Variation in the cervical range of motion over time measured by the "flock of birds" electromagnetic tracking system

A Novel Method for Tracking Neck Motions Using a Skin-Conformable Wireless Accelerometer: A Pilot Study

Introduction

Cervical spine disease is a leading cause of pain and disability. Degenerative conditions of the spine can result in neurologic compression of the cervical spinal cord or nerve roots and may be surgically treated with an anterior cervical discectomy and fusion (ACDF) in up to 137,000 people per year in the United States. A common sequelae of ACDF is reduced cervical range of motion (CROM) with patient-based complaints of stiffness and neck pain. Currently, tools for assessment of CROM are manual, subjective, and only intermittently utilized during doctor or physical therapy visits. We propose a skin-mountable acousto-mechanic sensor (ADvanced Acousto-Mechanic sensor; ADAM) as a tool for continuous neck motion monitoring in postoperative ACDF patients. We have developed and validated a machine learning neck motion classification algorithm to differentiate between eight neck motions (right/left rotation, right/left lateral bending, flexion, extension, retraction, protraction) in healthy normal subjects and patients.

Methods

Sensor data from 12 healthy normal subjects and 5 patients were used to develop and validate a Convolutional Neural Network (CNN).

Results

An average algorithm accuracy of 80.0 ± 3.8% was obtained for healthy normal subjects (94% for right rotation, 98% for left rotation, 65% for right lateral bending, 87% for left lateral bending, 89% for flexion, 77% for extension, 50% for retraction, 84% for protraction). An average accuracy of 67.5 ± 5.8% was obtained for patients.

Discussion

ADAM, with our algorithm, may serve as a rehabilitation tool for neck motion monitoring in postoperative ACDF patients. Sensor-captured vital signs and other events (extubation, vocalization, physical therapy, walking) are potential metrics to be incorporated into our algorithm to offer more holistic monitoring of patients after cervical spine surgery.

Variability of Active Cervical Range of Motion Within and Between Days in Healthy Participants: A Prospective Observational Study

OBJECTIVE

The purpose of this study was to determine the intraday and interday variability and systematic change over the day of active cervical range of motion (aCROM) measurements in asymptomatic persons using a clinically applicable measurement device.

METHODS

A prospective observational study was performed. Sixteen adults (8 men and 8 women, median age 51 years) without neck pain in the last 3 months were recruited in 2 physiotherapy practices. Active cervical range of motion was estimated using the Apple iPhone application "3D Range of Motion." Measurements were performed 3 times a day for 7 days and spread over a period of 3 weeks. Mean values of aCROM were calculated. Intraday and interday variability was estimated by calculating limits of agreement.

RESULTS

The limits of agreement for intraday variability ranged from ±12.1° for left rotation to ±15.5° for total rotation. For interday variability, the limits of agreement ranged from ±14.2° for right rotation to ±20.1° for total rotation. No systematic change over the day was found.

CONCLUSION

This study showed substantial intraday and interday variability of aCROM measurements in asymptomatic people. No trend toward an increased or decreased aCROM was observed during the course of the day. When interpreting aCROM values, clinicians should consider the degree of variation in aCROM measurements over time.

Assessment of range and quality of neck movement using a smartphone-based application

This study had the objective of measuring the validity of using a smartphone-based application to measure range of motion (ROM) and quality of movement (QOM) of neck motion by comparing it with 3D-motion capture analysis.

METHODS

Thirty healthy volunteers participated in this cross-sectional study. A helmet fitted with markers for motion capture analysis and a smartphone were fastened to the head of the participants. The smartphone recorded data using a beta version of Balancy (MEDEI, Denmark). Assessments of full active movement in transverse and sagittal planes were performed. Recordings were made simultaneously with the camera system and the smartphone. ROM and jerkiness were compared with a repeated measures ANOVA and a Pearson product moment was calculated to compare the outcomes from the different applications. Bland-Altman plots were generated to determine the levels of agreement.

RESULTS

No difference was found between modalities when comparing measurements of jerkiness or ROM. An excellent Pearson product moment was found for the outcomes of the two modalities for ROM (Pearson's r: 0.83 - 0.96) and jerkiness (Pearson's r: 0.86 - 0.95). The Bland-Altman plot revealed a systemic offset where the phone consistently measured higher values for ROM and lower values for jerkiness.

CONCLUSIONS

This study demonstrated that a smartphone-based application can be used to accurately measure ROM and jerkiness during neck movements. These results indicate the utility of using a smartphone-based application to assess neck movement in humans. The findings have implications for assessment of neck movement in research and clinical practice.

