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cta Otorrinolaringol Esp. 2012;63(5):332---338

www.elsevier.es/otorrino

RIGINAL ARTICLE

tatic Posturography With Dynamic Tests. Usefulness ofiomechanical Parameters in Assessing Vestibular Patients�

amón Balaguer García,a,∗ Salvador Pitarch Corresa,b José María Baydal Bertomeu,b

aría M. Morales Suárez-Varelac

Servicio de Otorrinolaringología, Hospital General Universitario de Elche, Elche, Alicante, SpainLínea de Valoración Biomecánica, Instituto de Biomecánica de Valencia, Universidad Politécnica de Valencia, Valencia, SpainÁrea de Medicina Preventiva y Salud Pública, Universidad de Valencia, Valencia, Spain

eceived 5 December 2011; accepted 22 March 2012

KEYWORDSBalance;Equilibrium;Postural control;Posturography;Vestibular disorders

AbstractIntroduction and objective: Posturography allows us in evaluating postural control. This studyshowed the posturographic parameters that were useful for assessing the functional ability tomaintain balance in our sample of vestibular patients.Material and methods: Of a total of 89 patients, 59 were healthy subjects and 30 had a periph-eral vestibular disorder. The subjects were studied using the posturographic NedSVE/IBV system,combining static (Romberg) and dynamic (stability limits and rhythmic weight shifts) tests. Wethen compared the measurements found in the groups.Results: Normal subjects showed significantly lower oscillations than our patients in all of theposturographic parameters studied (except the displacement angle). In testing the limits ofstability, although normal subjects achieved maximum displacements greater than the subjectswith the disorder, the differences found were not significant. In rhythmic weight shift tests,normal subjects showed more favourable results than did the vestibular patients, with signifi-cant differences in 3 of the 4 parameters studied: (1) anteroposterior ability, (2) mediolateralability, and (3) anteroposterior control and efficiency.Conclusion: Rhythmic weight shift tests and the static posturography test parameters used wereuseful in discriminating among the normal and pathological subjects in this study.© 2011 Elsevier España, S.L. All rights reserved.

PALABRAS CLAVE

Estabilidad;Equilibrio;Control postural;Posturografía;

Posturografía estática con pruebas dinámicas. Utilidad de los parámetrosbiomecánicos en la valoración del paciente vestibular

ResumenIntroducción y objetivos: La posturografía permite evaluar el control postural de un sujeto.En este estudio se presentan aquellos parámetros biomecánicos del sistema de posturografía

� Please cite this article as: Balaguer García R, et al. Posturografía estática con pruebas dinámicas. Utilidad de los parámetros biomecánicosn la valoración del paciente vestibular. Acta Otorrinolaringol Esp. 2012;63:332---8.∗ Corresponding author.

E-mail address: balaguergarcia@gmail.com (R. Balaguer García).

173-5735/$ – see front matter © 2011 Elsevier España, S.L. All rights reserved.

Static Posturography With Dynamic Tests 333

Trastornosvestibulares

empleado, que han resultado útiles para valorar funcionalmente los pacientes vestibulares denuestra muestra.Material y métodos: De un total de 89 participantes, 59 eran sujetos sanos y 30 presentabanun trastorno vestibular periférico. Todos ellos realizaron un estudio posturográfico medianteel sistema NedSVE/IBV que combina pruebas estáticas (Romberg) y dinámicas (límites deestabilidad y control rítmico-direccional). Posteriormente se compararon las medidas halladasen uno y otro grupo.Resultados: Los sujetos normales presentaron menores oscilaciones que los enfermos en losdistintos parámetros posturográficos estudiados (excepto en el ángulo de desplazamiento) deforma estadísticamente significativa. En la prueba de los límites de estabilidad, aunque lossujetos normales lograron desplazamientos máximos mayores que los enfermos, las diferenciashalladas no fueron significativas. En la prueba de control rítmico y direccional, los sujetosnormales presentaron resultados más favorables que los patológicos y las diferencias fueronsignificativas en 3 de los 4 parámetros estudiados: 1) habilidad anteroposterior, 2) habilidadmediolateral, y 3) control y eficacia anteroposterior.Conclusión: Los parámetros del sistema de posturografía estática empleado y la prueba decontrol rítmico y direccional resultaron de utilidad para discriminar entre los sujetos normalesy patológicos de nuestra muestra.© 2011 Elsevier España, S.L. Todos los derechos reservados.

