A COMPARATIVE ANALYSIS OF STATIC BALANCE

BETWEEN PATIENTS WITH LUMBAR

SPINAL CANAL STENOSIS AND

ASYMPTOMATIC PARTICIPANTS

Aleksandra Truszczyńska, MSc, PhD, a Justyna Drzał-Grabiec, MSc, PhD, b Zbigniew Trzaskoma, MSc, PhD, cKazimierz Rąpała, MD, PhD, d Adam Tarnowski, MSc, PhD, e and Krystyna Górniak, MSc, PhD f

a Assistant ProUniversity of Phy

b Assistant ProRzeszów, Rzeszó

c Professor, Faof Physical Educa

d Professor, PScience, Warsaw

e Professor, FWarsaw, Poland.

f Professor, FaPodlaska, JózefWarsaw, Warsaw

Submit requePhD, Assistant Pr(e-mail: aleksand

Paper submitt2014; accepted Ju

0161-4754Copyright ©http://dx.doi.o

ABSTRACT

Objective: The aimof this studywas to assess static balance in patientswith lumbar spinal canal stenosiswho qualified forsurgical decompression of associated neural structures and compare them with asymptomatic participants.Methods: This case-controlled study evaluated a sample of 50 patients with spinal canal stenosis (stenosis group) and48 participants with no history of clinical symptoms of back pain. Static balance was assessed by conductingquantitative analysis of balance reaction parameters in quiet standing with the eyes closed.Results: Higher values were observed in total length of center of pressure (COP) path, length of COP path in the anterior-posterior plane, mean amplitude of COP projection in the anterior-posterior plane, maximal amplitude between the 2 mostdistant points in the anterior-posterior plane, mean COP velocity, and sway area marked by the moving COP in the stenosisgroup compared with the asymptomatic group.Conclusions: This study showed statistically significant differences in static balance parameters between patientswith spinal canal stenosis compared with the asymptomatic group. (J Manipulative Physiol Ther 2014;xx:1-6)

Key indexing terms: Postural Balance; Lumbar Vertebrae; Spinal Stenosis

Postural stability is a fundamental aspect of motorcontrol that allows individuals to sustain andmaintain desired body positions.1 The assessment

of balance function is one of the most common functionaltests used under clinical conditions.2,3

fessor, Faculty of Rehabilitation, Józef Piłsudsksical Education in Warsaw, Warsaw, Poland.fessor, Institute of Physiotherapy, University ofw, Poland.culty of Rehabilitation, Józef Piłsudski Universitytion in Warsaw, Warsaw, Poland.hysiotherapy Department, University of Socia, Poland.aculty of Psychology, Warsaw University

culty of Physical Education and Sport in BiałaPiłsudski University of Physical Education in, Poland.sts for reprints to: Aleksandra Truszczyńskaofessor, Barcicka 47, 01-839 Warszawa, Polandra.rapala@wp.pl).ed February 4, 2014; in revised form June 28ne 29, 2014.

2014 by National University of Health Sciencesrg/10.1016/j.jmpt.2014.09.003

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The efficiency of a body balance system is influencedby various factors, including age and neurologicdysfunction,4 past cerebrocranial injuries, 5 and locomotorsystem disorders.6 The spine plays an essential role inmaintaining balance, and spinal disorders affect posturalcontrol in an upright position.7 One of the most commonspinal disorders is lumbar spinal canal stenosis.8 Stenosisis a syndrome of various etiologies, whose clinicalmanifestations include back pain, sciatica, and neurogenicclaudication. The morphologic manifestation of stenosis is anarrowing of the spinal canal, intervertebral foramina, andlateral recesses.9–14 In addition to a decline in physicalfunction with aging are symptoms and/or signs of stenosisimpair balance.10 Lumbar spinal canal stenosis leads to thetrunk bending forward, distortions inmotor coordination, andan asymmetrical load on the lower limbs. The relevantliterature does not explain towhat extent stenosis of the spinalcanal and intervertebral foramina impairs proprioceptionand deteriorates postural stability.15 The sway of the centerof pressure (COP) is measured with the help of force plates,and various parameters are then calculated from theCOP trajectory.2

The aim of this study was to assess static balance inpatients with lumbar spinal canal stenosis who qualified forsurgical decompression of associated neural structures andcompare them with asymptomatic participants.