Three-dimensional kinematics of the cervical spine using an electromagnetic tracking device. Differences between healthy subjects and subjects with non-specific neck pain and the effect of age

BACKGROUND

A cross-sectional observational study of three-dimensional cervical kinematics in 35 non-specific neck pain patients and 100 asymptomatic controls. To compare qualitative and quantitative aspects of cervical kinematics between healthy subjects and subjects with non-specific neck pain and to determine the effect of age on cervical kinematics in healthy subjects.

METHODS

Three-dimensional kinematics of active lateral bending and flexion-extension of 35 patients and 100 controls were registered by means of an electromagnetic tracking system. The means of several kinematic parameters were compared using t-tests. In addition, we assessed the age-dependency of the three-dimensional kinematic parameters by stratifying the 100 control subjects in 6 age categories.

FINDINGS

Comparison of the patient group with the control group reveals no statistically significant differences in qualitative and quantitative parameters. Analysis of the effect of age showed that the range of motion decreases significantly (p < 0.01) with increasing age. In lateral bending, the ratio between axial rotation and lateral bending increases significantly (p < 0.01) among older subjects. Differences in acceleration, jerk and polynomial fit are seen between the age categories, but are not significant.

INTERPRETATION

This study demonstrates no significant differences in kinematic parameters between healthy subjects and subjects with non-specific neck pain. Healthy subjects in higher age categories demonstrate higher ratios of coupled movements and lower ranges of motion. Future research should focus on classifying patients with non-specific neck pain in order to gain a better insight on possible subgroup specific differences in kinematics. More studies on this subject are warranted.

LEVEL OF EVIDENCE

4.

Three-dimensional Cervical Movement Characteristics in Healthy Subjects and Subgroups of Chronic Neck Pain Patients Based on Their Pain Location

STUDY DESIGN

A cross-sectional observational study of three-dimensional (3D) cervical kinematics in 41 chronic neck pain (CNPs) patients and 156 asymptomatic controls.

OBJECTIVE

The objective was to investigate 3D cervical kinematics by analyzing and comparing quantitative and qualitative parameters in healthy subjects and CNPs. Furthermore, subgroups were formed to explore the influence of pain-location on cervical kinematics. The possible correlation of kinematic parameters with the degree of functional disability was examined as well.

SUMMARY OF BACKGROUND DATA

In patients with chronic neck pain, a clear pathological cause is frequently not identifiable. Therefore, the need to assess neck pain with a broader view than structure or anatomical-based divergences is desirable.

METHODS

Movements of the cervical spine were registered using an electromagnetic tracking system. Quantitative and qualitative kinematics were analyzed for active axial rotation, lateral bending, and flexion-extension motion components.

RESULTS

During lateral bending, the range of the main motion demonstrated significant higher values (P = 0.001) in the controls (mean: 68.67° ± 15.17°) than patients (mean: 59.28° ± 15.41°). Significant differences were demonstrated between subgroups for several kinematic parameters (P < 0.05). Although differences were predominantly recorded between the "symmetrical" and "asymmetrical" pain group, some parameters also distinguished subgroups from controls. On average, the symmetrical group showed significant less harmonic movement patterns, expressed by qualitative parameters, in comparison with the "asymmetrical" group and controls. Furthermore, the "asymmetrical" group showed significant lower scores on quantitative parameters than the "symmetrical" group and controls. The degree of functional disability correlated moderately with changes in qualitative parameters.

CONCLUSION

In this study, chronic neck pain patients with a symmetrical pain pattern showed significant poorer quality of movement, while those with asymmetrical pain showed a significant reduction in quantitative measures. Subgrouping of neck patients based on pain location may be of help for further research and clinics.

LEVEL OF EVIDENCE

4.

Effects of Axial Torsion on Disc Height Distribution: An In Vivo Study

OBJECTIVES

Axial rotation of the torso is commonly used during manipulation treatment of low back pain. Little is known about the effect of these positions on disc morphology. Rotation is a three-dimensional event that is inadequately represented with planar images in the clinic. True quantification of the intervertebral gap can be achieved with a disc height distribution. The objective of this study was to analyze disc height distribution patterns during torsion relevant to manipulation in vivo.

