Effect of test duration and sensor location on the reliability of standing balance parameters derived using body-mounted accelerometers

BACKGROUND

Balance parameters derived from wearable sensor measurements during postural sway have been shown to be sensitive to experimental variables such as test duration, sensor number, and sensor location that influence the magnitude and frequency-related properties of measured center-of-mass (COM) and center-of-pressure (COP) excursions. In this study, we investigated the effects of test duration, the number of sensors, and sensor location on the reliability of standing balance parameters derived using body-mounted accelerometers.

METHODS

Twelve volunteers without any prior history of balance disorders were enrolled in the study. They were asked to perform two 2-min quiet standing tests with two different testing conditions (eyes open and eyes closed). Five inertial measurement units (IMUs) were employed to capture postural sway data from each participant. IMUs were attached to the participants' right legs, the second sacral vertebra, sternum, and the left mastoid processes. Balance parameters of interest were calculated for the single head, sternum, and sacrum accelerometers, as well as, a three-sensor combination (leg, sacrum, and sternum). Accelerometer data were used to estimate COP-based and COM-based balance parameters during quiet standing. To examine the effect of test duration and sensor location, each 120-s recording from different sensor locations was segmented into 20-, 30-, 40-, 50-, 60-, 70-, 80-, 90-, 100-, and 110-s intervals. For each of these time intervals, time- and frequency-domain balance parameters were calculated for all sensor locations.

RESULTS

Most COM-based and COP-based balance parameters could be derived reliably for clinical applications (Intraclass-Correlation Coefficient, ICC ≥ 0.90) with a minimum test duration of 70 and 110 s, respectively. The exceptions were COP-based parameters obtained using a sacrum-mounted sensor, especially in the eyes-closed condition, which could not be reliably used for clinical applications even with a 120-s test duration.

CONCLUSIONS

Most standing balance parameters can be reliably measured using a single head- or sternum-mounted sensor within a 120-s test duration. For other sensor locations, the minimum test duration may be longer and may depend on the specific test conditions.

Investigating the validity of a single tri-axial accelerometer mounted on the head for monitoring the activities of daily living and the timed-up and go test

BACKGROUND

Quantitative assessments of activities of daily living (ADL) play an essential role in evaluating the impact of disease and interventions on people's quality of life. Motion capture systems traditionally used for quantitative assessments of postural transitions and movement associated with ADL are limited to the laboratory setting. Wearable accelerometers can remove these limitations and enable easier-to-use, longer-term, and remote functional evaluations.

OBJECTIVE

To investigate the validity of a single tri-axial accelerometer mounted on the head for monitoring postural transition and the timed-up-and-go test.

METHODS

Two accelerometers with a sampling frequency of 100 Hz were attached to twelve able-bodied study participants' sternum and right mastoid process. We developed algorithms for the functional calibration of accelerometers and the detection of the postural transitions by measuring the head inclination angle and variations of the gravitational components of the accelerometer readout. Participants performed a battery of ADL tests involving a wide variety of postural transitions. The head-mounted accelerometers results were compared with a sternum-mounted accelerometer and validated against a video motion capture system as a gold standard reference.

RESULTS AND SIGNIFICANCE

The results indicate that, utilizing our proposed algorithm, a single tri-axial accelerometer mounted on the head can deliver high accuracy (>95 %), sensitivity (>90 %), and specificity (100 %) for detecting both postural transitions and walking events. Together with the small size and unobtrusive placement of the head-mounted accelerometer, these results demonstrate an attractive solution for the reliable assessment of ADLs and clinical evaluations based on functional tests such as the timed-up-and-go test.

