A review of functional outcome measures for cervical spine disorders: literature review

literature review

Andre

Bussieres,

BSc,RN,

DC*

Thepurposeofthispaper is toassessthereliability, validityand

usefulness ofthreeoutcomemeasures:cervicalrangesof motion,sagittal neck muscle strengthand presenceorabsence

oftheflexion relaxation phenomenon (FRP)inthe neck. The

literature search included the Index Medicus and computerized database ofMEDLINEfor relevant material. Articleswere

selectedifthey containedprimary dataonneck rangeofmotion,

sagittalmusclestrengthand FRP. Theresultsof59 articles and 2textbookswereanalyzed.Normativevaluesofcervical ROM

have been reportedinhealthy subjectsranginginagefrom18to

74years.Theextentofdegrees ofmotionlostper year didnot

differ between male orfemale subjects, butfemalesstarted with

higher

degrees ofactiverangeofmotion,whichtheymaintained

throughout life. Instrumentedmethodsofrecordingmuscle

strength

have includedstrain gaugedynamometersand

modified sphygmomanometers.Parameterssuchasgender,

ageandstature werealso observedtohaveimportant

effects

on

musclestrength. Theratioofextensiontoflexionmaximum

isometric

peakforce

has beenestimatedtorange between

1.40-1.70innormalsubjects. Therefore, theextensormuscles

of

the neckareapproximately40% stronger then theneckflexor muscles. Evidence suggestedthat neck painsufferershave

weakerneckflexors thannormalsubjects.TheFRPreferstothe

absence

of

myoelectrical activityin extensormuscles uponfull

forwardflexion

andhas been documentedinthecervicalspine

ofasymptomatic subjects.Inconclusion,inclinometric methods

usedformeasurementsofcervicalrange ofmotion werefound

tobesafe, effectiveand reliable. The Cervical RangeofMotion

Deviceappearedtobe wellsuitedforclinicalpractice. The ratioofcervical extension-flexionmaximum isometric

voluntarycontractionhasbeendeterminedinasymptomatic

subjects.

ThepresenceoftheFRPinthe neck has also been

observed in normals. Future

study

isneededtoinvestigate the

functional

limitationsrelatingto acuteand chronic mechanical

neck pain which accountforaportionoftotal neck disability.

(JCCA 1994; 38(1):32-40)

KEY WORDS: cervical vertebrae, objectivemeasurement, neck

strength

and

mobility,

rangeofmotion, myoelectric signal, flexion relaxation.

* Division of Graduate Studies and Research, Department of Graduate Studies,CanadianMemorialChiropractic College, 1900 Bayview Avenue, Toronto,OntarioM4G3E6.

Reprintrequests:AndreE.Bussieres,DC,1755 boul.St-Regis, Suite110, Dollard-des-Ormeaux,QuebecH9B2M9.

C JCCA 1994.

Cetteetudeporte sur

lafiabilite',

lavalidite'etl'utilite'de trois

me'thodes d'evaluation:lesdegre's de mobilite' cervicale, la

force des muscles sagittauxdu cou et la pre'sence oul'absence duphe'nomene deflexion-relaxation(PFR) au niveau cervical.

Ladocumentation utilise'ecomprenaitlere'pertoire Medicus et

des donne'esinformatiquesprovenant deMEDLINE.Les

articlesse'lectionne's devaientcontenirdes informations primairessurlamobilite cervicale, sur la puissance des

musclessagittaux et surlePFR.Lesre'sultats de 59 articles et de 2manuelsfurent analyse's.Desre'sultatsnormaux onte'te' obtenus dans lestestsde ROM (RangeofMotion-degre' de

mobilite)cervicauxchezdes sujets en sante dont

l'dge

variait

entre18et74ans.Ledegre'annuel deperte demouvements'est

ave're'leme^mechez lessujetsmasculinsetfiminins. Toutefois, lesfemmes pre'sententau

dipart

desdegre's demobiliti

superieureetellesconserventcettemargetouteleur vie.Les

mithodes instrumentales employe'espourmesurerla puissance

musculairecomprenaientdes dynamometres et des

sphygmomanometres modifies.Desparametres commele sexe,

1'dge

etlastature se sonte'galement ave're'sd'unegrande importancequanta' lapuissancemusculaire. Le

ratioflexioni

extensioncervicale @ puissance

isomitrique

maximale aiti estime'entre1,40 et1, 70, chezdessujetsnormaux.Donc, les

musclesextenseurs cervicauxpre'sentent environ 40% plus de

puissancequeles musclesdeflexioncervicale.II

apparait

e'videntquelespersonnessouffrant de douleurscervicales presentent

desflichisseurs

cervicaux plusfaibles que les sujets normaux.Le PFR

rifire

a'l'absenced'activiti myoilectrique desextenseurslorsd'un pleineflexionet aete' observe' dans la regioncervicalede sujets asymptomatiques. II en re'sulte que les

mithodes

inclinomitriques

utilise'espour mesurerle degre' de

mobiliti

cervicalese sontave're'es securitaires etefficaces.

