conduct of research or patient management. (J Manipulative Physiol Ther 2013;36:538-545) Key Indexing Terms: Arthrometry, Articular; Range of Motion, Articular; Neck; Cervical; Reproducibility of Results
easuring the range of motion of the cervical spine is important for both clinical and research applications. In both these settings, an accurate and reproducible method for measuring the range of motion of the cervical spine is necessary to quantify injury/disease, the response to an intervention, or residual disability. There are various methods available to measure neck movement including visual estimation, goniometry, inclinometry, radiography, and video tracking, 1,2 with radiog-
M
a Physician, Emergency Department, St George Hospital, Kogarah, NSW, Australia. b Conjoint Lecturer, Faculty of Medicine, University of New South Wales, Kensington, NSW, Australia. Submit requests for reprints to: Stephen E. Asha, MBBS, FACEM MMed(Clin Epi), c/o Emergency Department, St George Hospital, Gray St, Kogarah, NSW 2217, Australia. (e-mail: [email protected]). Paper submitted February 5, 2013; in revised form July 29, 2013; accepted July 29, 2013. 0161-4754/$36.00 Copyright © 2013 by National University of Health Sciences. http://dx.doi.org/10.1016/j.jmpt.2013.07.005
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raphy the accepted reference standard. 3 The cervical range of motion goniometer has been validated in reference to radiographic studies, 4-6 and the universal goniometer has been shown to be similarly reliable. 3 The universal goniometer consists of 2 arms connected at a point allowing rotation of the arms and incorporating a protractor so that angular distance between the arms can be measured. However, these methods are limited in their practical application in a clinical setting as they can be cumbersome, time consuming, or relatively expensive; involve exposure to radiation; or require specialist training. The use of a simple tape measure as a tool to assess cervical range of motion is attractive for its simplicity, availability, and very low cost, especially in the settings of a busy clinic, hospital ward, or emergency department (ED) where a goniometer or other measurement tool is rarely on hand for use. There have been previous studies evaluating the use of a tape measure as a means to assess cervical range of motion. 3,7,8 However, the information from these studies is limited, as they have only assessed selected cervical movements (rather than all of flexion/extension, rotation, and lateral flexion), they have used absolute distances rather
Journal of Manipulative and Physiological Therapeutics Volume 36, Number 8
than assessing a proportionate change in distance, and none have determined if a linear measurement can be converted to an angular distance. Each study also uses different landmarks from which to make linear measurements, making it difficult to compare results between studies. Using the absolute linear measurement is a potential problem because body size may be a confounder of tape measure methods 9, and the proportionate change in linear measure may be less influenced by body size. 10 Our aim was to establish a measure cervical spine range of motion where availability, simplicity, and low cost are important. Therefore, the purpose of this study was to validate a tape measure method of measuring cervical spine range of motion, using the universal goniometer as the reference standard, in all planes of motion (flexion/ extension, rotation, and lateral flexion). Secondary aims were to assess the reliability of the technique by determining the intrarater and interrater reliability and to derive equations to convert a linear measurement to an angular distance.
METHODS Study Setting and Population The study was conducted in the ED of a tertiary referral hospital located in Sydney, New South Wales, Australia, during November 2012. Participants were a convenience sample of healthy volunteers sourced from among the staff employed in the ED. Permission for the study was granted by the human research ethics committee of South Eastern Sydney Local Health District (Northern Sector). Written informed consent was obtained from all participants.
Study Protocol Measurements of all 6 neck movements (flexion/extension in the sagittal plane, rotation left and right, lateral flexion left and right) were made with each technique (universal goniometer and tape measure). For each movement, a measurement was first made in the neutral position, at the extreme of motion, and 2 positions in between chosen arbitrarily by the participant. The purpose of the additional “in between” measurements was to obtain data points across the full spectrum of the range of motion to demonstrate the linear (or otherwise) nature of the relation between the 2 variables. This would allow the results to be applied to people with limited range of motion, only able to move a fraction of the range of motion achieved by healthy volunteers. At each position, a measurement was taken using both methods, and the method of measurement to be used first was randomly assigned for each participant. The randomization sequence was generated using a random number table. All measurements were made by a single examiner. To determine the intrarater and interrater reliability, the primary examiner repeated measurements at the extreme of
Asha and Pryor Tape Measure Range of Motion
the range of motion for each movement on half the participants, and a second examiner took measurements at the extreme of the range of motion for each movement on the remaining participants, respectively.
