A Clinical Tool for Measuring Functional Axial Rotation

Technical Report

A Clinical Tool for Measuring Functional Axial

Rotation

Background and Purpose. Motion of the neck and back accompany many daily functional activities. Available range of motion is usually measured regionally and within single planes of motion. ir;his report describes a device and measurement technique that can be used to quantify m ' a l motion in a functionally relevant context. Functional axial rotation (FAR) refers to the available motion that persons use to turn toward the posterior, without regard to the plane of motion; Fm-p refers to the physical motion available, and FAR-u refen to the ability to identth objects. Subjects. Nine men and eight mmen, aged 20 to 74 years, participated. Methods. Functional axial rotation uias determined for each subject. ?;heseated subjects were measured on 2 dzferent days to detennine test-retest reliability. Fifteen subjects were measured by two dgerent examiners on the same day to determine interrater reliability. Intraclass cowelation coeficients (ZCCs) were computed to determine reliability.Results. m e FAR9 ranged from 78 to 190 degrees; FAR-v ranged from 135 to 250 degrees. Test-retest reliability of FAR# and FAR-v was excellent (ICCrl,U values of .95 and .90,respectively, to the right and equivalent to the left)). Intewater reliability likewise was excellent, with ICC(2,Z) values of .97 to the right and equivalent to the left. Conclusions and Discussion Functional axial rotation provides one means of quantifying a patient's axial motion as it would be used in functional context. m e FAR device is easy to construct and portable. Measurement of FAR provides the clinician with reliable information regarding the patient's functional use of available spinal motion, combined with visual ability. (Schenkman M, Hughes MA, Bowden MG, Studenski SA. A clinical tool for measuring functional axial rotation. Phys mer. 1995;75:151-156.1

Margaret Schenkman Michael A Hughem Mark G Bowden Stephanie A Studenski

Key Words: Functional, neck and trunk; N~eckand Trunk; Spplne;Tests and mmutwnents.

Neck and back motion is used during many daily activities. The trunk and neck rotate relative to the pelvis when people look over their shoulders while driving or when they roll from a supine to a side-lying position. Because the axial structures (neck and torso) form the supportive base from which movement of the limbs and head occurs, the ability to move the neck and torso also influences movement of the extremities. Everyday functional activities require spinal motion that combines movements of multiple

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regions of the spine and in varying planes of motion. Many devices have been developed that measure excursion or configuration of specific regions of the spine and in specific planes of motion.'-7 For example, devices are available to measure lumbar cervical motion? the degree of kyphosis? and a forward head position.7 In this technical report, we describe a device that we have developed to quantlfy the type of motion of the spine that is

used during functional activities. During functional tasks, spinal motion generally involves many spinal segments and crosses multiple body planes (ie, triplanar motion). For convenience, we use the term "combined spinal motion" to describe the axial movements that occur during the performance of functional activities. We believe that information obtained by measuring combined spinal motion complements information that is obtained from devices that measure specfic regional mobility.

Physical Therapy / Volume 75, Number 2 / February 1995

We use the term "functional axial rotation" (FAK) to refer to movements of the neck and torso that position the head toward the posterior as would occur when one looks behind oneself (eg, when backing a car). Functional axial rotation is a specific example of combined spinal motion. The combined motion includes movement of vertebral segments from the cervical to the lumbar spine. What we call FAR occurs predominantly in the transverse plane but may be accompanied by extension, lateral flexion, and sometimes even flexion of specific spinal regions. This pattern of FAR has two distinct purposes. The first purpose is to allow the head and thorax to move with respect to the pelvis so that functional activities can occur. Thts movement is exemplified by rotation of the head and thorax relative to the pelvis, as when one rolls from a side-lying to a supine position. Axial motion can be quantilied by the physical distance that the head can be moved with respect to the pelvis. The second purpose is to allow individuals to see objects positioned toward their posteriors. The ability of a person to use vision in combination with available axial mobility can be quantified by