Table 1. Biometrical Characteristics of Participants and Statistical Data

Variable

Stenosis Group Asymptomatic GroupMann-Whitney U Z P

EffectSizeMean Median Min Max Mean Median Min Max

Age (y) 52.74 56.67 26 74 56.24 57.11 40 69 1088.5 −1.115 .265 0.112Height (cm) 168.90 165.58 152 193 163.78 165.00 156 183 1091.0 −1.099 .272 0.110Body mass (kg) 79.53 76.25 58.2 121.5 74.09 70.77 49.9 94.4 1020.0 −1.586 .113 0.159

2 Journal of Manipulative and Physiological TherapeuticsTruszczyńska et alMonth 2014Postural Balance in Lumbar Stenosis

METHODS

The study population consisted of 50 patients (34women and 16 men) with lumbar spinal canal stenosis(stenosis group). The asymptomatic group consisted of 48participants (36 women and 12 men) with no history ofclinical symptoms of back pain.

Table 1 presents biometrical and statistical data.No biometrical differences were found between theanalyzed groups.

The inclusion criterion for the stenosis group wasspinal canal stenosis confirmed clinically and by imagingmethods (radiograph and magnetic resonance imaging[MRI]), accompanied by neurogenic claudication. Allpatients were qualified to receive surgical treatment. Thefollowing exclusion criteria were used: lack of consent toparticipate in the study, other serious pathologies of thelocomotor system, and having undergone surgery withina year prior to the study. The inclusion criteria for theasymptomatic group were no neurologic and motor systemdisorders that affected body posture, and no symptomsof spinal degenerative disorders in clinical examinationand radiograph.

All patients were hospitalized at the Departmentof Orthopedic Surgery, Center of Postgraduate MedicalEducation. They expressed informed consent to participatein the study. The consent to conduct the study was obtainedfrom the Bioethic Commission at the Medical Departmentof the University of Rzeszów. The tests were conducted fromJanuary to April, 2013.

To collect the necessary data, the participants were testedfor static balance (ie, quantitative analysis of their balancereaction parameters in quiet standing with eyes closed).This test is an indicator of static body control and allows foraccurate measurements of the participant's ability to controltheir center of gravity and balance without visual feedback.The goal of the test was to hold the static position of thebody for the duration of the test through anterior-posterior(AP) and medial-lateral (ML) movement of the feetand ankles. The patients stood with both feet placed parallelto each other, hip width apart, on the plate of the “CQStabtensometric” platform. The measurements were takenin two 30-second-long samples. The equipment analysesthe COP movement in the AP plane (or y-axis) and in theML plane (or x-axis). The plates of the equipment wereplaced 2 m away from the corner of the room. The patientswere instructed to assume a relaxed standing posture, facing

the equipment. Then, they were instructed to step onto theplatform and keep the head straight, eyes closed, and armsalong their body, and the balance quantification assessmentwas performed. The higher the variance of COP measure-ments, the higher values indicating more severe problems inmaintaining balance. All tests were conducted by the samewell-trained person. The parameters for analysis were chosenon the basis of generally accepted norms.

The measurements for those in the stenosis group weretaken at least 1 day prior to their surgery. During the tests,the patients were not under the influence of analgesic orsedative medicines. The balance parameters analyzed arelisted in Figure.

Information from the literature revealed that posturalcontrol in patients was more significantly influenced by thevisual system when compared with a control group.15,16,4,17

As such, we expected larger changes in postural stabilitywith the eyes closed compared with the eyes open.Therefore, we only analyzed parameters for the test withthe eyes closed.

Statistical AnalysisDescriptive statistics and mean parameter values were

calculated. The differences in means were calculated usingStudent t test, with statistical significance set at P b .05.Because of the relatively small sample size and the lack ofnormal distribution (confirmed by a Kolmogorov-Smirnovtest) with most of the variables, statistical analysis wasperformed using nonparametric methods. The distributionswere characterized by arithmetic mean, median, and rangevalues. The significance of differences between groups wasassessed by a Mann-Whitney U test.