METHODS

Eighty-one volunteers were computed tomography-scanned both in supine and in right 50° rotation positions. Virtual models of each intervertebral gap representing the disc were created with the inferior endplate of each "disc" set as the reference surface and separated into 5 anatomical zones: 4 peripheral and 1 central, corresponding to the footprint of the annulus fibrosus and nucleus pulposus, respectively. Whole-disc and individual anatomical zone disc height distributions were calculated in both positions and were compared against each other with analysis of variance, with significance set at P < .05.

RESULTS

Mean neutral disc height was 7.32 mm (1.59 mm). With 50° rotation, a small but significant increase to 7.44 mm (1.52 mm) (P < .0002) was observed. The right side showed larger separation in most levels, except at L5/S1. The posterior and right zones increased in height upon axial rotation of the spine (P < .0001), whereas the left, anterior, and central decreased.

CONCLUSIONS

This study quantified important tensile/compressive changes disc height during torsion. The implications of these mutually opposing changes on spinal manipulation are still unknown.

Relationship between postoperative axial symptoms and the rotational angle of the cervical spine after laminoplasty

INTRODUCTION

An axial symptom is one of the postoperative problems after cervical laminoplasty. The range of motion (ROM) of the cervical spine decreases after laminoplasty. It is speculated that the reduction in neck ROM is one of the causes of axial symptoms. However, most reports have focused on ROM of the cervical spine in flexion and extension, and few papers describe the rotational motion after surgery. It is impossible to assess the rotational motion in plain X-rays. This study was undertaken for the following two purposes: (1) to compare segmental rotational angles of the cervical spine between control subjects and patients with cervical laminoplasty ; (2) to analyze the relationship between postoperative axial symptoms and the range of cervical rotational angle after laminoplasty.

METHODS

Eleven young volunteers (control 1 group) and 10 elderly subjects (control 2 group) who did not have any neck problems and 23 patients who had en bloc cervical laminoplasty due to cervical spondylotic myelopathy were included. Dynamic CT scan was conducted in neutral, right, and left maximum rotational positions from C1 to T1. We measured the rotational angle in each vertebral segment. The axial symptoms, such as limited neck motion and neck stiffness, were assessed by a questionnaire. The rotational angle of the cervical spine was compared between the patients with axial symptoms and the subjects without.

RESULTS

The rotational angle in control 1 group was greater than that in control 2 group. The rotational angle was markedly decreased in the patients with cervical laminoplasty compared to that in control 2 group. The reduction was observed at the upper vertebral segment. Twelve patients were judged to have axial symptom after cervical laminoplasty (symptom + group), and 11 patients did not have symptoms (symptom - group). The rotational angle in the symptom + group was significantly smaller than that in symptom - group. The reduction in the rotational angle was found below C2 level, whereas the C1-2 angle was not significantly different in the two symptom groups.

CONCLUSION

Reduction of the rotational angle in the cervical spine was clearly observed in patients with cervical laminoplasty, compared to that in the controls. The marked reduction might be related to the axial symptoms after laminoplasty.

Immediate effects of inhibitive distraction on active range of cervical flexion in patients with neck pain: a pilot study

The purpose of this pilot study was to examine the immediate effects of a manual therapy technique called Inhibitive Distraction (ID) on active range of motion (AROM) for cervical flexion in patients with neck pain with or without concomitant headache. A secondary objective of this study was to see whether patient subgroups could be identified who might benefit more from ID by studying variables such as age, pain intensity, presence of headache, or pre-intervention AROM. We also looked at patients' ability to identify pre- to post-intervention changes in their ability to actively move through a range of motion. Forty subjects (mean age 34.7 years; range 16-48 years) referred to a physical therapy clinic due to discomfort in the neck region were randomly assigned to an experimental and a control group. We used the CROM goniometer to measure pre- and post-intervention cervical flexion AROM in the sagittal plane within a single treatment session. The between-group difference in AROM increase was not statistically significant at P<0.05 with a mean post-intervention increase in ROM of 2.4 degrees (SD 6.2 degrees ) for the experimental group and 1.2 degrees (SD 5.8 degrees ) for the placebo group. We were also unable to identify potential subgroups more likely to respond to ID, although a trend emerged for greater improvement in chronic patients with headaches, lower pain levels, and less pre-intervention AROM. In the experimental group and in both groups combined, subjects noting increased AROM indeed had a significantly greater increase in AROM than those subjects not noting improvement. In conclusion, this study did not confirm immediate effects of ID on cervical flexion AROM but did provide indications for potential subgroups likely to benefit from this technique. Recommendations are provided with regard to future research and clinical use of the technique studied.