L'appareil

calculant leniveaude

mobiliti

cervicale(Cervical RangeofMotion Device)s'est

rivele

efficace

enpratique

privee.Le ratiodecontraction

isomitrique

volontaire

maximale desextenseurs etdesflechisseurscervicauxa

eti

determine

dans lecasdessujets asymptomatiques.Lapresence

du PFR

aiegalement

eti

observeedans lecoudes sujets normaux.Des

itudes

subsequentesserontrequises

afin

d'itudier

leslimitationsfonctionnelles reliees a'la douleur

cervicaled'originemecanique, car,aiguesouchroniques, ces

douleurssontresponsables d'unepartie desdysfonctions

cervicales totales.

(JCCA

1994; 38(1):32-40)

MOTS-CLES :vertebre cervicale,mesuresobjectives, force et

mobilite

ducou,degre de mobilite, signal

myoelectrique,

Introduction

Musculoskeletal disordersarethemostfrequentcauseof phys-ical disability, affecting 5-7% of the Canadian population.' Twentypercentof Canadians have been estimatedtosufferfrom

significantillnessas aconsequeneof suchconditions,and about

30%of adults have musculoskeletal complaints.'

Neckpain isoneofthemore commonmusculoskeletal

com-plaints, withapoint prevalence of 9-14%amongstadults,anda

life-time prevalence of about 33%.2-4 The point prevalence increases withage,being highestinthe 50-59year-oldrange,

with about 30% of females being affected and about 15% of

males.3A commoncauseof chronicneckpainis fromwhiplash injuries resulting from motorvehicle accidents. Reports esti-mate that 45 to 85% ofpatients having suffered a whiplash injury, continuetocomplainof symptoms after five years. 5 This

highrateof persistingneckpainhasadirectimpactupon health care costsandpermanent disability.6

Inclinical practice, disabilityfrom neckinjuriesisfrequently

associated withimpairedfunction that isnotexplained by

struc-turallesions.7 Infact, physical impairmenthas beenreportedto

accountfor less than 50% of the totaldisability whileafurther

thirdof thedisabilitycould beexplained by psychologicaland

behavioral factors.8 Similarcontroversy isseeninotherareasof thespinewherepathologyfailstoexplainthepersistenceof the

pain.9,o

Since the usualgoalsoftherapyare toalleviatesymptoms and

improvepatient functioning,it isimportanttodeveloprelevant assessmentcriteria ofphysicalfunctioninneckpainsufferers.

Unfortunately, there is a paucity of information relative to

objectivemeasuresof functioninpatientswith neckpain.Much

of the availableliterature is derived from thestudyof

asympto-maticsubjects. Objectivemeasureshave concentratedprimarily

on neck ranges of motion, muscle strength and ergonomic

measures. The purpose of this paper istoreview the literature

pertinent

tothese

primary objective

measures.

Sources and methods

The initial search included Index Medicus and theMEDLINE

computerizeddatabase from 1966to 1992 for relevant articles. Articleswere selected ifthey contained primarydata on neck

rangesofmotion, sagittalmusclestrengthandflexion relaxation

phenomenon (FRP). The results of 59 articles and2textbooks wereanalyzed. The MedicalSubject Headingterms usedwere:

cervical vertebrae, objective measurement, neck strength and

mobility,

range of

motion,

neckmuscles, myoelectric signal, flexion

relaxation, kinesiology/biomechanics.

The

biblio-graphy of the retrievedarticleswereevaluated for further

refer-encesandadditionalsources weresuggested

following

personal communication withcontentexperts.

Results

Range of

motion

Restricted

cervical

spine

rangeof motion(ROM)often

accom-panies painful conditions.5Inclinical practice, measurement of

such restriction is importantfor both assessment of the patient's

condition andevaluation of treatment outcome. Several investi-gatorshave analyzed the normal cervical motion by means of

plain filmx-ray andcinematography.11-20Although accurate,

these methodsare costly and may be a health hazard. Several

non-invasiveinstruments have also been tested21-28 (see Table

1).Theselection of instrument use in clinical practice should be

guided by factorssuch as reliability, precision, ease of

applica-tion, interpretation and cost. The majority of goniometers,

regardless oftheir levels of sophistication (which ranges from

complex electrogoniometersto simple gravity assisted

pendu-lumtypes),tend to yield reproducible results.

