Intraobserver reliability of posturography in patients with vestibular neuritis

Characterization of Gait and Postural Regulation in Late-Onset Pompe Disease

Pompe disease is a multisystemic disorder with the hallmark of progressive skeletal muscle weakness that often results in difficulties in walking and balance. However, detailed characterization of gait and postural regulation with this disease is lacking. The objective of this investigation was to determine if differences exist between the gait and postural regulation of LOPD patients and a matched control group. The gaits of 16 patients with LOPD were assessed using a gait analysis mobile system (RehaGait) and a dynamometric treadmill (FDM-T 1.8). The Interactive Balance System (IBS) was used to evaluate postural regulation and stability. All measures were compared to individual reference data. Demographic (age, gender), morphological (body height, body mass) and clinical data (muscle strength according to the Medical Research Council Scale (MRC Scale), as well as the 6-min walking test and a 10-m fast walk) were also recorded. Compared to individual reference data, LOPD patients presented with reduced gait velocity, cadence and time in single stand. A total of 87% of LOPD patients had abnormalities during posturographic analysis presenting with differences in postural subsystems. This study provides objective data demonstrating impaired gait and posture in LOPD patients. For follow-up analysis and as outcome measurements during medical or physiotherapeutic interventions, the findings of this investigation may be useful.

Postural Stability and Regulation before and after High Tibial Osteotomy and Rehabilitation

Knee osteoarthrosis (OA) is a widespread orthopedic problem and a high tibial osteotomy (HTO) is a common treatment to minimize degeneration of the affected compartment. The primary aim of this study was to evaluate the postural regulation and stability among patients who underwent HTO and rehabilitation. This prospective study included 32 patients (55.3 ± 5.57 years) diagnosed with medial tibiofemoral OA. Each subject completed postural regulation and stability testing (Interactive Balance System), as well as pain intensity (visual analogue scale) and quality of life questionnaires (SF-36) prior to HTO (exam 1), and at six weeks (exam 2), twelve weeks (exam 3) and six months (exam 4) post HTO. For postural comparison, all patients were matched (sex, age, height) with asymptomatic subjects. Significant time effects (exam 1 vs. exam 4) were found for weight distribution index (WDI; ηp2 = 0.152), mediolateral weight distribution ηp2 = 0.163) and anterior–posterior weight distribution ηp2 = 0.131). The largest difference (exam 3: ηp2 = 0.251) and the most significant differences to the matched sample were calculated for the stability indicator (exam 1: ηp2 = 0.237; exam 2: ηp2 = 0.215; exam 3: ηp2 = 0.251; exam 4: ηp2 = 0.229). Pain intensity showed a significant reduction (ηp2 = 0.438) from exam 1 (50.7 ± 20.0 mm) to exam 4 (19.3 ± 16.0 mm). Physical pain was the quality of life parameter with the largest improvement between exams 1 and 4 (ηp2 = 0.560). HTO allows patients to improve their mediolateral weight distribution, whereas postural stability is consistently lower than in asymptomatic subjects. This surgery leads to marked improvements in quality of life and pain.

Postural regulation and stability with acoustic input in normal-hearing subjects

Background

Postural regulation is based on complex interactions among postural subsystems. The auditory system too appears to have an influence on postural control.

Objective

The aim of this study was to measure the influence of auditory input on postural control and to gain a deeper understanding of the interactions between auditory input and postural subsystems including subjective aspects.

Materials and methods

In 30 healthy normal-hearing subjects, postural regulation and stability was measured with the Interactive Balance System (IBS; Inc. neurodata GmbH, Wien, Österreich) in 8 test positions with noise (frontal presentation) and plugged without noise. The IBS is an electrophysiological measurement device that measures postural control at the product level (e.g., stability, weight distribution) and the mechanisms of postural subsystems at the process level based on frequency-oriented fast-Fourier analysis of force–time relation.