RESULTS

Analysis of the collected data revealed statisticallysignificant differences between parameters in patients withspinal canal stenosis (stenosis group) and the asymptomaticgroup (P b .05). Table 2 presents the collected data.

We observed higher values of total length of COP path,length of COP path in the AP plane, mean amplitudeof COP projection in the AP plane, maximal amplitudebetween the 2 most distant points in the AP plane, meanCOP velocity, and sway area marked by the movingCOP in the stenosis group (Table 2). Maximal amplitudebetween the 2 most distant points in the ML plane and

• Center of pressure (COP) path (SP) – total length of COP path [mm]

• Length of COP path in the anterior-posterior plane (SPAP) - length of COP path in the anterior-posterior plane, i.e., in the y-axis [mm]

• Length of COP path in the medial-lateral plane (SPML) - length of COP path in the medial-lateral plane, i.e., in the x-axis [mm]Mean amplitude of the COP projection (MA) - mean amplitude of the COP projection [mm]

• Mean amplitude of COP projection in the anterior-posterior plane (MAAP) - mean amplitude of COP projection in the anterior-posterior plane, i.e., in the y-axis [mm]

• Mean amplitude of the COP projection in the medial-lateral plane (MAML),- mean amplitude of the COP projection in the medial-lateral plane, i.e., in the x-axis [mm]

• Maximal amplitude between the two most distant points in the anterior-posterior plane (MaxAP) - maximal amplitude between the two most distant points in the anterior-posterior plane, i.e., in the y-axis [mm]

• Mean amplitude of the COP projection in the medial-lateral plane (MAML),- maximal amplitude between the two most distant points in the medial-lateral plane, i.e., in the x-axis [mm]

• Mean velocity (MV) - mean COP velocity [mm/s] • Mean COP velocity in the anterior-posterior plane

(MVAP) - mean COP velocity in the anterior-posterior plane, i.e., in the y-axis [mm/s]

• Mean COP velocity in the medial-lateral plane (MVML) - mean COP velocity in the medial-lateral plane, i.e., in the x-axis [mm/s]

• Sway area (SA) – sway area marked by the moving COP [mm2]

• Quotient of total length of COP path to the sway area marked by the path of the moving COP (SPSA) - quotient of total length of COP path to the sway area marked by moving COP path [mm/mm2].

Figure. Balance parameters measured in this study.

3Truszczyńska et alJournal of Manipulative and Physiological TherapeuticsPostural Balance in Lumbar StenosisVolume xx, Number

quotient of total length of COP path to the sway areamarked by the path of the moving COP were statisticallysignificantly lower in patients with stenosis than in theasymptomatic group.

Length of COP path in the ML plane, mean amplitude ofthe COP projection, mean amplitude of the COP projectionin the ML plane, mean COP velocity in the AP plane, andmean COP velocity in the ML plane were not significantlydifferent between groups.

DISCUSSION

Back pain, lower limb pain, neurogenic claudication,and decreased motor ability, which are characteristic signsof spinal canal stenosis, may lead to considerable disabilityand difficulty with proper functioning in society. Thisresulting disability and dysfunction, in turn, may lead todepression and an increased risk of falling.18,19 In ourstudy, we assessed postural stability in an upright positionin patients with lumbar spinal canal stenosis prior tosurgical treatment. We confirmed our hypothesis thatpatients' postural control was worsened by symptoms

of lumbar spinal canal stenosis. The parameters for COPamplitudes were significantly greater in patients with stenosisthan in the asymptomatic group.