Anexampleof agoniometer is theCervicalRange ofMotion

device (CROM)TM This pendular-type goniometer has been reported tohave goodtest-retestand interexaminerreliability,

with intraclasscorrelationcoefficientsreportedtobe

generally

greater than0.80.28 Youdas etal.28 alsotested theaccuracyof

theCROMbymeasuringthedifferences between known

angles

on a rotary table to those obtained from three CROM instru-mentsfor each of thedialmeters. On thebasisof small

differ-encesobtained (meandifferencesfor thetransverse,

sagittal

and

frontal planesrangedfrom0 to 2degrees, 0.5to0 degrees and

-1.5 to 2 degrees, respectively), they concluded that the

CROM was an accuratedevice. Although the standard

devia-tions were notreportedandtheprecision of the CROMremains

unknown, the objectivity of other cervical ROM instruments

has been determined. Comparing the Rolyan medical plastic

goniometer and the Spinal Rangiometer, Zachman et al.28

reported large confidence intervals betweenexaminers (20-40

degrees) andinterexaminer standarderrors of estimateof 5-12

degrees for both devices. They concluded that clinical trials

whichemploy these instrumentsshould usecautionin

interpret-ing results if smalltherapeutic changes (e.g. <20 degrees)are expected and small sample size employed. Although such

caution may alsoapplytotheCROM, thisparticular instrument

isideallysuitedforclinicalusesince it iseasy to use,

comfortab-ly worn by the

subject,

lightweight, easily interpreted and inexpensive. 27

Normativevaluesof cervical ROM have beendetermined in

healthy males andfemales subjects ranging in age from 12 to 79 years.18,19,28Among bothmalesandfemales of thesame age, females have a greater active ROM than males for all active

ROMs except neckflexion.28 Thatis, female subjects have 5 degrees greater cervical extension and 2-4 degrees greater lateral bending androtation than males of the same age. Foust et al.18 found that the mean andstandarddeviationsofcombined flexion andextension ROMwas137.2 14.8degreesin young adults(age 18-24), 1 15.5 + 17.4degreesintheearly

middle-age group(35-44 years), and 96.5 ± 16.2 degrees inthe elderly (62-74years). In asimilar

study,19

the range in all three planes wasfound to decreaselinearly with age beyond the third decade. Indeed, both sexes can expect a 40% decrease in cervical range of motionover alifetime,withalossofabout 25% for males and

TABLE 1

13%forfemalesbyearly-middleage. 15,18,28,29 Inthesagittal plane, extension motion decreases more than that in flexion. From apracticalstandpoint, with each

10-year change

inage, both males and females will lose about 5

degrees

of neck extension and about 3degreesof active ROM for each of the five other movements.28 It is,

therefore, important

thatclinicians andresearchers avoidusingpreviously

reported

singularvalues as estimates of normal cervical active ROM for both

genders

and across allages.28 Neckmusclestrength

Anotherobjectivemeasurethat isimportantin theassessmentof

patients with neckpainisneck musclestrength. Weaknessof the

anterior cervical muscles isthought tocontribute to

persistent

paininpatients

complaining

ofchronic neck

pain.30

Silverman

etal.30 postulated that necktrauma sustained in

whiplash

in-juries producesareflex inhibition of theflexor muscles via the

musclespindle system and, intime, the anterior neck muscles

weaken and atrophy, resulting in postural alteration and

in-creased susceptibility to injury. Few authors, however, have quantifiedthis weakness. The presentreview will

specifically

address cervical musclestrengthinthesagittal plane.

Quantification of muscle weakness isachieved using either

instrumented ornon-instrumented methods.Non-instrumented

methods(e.g. manual muscletesting)arecommonlyused

clin-ically and rely on subjective interpretations. Krout and

Ander-son,3 using manual muscle testing, found weakness in the anterior neck muscles in chronic neck pain patients. These methods, however, are far less reliable and valid than those obtained withinstruments.32

Instrumented methods of recording muscle strength include

strain gauge dynamometers and modified sphygmomano-meters. The modified sphygmomanometer dynamometer

(MSD) utilizes an inflated cuff attached to a digital pressure gauge torecordchanges inpressurewhile the subject provides

maximumresistance. Measures are reported in mmHg and are

comparedovertime, andwithother muscles. Using the MSD,

Vernon et al.33 attempted to determine the neck extension-flexion strength ratio (E/F ratio) in 40 healthy male young

adults. Extension strength was approximately 40% stronger

than flexion strength in normal subjects. When compared to

data obtained fromagroupof 12 male and 12 female neck pain

patients, 16 with non-traumatic chronic neck pain (average

duration 22.5 weeks) and 8 with "whiplash-type" injuries

(average duration 110 weeks), the symptomatic subjects

demonstrated an extension-flexion strength ratio (E/F ratio)

twicethat foundin normals. The authors concluded that

whip-lashsufferers, inparticular, demonstrated significant reduction

of the flexor's strength values(Table 2). Unfortunately,several

confounders were inherent in this study. The absence of a

TABLE 2

Neck

strength

of

both

asymptomatic and symptomatic patients

measured with

a

modified

sphygmomanometer

dynamometer*

restraining device with their apparatus may have allowed the

patient to use the trunk musculature during the assessment.

Other factors included an unequal sample size, asymptomatic subjects unmatched for age and sex, and finally, a lack of

standardized procedureasthe asymptomatic subjects were

in-structed to maintainconstant maximal pressure for 5 seconds

while patients with neckpain were told to produce a level of pressurethatreached,but did notexceed,tolerablepain. While

these considerationsmeetethicalstandards,it isobvious that the

symptomatic group did not reach maximal strength rendering

comparison difficult.