Measurements Participants were instructed to sit in a straight back chair looking forward, arms relaxed and resting on the thighs, their back resting against the chair, and their teeth gently clenched. Participants were asked to keep their shoulders still during all the measurements. For measurements using the tape measure, we used a previously described method. 11 Flexion and extension were measured from sternal notch to tip of chin. Rotation was measured from the tip of the chin to the most lateral palpable bony point on the tip of the shoulder opposite to the direction of neck movement (ie, if measuring rotation to left, measurements were made from the tip of the right shoulder). Lateral flexion was measured from the tragus of the ear to the tip of the shoulder both on the same side as the direction of neck movement (ie, if measuring left lateral flexion measurements were made from the tip of the left shoulder to the left tragus). For measurements using the universal goniometer, we used a previously described method. 12 For flexion and extension measurements, the examiner stood to the side of the participant, the axis of the goniometer was centered over the external acoustic meatus, the fixed arm was held vertical, while the movable arm was aligned with the base of the nares. Lateral rotation was measured with the examiner standing behind and looking down at the top of the participants head. The goniometer's axis was centered on the vertex of the participant's head, the fixed arm aligned parallel to an imaginary line between the participant's acromion processes, and the movable arm aligned with tip of the participant's nose. Lateral flexion was measured with the examiner in front of the participant, the axis of the goniometer positioned over the center of the participant's sternal notch, the fixed arm aligned parallel to an imaginary line between the participant's acromion process, and the movable arm aligned with the tip of the subject's nose. These measurement methods are illustrated in Figure 1.
Statistical Methods The distance measured with a tape measure is likely dependent not only on the range of motion but also on the overall size of the person, and so, the proportional change in distance may be more useful than the absolute measurement. To determine which linear measurement (absolute or proportionate) correlated best with the universal goniometer, comparisons were conducted using the change in linear measurement from the neutral position and the change in
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Fig 1. Positioning of the tape measure and universal goniometer for measurement of cervical range of motion. linear measurement as a percentage of the neutral measurement. For the purposes of the analysis, the data for rotation to the left and right sides were combined and analyzed as a single data set, as were the data for lateral flexion to the left and right side. The data were analyzed in a correlation matrix to determine Pearson correlation coefficient. Where the relationship between the 2 variables was demonstrated to be linear, simple linear regression was used to obtain R 2, the regression coefficient with 95% confidence intervals (CI), and the regression equation to enable the conversion of a linear measurement into an angular measurement. R 2 can be interpreted as the proportion of the total variation that can be accounted for by linear regression. The regression coefficient is an estimate of the average increase in angular measurement for a 1-unit increase in the linear measurement. This analysis was conducted using SAS statistical software version 9.2 (SAS Institute, Cary, NC).
Interrater and intrarater reliability of the linear measurements was calculated using the intraclass correlation coefficient (ICC). This analysis was conducted using IBM SPSS statistics version 20 (IBM Corp, Armonk, NY). The ICC can be interpreted as follows: 0 to 0.3 indicates poor agreement; 0.3 to 0.5, fair agreement; 0.5 to 0.7, moderate agreement; 0.7 to 0.8, strong agreement; and N 0.8, almost perfect agreement. 13 To estimate the number of participants required for this study where we planned to regress the values of the goniometer against the linear measurements, we first obtained estimates from the literature for the following measurements: • Mean and SD of linear measurements for lateral rotation expressed as a proportion of the measurement in the neutral position. This was 0.39 and 0.10, respectively. 10 • Mean and SD for angular measurements of lateral rotation. This was 56.44° and 19.85°, respectively. 7 • An estimate of the slope of the regression line, calculated from the above values to be 144.7.
Journal of Manipulative and Physiological Therapeutics Volume 36, Number 8
Asha and Pryor Tape Measure Range of Motion
Fig 2. Plots of goniometer measurements against percentage change in tape measurements. (Color version of figure is available online.) The sample size calculation also required a value for the correlation coefficient that would be acceptable to validate the tape measure method. A correlation coefficient between 0.25 and 0.50 suggests a fair relationship, values from 0.50 to 0.75 suggest a good relationship, while a correlations of 0.75 or greater suggests an excellent relationship between the 2 variables. 14 We prespecified that the minimum acceptable correlation coefficient would need to be 0.5 or greater. Based on these estimates and using an α level of 0.05, a minimum of 34 subjects would be required to reject the null hypothesis that there is no correlation between the 2 variables with a power of 90%. This analysis was conducted using PS power and sample size calculations version 3 (http://biostat.mc.vanderbilt.edu/wiki/Main/ PowerSampleSize).
RESULTS We enrolled 40 participants in the study. A complete set of data was available for all participants. Sixteen participants (40%) were male, the mean age was 30.5 years (SD, 9.1 years), and the mean body mass index (BMI) was 23.8 (SD, 3.6).