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Introduction

The ability to control posture spontaneously or in responseto external alterations is known as postural control (PC). Itconsists of maintaining the position of the body, specificallythe centre of gravity, within certain stability limits (SL). Thisprocess begins in the vestibular, visual, and somatosensoryreceptors, whose afferents are processed and integrated byvarious structures of the central nervous system and leadto mechanical actions of the musculoskeletal system. Theinstrumental study of PC as a means to quantify and objec-tify instability has led to the development of posturographytechniques which analyse standing balance in situations ofincreasing complexity and report on the functional status ofstudied subjects. They are based on the use of dynamomet-ric platforms which register the movements of the centre ofpressures of a subject.1---5

The ‘‘gold standard’’ technique for the study of PCis computerised dynamic posturography (CDP) or EquiTest(NeuroCom® Inc., Clackamas, OR, USA).6 The AmericanAcademy of Otolaryngology and Head and Neck Surgeryrecognises CDP as an appropriate test for the evaluation andtreatment of patients with vestibular lesions.7 The Ameri-can Academy of Neurology8 considers it as a useful system toanalyse the ability to maintain PC in both healthy and patho-logical individuals, while the American Medical Associationregards it as a method to objectify deficits and disabilities.

Other posturography models have been gradually devel-oped since the onset of CDP. These provide informationwhich, albeit not equivalent, may be equally useful in theassessment of unstable patients. One such system is theNedSVE®/IBV developed by the Institute of Biomechanics ofValencia (IBV).

The NedSVE® system created by the IBV is an applica-tion for the functional evaluation of balance disorders which

combines static posturography tests with dynamic exercises.The assessment of each test is based on the calculationof certain biomechanical parameters which reflect the dis-placement of the pressure centre of the subject.

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This work aims to determine which of the parameterssee ‘‘Material and Methods’’ section) used by the posturo-raphy system are relevant in the functional evaluation ofnstable patients. To do this, we compared the results oftatic posturography, SL tests, and rhythmic weight shiftsRWS) tests between healthy subjects and subjects sufferingestibular disorders of peripheral origin.

aterial and Methods

he sample consisted of 59 participants without known dis-ase, which we considered as normal subjects, and 30 withestibular disease, which we considered as pathological sub-ects.

ormal Subjects

ormal subjects underwent a detailed medical history inrder to rule out episodes of vertigo, imbalance or insta-ility. We excluded all those who presented neurological,phthalmological, psychiatric or musculoskeletal systemiseases. In addition, we did not include patients whoere following treatment with drugs affecting the centralervous system (antidepressants, neuroleptics, benzodi-zepines, anticonvulsants, vestibular sedatives, etc.).

athological Subjects

he pathological group consisted of previously diagnosedatients monitored at the Otolaryngology Service of Hos-ital Dr. Peset and Hospital de la Ribera in Valencia, whoad a clinical history of balance disorders due to peripheralestibular disease. We excluded subjects with neurological,phthalmological, psychiatric or musculoskeletal system

iseases which could be the cause of imbalance or whichmpeded understanding or conducting the tests. Moreover,e did not include patients following treatment with drugshich acted on the central nervous system (antidepressants,

334

Table 1 Clinical Diagnosis of Pathological Subjects.

No.

Unilateral Ménière’s disease 15Vestibular neuritis 3Labyrinthitis 2Vertigo of undetermined origin 7Labyrinthectomy 1Drug ototoxicity 1Perilymphatic fistula 1

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euroleptics, benzodiazepines, anticonvulsants, vestibularedatives, etc.).