having the person identrfy objects located toward the posterior. The FAR device we have developed is designed to reflect physical action (movement) and visual performance. First, the device is used to measure the physical distance that people can turn when they are not constmined to a particular strategy. This device is only intended to reflect the subject's capability for movement without determining the causes of limitations (eg, joint or soft tissue restrictions, pain). Second, the device is used to measure the range through which people can identlFy symbols when they turn. This ability is determined in part by FAR, but may be further limited by visual deficits (eg, loss of acuity, visual-field limitations, perceptual deficits, or other impairments of the visual system).s The FAR measures are designed to determine how successful a person can be in physically moving the spine and in identrfying objects to the posterior without consideration for the specific impairments that might limit performance. We had several criteria for the device. First, we wanted to be able to measure rotation of the neck and trunk relative to the fixed pelvis in order to

M Schenkman, PhD, PT, is Associate Professor, Graduate Program in Physical Therapy, Senior Fellow, Center for the Study of Aging and Human Development, and Co-Director, Claude Pepper Older American Independence Center, Duke University, Durham, NC 27710. Address all correspondence to Dr Schenkman at the Center for the Study of Aging and Human Development, Duke University Medical Center, PO Box 3003, Durham, NC 27710 (USA). MA Hughes, is Biomedical Engineer, Postural and Balance Control Laboratory, Department of Veterans Alfairs, Durham, NC 27701.

MG Bowden, is Research Assistant, Postural and Balance Control Laboratory, Duke Un~versity. SA Studenski, MD, is Director, Center for the Study of Aging and Human Development, University of Kansas, Lawrence, KS 66045. She was Director, Rehabilitative Medical Services, Department of Veterans Mairs, Durham, NC, when this work was initiated. The study was approved by the Institutional Review Board of the Department of Veterans Afairs, Durham, NC. This work was supported by the National Institutes of Health, National Institute on Aging, Claude D Pepper Older Americans Independence Center Grant P6O AG 11268 and by a Duke University Medical Center Small Research Grant. This work was presented in part at the 1992 meeting of the Gerontological Society of America, Washington, DC.

reflect axial motion. We therefore chose to use the seated position to assist in stabilizing the pelvis. Second, we wanted the device to be inexpensive, practical for use in most clinics, and portable for use in a variety of community settings. Third, we wanted it to have a minimum resolution of 5 degrees in order to be useful for detecting clinically meaningful changes over time and between subjects. Finally, we wanted to differentiate between the range of motion (ROM) of subjects and their capability to use that motion visually.

Equipment

The FAR measurement tool that we developed consists of a 1-mdiameter circular hoop that is suspended, by tripods, at eye level around the seated subject (Figure). We used a commercially available child's toy hoop* for this purpose in our prototype. We subsequently developed a more permanent device, using a 2.54-cm-wide, flat metal band, secured by rivets to create a hoop that is 1 m in diameter. The hoop is dvided into four equal quadrants by marking it with vertical lines that can be aligned with the subject's body. We placed symbols, consisting of numbers and letters, in 5degree increments around the inner ring of the hoop (Figure). The symbols are randomly ordered to provide a value-neutral target for the subject. We constructed a key relating each symbol to the amount of rotation it represents in order to convert symbols to ROM values. A pointer is affixed to the subject's forehead, using the headpiece provided by the cervical range Alof motion device (CROMTM).~~ though we choose to use the headpiece of the CROMTMfor convenience, we believe any method for fixing a horizontal pointer to the head could be used. With the FAR device, combined axial motion is quantified in two ways:

This article was submitted June 10, 1994, and was accepted September 8, 19%.

'Hula HooprM,Wham-0 Manufacturing Co, 835 E El Monte, San Gabriel, CA 91778. tPerfornlance Attainment Associates, 958 Lydia Dr, Roseville, MN 55113

Physical Therapy/ Volume 75, Number 2 /February 1995

1. The displacement of the subject's head relative to the fixed pelvis is detennined by the location of the

back pain. They were also excluded if they reported focal neurologic conditions that might potentially contribute to functional impairment (eg, Parkinson's disease, stroke). Nine men and eight women, ranging in age from 20 to 74 years, participated (Tab. 1). All subjects gave informed consent prior to participation in the study.

