Dynamic measurement of lumbar curvature using fibre-optic sensors

Validity and reliability of inertial measurement units used to measure motion of the lumbar spine: A systematic review of individuals with and without low back pain

Low back pain (LBP) is a leading cause of disability, resulting in aberrant movement. This movement is difficult to measure accurately in clinical practice and gold standard methods, such as optoelectronic systems involve the use of expensive laboratory equipment. Inertial measurement units (IMU) offer an alternative method of quantifying movement that is accessible in most environments. However, there is no consensus around the validity and reliability of IMUs for quantifying lumbar spine movements compared with gold standard measures. The aim of this systematic review was to establish concurrent validity and repeated measures reliability of using IMUs for the measurement of lumbar spine movements in individuals with and without LBP. A systematic search of electronic databases, incorporating PRISMA guidelines was completed, limited to the English language. 503 studies were identified where 15 studies met the inclusion criteria. Overall, 305 individuals were included, and 109 of these individuals had LBP. Weighted synthesis of the results demonstrated root mean squared differences of <2.4° compared to the gold standard and intraclass correlations >0.84 for lumbar spine movements. IMUs offer clinicians and researchers valid and reliable measurement of motion in the lumbar spine, comparable to laboratory methods, such as optoelectronic motion capture for individuals with and without LBP.

Posture Monitoring and Correction Exercises for Workers in Hostile Environments Utilizing Non-Invasive Sensors: Algorithm Development and Validation

Personal protective equipment (PPE) is an essential key factor in standardizing safety within the workplace. Harsh working environments with long working hours can cause stress on the human body that may lead to musculoskeletal disorder (MSD). MSD refers to injuries that impact the muscles, nerves, joints, and many other human body areas. Most work-related MSD results from hazardous manual tasks involving repetitive, sustained force, or repetitive movements in awkward postures. This paper presents collaborative research from the School of Electrical Engineering and School of Allied Health at Curtin University. The main objective was to develop a framework for posture correction exercises for workers in hostile environments, utilizing inertial measurement units (IMU). The developed system uses IMUs to record the head, back, and pelvis movements of a healthy participant without MSD and determine the range of motion of each joint. A simulation was developed to analyze the participant's posture to determine whether the posture present would pose an increased risk of MSD with limits to a range of movement set based on the literature. When compared to measurements made by a goniometer, the body movement recorded 94% accuracy and the wrist movement recorded 96% accuracy.

A Wearable Device Based on a Fiber Bragg Grating Sensor for Low Back Movements Monitoring

Low back pain (LBP) is one of the musculoskeletal disorders that most affects workers. Among others, one of the working categories which mainly experiences such disease are video terminal workers. As it causes exploitation of the National Health Service and absenteeism in workplaces, LBP constitutes a relevant socio-economic burden. In such a scenario, a prompt detection of wrong seating postures can be useful to prevent the occurrence of this disorder. To date, many tools capable of monitoring the spinal range of motions (ROMs) are marketed, but most of them are unusable in working environments due to their bulkiness, discomfort and invasiveness. In the last decades, fiber optic sensors have made their mark allowing the creation of light and compact wearable systems. In this study, a novel wearable device embedding a Fiber Bragg Grating sensor for the detection of lumbar flexion-extensions (F/E) in seated subjects is proposed. At first, the manufacturing process of the sensing element was shown together with its mechanical characterization, that shows linear response to strain with a high correlation coefficient (R² > 0.99) and a sensitivity value (S_ε) of 0.20 nm∙mε⁻¹. Then, the capability of the wearable device in measuring F/E in the sagittal body plane was experimentally assessed on a small population of volunteers, using a Motion Capture system (MoCap) as gold standard showing good ability of the system to match the lumbar F/E trend in time. Additionally, the lumbar ROMs were evaluated in terms of intervertebral lumbar distances (ΔdL3−L1) and angles, exhibiting moderate to good agreement with the MoCap outputs (the maximum Mean Absolute Error obtained is ~16% in detecting ΔdL3−L1). The proposed wearable device is the first attempt for the development of FBG-based wearable systems for workers’ safety monitoring.