Table 1 describes the clinical entities presented by stud-ed patients. All subjects in the sample reported vertigo,izziness or instability within the 6 weeks prior to theompletion of posturography. The monitoring period foriagnosis ranged from 1 to 5 years.

Patients underwent a detailed history, a completetoneurological examination and an audio-vestibular study.he otoneurological examination included an analysis ofpontaneous nystagmus (with and without fixed vision), posi-ional nystagmus, oculocephalic manoeuvre, and cephalichaking nystagmus. The audio-vestibular study was basedn: (1) liminal tone audiometry along with other audiologi-al tests (depending on the liminal tonal audiometry) with

clinical audiometer (Interacoustics® A/S AC 40 with TDH9 earphones and a Radioear® B71 bone conductor), and2) a study of the extrinsic ocular motility (saccades, track-ng and optokinetic nystagmus) along with caloric tests (CT)rrigating the external auditory canal with water (150 �l at0---44 ◦C in 30 s), and nystagmus recorded by videonystag-ography (Ulmer VNG, v.1.4, SYNAPSIS®, Marseille, France).he parameters used were canalicular paresis and direc-ional preponderance, according to the Jongkees formula.alues below 20% and 28%, respectively, were consideredormal.

All patients underwent a consultation at the Neurologyervice, in order to discard any disorders with a centralrigin.

This exploration was conducted in support of the diag-osis of vestibulopathy. Its results were compared withhose found through the instrumental exploration, which areescribed below.

All subjects in the sample underwent an instrumentaltudy using the NedSVE®/IBV system and following the pro-ocol and methodology recommended by the IBV, includingtatic posturography with dynamic tests.9

nstrumental Study

tatic Posturography TestsC was measured under various conditions: Romberg withpen eyes (ROE), Romberg with closed eyes (RCE), Romberg

n a foam mattress with open eyes (RFO), Romberg on a foamattress with closed eyes (RFC). Tests were conducted by

ncreasing difficulty: (1) ROE, (2) RCE, (3) RFO and, finally,4) RFC.

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The following biomechanical parameters were recordeduring each of these tests: (1) displacement angle (◦): thiss the orientation of the displacement vector expressed inegrees. The displacement vector extends from the initialtarting point of the subject to the final position; (2) sweeprea (mm2): this is the approximate area in which subjectalancing takes place. In order to obtain this calculation,he software application determines an ellipse encompass-ng a cloud of points representing the path of the subjecturing the duration of the test; (3) mean speed (m/s):his is the total distance travelled by the pressure centreuring the test divided by the time elapsed; (4) maximumediolateral and anteroposterior displacements (mm):

hese represent the farthest point reached by the centref pressures in the mediolateral and anteroposterior axesuring the registration time; and (5) maximum mediolateralnd anteroposterior forces (N): these are the maximumorces registered during the exercise in a mediolateral andnteroposterior direction, expressed in Newtons.

ontrol and Ability Assessment Testshis included the assessment of SL and analysis of the RWS.

n the SL test, subjects had to seek the position of greatesttability whilst standing with arms relaxed and parallel tohe body and feet positioned so that the heels were touchingnd the toes were diverging at an angle of 30◦. Next, whilstooking at a computer monitor placed in front and at eyeevel and without altering their base of support, subjects hado move a cursor which reflected the position of their cen-re of gravity towards 8 targets located in their theoreticalL, at intervals of 45◦. The subjects were given 8 s to moveheir centre of gravity to each target and had to remainhere as long as they could. The distance at which each ofhem appeared depended on the age and height of the sub-ect. The biomechanical parameter calculated for each SLfront, front-right, right, rear-right, rear, rear-left, left andront left) was the maximum displacement (%), which wasepresented by the percentage obtained with respect to theormality pattern (segmented by gender, age and height) ofreatest displacement achieved in each direction.