To position each subject, the hoop, suspended from two adjustable tripods, was placed around the seated subject (Figure). The height of the hoop was adjusted to eye level. To ensure that the hoop had the same orientation from trial to trial, the front of the hoop (0°), marked by a vertical line, was aligned with the midline of the subject's face, and the back of the hoop (180") was aligned with the seventh cervical vertebra. The hoop was then moved in the anterior/posterior direction until the two lines, at 90 and 270 degrees, respectively, were positioned in line with the subject's greater trochanters. To ensure that rotational motion was accomplished without Ming the pelvis, the subject's pelvis was secured to the chair seat using two straps, crossed to form a figure eight. The headpiece was then fitted over the subject's head with the pointer oriented toward the hoop. Figure.

The functional axial rotation measuring device consists of a hoop, suspended by t t ~ vtripods so that it can be adjusted relative to each subject's height. The seated stbject turns as far to the posterior as possible without Iifiing the buttock from the chair seat. The degree of motion is determined using a pointer a@ed to the bead. Motion is determined by the alignment of the pointer with symbols, located 5 degrees apart, on the inner surfrrce of the hoop.

symbol with which the headpiece is aligned once motion is completed (Figure). We call this measure "functional axial rotationphysical" (FAR-p). 2. The subject's success in visualizing objects in the transverse plane is detemlined by the symbol that the subject can read when rotating as far as possible in one direction. We call this measure "functional axial rotation-visual" (FAR-v).

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Subjects were recruited from the Duke Medical Center Aging Center registry, the Department of Veteran's Mairs Medical Center in Durham (NC), and the Duke University Graduate Program in Physical Therapy. Subjects were excluded if they had pathology of the axial skeleton (eg, fusion of the spine or compression fractures), if they had reportedly been on bed rest during the past year because of back pain, or if they were currently experiencing

To measure FAR, subjects were instructed to let their hands hang loosely by their sides and to turn as far to the left or right as possible and read the farthest symbol that they could see. Subjects were also instructed to move the neck and torso as much as they could but to refrain from gripping the chair seat with their hands. Subjects were not restricted with respect to the motion of the torso (eg, axial extension, lateral flexion, flexion). The tester observed the motion carefully to ensure that the subjects' buttocks were not lifted from the chair seat. Data were obtained for rotation (FAR-p) and for reports of symbols (FAR+) to both the left and to the right. Three trials were collected for each side, alternating from right to left side between trials. The first trial in


-

determined and used in further analyses. We used the ICQ to determine interrater reliability (ICC[2,11) and testretest reliability (ICC[1,11).

Table 1 . Subject Characteristics (N= 1 7) Minimum

Maximum

152.4 (60)

Weight (kg)b

50.8 (112)

SD

48.8

74

20

Age (Y) Height (cmy

X

185.4 (73) 97.5 (215)

21.6

8.9 (3.5)

167.9 (66.1) 69.2 (152.5)

16.2 (35.6)

aNonrnetric equivalent (in inches) shown in parentheses. %onmetric equivalent (in pounds) shown in parentheses

each direction was a practice trial; the second and third trials to each side were test trials.

measure of the symbol reported by the subject). Data Analysis

Measurements of FAR-p and FAR+ were taken on 2 dierent days (5-10 days apart) to determine test-retest reliability. On the second day of testing, FAR-p was measured by two different raters (FAR-v was not measured by two raters because this is a

-

Data from the two test trials for FAR-p were averaged to determine FAR-p right and FAR-p left, respectively. Averaged values were used for further analysis. Similarly, the average values for FAR-v right and FAR-v left were