A Multi-Parametric Wearable System to Monitor Neck Movements and Respiratory Frequency of Computer Workers

Musculoskeletal disorders are the most common form of occupational ill-health. Neck pain is one of the most prevalent musculoskeletal disorders experienced by computer workers. Wrong postural habits and non-compliance of the workstation to ergonomics guidelines are the leading causes of neck pain. These factors may also alter respiratory functions. Health and safety interventions can reduce neck pain and, more generally, the symptoms of musculoskeletal disorders and reduce the consequent economic burden. In this work, a multi-parametric wearable system based on two fiber Bragg grating sensors is proposed for monitoring neck movements and breathing activity of computer workers. The sensing elements were positioned on the neck, in the frontal and sagittal planes, to monitor: (i) flexion-extension and axial rotation repetitions, and (ii) respiratory frequency. In this pilot study, five volunteers were enrolled and performed five repetitions of both flexion-extension and axial rotation, and ten breaths of both quite breathing and tachypnea. Results showed the good performances of the proposed system in monitoring the aforementioned parameters when compared to optical reference systems. The wearable system is able to well-match the trend in time of the neck movements (both flexion-extension and axial rotation) and to estimate mean and breath-by-breath respiratory frequency values with percentage errors ≤6.09% and ≤1.90%, during quiet breathing and tachypnea, respectively.

Analyzing Spinal Shape Changes During Posture Training Using a Wearable Device

Lower back pain is one of the most prevalent diseases in Western societies. A large percentage of European and American populations suffer from back pain at some point in their lives. One successful approach to address lower back pain is postural training, which can be supported by wearable devices, providing real-time feedback about the user’s posture. In this work, we analyze the changes in posture induced by postural training. To this end, we compare snapshots before and after training, as measured by the Gokhale SpineTracker™. Considering pairs of before and after snapshots in different positions (standing, sitting, and bending), we introduce a feature space, that allows for unsupervised clustering. We show that resulting clusters represent certain groups of postural changes, which are meaningful to professional posture trainers.

Polymer Optical Fiber Sensors in Healthcare Applications: A Comprehensive Review

Advances in medicine and improvements in life quality has led to an increase in the life expectancy of the general population. An ageing world population have placed demands on the use of assistive technology and, in particular, towards novel healthcare devices and sensors. Besides the electromagnetic field immunity, polymer optical fiber (POF) sensors have additional advantages due to their material features such as high flexibility, lower Young’s modulus (enabling high sensitivity for mechanical parameters), higher elastic limits, and impact resistance. Such advantages are well-aligned with the instrumentation requirements of many healthcare devices and in movement analysis. Aiming at these advantages, this review paper presents the state-of-the-art developments of POF sensors for healthcare applications. A plethora of healthcare applications are discussed, which include movement analysis, physiological parameters monitoring, instrumented insoles, as well as instrumentation of healthcare robotic devices such as exoskeletons, smart walkers, actuators, prostheses, and orthosis. This review paper shows the feasibility of using POF sensors in healthcare applications and, due to the aforementioned advantages, it is possible to envisage a further widespread use of such sensors in this research field in the next few years.

Measurement and Geometric Modelling of Human Spine Posture for Medical Rehabilitation Purposes Using a Wearable Monitoring System Based on Inertial Sensors

This paper presents a mathematical model that can be used to virtually reconstruct the posture of the human spine. By using orientation angles from a wearable monitoring system based on inertial sensors, the model calculates and represents the curvature of the spine. Several hypotheses are taken into consideration to increase the model precision. An estimation of the postures that can be calculated is also presented. A non-invasive solution to identify the human back shape can help reducing the time needed for medical rehabilitation sessions. Moreover, it prevents future problems caused by poor posture.

[Motion Analysis of Lumbar Spine and Hip Joint on Sequential Radiographs Acquired with a Dynamic Flat-panel Detector (FPD) System]

PURPOSE

To design an evaluation method for lumbar spine and hip joint function using dynamic radiography using a flat-panel detector (FPD) system.

METHOD

Sixteen healthy subjects (males; age range, 22-60 years; median, 27 years) and 9 patients (7 males and 2 females; age range, 67-85 years; median, 73 years) with L4 degenerative spondylolisthesis were examined using a dynamic FPD system (CANON Inc.). Sequential images were captured with the subjects in the standing position with maximal forward bending followed by backward bending for 10 s. The lateral lumbar radiographs were obtained at 2 frames/s (fps). The flexion-extension angles of L1 and S1 were measured on those images.