Texture analysis in the classification of T2 -weighted magnetic resonance images in persons with and without low back pain

Magnetic resonance imaging findings often do not distinguish between people with and without low back pain (LBP). However, there are still a large number of people who undergo magnetic resonance imaging to help determine the etiology of their back pain. Texture analysis shows promise for the classification of tissues that look similar, and machine learning can minimize the number of comparisons. This study aimed to determine if texture features from lumbar spine magnetic resonance imaging differ between people with and without LBP. In total, 14 participants with chronic LBP were matched for age, weight, and gender with 14 healthy volunteers. A custom texture analysis software was used to construct a gray-level co-occurrence matrix with one to four pixels offset in 0° direction for the disc and superior and inferior endplate regions. The Random Forests Algorithm was used to select the most promising classifiers. The linear mixed-effect model analysis was used to compare groups (pain vs. pain-free) at each level controlling for age. The Random Forest Algorithm recommended focusing on intervertebral discs and endplate zones at L4-5 and L5-S1. Differences were observed between groups for L5-S1 superior endplate contrast, homogeneity, and energy (p = .02). Differences were observed for L5-S1 disc contrast and homogeneity (p < .01), as well as for the inferior endplates contrast, homogeneity, and energy (p < .03). Magnetic resonance imaging textural features may have potential in identifying structures that may be the target of further investigations about the reasons for LBP.

Immediate effect of prefabricated and UCBL foot orthoses on alignment of midfoot and forefoot in young people with symptomatic flexible flatfoot: A radiographic evaluation

BACKGROUND

Radiographic imaging has been considered the gold standard in evaluating the skeletal alignment of the foot in static weightbearing. The effects of foot orthoses on the alignment of foot bones have been mostly evaluated using lateral view x-rays. The posterior-anterior view has not been investigated extensively.

OBJECTIVES

To investigate the effects of 2 foot orthoses: University of California Biomechanics Laboratory Orthosis (UCBL) and a prefabricated orthosis (P-FFO) on the alignment of foot bones on anterior-posterior x-rays in young people with symptomatic flexible flatfoot (SFF).

STUDY DESIGN

This is a randomized, crossover study.

METHODS

Fifteen participants (mean [SD], 23.67 ± 2 years) with SFF were randomly imaged in 3 different conditions: shoes only, shoes + P-FFO, and shoes + UCBL. The talonavicular coverage, the first and the second talometatarsal angles, the intermetatarsal angle, and the cuboid abduction angle (CAA) were measured on weightbearing, anterior-posterior x-ray images for each condition.

RESULTS

Both orthotic designs demonstrated a significant reduction in the talonavicular coverage, the first and the second talometatarsal angles, and the CAA compared with the shoe-only condition (P < .001). The talonavicular coverage angle reduced by ∼11% using P-FFO compared with UCBL (P < .005). No significant differences were observed for other angles between the 2 orthotic conditions.

CONCLUSIONS

Both orthotic conditions improved the talonavicular coverage, first and the second talometatarsal angle, and CAA in young people with SFF. The walls of the UCBL orthosis did not result in further correction of the talonavicular coverage angle compared with the prefabricated FFO design.

Timing and dosage of FES cycling early after acute spinal cord injury: A case series report

OBJECTIVE

To understand the progression in parameters of functional electrical stimulation (FES) cycling dosage (including duration, velocity, stimulation amplitudes, power output), and the resulting changes in muscle mass early after acute spinal cord injury (SCI).

METHODS

Three participants, 24-38 years old, with neurological injury level C4-T4, severity AIS (American Spinal Injury Association Impairment Scale) A-C, started FES cycling 16-20 days post injury while admitted at a level-1 trauma center in Canada, and continued for 8-13 weeks in a rehabilitation hospital. They performed three sessions/week of 15-45 min FES cycling, supine or sitting. FES parameters, cycling performance, and muscle cross-sectional area (CSA) in thighs and calves were measured every 2 weeks.

RESULTS

Progression in power output, but not in session duration, was limited in two participants who experienced stimulation-associated referred pain or apprehension, requiring limitation of stimulation amplitudes for up to 65 days after the start of FES cycling. Participants started with 15 min cycling at 20 RPM with no resistance (0 W), and progressed to 30-45 min at 30 RPM producing 8.8-19.0 W average power/session after 2-3 months. Initially, muscle CSA decreased in all 3 participants (up to 16% after 6 weeks), and recovered later after a variable period of FES cycling (up to 16% at 13.3 weeks).

CONCLUSION

Progression of FES cycling in the first 3 months after injury required a highly individualized approach, guided by participant response, rather than standardized increments in stimulation intensity or duration. Changes in muscle CSA did not always correspond with the dose of FES cycling.