Studies by other authors confirm our results. Significantdisorders in postural control were found in patients withpain syndrome of the lumbar spine.20 These disorders weremost likely caused by severe and chronic pain21,22 andaccompanying neurologic disorders.23–26 Sasaki et al10

examined the change of COP on postural sway during quietstanding for 32 female patients with lumbar spinal canalstenosis; their results showed that total path length of COPsignificantly increased after neurogenic intermittent clau-dication. Moreover, the COP moved from the asymptom-atic side (before neurogenic intermittent claudication) tothe symptomatic side. However, in contrast to our results,no significant between-group difference (older women withchronic low back pain vs age-matched pain-free controls) wasfound for COP velocity, a measure of postural stability.3

Yagci et al27 conducted functional reach test to measurebalance ability in a study population of 240 volunteers. Thestudy analyzed correlations between pain in the lower bodyand balance performance in 2 age groups: elderlyparticipants and middle-aged participants. Regarding pos-tural stability testing, the elderly participant group hadpoorer results than did the middle-aged group with the samepain-related problems. The elderly participants also report-ed more incidences of falling. Specifically, an increasedpain intensity at an older age resulted in a higher risk offalling and a decreased quality of balance reactions.

Descarreaux et al28 analyzed changes in motoric patternsrelated to lowback pain. The study concluded that themean timefor muscle peak force production was longer for pain-sufferingparticipants than for pain-free participants.Moreover, changes inmotoric control and muscle activation patterns of trunk muscleswere related not only to the neurophysiologic adaptationto pain but also to cognitive adaptations. These cognitiveadaptations were modulated by fear of painful movement andrelated exacerbation of symptoms.

Current literature lacks reports on the impact of spinalcanal stenosis on the quality of balance reactions and posturalstability. The impact of spinal canal stenosis on posturalstability in comparison with the asymptomatic group in thepresented evidence calls for further discussion. Mok et al29

found a decreased ability to control posture with the use of thehip joint in patients with low back pain. In studies of staticbalance in healthy participants, ankle strategies are usedto recover balance in easy tasks.30 However, during moredifficult tests, the participants start to stabilize posture withthe use of the pelvic girdlemuscles.When a function of one ofthe subsystems of balance control worsens, it is possible touse the pelvic girdle muscles even in relatively simple tests.The ankle joint control in patients with stenosis is most likelyweakened because of the inefficiency of inefficiency ofmuscles controlling the ankle join: tibialis anterior, extensorhallucis longus, peroneus longus, and peroneus brevis and

Practical Applications• The data revealed statistically significantdifferences between balance parameters forpatients with spinal canal stenosis and

Table 2. Descriptive Statistics of Measured Parameters and the Nonparametric Mann–Whitney U Test Values for Eyes Closed

No.

Stenosis Group Asymptomatic groupMann–WhitneyU test Z Significance

EffectSizeMean Median Min Max Mean Median Min Max

SP (mm) 233.02 210.00 103 745 172.98 161.50 111 279 772 −3.296 .001 0.330SPAP (mm) 200.08 181.50 74 709 132.14 126.50 73 227 661 −4.061 b 0.001 0.406SPML (mm) 81.76 73.43 52 180 84.10 77.50 54 166 1123 −0.876 .381 0.088MA (mm) 3.42 3.00 1.1 7.9 2.86 2.70 1 7 991 −1.787 .074 0.179MAAP (mm) 3.12 2.72 1 7.8 2.42 2.03 0.7 5.6 888 −2.497 .013 0.250MAML (mm) 0.91 0.67 0.3 2.9 1.07 0.90 0.3 3.4 1026.5 −1.549 .121 0.155MaxAP (mm) 12.61 11.90 4.4 31.9 7.34 6.80 2 21.7 543 −4.874 b 0.001 0.487MaxML (mm) 3.34 2.62 1.1 10.7 4.34 3.64 1.4 13.4 938.5 −2.148 .032 0.215MV (mm/s) 7.77 7.00 3.4 24.8 4.72 4.55 1.8 9.3 492.5 −5.224 b 0.001 0.522MVAP (mm/s) 6.67 6.05 2.5 23.6 48.38 5.23 2.4 239 1204 −0.317 .751 0.032MVML (mm/s) 2.72 2.45 1.7 6 2.37 2.38 1.04 5.5 1004.5 −1.696 .090 0.170SA (mm2) 196.20 153.50 37 967 106.61 89.00 0.18 557 673.5 −3.975 b 0.001 0.398SPSA (mm/mm2) 1.50 1.40 0.64 3.11 4.70 1.95 0.45 25 884 −2.523 .012 0.252

Statistical significance set at P b .05.MA, mean amplitude of the COP projection;MAML, mean amplitude of the COP projection in the ML plane;MAAP, mean amplitude of COP projectionin the AP plane; MaxAP, maximal amplitude between the 2 most distant points in the AP plane; MV, mean COP velocity; MVAP, mean COP velocity inthe AP plane; MVML, mean COP velocity in the ML plane; SA, sway area marked by the moving COP; SP, total length of COP path; SPAP, length oCOP path in the AP plane; SPML, Length of COP path in the ML plane.