RESULTS AND DISCUSSION

The range of motion (ROM) of the lumbar joints was significantly larger in the healthy group (82.4 ± 8.7°) than in the disease group (50.4 ± 8.5°; p<0.05). The ROM of the pelvic region was significantly smaller in the healthy group (26.9 ± 17.1°) than in the disease group (53.1 ± 17.6°; p<0.05). The healthy subjects exhibited a normal lumbar-pelvic rhythm. In the disease group, hip joint movements tended to be completed earlier compared with those in the healthy group. In the disease group, the loss of lumbar flexibility was compensated by an increase in hip joint motion due to the lumbar disease.

CONCLUSION

The dynamic FPD system is a convenient imaging modality for the diagnosis of lumbar diseases through the assessment of locomotive function in the lumbar spine and hip joints.

Development of a New Ultrasound-Based System for Tracking Motion of the Human Lumbar Spine: Reliability, Stability and Repeatability during Forward Bending Movement Trials

The aim of this study was to develop a new method for quantifying intersegmental motion of the spine in an instrumented motion segment L4-L5 model using ultrasound image post-processing combined with an electromagnetic device. A prospective test-retest design was employed, combined with an evaluation of stability and within- and between-day intra-tester reliability during forward bending by 15 healthy male patients. The accuracy of the measurement system using the model was calculated to be ± 0.9° (standard deviation = 0.43) over a 40° range and ± 0.4 cm (standard deviation = 0.28) over 1.5 cm. The mean composite range of forward bending was 15.5 ± 2.04° during a single trial (standard error of the mean = 0.54, coefficient of variation = 4.18). Reliability (intra-class correlation coefficient = 2.1) was found to be excellent for both within-day measures (0.995-0.999) and between-day measures (0.996-0.999). Further work is necessary to explore the use of this approach in the evaluation of biomechanics, clinical assessments and interventions.

Application of a novel spinal posture and motion measurement system in active and static sitting

The quantification of work-related musculoskeletal risk factors is of great importance; however, only a few tools allow objective, unrestricted measurements of spinal posture and motion in workplaces. This study was performed to evaluate the applicability of the Epionics system in a sedentary workplace. The system is mobile and wireless and assesses lumbar lordosis, pelvic orientation and spinal motion, without restricting subjects in their movements. In total, 10 males were monitored while sitting for 2 h on static and dynamic office chairs and on an exercise ball, to evaluate the effect of dynamic sitting. The volunteers were able to perform their work unhampered. No differences among the tested furniture could be detected with respect to either the lordosis or the number of spinal movements after habituation to the furniture; however, differences in pelvic orientation were statistically significant. The results of the present study indicate that Epionics may be useful for the quantitative assessment of work-related risk factors. Practitioner Summary: Only a few tools allow objective, unrestricted measurements of spinal posture and motion in the workplace. Epionics SPINE measures lumbar lordosis, pelvic orientation and spinal motion under nearly unrestricted conditions and can be used to quantify work-related musculoskeletal risk factors. We demonstrated the use of this tool in the workplace-analysis.

Midsagittal anatomy of lumbar lordosis in adult egyptians: MRI study

Despite the increasing recognition of the functional and clinical importance of lumbar lordosis, little is known about its description, particularly in Egypt. At the same time, magnetic resonance imaging (MRI) has been introduced as a noninvasive diagnostic technique. The aim of this study was to investigate the anatomy of the lumbar lordosis using midsagittal MRIs. Normal lumbar spine MRIs obtained from 93 individuals (46 males, 47 females; 25–57 years old) were evaluated retrospectively. The lumbar spine curvature and its segments “vertebrae and discs” were described and measured. The lumbar lordosis angle (LLA) was larger in females than in males. Its mean values increased by age. The lumbar height (LH) was longer in males than in females. At the same time, the lumbar breadth (LB) was higher in females than in males. Lumbar index (LI = LB/LH × 100) showed significant gender differences (P < 0.0001). Lordosis was formed by wedging of intervertebral discs and bodies of lower lumbar vertebrae. In conclusion, MRI might clearly reveal the anatomy of the lumbar lordosis. Use of LI in association with LLA could be useful in evaluation of lumbar lordosis.

Prospective quantitative assessment of spinal range of motion before and after minimally invasive surgical treatment of vertebral body fractures

INTRODUCTION

Randomized clinical trials have generated doubts regarding the therapeutic effectiveness of spinal kyphoplasty to reduce pain and improve quality of life in patients with vertebral fractures. There is a paucity of data on the influence of kyphoplasty on spinal range of motion. To quantify early postoperative changes following kyphoplasty in spinal motion, a noninvasive, radiation-free measurement method was used and results related to clinical and radiological parameters.