The feasibility of implementing an English language version of GLA:D Back

BACKGROUND

Evidenced-based clinical guidelines for the treatment of low back pain (LBP) consistently suggest educating patients about their back pain, its natural course, and providing advice to keep active and continue working. Despite this evidence, clinicians routinely do not follow these recommendations resulting in ineffective and fragmented care. GLA:D® Back, a standardized care package, was originally developed in Denmark to assist clinicians in implementing evidence-based care. This study will evaluate the feasibility of implementing the English version of the Danish GLA:D® Back program in Alberta, Canada.

METHODS

Thirty-five clinicians from nineteen clinics in Alberta, Canada, participated. Feasibility of program implementation, our primary objective, was evaluated within 3 months. Feasibility success was defined as 50% clinician/clinic adoption in addition to 66-88 enrolled participants registered in the database. Our secondary objectives included collecting data pertaining to clinician confidence, attitudes and behaviour of treating patients, perceived barriers and facilitators of program in addition to collecting patient-data regarding pain, function, general health and self-efficacy.

RESULTS

The majority of the clinics (15/19, 79%) offered GLA:D® Back to their patients within the study period. Of the participating clinicians, GLA:D® Back was delivered by (25/35, 71%) of clinicians. In total, 78 patients were enrolled in the program and (69/78, 88%) participants attended the final assessment. Secondarily, clinicians demonstrated a biomedical and behavioural orientation along with high confidence when treating LBP patients while patient outcomes trended toward improvement.

CONCLUSION

The English translation of the Danish GLA:D Back program was feasible for Albertan clinicians to implement into practice in both urban and rural settings.

Comparing the effectiveness of group-based exercise to other non-pharmacological interventions for chronic low back pain: A systematic review

Background

Low back pain (LBP) is the leading cause of disability worldwide with a substantial financial burden on individuals and health care systems. To address this, clinical practice guidelines often recommend non-pharmacological, non-invasive management approaches. One management approach that has been recommended and widely implemented for chronic LBP is group-based exercise programs, however, their clinical value compared with other non-pharmacological interventions has not been investigated systematically.

Objective

To compare the effectiveness of group-based exercise with other non-pharmacological interventions in people with chronic LBP.

Methods

Four electronic databases were searched by two independent reviewers. Only randomized controlled trials that compared group-based exercise with other non-pharmacological interventions for chronic LBP were eligible. Study quality was assessed using the Cochrane Handbook for systematic reviews of Interventions by two independent reviewers.

Results

Eleven studies were eligible. We identified strong evidence of no difference between group exercise and other non-pharmacologic interventions for disability level and pain scores 3-month post-intervention in people with chronic LBP. We could not find any strong or moderate evidence for or against the use of group-based exercise in the rehabilitation of people with chronic LBP for other time-points and health measurement outcomes. We found no statistically significant differences in disability and quality of life and pain between the group and individual non-pharmacological interventions that included exercise.

Conclusion

With this equivocal finding, group-based exercise may be a preferred choice given potential advantages in other domains not reviewed here such as motivation and cost. Further research in this area is needed to evaluate this possibility.

Could compression and traction loading improve the ability of magnetic resonance imaging to identify findings related to low back pain?

BACKGROUND

Diagnostic imaging is routinely used to depict structural abnormalities in people with low back pain (LBP), but most findings are prevalent in people with and without LBP. It has been suggested that LBP is related to changes induced in the spine due to loading. Therefore, new imaging measurements are needed to improve our ability to identify structures relating to LBP.

OBJECTIVES

To investigate the response of the lumbar spine to compression and traction in participants with and without chronic LBP using MRI T₂-mapping.

METHOD

Fifteen participants with chronic LBP were matched for age, weight, and gender with 15 healthy volunteers. All participants underwent MRI under three loading conditions maintained for 20 min each: resting supine, followed by compression and traction, both using 50% body weight. Participants were imaged in the last 5 min of each loading condition. Disc morphometric and fluid-based measurements from T₂-maps were obtained.