Nevertheless, similar findings have also been reported by

authors using strain gauge dynamometers (SGD) suggesting

that neckpain patients have significantly weaker flexors than

asymptomatic

subjects.31

Accordingto Krout andAnderson,3' straingaugedynamometersgave themost accuratemeasureof

muscle strength. Using such an instrument, Levoska et al.34

tested the cervical strength of asymptomatic subjects in the

supine and prone positions. The reported reliability of this

method for extension and lateral bending was satisfactory (r=

0.72-0.80)

butpoorfor flexion forcemeasurements(r=

0.54).

Whenneckmuscle strengthtesting is combined with

electro-myography (EMG), the relationship between muscle activity

and force generated can be calculated. If the relationship be-tween EMG activity and muscular force is known, the EMG

valuescanbe used to evaluate the muscular strength exerted in a

particular task.35

The EMG activity of the posterior neck muscles during

isometriccontraction has been studied. The semispinalis, splen-ius, longissimus, and to alesser extent the trapezius muscles, are considered neck extensor muscles.36-39 While these muscles also produce other movements of the neck, the

semi-spinalis capitismuscle is equally activated in extension and in a

direction falling mid-way between pure extension and pure

lateral bending. As a result, it is the muscle most frequently chosen to measure themyoelectrical response during strength testing of the extensor muscles of the neck.40

Few studies have dealt with EMG recordings of the neck

flexors. Costa et al.,4 Sousa et al.42 and Vitti et al.43 have described the actionofthestemocleidomastoidmuscle (SCM) asbeing representative of the flexion component of neck move-ment. Using surface EMG, Ashton-Miller et al.44 measured

muscle activity during isometric neck flexion strength tests

(submaximalandmaximal voluntarycontraction) in ten healthy

adult males. Electrodesweretapedbilaterallyover the

follow-ingeighttarget musclesattheC4level: SCM, erector spinae,

splenius capitis and infrahyoid. Asexpected, a positive linear

TABLE

3

correlation was found between muscle activity signal and the

measured flexion effortlevel(force)for bothrightand left SCM

andinfrahyoid muscles. However, itwasgenerally noted that

the extensors (erector spinae) and lateral flexor/extensors (splenius capitis) were essentially quiescent, except at 100%

maximum voluntary contraction. This suggests that the

anta-gonist musculature is activated duringmaximum effort. Perhaps this helps stabilize the head and neckorprevent injury tothe

flexor musclesorotherneckstructuresby actingas a

"restrain-ing device".

Therelationship between the neck extensor and flexor muscle groups has also beenreported. Dataderived fromFoust etal.18 revealed that the maximal

E/F

ratios measured by EMG and strain gauge ranged from 1.1:1 to 1.75:1,averaging 1.40:1 for

both males andfemales(Appendix, Table 3). Moroneyetal.45

calculatedslightlyhighermean

E/F

ratios usingasophisticated biomechanical model.Theyalso concluded thatthe neck

exten-sorswerenormallyabout 40% stronger than the flexor. These findings are consistent with Vernon et al.'s results discussed

earlier.

Parameters such as gender, age and stature were also

ob-served to have

important

effects on muscle

strength.18

For

example,themean

sagittal

isometric

peak

contractions of males were shown to be about 60% greaterthan that of females in every ageandstaturegroup. Forboth sexes,maximum volun-tary strength diminished by anaverage of 25% overthe adult lifespan. With thefemalesstrength tendedtodecrease

gradual-ly, butonly slightly throughouttheirlives, while males were

often stronger at middle-age than when they were younger.

Finally, groups of shorter stature were shown to be slightly

weaker throughout their lives while taller men tended to be

strongerintheiryouth.18

Isometricstrengthtestingappears verypromising in the eval-uation ofpatient's status. Researchers andclinicians however,

need to be aware of the importance to properly control for variables such as age, gender and stature when assessing patient's neck muscle strength.

Fkxion

relaxation

phenomenon

The flexion relaxation phenomenon refers to the absence of myoelectrical activity in extensor muscles upon full forward

flexion ofthelumbar'0,48,49and cervicalspine.37-39,5 53This

would suggest that as full flexion is reached, the

antagonist

supportiveroleof theextensormuscles isreplaced by themore

passivesupportfromthe

ligamentous

and articularstructures.54 Inawelldesignedstudy conductedinthe mid 1960's

Pauly50

used needle electromyography and reported silence or near

silence of the

semispinalis

muscle when the headwas

permitted

tohang

freely

duringfull trunkflexion. The EMGsignal used in thisstudywasfiltered,integratedandlinearly amplified. Recent

evidence supporting the existence of suchaflexionrelaxation

responsein thecervicalspine hascomefromergonomic studies

oftheeffect of various headpositionsonneck muscleactivity in

asymptomatic

manual workers.39,52 Recently, Meyeret

al.59

examined 10asymptomaticsubjectswhoexhibited

comparable

cervicalparaspinal muscleactivity duringeccentric concentric

sagittal motionand observedsilenceof the EMGactivityonfull neckflexion.