Figures 2 and 3 are scatter plots of cervical range of motion in angular distance plotted against the linear measurements. These demonstrate a linear relationship between these variables. Goniometer measurements of flexion, extension, rotation, and lateral flexion had good to excellent correlation with both the absolute change and the percentage change in tape measurement, with correlation coefficients ranging from 0.74 to 0.94 and 0.75 to 0.91, respectively (Tables 1 and 2). Correlation was highest for flexion and extension and lowest for rotation and lateral flexion. The amount of variability in the data that can be explained by the linear regression models, as described by the value of R 2, varied from 55% to 89% (Table 1 and 2). The regression coefficients for the simple linear regression models and their 95% CI are also presented in Tables 1 and 2. Using the values of the intercept and the regression coefficients from regression models, equations were derived to enable conversion of a tape measurement to an angular distance for each of flexion, extension, rotation, and lateral flexion. These are presented in Table 3. Twenty participants had repeat measurements for testing intrarater reliability, and the remaining 20 participants had repeat measurements for testing interrater reliability. This
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Asha and Pryor Tape Measure Range of Motion
Journal of Manipulative and Physiological Therapeutics October 2013
Fig 3. Plots of goniometer measurements against absolute change in tape measurements. (Color version of figure is available online.) Table 1. Correlation of goniometer measurements to percentage change in tape measurement
Flexion Extension Rotation Lateral flexion
Correlation coefficient
P
0.91 0.82 0.78 0.75
b.001 b.001 b.001 b.001
R2 (%)
Regression coefficient (95% CI)
P
83 68 61 56
0.66 (0.61-0.71) 0.66 (0.58-0.74) 1.55 (1.39-1.70) 0.80 (0.71-0.90)
b .001 b .001 b .001 b .001
ranged from fair to moderate with values for the ICC varying from 0.44 to 0.69 and 0.38 to 0.59 for intrarater and interrater reliability, respectively (Table 4). Reliability was greatest for flexion and extension and lowest for rotation and lateral flexion.
DISCUSSION This study demonstrated that the tape measure as a tool to measure cervical spine range of motion has good to excellent correlation when compared with a universal
goniometer. This correlation was best for the movements of flexion and extension, and the high correlation was true for both the absolute change in linear measurements as well as the proportionate change in linear measurement. As the relationship between the 2 methods of measurement was linear, equations were derived that enabled linear measurements to be converted into angular units. As a linear measurement is difficult to conceptualize as a descriptor for cervical spine motion, these equations may be of use to researchers who have conducted research using the tape measure, allowing presentation of results in angular units, which is more straightforward for readers to understand. This ability to make conversions will also allow comparisons to be made with other research conducted using angular measurement instruments. The reproducibility of measuring at the extreme of the range of cervical spine motion when repeated by the same observer or a different observer using the tape measure demonstrated variability in these measurements. The ICC, which was used to assess this reproducibility, was best for the movements of flexion and extension, where it was rated as moderate and fair for the movements of rotation and
Journal of Manipulative and Physiological Therapeutics Volume 36, Number 8
Asha and Pryor Tape Measure Range of Motion
Table 2. Correlation of goniometer measurements to absolute change in tape measurement
Flexion Extension Rotation Lateral flexion
Correlation coefficient
P
0.94 0.86 0.79 0.74
b .001 b .001 b .001 b .001
Table 3. Equations to convert tape measurements to range of motion in degrees Flexion
R2 (%)
Regression coefficient (95% CI)
P
89 73 62 55
0.52 (0.49-0.56) 0.60 (0.53-0.66) 0.63 (0.57-0.70) 0.38 (0.34-0.43)
b.001 b.001 b.001 b.001
lateral flexion. An important factor that probably contributed to the relatively low scores for reproducibility was participant compliance. An observation made by the investigators during the study was that holding the head at the extreme of motion was frequently uncomfortable for participants. As a result of this experience, participants tended to choose a slightly reduced position for the extreme of the range of motion for the repeated measure resulting in the observed variability in these measurements. This research is a valuable addition to existing knowledge in this area, as it provides a thorough validation of the tape measure in all 3 planes of motion for the cervical spine and over the full range of these movements (not just the extremes of movement), in contrast to previous research where only selected movements have been studied. 3,7,8 We also found much better agreement with the reference standard than was found in some of these studies. 3,8 In contrast, other studies have found the interrater reliability of the tape measure method to be better than that suggested by our investigations. 7 Although the cervical range of motion goniometer or the universal goniometer would provide the most reliable measurements, our results indicate that the tape measure is a useful tool to measure cervical spine range of motion and provides a good compromise in the ED or outpatient clinic setting where the principals of simplicity, ease of use, and cost are important considerations for the successful conduct of research. The performance of the tape measure is best for the movements of flexion and extension for both correlations to the universal goniometer and the reproducibility of the measurements. An important question to ask is: why not use the universal goniometer, which also satisfies these requirements? It is the experience of the researchers and physiotherapists at this institution that the major drawback to the universal goniometer is the ease with which it is misplaced or purloined, in contrast to the availability of disposable paper tape measures. An additional benefit of disposable paper tape measures is from an infection-control perspective. The nondisposable nature of the goniometer renders it a potential fomite for the transmission of infections between patients. It was an unexpected finding that the correlation of the tape measure with the universal goniometer was virtually the same for absolute changes and proportionate changes in