Results

At the process level, we found a relevant reduction (η_p² ≥ 0.10) of postural regulation with noise in the frequency bands F1 (visual and nigrostriatal system η_p² = 0.122) and F2–4 (peripheral vestibular system η_p² = 0.125). At the product level, the weight distribution index (WDI) parameter showed a relevant increase with noise (η_p² = 0.159). No difference between the auditory conditions was found for postural stability (parameter: stability indicator, ST). Substantial interindividual variations in the subjective estimation of the influence of auditory inputs on stability were observed.

Conclusion

In this study, a shift in the activity of postural subsystems was observed with auditory input, while no difference was seen in ST. This leads to new insights into mechanisms of audiovestibular interaction.

[Postural regulation and stability with acoustic input in normal hearing subjects. German version]

BACKGROUND

Postural regulation is based on complex interactions among postural subsystems. The auditory system too appears to have an influence on postural control.

OBJECTIVE

The aim of this study was to measure the influence of auditory input on postural control and to gain a deeper understanding of the interactions between auditory input and postural subsystems including subjective aspects.

MATERIALS AND METHODS

In 30 healthy normal-hearing subjects, postural regulation and stability was measured with the Interactive Balance System (IBS; Inc. neurodata GmbH, Wien, Österreich) in 8 test positions with noise (frontal presentation) and plugged without noise. The IBS is an electrophysiological measurement device that measures postural control at the product level (e.g., stability, weight distribution) and the mechanisms of postural subsystems at the process level based on frequency-oriented fast-Fourier analysis of force-time relation.

RESULTS

At the process level, we found a relevant reduction (η_p² ≥ 0.10) of postural regulation with noise in the frequency bands F1 (visual and nigrostriatal system η_p² = 0.122) and F2-4 (peripheral vestibular system η_p² = 0.125). At the product level, the weight distribution index (WDI) parameter showed a relevant increase with noise (η_p² = 0.159). No difference between the auditory conditions was found for postural stability (parameter: stability indicator, ST). Substantial interindividual variations in the subjective estimation of the influence of auditory inputs on stability were observed.

CONCLUSION

In this study, a shift in the activity of postural subsystems was observed with auditory input, while no difference was seen in ST. This leads to new insights into mechanisms of audiovestibular interaction.

Towards computerized diagnosis of neurological stance disorders: data mining and machine learning of posturography and sway

We perform classification, ranking and mapping of body sway parameters from static posturography data of patients using recent machine-learning and data-mining techniques. Body sway is measured in 293 individuals with the clinical diagnoses of acute unilateral vestibulopathy (AVS, n = 49), distal sensory polyneuropathy (PNP, n = 12), anterior lobe cerebellar atrophy (CA, n = 48), downbeat nystagmus syndrome (DN, n = 16), primary orthostatic tremor (OT, n = 25), Parkinson's disease (PD, n = 27), phobic postural vertigo (PPV n = 59) and healthy controls (HC, n = 57). We classify disorders and rank sway features using supervised machine learning. We compute a continuous, human-interpretable 2D map of stance disorders using t-stochastic neighborhood embedding (t-SNE). Classification of eight diagnoses yielded 82.7% accuracy [95% CI (80.9%, 84.5%)]. Five (CA, PPV, AVS, HC, OT) were classified with a mean sensitivity and specificity of 88.4% and 97.1%, while three (PD, PNP, and DN) achieved a mean sensitivity of 53.7%. The most discriminative stance condition was ranked as "standing on foam-rubber, eyes closed". Mapping of sway path features into 2D space revealed clear clusters among CA, PPV, AVS, HC and OT subjects. We confirm previous claims that machine learning can aid in classification of clinical sway patterns measured with static posturography. Given a standardized, long-term acquisition of quantitative patient databases, modern machine learning and data analysis techniques help in visualizing, understanding and utilizing high-dimensional sensor data from clinical routine.

Does low back pain affect the reliability of postural regulation?