METHODS

The study group included 30 patients with an overall number of 54 symptomatic pathological vertebral compression fractures. All patients were treated with balloon kyphoplasty. Clinical results were recorded using the visual analog scale, SF 36, Roland Morris Score and the Oswestry Disability Index, at three time points; preoperative, 2 days postoperative, and at 12 weeks postoperative. The kyphosis angle/sagittal index were determined with biplanar X-rays. Amplitude/velocity of motion in extension/flexion was measured at each time point by use of the EpionicsSPINE(©) system (Epionics Medical GmbH; Potsdam, Germany) using two external sensor strips.

RESULTS

Preoperative magnetic resonance imaging scans showed bone marrow edema in all vertebral bodies indicative of a recent, non-consolidated fracture. Pain and quality of life was significantly improved by kyphoplasty, both for the immediate postoperative period, as well as at 12 weeks postoperative. Radiological parameters also showed significant improvement following surgery. Total ROM did not significantly change 2 days after kyphoplasty, but amplitude and velocity were found to be increased 12 weeks postoperatively. Significant positive correlations were observed between increased range of motion and improved clinical/radiological scores.

CONCLUSION

Significant clinical and radiological improvement following kyphoplasty supports the rational for cement augmentation in patients with pathological vertebral body fractures. To the knowledge of the authors, no prior study has assessed the influence of preservation and improvement of spinal range of motion on clinical outcome following kyphoplasty.

Agreement between fiber optic and optoelectronic systems for quantifying sagittal plane spinal curvature in sitting

Spinal posture affects how individuals function from a manual wheelchair. There is a need to directly quantify spinal posture in this population to ultimately improve function. A fiber optic system, comprised of an attached series of sensors, is promising for measuring large regions of the spine in individuals sitting in a wheelchair. The purpose of this study was to determine the agreement between fiber optic and optoelectronic systems for measuring spinal curvature, and describe the range of sagittal plane spinal curvatures in natural sitting. Able-bodied adults (n = 26, 13 male) participated. Each participant assumed three sitting postures: natural, slouched (accentuated kyphosis), and extension (accentuated lordosis) sitting. Fiber optic (ShapeTape) and optoelectronic (Optotrak) systems were applied to the skin over spinous processes from S1 to C7 and used to measure sagittal plane spinal curvature. Regions of kyphosis and lordosis were identified. A Cobb angle-like method was used to quantify lordosis and kyphosis. Generalized linear model and Bland-Altman analyses were used to assess agreement. A strong correlation exists between curvature values obtained with Optotrak and ShapeTape (R(2) = 0.98). The mean difference between Optotrak and ShapeTape for kyphosis in natural, extension, and slouched postures was 4.30° (95% LOA: -3.43 to 12.04°), 3.64° (95% LOA: -1.07 to 8.36°), and 4.02° (95% LOA: -2.80 to 10.84°), respectively. The mean difference for lordosis, when present, in natural and extension postures was 2.86° (95% LOA: -1.18 to 6.90°) and 2.55° (95% LOA: -3.38 to 8.48°), respectively. In natural sitting, the mean ± SD of kyphosis values was 35.07 ± 6.75°. Lordosis was detected in 8/26 participants: 11.72 ± 7.32°. The fiber optic and optoelectronic systems demonstrate acceptable agreement for measuring sagittal plane thoracolumbar spinal curvature.

Plastic optical fibre sensor for spine bending monitoring with power fluctuation compensation

This paper presents the implementation of power fluctuation compensation for an intensity-based optical fibre bending sensor aimed at monitoring human spine bending in a clinical environment. To compensate for the light intensity changes from the sensor light source, a reference signal was provided via the light reflection from an aluminum foil surface fixed at a certain distance from the source fibre end tips. From the results, it was found that the investigated sensor compensation technique was capable of achieving a 2° resolution for a bending angle working range between 0° and 20°. The study also suggested that the output voltage ratio has a 0.55% diversion due to input voltage variation between 2.9 V and 3.4 V and a 0.25% output drift for a 2 h measurement. With the achieved sensor properties, human spine monitoring in a clinical environment can potentially be implemented using this approach with power fluctuation compensation.