4 Journal of Manipulative and Physiological TherapeuticsTruszczyńska et alMonth 2014Postural Balance in Lumbar Stenosis

gastrocnemius. These patients also experience changes insensation to the foot and lower leg. This combination ofmotor and sensory impairments explainswhy postural controlmost likely contains elements of ankle and hip strategiesof stabilizing, although their interrelationship may differdepending on the level of damage.31

Biomechanically, postural stabilization using an anklestrategy has a low amplitude of sways because of the largemoment of inertia of the body in the region around theankles. Conversely, when using a hip strategy, the upperand lower bodies relatively independently of each other.The upper and lower bodies each has a significantly lowermoment of inertia in relation to the whole body; thisdecreased inertia enables sways of higher frequencybut not a greater sway path. Mok et al29 found that theabove-mentioned factors may serve as predictors of balancedisorders in patients with stenosis. Kuo32 indicated jointproprioception disorders as a cause of balance deficits.These proprioception disorders may have resulted frompain, which, in turn, is a clinical symptom of stenosis.Results presented by Sasaki et al10 suggest that patientswith lumbar spinal canal stenosis are at risk for falling onthe symptomatic side, especially those with a high bodymass index.

Our study was conducted on a homogeneous group ofpatients with considerable locomotor system dysfunction.Our study suggests that long-lasting behavioral patternsdue to lumbar spinal canal stenosis may cause significantdifficulties in performing correct balance responses.

asymptomatic participants.• Long-lasting behavioral patterns in lumbarspinal stenosis may significantly disturb thebalance system.

Limitations of This StudyIn our study, sex distribution was uneven. This uneven

distribution caused us to include an uneven proportion of

f

men and women in the asymptomatic group. The reasonsfor the sex distribution were more frequent occurrence ofspinal stenosis among women and a higher refusal rate ofmen to participate in the study.

In the present conducted study, we did not correlatepostural balance disorders with disability scales or painintensity. However, we plan to perform these correlations infuture research.

CONCLUSIONS

Analysis of the collected data in this group ofparticipants revealed statistically significant differences inbalance parameters between patients with lumbar spinalcanal stenosis and the asymptomatic group. The parametersfor COP amplitudes were significantly greater in patients withlumbar spinal canal stenosis compared with the asymptomaticgroup. This suggests that spinal stenosis symptomsmay lead tothe worsening of postural control.

5Truszczyńska et alJournal of Manipulative and Physiological TherapeuticsPostural Balance in Lumbar StenosisVolume xx, Number

FUNDING SOURCES AND POTENTIAL CONFLICTS

OF INTEREST

The statutory research program No. DS.168 of PhysicalEducation and Sport Faculty in Biała Podlaska,Jozef Pilsudski University of Physical Education, Poland,funded this study. No conflicts of interest were reported forthis study.

CONTRIBUTORSHIP INFORMATION

Concept development (provided idea for the research):J.D-G., A.Tr

Design (planned the methods to generate the results):J.D-G., A.Tr

Supervision (provided oversight, responsible fororganization and implementation, writing of the manu-script): J.D-G., A.Tr, K.R.

Data collection/processing (responsible for experiments,patient management, organization, or reporting data): J.D-G.,A.Tr

Analysis/interpretation (responsible for statisticalanalysis, evaluation, and presentation of the results):J.D-G., A.Tr, A.Ta

Literature search (performed the literature search):A.Tr, Z.T.

Writing (responsible for writing a substantive part of themanuscript): A.Tr, Z.T.

Critical review (revised manuscript for intellectualcontent, this does not relate to spelling and grammarchecking): A.Tr, Z.T., K.G., K.R.

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