The aim of this study was to examine the intraobserver reliability of a posturographic assessment in patients with low back pain. We investigated 24 symptomatic subjects with defined low back pain (mean: 57.9 years) and a pair-matched control group including 24 asymptomatic persons (mean: 58.1 years). Each participant underwent two measurements on a posturographic device (32 Hz sampling rate) based on the Interactive Balance System (time interval: 7 d). Test procedure consisted of tests on solid ground with eyes open (1) and eyes closed (2). Data analysis included parameters of motor output and a frequency band analysis. Reliability tests were realized using by intraclass correlations (ICC). Coefficients of ICC ranged from 0.36 (95% CI: 0.01-0.73) to 0.94 (95% CI: 0.86-0.97) in both test positions. For 69% (11/16) of the investigated parameters a high level (ICC > 0.75) of intraobserver reliability was reached. Based on the results, the posturographic measurement system used in this study seems to be appropriate for use in longitudinal study designs in an orthopaedic setting.

Postural stability and regulation before and after anterior cruciate ligament reconstruction - A two years longitudinal study

OBJECTIVES

To evaluate postural regulation and stability among patients who underwent anterior cruciate ligament reconstruction (ACLR) and rehabilitation over a two-year follow-up period.

DESIGN

Longitudinal; SETTING: Biomechanics laboratory; PARTICIPANTS: 30 ACLR patients (32.0 ± 12.2 years, 14 males) with isolated ACL rupture.

MAIN OUTCOME MEASURES

Postural regulation was tested before ACLR, as well as at six-weeks, twelve-weeks, six-months, one-year and two-years post-ACLR and standardized rehabilitation. Postural regulation was measured for stability indicator (ST), weight distribution index (WDI), synchronization (foot coordination) and sway intensities (postural subsystems).

RESULTS

Significant time effects (pre-vs. two-years postoperative) were found for WDI (η_p² = 0.466), synchronization (η_p² = 0.368), mediolateral weight distribution (η_p² = 0.349), ST (η_p² = 0.205), visual/nigrostriatal systems (η_p² = 0.179) and peripheral-vestibular system (η_p² = 0.102). The largest difference (preoperative: η_p² = 0.180) to the matched sample was calculated for WDI. The most significant differences to the matched sample were observed for ST (preoperative: η_p² = 0.126; six-weeks postoperative: η_p² = 0.103) and WDI (preoperative: η_p² = 0.180; six-weeks postoperative: η_p² = 0.174).

CONCLUSION

ACLR and rehabilitation influence postural subsystems, postural stability, weight distribution and foot synchronization. Normalization of mediolateral weight distribution requires one year following ACLR. The ACLR leads to a suppression of the somatosensory and cerebellar system which was compensated by a higher activity of the visual and nigrostriatal systems.

Comparison of posturographic outcomes between two different devices

The Interactive Balance System (IBS), a posturography device for assessing posture control, is widely used in clinical and rehabilitation settings. However, data on the validity of the device are unavailable. Fluctuations of the center of pressure (COP) were measured in 24 healthy participants (age: 29 ± 5 (mean ± SD) years, 12 females) synchronously using the IBS, which was rigidly mounted on a Kistler platform. Four different bipedal conditions were examined: eyes open or closed on stable or soft surfaces. Time series were compared using congruity (CON, proportion of the measurement time during which values of both devices changed similarly in direction), whereas IBS-specific postural outcomes were correlated with traditional postural control outcomes of the Kistler force platform. The time-displacement curves showed similar shapes for CON (>0.9) for each of the four standing conditions without differences between male and female participants (P > 0.39). The path length results of both devices showed very high linear associations, explaining on average 92% (medio-lateral) or 96% (anterior-posterior) of the common variance. The Kistler path length of the anterior-posterior direction revealed nearly perfect linear associations with the stability index of the IBS (r² > 0.99). The results of this study indicate that the IBS provides valid posturographic results. Since the medial-lateral and anterior-posterior trajectories of the IBS can be used to calculate COP fluctuations, comparisons between different measurement systems are possible.