The effect of pain relief on dynamic changes in lumbar curvature

Lumbar curvature is important in the assessment of low back pain (LBP). It is often reported that changes in curvature seen in LBP sufferers are an adaptive response to pain. Studies investigating this hypothesis employing an experimental pain relief model have failed to isolate pain relief in their interventions. Therefore the purpose of this study was to investigate the immediate effects of pain relief on dynamic lumbar curvature. Twenty acute and 20 chronic LBP sufferers had their dynamic curvature measured using a novel fibre-optic device during flexion, extension and lifting before and after administration of oral analgesics. Peak curvature changes were examined using paired t-tests, numbers of responders to pain relief and changes in lumbar curvature sequencing were compared between groups using Chi-squared testing. A significant reduction in movement evoked pain was achieved. A significant reduction in kyphosis at end range flexion and lifting was identified for the acute LBP group following pain relief. No significant differences were observed for the chronic low back pain (CLBP) group. Neither the acute nor chronic LBP group were more likely to respond to pain relief by demonstrating alterations in peak curvature or in lumbar sequencing behaviour. These results demonstrate simple targeted pain relief did not result in gains in peak curvature challenging the assumption of movement alteration being possible through pain relief. Dynamic changes in curvature as displayed by sequencing showed that neither acute nor chronic LBP sufferers were more likely to respond to pain relief.

Velocity of lordosis angle during spinal flexion and extension

The importance of functional parameters for evaluating the severity of low back pain is gaining clinical recognition, with evidence suggesting that the angular velocity of lordosis is critical for identification of musculoskeletal deficits. However, there is a lack of data regarding the range of functional kinematics (RoKs), particularly which include the changing shape and curvature of the spine. We address this deficit by characterising the angular velocity of lordosis throughout the thoracolumbar spine according to age and gender. The velocity of lumbar back shape changes was measured using Epionics SPINE during maximum flexion and extension activities in 429 asymptomatic volunteers. The difference between maximum positive and negative velocities represented the RoKs. The mean RoKs for flexion decreased with age; 114°/s (20–35 years), 100°/s (36–50 years) and 83°/s (51–75 years). For extension, the corresponding mean RoKs were 73°/s, 57°/s and 47°/s. ANCOVA analyses revealed that age and gender had the largest influence on the RoKs (p<0.05). The Epionics SPINE system allows the rapid assessment of functional kinematics in the lumbar spine. The results of this study now serve as normative data for comparison to patients with spinal pathology or after surgical treatment.

A novel approach to the clinical evaluation of differential kinematics of the lumbar spine

Clinical measurement of lumbar motion has traditionally been limited to range of motion (ROM). Despite this, deficits in angular velocities and accelerations are more pronounced compared to ROM in low back pain (LBP) sufferers. There is increasing interest in movement quality among manual therapists and therefore the ability to measure angular velocities and accelerations within the clinical environment is becoming increasingly important. The aims of this study were to (1) investigate the reliability of a clinic based inertial sensor system to measure ROM along with angular velocities and accelerations in low back pain sufferers; (2) introduce the feasibility and reliability of using the relationship between ROM and velocity to investigate movement trajectory and irregularity. Forty LBP sufferers completed three trials of spinal movements and lifting. The ROM curve was differentiated and double differentiated to yield angular velocities and accelerations. Repeated measures reliabilities were determined by comparisons of kinematic curves as well as peak values. ROM and angular velocity relationships were investigated for their use in describing the movement trajectory and irregularity. Results show excellent similarities of ROM and angular velocity curves and moderate-to-good similarities for angular acceleration curves. Peak value similarities were excellent with small error measurements for all variables. The quantification of ROM-angular velocity plots was reliable with small mean absolute differences in motion irregularity scores. Such a method was able to demonstrate differences in movement irregularity. This method provides clinicians with the ability to yield important additional movement related information including angular velocity, acceleration and movement irregularity.

Dynamic lumbar curvature measurement in acute and chronic low back pain sufferers

OBJECTIVES

(1) To determine the reliability of a novel fiber-optic method to dynamically measure lumbar curvature in low back pain (LBP) sufferers, and (2) to investigate the dynamic lumbar curvature in acute and chronic LBP sufferers.

DESIGN

Cross-sectional study.

SETTING

Physiotherapy clinic.

PARTICIPANTS

Acute (n=20) and chronic (n=20) LBP sufferers recruited from general practitioner and therapist referrals.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

A fiber-optic device was used to measure curvature through time during flexion, lifting, and extension movements. Repeated-measures reliability for curvature-time curves was tested using coefficients of multiple correlation (CMCs) and root mean square error, and for peak curvature values intraclass correlation coefficients (ICCs) and mean absolute errors were used. Acute and chronic LBP groups were compared using peak curvatures and sequencing of curvature change.