Quantifying the effect of age on passive range of motion of the cervical spine in healthy working-age women

STUDY DESIGN

Cross-sectional study.

OBJECTIVES

To assess age-related changes and determine reference values for passive range of motion of the cervical spine in healthy women of working age.

BACKGROUND

Although cervical mobility is age dependent, the amount in which aging affects passive range of motion has not been previously reported. It is clinically important to know the effect of normal aging process on cervical motion to be able to separate and evaluate the possible effect of pathological processes.

METHODS AND MEASURES

Two hundred twenty healthy women, aged 20 to 59 years, participated in the study. Passive range of motion of the cervical spine in flexion, extension, lateral flexion, and axial rotation was measured with the Cervical Measurement System. Measurements to calculate intrarater reliability were obtained on 22 subjects.

RESULTS

Passive range of motion of the cervical spine diminished linearly with increasing age in all measured movement planes (P<.001 for all movements except for flexion which was P = .018). Mean body mass index adjusted reduction in passive range of motion was 0.5 degrees per 1-year increase in age. Intraclass correlation coefficients for intrarater reliability ranged from 0.79 to 0.92.

CONCLUSION

A gradual age-related reduction in passive cervical range of motion was observed in women of working age.

Three-dimensional analysis of cervical spine motion: reliability of a computer assisted magnetic tracking device compared to inclinometer

We aimed to investigate the reliability and reproducibility of a magnetic tracking technique for the assessment of overall cervical spine motion (principal and coupled movements). Ten asymptomatic male volunteers with a mean age of 29.3 years (range 20-37 years) were included in the study. Flexion, extension, left and right lateral bending and left and right axial rotation were measured using a magnetic tracking device (MTD) mounted onto a custom head-piece. For rotational movements in the frontal and sagittal planes the results were compared with the measurements of two standard inclinometers. Intra-observer, inter-observer and intra-instrument reliability was assessed with the intraclass correlation coefficient method. There were no significant differences for all motion measurements between the MTD and the inclinometer. High inter-observer reliability was found in flexion, extension, axial rotation and lateral bending indicating that the testing routine is applicable for different examiners. The intra-observer variability was high in flexion and extension, whereas in lateral bending the reliability coefficients were lower and displayed a fair to good reliability for most of the measurements with the MTD. The results of the MTD were found to be highly comparable with the inclinometer results with an inter-instrument correlation coefficient ranging from 0.88 to 0.99. The MTD is a reliable, reproducible method for three-dimensional motion analysis of the cervical spine and therefore a valuable method both for the clinical assessment of various degenerative and traumatic disorders and as a supplement of different therapeutic procedures and rehabilitation.

Assessment of the cervical range of motion over time, differences between results of the Flock of Birds and the EDI-320: A comparison between an electromagnetic tracking system and an electronic inclinometer

The objective of this study was to analyse cervical range of motion, assessed over time by means of a digital inclinometer (EDI-320) and a three-dimensional electromagnetic tracking device (Flock of Birds). The maximum active cervical range of motion was assessed with two measurement devices in three sessions over time, with 6-week intervals. In total, 26 women and 24 men (mean age: 44.4, SD: 9.9) without known pathology of the cervical spine participated. Four movements were measured axial rotation with the cervical spine in a flexed and in an extended position, flexion-extension, and lateral bending. The results showed that the factor time was significant for rotation in extension and rotation in flexion. The factor device was significant for all movements measured, and the interaction term between time and device was significant for all movements except rotation in extension. The Flock of Birds measured significantly higher ranges of motion on all motions except for lateral bending. A substantial variation in cervical range of motion was observed over time (ranging from -5.6 to 8.1) as well as between devices (ranging from -13.1 to 29.9). Substantial and significant differences in cervical range of motion were found over time as well as differences between the Flock of Birds and the EDI-320.

Clinimetric evaluation of active range of motion measures in patients with non-specific neck pain: a systematic review

The study is to provide a critical analysis of the research literature on clinimetric properties of instruments that can be used in daily practice to measure active cervical range of motion (ACROM) in patients with non-specific neck pain. A computerized literature search was performed in Medline, Cinahl and Embase from 1982 to January 2007. Two reviewers independently assessed the clinimetric properties of identified instruments using a criteria list. The search identified a total of 33 studies, investigating three different types of measurement instruments to determine ACROM. These instruments were: (1) different types of goniometers/inclinometers, (2) visual estimation, and (3) tape measurements. Intra- and inter-observer reliability was demonstrated for the cervical range of motion instrument (CROM), Cybex electronic digital instrument (EDI-320) and a single inclinometer. The presence of agreement was assessed for the EDI-320 and a single inclinometer. The CROM received a positive rating for construct validity. When clinical acceptability is taken into account both the CROM and the single inclinometer can be considered appropriate instruments for measuring the active range of motion in patients with non-specific neck pain in daily practice. Reliability is the aspect most frequently evaluated. Agreement, validity and responsiveness are documented less frequently.