Interestingly, the FRP has been reported to be absent in patients presenting with pain in the lumbar spine. In other

words, continuous activity ofextensor muscles has been

ob-served during maximal flexion.55 It is postulated that

contin-uous muscle contraction may serve to transmit loads through

muscles rather thanthroughinjured spinal ligamentsin aneffort

toavoid increased

pain.'0

Ithas also beentheorized that

col-lateral muscle groups would be activated to compensate for

actual oranticipatedpain.10,5658

Harms-Ringdhal and Ekholm60 recordedvery low levels of

muscular activity (0-6% of maximum) in the posterior neck muscles duringthefirst few minutesofextremelower cervical-thoracicspinal flexion. However, theyreported that allsubjects perceivedaprogressiveincreaseinpainlevelafter 15 minutes if maintainedflexion, and subsequentlyaslight increase in EMG activity wasnoted inthetrapeziusandsplenius muscles. They concludedthat thisincreasewaspossibly duetopain, indicating that tonic(sustained)reflex mechanismsmight have been

elicit-ed. Thishypothesis has been testedby Ashton-Miller etal.44

whohave reported subtle butsignificantsystematic increase in

myoelectric activitywhen deepexperimentalmuscle pain was induced by injecting 5 ml of hypertonic (5%) saline solution in

activeandresting SCM muscles of 10 healthyadultmales. The

authors demonstrated thatdeepmusclepainin one muscle can cause associatedchanges to motor output in related synergists andantagonists.

While these latter

findings

may suggest anabsenceof the FRP inexperimentally induced neck pain conditions, further study is necessary toverify its presence in chronic and acute neck pain

patients. Discussion

Theuse of objectiveoutcome measures play a very important

role in the assessment and management of spinal health care.

Toooften, however, the reliability, precision and accuracy of

thesemethods is unknown and knowledge of thenormalvalues

can notbe generalized, thereby makingthe interpretationand

conclusionof each testdifficult.This literature review outlines

normative values and reliability studies available for cervical range ofmotion, sagittal neck isometric strength and the

pre-sence orabsence of electricalactivity(Relaxation Phenomenon)

during

cervical maximalflexion.

Gender,

ageandpainlevels are three variables that can affect

cervical ROM. The cervical spinerangeof motion was slightly greater in females compared to males for all active ROMs except neck flexion when age

matched.28 Also,

the cervical

spine

motion inall threeplanes has been reported to decrease

linearly with age from the third decade on. Both males and

femalescanexpect a40% decrease in cervical ranges of motion

over a lifetime.15,18,28,29 Specifically, with each 10-year

change in age, the decrease in active ROM will be about 5

degrees in extension and 3 degrees in each of the five other movements.

The ratio ofcervicalextension-flexion maximum isometric

voluntary muscle contraction has been estimated to range be-tween1.40 and 1.70in normalsubjects,reflecting approximate-ly a 40% greater strength of the extensor versus the flexor

muscles.18,33,45Ifthe workreported on the lumbarspine46can

beextrapolated,then the cervicalE/Fratio may beanindicator

of neckinjuryand providean importantoutcome measurefor

the success ofrehabilitation programs ofinjured patients. It

appearedfrom theliteraturereview that neckpainsufferers have weaker neckflexors thannormal subjects. It, therefore, would seemlogicalthatrehabilitation programs should concentrateon

restoring the strength of the anterior neck musculature resulting innormalizationof the ratio.Todate, no studies have

specifical-ly reportedonchanges incervical flexor muscle strength after

rehabilitation. Of interest however, is a recent before-after

study conducted inarehabilitationcenterby Highlandetal.47 They reported

significant

gains in isometricextensor strength and rangeofmotion of the cervical spine after

eight

weeksof

clinical rehabilitation in 90

patients suffering

from neck

pain

withorwithoutarmpain. Perceivedpainwasalsosignificantly reduced. Personal communication with one of the authors

re-vealed that the patientswerealso instructedonhomestretching exercises and

performed regular

aerobic exercise which may be

considered as co-interventions.

Nevertheless,

it

supported

the concept that

joint

motion as well as specific and

general

strengthening

programsareindicatedin rehabilitation of

chron-ic neckinjuries. Otherparameters suchasgender,age, stature

were observed to affect neck muscle strength performances supportingtheimportancetocompare clinical results with well

establishednormative data.

Theuseofisometrictesting to describe human performance is

widespread. However, there are few "real-life" situations that

would require an individual to sustain a maximal contraction except perhaps in response to an anticipated sport injury or

whiplash. Isometric (static) testingcanevaluate variables such

asduration,force andrepetitionbutfailstolookatdisplacement and motion variables (velocity and acceleration). Although knowledge ofthenormativedata andcomparisonto

symptoma-tic groups from an essential clinical and research basis, this

information may be of limited use. Future research should

investigate measuresofacceleration and velocitychangesthat

more truly represent "real-life" functional neckcapabilities.