In the RWS test, subjects had to look at a monitor placedn front and at eye level and follow the rhythmic motionf a moving target with the projection of their centre ofravity. The study consisted of 2 tests; one in which thearget moved horizontally and another in which it movedertically at 3 different speeds: slow, medium, and fast.n order to perform this exercise, it was necessary to havereviously determined the SL of the subject. The followingiomechanical parameters were calculated in this test: (a)bility (%): this estimated how closely the subjects followedhe motion of the target with the movement of their centref gravity; and (b) control and efficacy (%): this estimatedow closely the subjects followed the motion of the targetith the perpendicular movement of their centre of gravity.

tatistical Analysis

he final database was elaborated using the softwareackage SPSS® v.17. The evaluation of results consisted of aescriptive analysis and a comparative analysis.

Static Posturography With Dynamic Tests 335

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30

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Table 3 Mean and Standard Deviation of the Static Post-urography Parameters in the ROE, RCE, RFO and RFC Tests.

Normal Pathological

Displacement angle,◦

ROE 161.01 ± 81.02 215.10 ± 79.84RCE 166.92 ± 77.32 183.60 ± 81.62RFO 175.98 ± 87.37 173.64 ± 82.68RFC 175.59 ± 80.55 205.49 ± 96.58

Sweep area, mm2

ROE 39.97 ± 23.58 83.03 ± 91.71RCE 80.50 ± 46.65 201.86 ± 239.43RFO 104.63 ± 44.39 205.78 ± 147.32RFC 748.62 ± 377.16 994.64 ± 522.86

Mean velocity, m/sROE 0.011 ± 0.002 0.014 ± 0.006RCE 0.016 ± 0.006 0.022 ± 0.011RFO 0.019 ± 0.004 0.027 ± 0.007RFC 0.057 ± 0.017 0.068 ± 0.022

Mediolateral displacement, mmROE 13.33 ± 4.19 18.12 ± 8.94RCE 23.06 ± 7.10 31.46 ± 17.60RFO 22.29 ± 3.91 29.26 ± 8.71RFC 68.56 ± 16.93 80.10 ± 23.96

Anteroposterior displacement, mmROE 17.08 ± 4.81 26.27 ± 12.49RCE 22.54 ± 6.55 38.18 ± 23.56RFO 32.62 ± 7.62 46.67 ± 19.09RFC 72.72 ± 15.17 81.37 ± 21.13

Maximum mediolateral force, NROE 3.69 ± 2.10 6.73 ± 3.91RCE 5.47 ± 2.97 9.91 ± 7.59RFO 6.52 ± 3.30 11.98 ± 6.11RFC 16.15 ± 8.19 25.77 ± 14.27

Maximum anteroposterior force, NROE 4.84 ± 2.04 6.40 ± 4.02RCE 7.48 ± 3.61 12.19 ± 14.19RFO 10.57 ± 3.53 14.73 ± 7.70RFC 28.38 ± 8.44 31.71 ± 17.29

RCE: Romberg closed eyes; RFC: Romberg on foam and closed

Figure 1 Gender distribution of normal and pathological sub-jects.

The descriptive analysis of variables took into accountwhether they presented a parametric distribution or not(Kolmogorov---Smirnov test). If they were parametric, thenthe arithmetic mean and standard deviation were used asmeasures of central tendency and dispersion, respectively.

Sample differences were considered statistically signifi-cant when they reached values of P<.05.

Results

The total sample consisted of 43 males and 46 females.Among the normal subjects, 29 were male and 30 werefemale. Among the pathological subjects, 14 were male and16 were female (Fig. 1). The general characteristics of bothgroups are reflected in Table 2. Sample subjects reportedsuffering symptoms of vertigo, dizziness or unsteadiness22.36±13.66 days prior to posturography.

All subjects underwent the instrumental study. Weobserved that both normal and pathological patients hadless balancing in the ROE test, somewhat greater in the RCEtest, greater still in the RFO test, and the greatest oscilla-tions were recorded in the RFC test. This oscillation increasewas reflected in all parameters of the static posturography,with the exception of the displacement angle (Table 3).

