Intraobserver reliability of posturography in healthy subjects

Effects of Different Forms of Sensorimotor Training on Postural Control and Functional Status in Patients with Chronic Low Back Pain

The aim of this study was to compare three sensorimotor training forms in patients with chronic low back pain to determine their effects on the reduction of pain-related impairment and changes in posturography. Over two weeks, during the multimodal pain therapy (MMPT) period, six sessions of sensorimotor physiotherapy or training in the Galileo® or Posturomed® (n = 25 per group) were performed. A significant reduction in pain-related impairment after the intervention phase was shown across all groups (time effect: p < 0.001; ηp2 = 0.415). There was no change in postural stability (time effect: p = 0.666; ηp2 = 0.003), but there was a significant improvement in the peripheral vestibular system (time effect: p = 0.014; ηp2 = 0.081). An interaction effect was calculated for the forefoot-hindfoot ratio (p = 0.014; ηp2 = 0.111). Only the Posturomed® group showed an improvement in anterior-posterior weight distribution (heel load: 47% vs. 49%). These findings suggest that these forms of sensorimotor training in the context of MMPT are suitable for reducing pain-related impairment. Posturography demonstrated stimulation of a subsystem, but no improvement in postural stability.

Standing Steadiness and Asymmetry after High Tibial Osteotomy Surgery: A 2 Year Follow-Up Study

(1) Background: Knee osteoarthritis (OA) is a serious orthopedic problem. In this context, the high tibial osteotomy (HTO) is an established surgical procedure to reduce the load and degeneration of the affected compartment. The aim of this investigation was to judge standing steadiness and asymmetry, pain intensity and quality of life among patients who underwent HTO surgery. (2) Methods: Twenty-five male patients with medial tibiofemoral OA finished this 2 year follow-up study. Standing balance was captured using force plates with four uniaxial sensors before, 6 weeks after, 1 year after, and 2 years after HTO surgery. The percentage weight (PW) under the foot at one side, the stability (ST) index and the weight distribution (WD) index were the main outcomes. Comparisons were conducted using repeated measures analyses of variance. (3) Results: Over time, the PW under the foot at the HTO side increased on average (p < 0.001). In terms of standing steadiness, the average ST remained similar over the time points (p = 0.71). The WD index was affected by time (p = 0.003). (4) Conclusions: In order to judge short-term effects, the PW is recommended, whereas long-term effects can be identified either through the PW or the WD index.

Influence of Hearing Rehabilitation With Active Middle Ear and Bone Conduction Implants on Postural Control

Background

As audition also seems to contribute to balance control, additionally to visual, proprioceptive, and vestibular information, we hypothesize that hearing rehabilitation with active middle ear and bone conduction implants can influence postural control.

Methods

In a prospective explorative study, the impact of hearing rehabilitation with active middle ear [Vibrant Soundbrige (VSB), MED-EL, Innsbruck, Austria] and bone conduction implants [Bonebridge (BB), MED-EL, Innsbruck, Austria] on postural control in adults was examined in three experiments. Vestibulospinal control was measured by cranio-corpography (CCG), trunk sway velocity (°/s) by the Standard Balance Deficit Test (SBDT), and postural stability with a force plate system, each time in best aided (BA) and unaided (UA) condition with frontal-noise presentation (Fastl noise, 65 dB SPL), followed by subjective evaluation, respectively.

Results

In 26 subjects [age 55.0 ± 12.8 years; unilateral VSB/BB: n = 15; bilateral VSB/BB: n = 3, bimodal (VSB/BB + hearing aid): n = 8], CCG-analysis showed no difference between BA and UA conditions for the means of distance, angle of displacement, and angle of rotation, respectively. Trunk sway measurements revealed a relevant increase of sway in standing on foam (p = 0.01, r = 0.51) and a relevant sway reduction in walking (p = 0.026, r = 0.44, roll plane) in BA condition. Selective postural subsystem analysis revealed a relevant increase of the vestibular component in BA condition (p = 0.017, r = 0.47). As measured with the Interactive Balance System (IBS), 42% of the subjects improved stability (ST) in BA condition, 31% showed no difference, and 27% deteriorated, while no difference was seen in comparison of means. Subjectively, 4–7% of participants felt that noise improved their balance, 73–85% felt no difference, and 7–23% reported deterioration by noise. Furthermore, 46–50% reported a better task performance in BA condition; 35–46% felt no difference and 4–15% found the UA situation more helpful.

Conclusions

Subjectively, approximately half of the participants reported a benefit in task performance in BA condition. Objectively, this could only be shown in one mobile SBDT-task. Subsystem analysis of trunk sway provided insights in multisensory reweighting mechanisms.

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.

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.

Modified head shake sensory organization test: Sensitivity and specificity

The Sensory Organization Test (SOT) of Computerized Dynamic Posturography (EquiTest™ equipment) is a valuable tool for investigating how an individual uses balance system sensory input (vestibular, vision, proprioception/somatosensory) to maintain quiet stance; however, it is limited as a screening tool for identifying peripheral vestibular system dysfunction. Previous research has shown that adding horizontal head-shake to portions of the standard SOT battery improved the identification of peripheral vestibular system asymmetry; however, flaws in the methods were noted. The objective of this work was to evaluate the sensitivity and specificity of the modified head-shake SOT (HS-SOT) protocol for identification of peripheral vestibular system lesion. Fifteen patients with chief complaint of instability, vertigo, and/or lightheadedness, with and without a caloric unilateral weakness (UW) and fifteen age-matched healthy controls were included in the final analysis. Ten of the 15 patients demonstrated a caloric UW≥25%. Participants completed standard conditions 2 and 5 of SOT with head still and during four horizontal head-shaking tasks (i.e., HS-SOT2-60°/s, HS-SOT2-120°/s, HS-SOT5-15°/s, and HS-SOT5-60°/s). Average equilibrium scores decreased as condition difficulty increased (SOT2, HS-SOT2-60°/s, HS-SOT2-120°/s, SOT 5, HS-SOT5-15°/s, and HS-SOT5-60°/s) for each group; as expected, a lower decline was noted for controls (slope=-6.59) compared to patients (slope=-11.69). The HS-SOT5-15°/s condition was superior for identifying peripheral vestibular asymmetry (AUC=0.90 sensitivity=70%, specificity=100%), with the strongest correlation to caloric UW% (rs=-0.743, p=0.000006). HS-SOT5-15°/s appears to be a promising screening measure for peripheral vestibular asymmetry.

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.