Isoinertial and freedynamictestingaresuchmeasures.

The FRPrefers to the absence ofmyoelectrical activity in

extensormusclesupon fullforwardflexion and has been docu-mented in the cervical spine ofasymptomatic subjects. 10,37-39,5053 Whilesome studies have suggestedanabsence ofthe

RFP in

expenrimentally

induced pain conditions,44,60 further study is necessary toverify its presence in chronic and acute neck pain patientsand todetermine whetherthis phenomenon willhavesimilarclinicalapplicationsasreportedfor the lumbar

spine. Triano and Schultz10 compared results of a disability

questionnaire to measures of lower trunk motion and muscle function. They found theOswestry Low Back PainDisability

Questionnaire relatedsignificantlytothe presence or absence of relaxationof back musclesduring fulltrunkflexion.

Also,

mean

trunk strength ratios of extension to flexion were inversely

related todisability scores, and trunkmobilitywas

meaningful-ly reduced. Suchobservationssuggestthatanassociation exists between theOswestryDisability ratingsandtheobjective

mea-suresofmyoelectrical signal levels, trunkstrength ratios, and rangesof trunk motion.

Much ofthe available literatureregardingdisability

question-naireshave concentrated upon low backpain andactivitiesof

daily living (ADL). Recently, aneckdisability questionnaire,

fashioned after Oswestry Low Back Pain Questionnaire, was developedatCMCC.61 The NeckDisabilityIndex(NDI)

mea-sures specific ADL in neckpain patients. The NDI has been

reported to bereliable and haveface validity, but has not been tested in acutely injured patients or compared with objective

measuresof neckfunction.Examining the relationship between the limitations of activities of ADL and functional outcome measures such as cervical range of motion, neck muscle strength and presence or absence of the FRP could helpestablish

abetterrationale for rehabilitation ofchronic mechanical neck pain.

Conclusion

Normativevaluesof cervical rangeofmotion have been

deter-mined fromplainfilm x-ray andgoniometric studiesinhealthy subjectsranginginagefrom 18to74 yerars. Females havebeen reported to have a greateractiveROM than malesinallplanes

except in flexion.

Instrumented methods ofrecording muscle strength included

modified sphygmomanometers, strain gauge dynamometers

andelectromyography. The ratio of extension to flexion

max-imum isometric voluntary contraction has been estimated to rangebetween1.40-1.70 in normal subjects. This suggests that

theextensormuscles of the neck are approximately 40%

strong-erthen theneckflexormuscles. Gender,age, stature andpain

level are all parameters affecting peak isometric strength

per-formancesinnormalsubjects.

The FRP refers to the absence ofmyoelectrical activity in

extensormusclesupon fullforwardflexionand hasbeen

docu-mentedin thecervical spine. Presence orabsenceofthis

phe-nomenoninneckpain patients remains to be clearlyestablished.

Forclinical purposes, mostgoniometers appear togive repro-ducible results and are inexpensive. The CROM fulfills the

criteria foragoodinstrument. However,the "in office"useof

instrumented methods for testing isometric strength remains

uncommondue tothe absence ofsimple, inexpensive devices

with testedreliability. Sophisticated instrumentsare inaccessi-ble duetotheircostsand aretherefore restrictedtoresearch labs andrehabilitation centers. The FRP should befurther investi-gatedbeforemakinganyclaimsas toitsclinicalsignificance.In

addition, future study is needed to investigate the functional

impairmentaspectof physical disability, whichaccountsfor a

portion of total neck disability.

Acknowledgements

The author wishes to acknowledge the Canadian Memorial

Chiropractic College and Chiropractic Foundation for Spinal

Research (grant #4931)for financialsupport,and Drs.Silvano

Mior and PeterAkerfor their assistance inthe preparation ofthis

manuscript.

References

I BadleyE. Theimpactofmusculoskeletaldisorders on theCanadian

population.JReumatol 1992; 19:337-340.

2 BlandJH. Disorders of the cervical spine. Philadelphia: Saunders,

1987: 1-8.

3 DonkJ, Schouten JSA, Passchier J, Roumunde LKJ,

Vankenburg HA. Traits in a general population. J Rheumatol 1991; 18:1884-1889.

4 ShekellePG,Brook RH.Acommunity-based study of theuseof chiropractic services. Am J Pub Health 1991; 81:439-442.

5 WatinsonA,GarganMF,Bannister GC. Prognostic factors in soft

tissueinjuriesof the cervicalspine. Injury 1991;22:307-309.

6 Insurance Bureau of Canada. Factbook. 15thed.Toronto:IBC, 1987: 20-23.

7 JandaJ.Someaspectsof extracranial causes of facialpain.

JProsthet Dent1986; 56:484-487.

8 Waddell G, Main CJ, Morris EW, Di Paola M, Gray ICM. Chronic low-back pain, psychologic distress, and illness behaviour. Spine

1984;9:209-213.