Normal subjects presented less oscillations than allpathological subjects in the different biomechanical param-eters studied (except for the displacement angle), with

statistically significant differences (Table 4).

In the SL test, normal subjects achieved greater maxi-mum displacements than pathological subjects (except forthe rear SL), although the differences found were not

Table 2 Mean and Standard Deviation of the General Char-acteristics of the Sample.

Normal Pathological

Age, years 49.15 ± 18.15 48.15 ± 9.89Weight, kg 74.00 ± 16.13 75.17 ± 16.99Size, cm 167 ± 9.26 167.33 ± 8.97BMI 26.42 ± 4.70 26.71 ± 5.00

BMI: body mass index.

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eyes; RFO: Romberg on foam and open eyes; ROE: Romberg openeyes.

tatistically significant. The descriptive and comparativeesults of this test are shown in Tables 5 and 6, respectively.

Normal subjects presented more favourable results thanathological subjects in the rhythmic weight shifts testTable 7). The differences between both groups were sta-istically significant in 3 of the 4 parameters studied: (1)nteroposterior ability, (2) mediolateral ability, and (3)nteroposterior control and efficacy (Table 8).

iscussion

n some patients, posturography can detect the negativenfluence exerted by a vestibular alteration on postural sta-ility. It does not replace the classic tests which evaluate

336 R. Balaguer García et al.

Table 4 Statistical Significance (P) of the Comparison of Results Between the Different Parameters of Static Posturography ofNormal and Pathological Subjects.

ROE RCE RFO RFC

Displacement angle,◦ .003 .302 .815 .426Sweep area, mm2 .004 .001 .001 .002Mean velocity, m/s .001 .002 .001 .003Mediolateral displacement, mm .003 .002 .001 .002Anteroposterior displacement, mm .001 .001 .001 .005Maximum mediolateral force, N .001 .001 .001 .001Maximum anteroposterior force, N .007 .006 .001 .040

the vestibulo-ocular reflex, but instead provides comple-mentary information, enabling a better understanding of thefunctional status of patients with instability.

In his posturography work, Norré studied 3 classicalgroups of vestibular conditions: (1) patients with benignparoxysmal positional vertigo (BPPV); (2) patients with spon-taneous vertigo crises, including patients with Meniere’sdisease or those suffering recurrent vertigo without audi-tory involvement classified as recurrent vestibulopathy; and(3) patients with sudden unilateral hearing loss, of a vesti-bular neuronitis type.10,11 Coinciding with Norré, our studyincluded patients with vestibular disorders, although witha more heterogeneous distribution of conditions. In turn,we could not include patients with BPPV in the study sincesuch patients were not available during the data collectionperiod.

Table 5 Mean and Standard Deviation of the Maximum Dis-placements of Normal and Pathological Subjects.

Normal Pathological

Mean SD Mean SD

Front 108.66 5.97 105.82 16.64Front right 102.21 8.85 101.66 17.21Right 104.69 10.01 102.34 12.26Rear right 109.02 9.12 108.14 13.77Rear 102.45 12.41 112.47 18.72Rear left 104.16 10.48 104.63 17.06Left 102.88 10.36 99.69 12.05Front left 102.38 7.26 99.05 11.50

SD: standard deviation.

Table 6 Statistical Significance (P) of the Comparison ofMaximum Displacements (%) of the Various Stability LimitsBetween Normal and Pathological Subjects.

P

Front .452Front right .545Right .077Rear right .195Rear .130Rear left .725Left .445Front left .096

This work has included both patients with acute vertigoand those with symptoms of dizziness or unsteadiness. Sincewe included cases with such heterogeneous diagnoses andsymptoms, we could not determine the time elapsed sincethe last crisis until the time of the study, because not allpatients followed the same pattern. It would also have beendesirable to establish the compensation status of patients,but we did not conduct the examinations required for thispurpose. In any case, all subjects in the sample reportedvertigo, dizziness or instability within 6 weeks prior to thecompletion of the posturography assessment.