Extension
Rotation
Lateral flexion
Range of motion in degrees = − 0.54 + 0.66 × (percent change in linear measure) Range of motion in degrees = − 0.37 + 0.52 × (absolute change in linear measure) Range of motion in degrees = 5.21 + 0.66 × (percent change in linear measure) Range of motion in degrees = 3.69 + 0.60 × (absolute change in linear measure) Range of motion in degrees = 12.8 + 1.55 × (percent change in linear measure) Range of motion in degrees = 12.5 + 0.63 × (absolute change in linear measure) Range of motion in degrees = 7.31 + 0.80 × (percent change in linear measure) Range of motion in degrees = 7.37 + 0.38 × (absolute change in linear measure)
linear measurements. We had predicted that correlation with the proportionate change in linear measurements would be better based on the results of a previous study, which found that differences in body size had an important influence on absolute linear measurements. 10 A possible explanation for this is that discrepancies in absolute linear measurement may only arise at extremes of height or weight, which was not captured in our sample that had a relatively small SD in the BMI. Our results, therefore, may not be applicable to people with very high or very low BMIs. Although our results are promising for the use of the tape measure, our study was carried out among healthy participants. It is possible that the disease of the cervical spine may alter the mechanics of cervical spine motion. We recommend that further research into the tape measure should focus on similar validation methodology among a patient population with diseases affecting cervical spine mobility.
LIMITATIONS There were several other limitations to our study. It would have been optimal to validate the tape measure against the ideal criterion standard of radiography; however, we chose not to use this due to funding limitations and ethical concerns regarding the exposure of healthy volunteers to radiation. The applicability of these results to the extremes of age may be limited as the sample consisted largely of adults younger than 50 years, and no children were enrolled in the study. The study population consisted of healthy and cooperative volunteers sourced from ED staff, which may also affect the generalizablity to the population as a whole. Accurate measurement depended on participant compliance in remaining still during the arbitrary positions between neutral and full range of motion and avoiding shoulder movement when measuring lateral flexion, and this may have affected our measurements of correlation. The measurements of intrarater and interrater
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Asha and Pryor Tape Measure Range of Motion
Journal of Manipulative and Physiological Therapeutics October 2013
Table 4. Intrarater and interrater reliability of tape measurements Intrarater reliability Flexion Extension Rotation Lateral flexion Interrater reliability Flexion Extension Rotation Lateral flexion
ICC
95% CI
P
0.56 0.69 0.44 0.56
0.18-0.80 0.38-0.87 0.15-0.66 0.31-0.74
.004 b.001 .002 b.001
0.59 0.58 0.38 0.44
0.22-0.82 0.21-0.81 0.08-0.61 0.16-0.66
.002 .002 .007 .002
ICC, intraclass correlation coefficient.
reliability may be underpowered given that only half the participants were used for each of these calculations.
CONCLUSION Measurements made with a tape measure correlated well with the universal goniometer, and this correlation was best for the movements of flexion and extension. The high correlation was true for both the absolute change in linear measurements as well as the proportionate change in linear measurement. The tape measure may be a useful tool for measuring cervical spine range of motion in the setting where the principals of simplicity, ease of use, and cost are important considerations such as in the conduct of research and patient management.
Practical Applications • Measurements of cervical range of motion made with a tape measure correlated well with the universal goniometer, and this correlation was best for the movements of flexion and extension. • The high correlation was true for both the absolute change in linear measurements as well as the proportionate change in linear measurement. • The tape measure is a useful tool for measuring cervical spine range of motion in settings where ready availability, simplicity, and low cost of a measurement tool are important considerations for the conduct of research or patient management.
FUNDING SOURCES AND POTENTIAL CONFLICTS OF INTEREST No funding sources or conflicts of interest were reported for this study.
CONTRIBUTORSHIP INFORMATION Concept development (provided idea for the research): SEA, RP Design (planned the methods to generate the results): SEA, RP Supervision (provided oversight, responsible for organization and implementation, writing of the manuscript): SEA, RP Data collection/processing (responsible for experiments, patient management, organization, or reporting data): SEA, RP Analysis/interpretation (responsible for statistical analysis, evaluation, and presentation of the results): SEA, RP Literature search (performed the literature search): SEA, RP Writing (responsible for writing a substantive part of the manuscript): SEA, RP Critical review (revised manuscript for intellectual content, this does not relate to spelling and grammar checking): SEA, RP
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Asha and Pryor Tape Measure Range of Motion
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