Test Day

Side

FAR-p

Right

1

FAR-p

Right

2

FARp

Left

1 2

FAR-p

Left

FAR-v

Right

1

FAR-V

Right

2

FAR-v

Left

1

FAR-v

Left

2

Minimum Displacement

Maximum Displacement

X

SD

Table 3. Functional Axial Rotation-Physical (FAR?) (in Degrees) Measured by Two Different Raters (n= 15)

Variable

Side

Rater

Minimum Displacement

FAR-p

Right

1

80

FARp

Right

2

FAR-P

Left

1

80 78

FAR-P

Left

2

80

Maximum Displacement


X

Test-retest reliability was excellent for both FAR-p and FAR-v (ICCI1,ll values of .95 and .W, respectively, were obtained for rotation to the right and to the left). Interrater reliability likewise was excellent (ICC[2,1]values of .97 were obtained for rotation to the right and to the left).

D i i o n

Table 2. Functional Axial Rotation-Physical (FAR$) and Functional Axial Rotation- Visual (FAR-v) (in Degrees) in 2 D@rent Days (N= 1 7)

Variable

For the 17 subjects and the 2 days of measurement, FAR-p ranged from 92 to 190 degrees and FAR+ ranged from 135 to 250 degrees (Tab. 2). The mean difference between days was 8 degrees for FAR-p and 9 degrees for FAR-V.Ditferences between raters in measuring FAR-p are shown in Table 3. The mean dserence between the two raters in the determination of FAR-p was 1 degree.

This technical report illustrates a method for estimating the extent to which a person can use combined spinal motion for function. We believe the method may provide a more functional approach to determining capability than d o the specific measures of regional mobility or vision. The fact that people have a particular amount of axial mobility at specific joints-or a particular acuity, visual field, percep tual ability, and so forth-does not ensure that they will use those abilities in functional contexts. Specific regional restrictions also d o not necessarily imply that people will fail in a functional context. People may adopt a movement strategy, such as leaning back while rotating, to extend the functional ROM through which they can move the torso.

SD

The FARp and FAR-v measures p o tentially quanhfy two different aspects of function that depend on combined spinal movements. The FAR-p measure quantifies the available ROM through which the seated subject can turn the torso relative to the pelvis.

This measure could be limited by impairments such as joint restrictions or rnalalignment, soft tissue tightness, or pain. If FAR-p is limited, further testing would be required to determine the underlying causes. The FAR-v measure quantifies the person's ability to describe objects located to the posterior. In concept, this measure is related to whether a person will "see the child on the bicycle that he or she is about to back into." This measure is analogous to the FAR-p measure in that it could quantlfy how successfully a person can complete a functional task-not the reasons for dilKculty or failure. The FAR-v measure depends on both RUM and vision. This measure, therefore, is interpreted with respect to both factors. If people demonstrate limited FAR-v relative to FAR-p, further testing would be necessary to determine whether they have deficits of acuity, visual fields, perceptual ability, or a host of other visual andlor cognitive possibilities. The FAR-v and FAR-p measures are closely related but would not necessarily have a one-teone correlation, because the abiIity to describe objects located to the posterior requires more than the ability to rotate the axial skeleton. Research is needed to validate functional inferences regarding both measures. We developed the FAR measures in order to investigate the functional importance of axial rnobility.10 It is clear from a clinical perspective that the axial structures play an important role in many functional activities. Yet, there are few physical performance measures available that capture information related to motion of the axial segments. We were particularly concerned with the functional use of rotational motion because of its importance for many daily activities, including bed mobility, dressing, and driving a car. A first step toward using this measure-

ment approach, either for clinical practice or for research, was to establish that the FAR measure provides reliable information. Intertester reliability is important because the device should be useful for more than one