Significance of Stabilometry for Assessing Postoperative Body Sway in Patients with Cervical Myelopathy

Study Design

Prospective study.

Purpose

To examine the changes in body sway using stabilometry in patients who underwent cervical laminoplasty for cervical myelopathy.

Overview of Literature

Although the patients of cervical myelopathy complain body sway there are few report to examine body sway objectively.

Methods

Patients who received treatment for cervical myelopathy between October 2010 and February 2013 were included. Twenty-one patients underwent cervical laminoplasty (myelopathy group). Body sway was assessed using stabilometry, wherein patients stood on a stabilometer with their eyes closed for 30 seconds. The Romberg ratio, outer peripheral area (OPA) with eyes closed (cm2), and total locus length per unit area (L/A) with eyes closed (/cm) were examined. Examinations were performed preoperatively (at baseline) and at 8 weeks postoperatively. Examination results of patients in the myelopathy group were compared with those of 17 healthy individuals (control group). Clinical symptoms were evaluated using the Japanese Orthopaedic Association scale score (JOA score) and the timed up and go (TUG) test.

Results

In the myelopathy and control groups, the mean baseline Romberg ratio, OPA, and L/A were 2.3±1.2, 8.9±5.5 cm², and 14.2±5.3/cm and 1.4±1.0, 4.3±2.8 cm², and 23.7±10.1/cm, respectively. Eight weeks after laminoplasty, only L/A showed significant improvement from baseline in the myelopathy group (23.2±10.1 to 16.8±7.9; p=0.03). The Romberg ratio and OPA showed improvement in the myelopathy group, but the changes were not statistically significant. JOA scores and TUG test results in this group significantly improved from baseline to 8 weeks after laminoplasty (12.7 to 13.4 and 10.8 to 8.0 seconds, respectively; both p<0.05).

Conclusions

L/A is a useful parameter for measuring body sway to assess the recovery of body sway after laminoplasty.

Comparison of intraobserver single-task reliabilities of the Interactive Balance System (IBS) and Vertiguard in asymptomatic subjects

The intraobserver reliabilities of the Interactive Balance System (IBS) and Vertiguard were compared in 30 asymptomatic volunteers. Relative reliability for all IBS single tasks and parameters in the IBS was excellent (intraclass correlation coefficient, ICC ≥0.75). The ICC values ranged from 0.78 to 0.89. The ICC values of the Vertiguard system ranged from 0 to 0.75. The cumulative measure of injury risk of the Vertiguard system was highly reliable.

Validity and Reliability of the New Handball-Specific Complex Test

The purpose of this study was to determine the intraobserver reliability (IR) of the handball-specific complex test (HBKT) and the validity of the HBKT and nonspecific tests. Thirty experienced players (25.7 ± 3.9 years) executed the HBKT twice (time interval: 2 days). Lactate, heart rate (HR), time, throwing velocity and number of errors were measured. Afterwards, players' match performances (MPs) in 30 matches were evaluated using video analysis to compare it with the test parameters. Resting HR between first half and second half (r(2) = 0.26), standing long jump (r(2) = 0.18), jump and reach (r(2) = 0.16), and HR before second half (r(2) = 0.14) were proven to be the most valid tests or parameters. The amounts of explained variance concerning the MP of all other tests/parameters were below 10%. Overall, 41% (12/29) of the parameters showed a high relative intraclass correlation coefficient (ICC > 0.75) and absolute coefficient of variation (CV ≤ 5%) IR. Results suggest that the HBKT can be certified with an insufficient validity and a sufficient absolute (∅CV = 11.3%) and relative (∅ICC = 0.67) IR. The reasons could be insufficient tests or insufficient score of MP. The current findings suggest that the coaches and scientists should recognize a lot of effort is necessary to measure MP and to develop valid tests. Additional research should aim to connect test and MP with each other. Before a coach applies a test, he should thoroughly check whether the test is valid (gold standard: MP) and reliable. The frequent and long-term test application (very common argument of the coaches in practice) is not a proof of validity.