RESULTS

Traditional MRI measurements (i.e. disc height, width and mean signal intensity) were not able to capture any differences in the changes measured in response to loading between individuals with and without pain. The location of the T₂ weighted centroid (WC) was able to capture the difference between groups in response to compression in the horizontal (p < 0.01) and vertical direction (p < 0.01), and in response to traction in the vertical direction (p < 0.01). While the location of T₂WC moved anteriorly (Effect Size (ES): 0.44) and inferiorly with compression in those with pain (ES: 0.34), it moved posteriorly (ES: -0.14) and superiorly (ES: -0.05) in the group without pain. In response to traction, the vertical location of T₂WC moved superiorly in both groups but the change was larger in those with pain (ES _Pain = -0.52; ES _{No Pain}: -0.13).

CONCLUSION

The novel measurements of the location of the T₂WC in the intervertebral discs were the only measurements capturing differences in response to loading between those with and without low back pain.

Reliability and validity of lumbar disc height quantification methods using magnetic resonance images

Disc height has been a focus of research on disc degeneration and low back pain (LBP). However, choosing an appropriate method to quantify disc height remains controversial. The aim of the present study was to determine the reliability and construct validity of disc height quantification methods. Repeated semi-automatic measurements of L4-5 and L5-S1 discs were obtained from 43 T2-weighted mid-sagittal 3T magnetic resonance (MR) images of 22 subjects with LBP (43±13 years), blinded to prior measurements. Heights were calculated with area-based methods (using 60%, 80% and 100% of the disc width), and point-based methods (Hurxthal's, Dabbs' and combining the two). Intra-class correlation coefficients (ICC) and standard error of measurement (SEM) were estimated. Construct validity was assessed using correlation coefficients. Intra-rater ICC(3,1) of the area-based disc height measurements ranged from 0.84 to 0.99 with an inter-rater ICC(2,1) of 0.99. Measurements with point-based methods had lower intra- and inter-rater reliability ranging between 0.76 and 0.96 and between 0.84 and 0.98, respectively. Inter-rater SEM varied between 0.2 and 0.3 mm for area-based methods and between 0.3 and 0.7 mm for point-based methods. Excluding Dabbs', high correlations (r>0.9) were observed between methods. Area-based height measurements using partial disc width demonstrated excellent reliability and construct validity and outperformed point-based methods.

Is the location of the signal intensity weighted centroid a reliable measurement of fluid displacement within the disc?

Degenerated discs have shorter T2-relaxation time and lower MR signal. The location of the signal-intensity-weighted-centroid reflects the water distribution within a region-of-interest (ROI). This study compared the reliability of the location of the signal-intensity-weighted-centroid to mean signal intensity and area measurements. L4-L5 and L5-S1 discs were measured on 43 mid-sagittal T2-weighted 3T MRI images in adults with back pain. One rater analysed images twice and another once, blinded to measurements. Discs were semi-automatically segmented into a whole disc, nucleus, anterior and posterior annulus. The coordinates of the signal-intensity-weighted-centroid for all regions demonstrated excellent intraclass-correlation-coefficients for intra- (0.99-1.00) and inter-rater reliability (0.97-1.00). The standard error of measurement for the Y-coordinates of the signal-intensity-weighted-centroid for all ROIs were 0 at both levels and 0 to 2.7 mm for X-coordinates. The mean signal intensity and area for the whole disc and nucleus presented excellent intra-rater reliability with intraclass-correlation-coefficients from 0.93 to 1.00, and 0.92 to 1.00 for inter-rater reliability. The mean signal intensity and area had lower reliability for annulus ROIs, with intra-rater intraclass-correlation-coefficient from 0.5 to 0.76 and inter-rater from 0.33 to 0.58. The location of the signal-intensity-weighted-centroid is a reliable biomarker for investigating the effects of disc interventions.

MRI evaluation of the effects of extension exercises on the disc fluid content and location of the centroid of the fluid distribution

BACKGROUND

McKenzie prone press-up exercises have been hypothesised to reduce intradiscal pressure, allowing fluid to be reabsorbed into the disc, which could improve the internal stability and local chemical milieu of the disc, potentially reducing symptoms.

OBJECTIVE

To investigate the immediate effects of prone press-up exercises on lumbar disc fluid content and movement.

DESIGN

Quantification of MRI changes before and after a single exercise session.