Assessing the range of cervical rotation in patients with rheumatoid arthritis after atlantoaxial screw fixation using axial CT

STUDY DESIGN

Case-series study.

OBJECTIVE

To assess range of cervical rotation possible after atlantoaxial fixation in rheumatoid arthritis (RA) patients using axial CT.

SUMMARY OF BACKGROUND DATA

The atlantoaxial complex is primarily responsible for rotation, and the percentage of global cervical rotation dependent on C1-C2 is 60%. Fusion of C1-C2 was expected to cause a loss of almost half the normal cervical rotation. However, some authors had reported that cervical rotation in RA patients increased after atlantoaxial fixation because of pain relief.

METHODS

Nineteen consecutive patients with atlantoaxial instability secondary to RA who had undergone transarticular fixation were included in our study. Visual analog scale was used for assessment of neck pain. We recorded functional CTs to assess C1 to T1 rotation angles before surgery and 6 months after surgery. The patient actively rotated his neck toward right as far as possible, taking care that the shoulders remained in the horizontal plane.

RESULTS

The average visual analog scale for neck pain decreased significantly from 7 (range, 4-9) before surgery to 3 (range, 0-5) at 6 months after surgery. The average preoperative C1-T1 rotation angles that were measured using axial CT were 80 degrees in total. C1-T1 rotation angle significantly decreased (55% decrease) after surgery, but there was no difference between right and left motion. Average subaxial rotation (C2-T1) was 31 degrees before surgery and did not increase after surgery.

CONCLUSION

All 19 patients with RA and atlantoaxial instability in our study had relief of pain and a significant decrease in the C1-T1 rotation angle after atlantoaxial fixation. Subaxial rotation did not change from before to after the operation.

Assessing Range of Cervical Rotation After Laminoplasty Using Axial CT

PURPOSE

Although many authors have reported on cervical range of motion after laminoplasty, they have focused on flexion and extension based on lateral radiographs, not on axial rotation. In this study, we assessed cervical rotation from C1 to T1 after laminoplasty using computed tomography.

PATIENTS AND METHODS

Eighteen consecutive patients with cervical myelopathy who had undergone laminoplasty were observed. Patient was placed in the supine position on the computed tomography scan table. After the scans in this neutral position were completed, the patient actively rotated his neck as far as possible taking care that the shoulders remained in the horizontal plane. We measured the C1 to T1, C1 to C2, and C2 to T1 rotation angles preoperatively, and at 2 weeks and 6 months after surgery.

RESULTS

The average C1 to T1 rotation angles preoperatively were 46 degrees on the right and 45 degrees on the left. The percentage of C1 to C2 rotation during global cervical rotation (C1 to T1) was 62%. C1 to T1 rotation angle significantly decreased at two weeks after surgery but recovered to almost preoperative levels (11% decreases) by 6 months after surgery with no difference between right and left motion. The average C2 to T1 subaxial rotation angles did not significantly decreased after surgery.

CONCLUSIONS

Rotation angle after laminoplasty decreased slightly at 2 weeks after surgery but recovered almost to preoperative levels by 6 months. Subaxial rotation (C2 to T1) angles did not significantly decreased after surgery.

Measurement of active rotation in standing: reliability of a simple test protocol

Interrater and intrarater reliability were evaluated for a test measuring active rotation range in a standing position. Subjects stood with their feet comfortably apart while a horizontal bar rested on their shoulders. A plumb bob attached to the end of the bar was allowed to drop to the floor, indicating maximal rotation range achieved. Two raters measured 24 subjects (M age = 35 +/- 14 yr.), who were sedentary office workers and active recreational golfers, on two occasions separated by two weeks to obtain values for left and right trunk rotation range. The test had good intrarater and interrater reliabilities, with standard error of measurement values varying from 5.6 degrees to 8.6 degrees against an overall mean range of 128 degrees. This simple active rotation test requires inexpensive equipment and could be incorporated into clinical examinations when there is a need to assess active rotation in standing with minimal constraints.