9 Haldeman S. Failure of thepathologymodeltopredictbackpain. Spine 1990;15:715-724.

10 TrianoJJ,SchultzAB.Correlation ofobjectivemeasureof trunk motionand muscle functionwithlow-backdisability ratings. Spine 1987; 12:561-565.

11 DvorakJ,FroehlichD, PenningL,Baumgartner H, PanjabiMM.

Functionalradiographicdiagnosisof the cervicalspine:Flexion/

extension.Spine 1988; 13:748-755.

12 FieldingJW.Cineroentgenographyof the normal cervicalspine.

JBoneJoint Surg 1957; 39-A: 1280-1288.

13 FieldingJW. Normal and selected abnormal motion of the second cervical vertebratothe seventh cervical vertrbra basedon

cineroentgenography.J BoneJointSurg1964;46-A: 1779-1782. 14 Hohl M. Normal motion in the upperportionof the cervicalspine.

JBoneJointSurg 1964;46-A:1777-1778.

15 Lysell E. Motionin thecervicalspine:Anexperimental studyon

autopsyspecimens.ActaOrthopScand1969; Supp 123:61. 16 PenningL.Normalmovementofthespine.AmJRoentgenol 1978;

130:317-326.

17 AlundM, Larsson SE. Three-dimensionalanalysisof neck motiona

clinicalmethod.Spine 1990;15:87-91.

18 FoustDR,ChaffinBC, Snyder RG,Baum JK.Cervical range of

motion anddynamicresponseandstrengthof cervical muscles.

SAETransactions 1973;82:3222-3234.

19 LindB, Sihlbom H,NorwallA,Malchau H. Normal rangeof

motion of the cervicalspine.ArchPhys Med Rehabil 1989;

70:692-695.

20 White,lII AA, Panjabi MM. Clinicalbiomechanicsof the spine. 2nd ed.Philadelphia:JBLippincott, 1990: 85-110.

21 BuckCA,Dameron FB, Dow MJ, Skowlund HV.Studyof the

normalrangeofmotion in the neck utilizing a bubblegoniometer.

Arch Phys MedRehabil1959;40:390-392.

22 Defibaugh JJ. Measurement of head motion. Part 2. An

experimentalstudy of head motion in adult males. PhysTherapy 1964; 40:163-168.

23 FerlicD.Therangeof motion of the normal cervicalspine. John

Hopkins HospBull 1962;110:59-65.

24 LeightonJR. Flexibilitycharacteristicsof fourspecializedskill groupsof college athletes.Arch Phys Med Rehabil 1957;38:24-28. 25 Zachman ZJ, TrainaAD,Keating JC,BollesST, Braun-Porter L.

Interexaminer reliabilityand concurrent validity of two instrument

of cervicalrangesofmotion. JManipulative Physiol Ther1989; 12:205-210.

26 MiorS, Gluckman J, Fournier G. Validity andreliabilityof a three dimensionalcomputerizedgoniometer. Proceedings of the 1991

InternationalConference onSpinal Manipulation. Arlington:

FoundationforChiropracticEducation and Research, 1991: 45-47.

27 Capuano-PucciD, Rheault W, Aukai J, Day R, Pastrick M. Intratesterand intertester reliability of the cervical range of motion

device. Arch PhysMed Rehabil 1991;72:338-340.

28 Youdas JW, Garret TR,SumanVJ,Bogard CL, HallmanHO, CareyJR. Normal range of motion of the cervical spine: an initial

goniometerstudy.PhysTher1992;72:16-26.

29 PenningL.Functionalpathologyof thecervical spine.Amsterdam,

ExpertaMedica, 1968. In: White,III AA,PanjabiMM.Clinical

biomechanicsof thespine.2nd ed. Philadelphia: JBLippincott, 1990:118.

30 Silverman JL, RodriquezAA, Agre JC.Quantitativecervical

strengthinhealthysubjectsand insubjectswith mechanical neck

pain.ArchPhysMedRehabil1991;72:676-681.

31 Krout KM, AndersonTP. Role of anterior cervical muscles in

production ofneckpain.ArchPhysMed Rehabil 1966.

32 BohannonRW,LusardiMM.Modifiedsphygmomanometerversus straingaugehand-helddynamometer.Arch PhysMedRehabil

1991; 72:911-914.

33 VernonH, Aker P,Armenko M,BattershillD,Alepin A, Penner T. Evaluation of neck muscle strength with a modified

sphygmomanometer dynamometer:reliability and validity. JManipulative PhysiolTher1992;15:343-349.

34 LevoskaS,Keinanen-kiukanniemiS,Hamalainen 0,Jasma T,

VanharantaH.Reliabilty of a simple method ofmeasuring isometricneck muscle force. ClinBiomech 1992; 1:33-37.

35 Schuldt K. On neck muscleactivityand loadreductioninsitting

postures. Anelectromyographicstudyandbiomechanicalstudy withapplicationinergonomyandrehabilitation.Scan JRehab Med

1988,Suppl19:11-13.