METHODS

The mid-sagittal T₂-weighted MR images of 22 volunteers with low back pain were obtained before and immediately after performing press-up exercises. The whole disc and nucleus regions of the L4-5 and L5-S1 discs were then segmented, and their mean signal intensity (MSI) and signal intensity weighted centroid (SIWC) were computed to estimate disc fluid content and displacement.

RESULTS

There were no significant differences between the MSI and the vertical position of the SIWC of the whole disc before and after extension at either disc level (effect size [ES]: -0.23 to 0.09). There was a significant anterior displacement (0.1 ± 5.4 mm) of the location of the SIWC of the disc after extension exercise at L4-5 (ES: 0.22), but not at L5-S1 (ES: 0.00) or at either level for the nucleus region (ES: -0.06; 0.16).

CONCLUSION

Little evidence was found supporting the hypothesis that press-up exercises affect disc fluid content and distribution. Novel parameters reflecting fluid distribution detected similar or larger effects of the extension than MSI. If such exercises are effective in reducing symptoms, it is likely through other mechanisms than by changing fluid content or distribution.

Comparing the immediate effects of UCBL and modified foot orthoses on postural sway in people with flexible flatfoot

BACKGROUND

Different types of foot orthoses have been prescribed for patients with flatfoot. Results of several studies have shown that orthoses were able to change balance parameters in people with flatfoot. However, the possible effect of orthosis flexibility on balance has not yet been investigated.

OBJECTIVES

The aim of the current study was to investigate the immediate effect of a rigid University of California Berkeley Laboratory (UCBL) foot orthosis, a modified foot orthosis, and a normal shoe on the postural sway of people with flexible flatfoot.

STUDY DESIGN

Quasi-experimental.

METHODS

In all, 20 young adults with flatfoot (aged 23.5 ± 2.8 years) were invited to participate in this study. The Biodex Stability System was employed to perform standing balance tests under three testing conditions, namely, shoe only, UCBL, and modified foot orthosis. Total, medial-lateral, and anterior-posterior sway were evaluated for each condition.

RESULTS

The results of this study revealed no statistical difference in the medial-lateral and anterior-posterior stability indices between foot orthoses and shoed conditions. The overall stability index with the UCBL foot orthosis, however, was significantly lower than that with the modified foot orthosis.

CONCLUSION

The UCBL foot orthosis was able to decrease total sway and improve balance in people with flexible flatfoot.

CLINICAL RELEVANCE

Results of previous studies have indicated that foot orthoses were able to affect the balance of people with flatfeet. However, the possible effects of flexible orthoses on balance have not been examined. The results of this study may provide new insight into material selection for those people with balance disorders.

The effects of a prophylactic knee brace and two neoprene knee sleeves on the performance of healthy athletes: a crossover randomized controlled trial

Knee injury is one of the major problems in sports medicine, and the use of prophylactic knee braces is an attempt to reduce the occurrence and/or severity of injuries to the knee joint ligament(s) without inhibiting knee mobility. The aim of the present study was to examine the effect of one recently designed prophylactic knee brace and two neoprene knee sleeves upon performance of healthy athletes. Thirty-one healthy male athletes (age = 21.2 ± 1.5) volunteered as participants to examine the effect of prophylactic knee brace/sleeves on performance using isokinetic and functional tests. All subjects were tested in four conditions in a random order: 1. nonbraced (control) 2. using a neoprene knee sleeve 3. using a knee sleeve with four bilateral metal supports and 4. using a prophylactic knee brace. The study design was a crossover, randomized, controlled trial. Subjects completed single leg vertical jump, cross-over hop, and the isokinetic knee flexion and extension (at 60, 180, 300°/sec). Data were collected from the above tests and analyzed for jump height, cross-over hop distance, peak torque to body weight ratio and average power, respectively. Comparisons of these variables in the four testing conditions revealed no statistically significant difference (p>0.05). The selected prophylactic brace/sleeves did not significantly inhibit athletic performance which might verify that their structure and design have caused no complication in the normal function of the knee joint. Moreover, it could be speculated that, if the brace or the sleeves had any limiting effect, our young healthy athletic subjects were well able to generate a mean peak torque large enough to overcome this possible restriction. Further studies are suggested to investigate the long term effect of these prophylactic knee brace and sleeves as well as their possible effect on the adjacent joints to the knee.