rater. Test-retest reliability is particularly important because FARp is not constrained to a single plane or a single region of the spine. There is no attempt to restrict how the motion is accomplished; thus, there is considerable potential for variability in the way that the task might be camed out on different occasions. Variability in performance of the task could lead to variability of the available KOM measured by the FAR device. Our results indicate that this functionally relevant approach to measurement of axial motion can provide highly reliable results, both when used by dderent raters and when the same subjects are measured on different days. Because of our interest in determining how FAR mobility changes with age, we chose to investigate healthy individuals in this work. Additional studies are needed to determine reliability for other populations. One potential concern in using the FAR device was that the subjects might use the symbols as a guide when repositioning their torso on repeated tests. The excellent test-retest reliability across a week argues against this. Furthermore, we have used this measure to quant* axial mobility of patients with Parkinson's disease.'O Using an analysis of variance to compare the data obtained on 4 different days of testing, we established that there is no systematic dilference by day or week of testing. In light of the data in this report, as well as the data we obtained with patients who have Parkinson's disease, it is hghly unlikely that the reliability that we obtained simply reflects the subjects' ability to recall the symbols. Improvement of a patient's mobility of the neck or back through mobilization, other manual therapy techniques, or exercise should lead to improvement of the coordinated use of spinal movements for activities such as looking over one's shoulder. Clinicians should be able to quantlfy improvements in this ability. The FAR measurement device is easy to construct, easy to use, and portable. The device can be used in clinical as well as research settings and can provide the

clinician with a new and important measure of functional capability. Further work is under way in our laboratories to establish the reliability of this measurement approach for indviduals with a specdic pathology,ll to determine how FAR relates to other aspecs of physical performance,Gnd to determine whether improvements of FAR lead to improvements of ability for a variety of activities. Conclusion

The FAR device that we have developed was designed as one means of quantifying a patient's combined axial motion as it would be used in functional contexts. The device is easy to construct, portable, and easy to use in the clinic or in the patient's home. The device provides the clinician with informa tion regarding the patient's ability to move the spine in an integrated fashion and permits the clinician to characterize the patient's ability to see objects toward the posterior. Further research is needed to establish the reliability and validity of measurements obtained with the FAR device on other clinically relevant populations. References 1 Fitzgerald GK, Wynveen KJ, Rheault W, Rothschild B. Objective assessment with establishment of normal values for lumbar spinal range of motion. Phys Ther. 1983;63:17761781. 2 Mayer TG, Tencer AF, Kristoferson S, Mooney V. Use of noninvasive techniques for quantification of spinal range-of-motion in normal subjects and chronic low-back dysfunction patients. Spine. 1984;9:588-595. 3 Dillard J, Trafimow J, Andersson GW, Cronin K. Motion of the lumbar spine: reliability of two measurement techniques. Spine. 1991; 16:321-324. 4 Salisbury PJ, Porter RW. Measurement of lumbar sagittal mobiliry: a comparison of methods. Spitze. 1987;12:190-193. 5 Rheault W, Albright B, Byers C, et a]. Intertester reliability of the cervical range of motion device. J Orthop Sports Phys Ther. 1992; 15:147-150. 6 Ohlen G, Spangefort E. Tingvall C. Measurement of spinal sagittal configuration and mobility with Debrunner's Kyphorneter. Spzne. 1989;14:580-583. 7 Hanter. WP, Lucio RM. Russell JL, Brunt D. Assessment of total head excurbion and resting head posture. Arch Phys Med Rehabil. 1991;72:877-880.

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8 Green HA, Madden DJ. Adult onset differences in visual acuity stereopsis and contrast sensitivity. Am J Optorn Pb.~~siol Optics. 1987; 64:749-753. 9 Shrout PE, Fleiss JL. Intraclass correlations: uses in assessing rater reliability. Psycho! Bull. 1779;86:420-428.

10 Schenkman M, Cutson T, Chandler J, et al. Reliability of measures for Parkinson's disease. In: Ptoceedings of the Annual Meeting of the American Geriatrics Society; Los Angeles, CaIg May 2*, 1994.19943sA-77. 11 Prescott RI., Schenkman M, Bowden MG, et al. Spinal mobility: age effects and relation-

ship to functional performance. In: Proceedings of the Gerontological Socie@ of America. 1992:127-128.

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