RESULTS

The fiber-optic method was shown to be highly reliable in measuring both whole lumbar and lower lumbar curvature with CMC values >.81 and ICC values >.99. Chronic LBP sufferers displayed greater peak curvatures during flexion and lifting for the whole lumbar spine and lifting for the lower lumbar spine. The sequencing behavior demonstrated that the quartile of movement associated with the greatest curvature change was the second for flexion and lifting and first and second for extension across both groups. No significant differences in sequencing were demonstrated between the 2 groups.

CONCLUSIONS

This method is reliable for dynamic lumbar curvature measurement in back pain sufferers and is a viable option for clinicians. Acute LBP sufferers display less kyphosis during flexion and lifting. Sequencing of curvature change is similar across the 2 groups.

Comparative evaluation of a novel measurement tool to assess lumbar spine posture and range of motion

PURPOSE

The diagnosis of low back pain pathology is generally based upon invasive image-based assessment of structural pathology, but is limited in methods to evaluate function. The accurate and robust measurement of dynamic function may assist in the diagnosis and monitoring of therapy success. Epionics SPINE is an advanced strain-gauge measurement technology, based on the two sensor strips SpineDMS system, which allows the non-invasive assessment of lumbar and thoraco-lumbar motion for periods of up to 24 h. The aim of this study was to examine the reliability of Epionics SPINE and to collect and compare normative data for the characterisation of spinal motion in healthy subjects. Furthermore, the identification of parameters that influence lumbar range of motion (RoM) was targeted.

METHODS

Spinal shape was measured using Epionics SPINE in 30 asymptomatic volunteers during upright standing, as well as maximum flexion and extension, to check intra-rater reliability. Furthermore, back shape was assessed throughout repeated maximum flexion and extension movements in 429 asymptomatic volunteers in order to collect normative data of the lordosis angle and RoM in different gender and age classes.

RESULTS

The lordosis angle during standing in the healthy collective measured with Epionics SPINE was 32.4° ± 9.7°. Relative to this standing position, the average maximum flexion angle was 50.8° ± 10.9° and the average extension angle 25.0° ± 11.5°. Comparisons with X-ray and Spinal Mouse data demonstrated good agreement in static positions. Age played a larger role than gender in influencing lumbar posture and RoM.

CONCLUSIONS

The Epionics SPINE system allows the practical and reliable dynamic assessment of lumbar spine shape and RoM, and may therefore provide a clinical solution for the evaluation of lower back pain as well as therapy monitoring.

Test-retest reliability of 3D ultrasound measurements of the thoracic spine

OBJECTIVE

To explore the reliability of the Zebris CMS 20 ultrasound analysis system with pointer application for measuring end-range flexion, end-range extension, and neutral kyphosis angle of the thoracic spine.

SETTING

The study was performed within the School of Physiotherapy in cooperation with the Orthopedic Department at a University Hospital.

PARTICIPANTS

The thoracic spines of 28 healthy subjects were measured.

METHODS

Measurements for neutral kyphosis angle, end-range flexion, and end-range extension were taken once at each time point. The bone landmarks were palpated by one examiner and marked with a pointer containing 2 transmitters using a frequency of 40 kHz. A third transmitter was fixed to the pelvis, and 3 microphones were used as receiver. The real angle was calculated by the software. Bland-Altman plots with 95% limits of agreement, intraclass correlations (ICC), standard deviations of mean measurements, and standard error of measurements were used for statistical analyses. The test-retest reliability in this study was measured within a 24-hour interval.

MAIN OUTCOME MEASUREMENTS

Statistical parameters were used to judge reliability.

RESULTS

The mean kyphosis angle was 44.8° with a standard deviation of 17.3° at the first measurement and a mean of 45.8° with a standard deviation of 16.2° the following day. The ICC was high at 0.95 for the neutral kyphosis angle, and the Bland-Altman 95% limits of agreement were within clinical acceptable margins. The ICC was 0.71 for end-range flexion and 0.34 for end-range extension, whereas the Bland-Altman 95% limits of agreement were wider than with the static measurement of kyphosis. Compared with static measurements, the analysis of motion with 3-dimensional ultrasound showed an increased standard deviation for test-retest measurements.

CONCLUSIONS

The test-retest reliability of ultrasound measuring of the neutral kyphosis angle of the thoracic spine was demonstrated within 24 hours. Bland-Altman 95% limits of agreement and the standard deviation of differences did not appear to be clinically acceptable for measuring flexion and extension.