The static posturography measurements obtained in ourstudy reflected a progressive and logical evolution in thedegree of difficulty of the tests. The simplest test was theROE, followed by the RCE, the RFO, and finally the RFC, thuscorroborating the reports of Norré.10

Table 7 Mean and Standard Deviation of the Ability andControl and Efficacy Results in the Rhythmic Weight ShiftsTest Between Normal and Pathological Subjects.

Normal Pathological

Mean SD Mean SD

Mediolateralability

99.07 3.46 90.25 13.85

Mediolateralcontrol andefficacy

97.33 8.34 93.47 15.05

Anteroposteriorability

99.37 2.36 89.68 16.25

Anteroposteriorcontroland efficacy

97.78 6.93 84.59 20.91

SD: standard deviation.

Table 8 Statistical Significance (P) of the ComparisonBetween Parameters of the Rhythmic Weight Shifts TestBetween Normal and Pathological Subjects.

P

Mediolateral ability .027a

Mediolateral control and efficacy .397Anteroposterior ability .035a

Anteroposterior control and efficacy .031a

a P<.05.

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With the exception of the displacement angle, allbiomechanical parameters of the static posturography werecapable of discriminating between the normal and patho-logical subjects in our sample. The reason for this exceptionis that the displacement angle does not measure the levelof oscillation, but only the direction of displacement of thecentre of pressures.

Unlike the observations by Ortuno-Cortés et al.,12 themean speed showed a similar pattern to the other parame-ters, as it correctly reported the oscillations of the examinedsubject.10,13,14

Pressure centre studies using dynamometric platformshave mostly focused on static posturography tests orthe sensory organisation test in CDP. However, very fewworks have investigated the SL and their importance inthe functional assessment of unstable patients. The sameapplies to rhythmic weight shifts studies, as we will seelater.

The SL can be defined as the maximum angle, measuredfrom the vertical, which an individual can bend withoutchanging his base of support.15 The results can be affectedby different factors: they are worse in patients with total hipprostheses,16 Parkinson’s disease patients in the off stage17

and also when subjects carry a load near the top of thebody.18 By contrast, an increase in quadriceps strength,19

a balance training programme in patients with Parkinson’sdisease20 and intensive practice of Tai Chi are related to animprovement in these values.21

Normal and pathological subjects studied obtained simi-lar scores in the maximum displacements of the SL, so thesetests do not seem to be relevant for the functional assess-ment of patients in our sample. This finding is consistentwith that reported by Ortuno-Cortés et al.22

Like the SL, the RWS test reports on the capacity ofsubjects to carry out movements in a safe manner. Thedescriptive study of our sample indicated that the groupof pathological patients obtained worse scores than thatof normal subjects, and that these differences were sta-tistically significant in 3 of the 4 parameters studied: (1)anteroposterior ability, (2) mediolateral ability, and (3)anteroposterior control and efficiency. These results differfrom those observed by Ortuno-Cortés et al.,22 since thisauthor found no differences between the patient group andthe control group, although the scores of normal participantswere better in the descriptive study.

In light of the findings, vestibular disorders may beable to significantly alter the voluntary control of rhythmicmovement whilst standing. However, since our results wereobtained with a heterogeneous and small sample comparedwith the control group, no conclusions can be extrapo-lated to vestibular condition in general. Further studies withgreater casuistry would be required in order to determinethe usefulness of the RWS test to discriminate vestibularpatients from healthy subjects.

Conclusions

--- With the exception of the displacement angle, all biome-chanical parameters of static posturography were able todiscriminate between normal and pathological subjectsin our sample.

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-- The SL test had little interest for functional assessmentof patients in our sample.

-- The RWS test proved useful to discriminate betweennormal and pathological subjects in our population.Therefore, vestibular disorders may be able to signifi-cantly alter the voluntary control of rhythmic movementwhilst standing.

onflict of Interests

he authors have no conflict of interests to declare.

cknowledgement

he authors wish to thank Drs. Rafael Ramírez Llorens anduís Mompó Romero.

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