36 TournayA, Paillard J. Etudeelectromyographiquedemouvements volontairesetinvolontairesducou. Rev Neur 1952;86:685-687.

37 FountainFP, MinearWL, Allison RD.Function ofthe longuscolli

andlongissimuscervicis muscles in man. ArchPhysMedRehabil 1966; 47:665-669.

38 Takabe K, VittiM, Basmajian JV. The functions of thesemispinalis capitis and spleniusmuscles: anelectromyographicstudy. Anat Rec1974; 179:477-480.

39 Schuldt K,Harms-RingdahlK. Cervicalspinepositionversus EMGactivityin the neck musclesduringmaximum isometric neck extension. Clin Biomech 1988; 3:129-136.

40 Keshner EA,CampbellD, Katz RT, Paterson BW.Neck muscle

activationpatterns in humans during isometric headstabilization.

ExpBrain Res 1989; 75:335-344.

41 Costa D, Vitti M,Tosello DDO,Electromyographicstudyof the

sternocleidomastoidmuscle in head movements. ElectromyographyClinNeurophysiol 1990;30:429-434.

42 SousaOM, et al. Etudeelectromyopgraphique dum.

sternocleidomastoideus. ElectromyogrClinNeurophysiol1973;

13:93-106.

43 VittiM, Fujiwara M, Basmajian JV. Theintegrated rolesof longus

colli andsternocleidomastoidmuscles: anelectromyographic study.

AnatRec 1973;177:471-484.

44 Ashton-MillerJA,McGlashenKM,Herzenberg JE, Stohler CS. Cervical musclemyoelectricresponse to acuteexperimental sternocleidomastoidpain. Spine1990; 15:1006-1012.

45 MoroneySS,Schultz AB, MillerJAA. Analysis and measurements of neck loads. JOrthopRes1988;6:713-720.

46 BeimbornDS,MorrisseyMC. Areview of the literaturerelatedto trunk muscleperformance.Spine 1988;13:655-660.

47 Highland RT, Dreisinger TE, Vie LL, Russel GS. Changes in isometric strength and motion of the isolated cervical spine after eight weeks ofclinical rehabilitation. Spine 1992; 6Suppl:S77-81. 48 Kipper V,Parker AW. Posturerelatedtomyoelectricsilence of the

erectorspinae duringtrunkflexion. Spine 1984;9:740-745.

49 SchultzAB,Haderspeck-GribK, Sinkora G, Warwick DN. Quantitative studies of theflexion-relaxation phenomenon in the

backmuscles. JOrthopRes1985;3:189-197.

50 PaulyJE. Anelectromyographicanalysis of certainmovementsand exercises. Anat Rec1966;153:223-234.

51 Steen B. Thefunctionof certain neckmusclesindifferent positions

of the head with andwithout loading of the cervical spine. ActaMorphol Neerl Scand 1966; 6:301-3 10.

52 Harms-RingdahlK, Ekholm J.Influenceof armpositiononneck muscular activity levels duringflexion-extensionmovementsofthe cervical spine. In: Jonsson B.editor.BiomechanicsX-A.Illinois:

Human KineticsPublisher, 1987:249-254.

53 Harms-RingdahlK,Ekholm J, Schultz K, NemethG,

Arborelius UP. Load moments andmyoelectricalactivitywhen the

cervicalspineisheld in fullflexionand extension.Ergonomics 1986; 29:1539-1552.

54 GracovetskyS, KaryDJ, Ben Said R,PitcehI,HelieJ.Analysis of spinalandmuscularactivity duringflexion/extensionandfree lifts. Spine 1990;15:1333-1339.

55 AhernDK, Hannon DJ,GorecznyJ, Follick MJ,ParzialeJR. Correlationof chronic low-back pain behavior andmusclefunction

examinationoftheflexion-relaxationresponse.Spine 1990;

15:92-95.

56 Ahern DK, FollickMJ,Council JR, Lasre-Wolton N,Litchman H. Comparisonoflumbar paravertebral EMGpatternsinchronic

low-backpainpatientandnon-patientcontrols.Pain1988;34:153-160.

57 GoldingJRS.Electromyography of theerectorspinae inlowback pain. Postgrad Med1952; 28:401-406.

58 Floyd WF, Silver PHS. The function of the erectorspinaemuscle

incertainmovement and posture in man. J Physiol 1955;

129:184-203.

59 Meyer JJ, Berk RJ, Anderson AV.Recruitmentpatternsinthe

cervical musclesduringcervicalforward flexion:evidence of

cervicalflexion-relaxation. Electromyogr Clin Neurophysiol.

Inpress.

60 Harms-Ringdahl K, EkholmJ.Intensity and character of pain and

muscularactivity levels elicited bymaintainedextremeflexion positionofthelower-cervical-upper-thoracicspine.Scan JRehab

Med1986; 18:117-126.

61 VernonH, Mior S. The neckdisability index;astudyofreliability