The Importance of an Early Positive The Importance of an Early Positive Change in Neck Function in Change in Neck Function in

Predicting Improvement Following a Predicting Improvement Following a Tailored Cervical Strengthening Tailored Cervical Strengthening Program for Chronic Neck Pain.Program for Chronic Neck Pain.

Dr Lauren Harding Dr Lauren Harding OsteopathOsteopath

M.H.Sc. (Osteo) B.Sc.(Clin.Sc.) B.App.Sc.(H.Mvt.)M.H.Sc. (Osteo) B.Sc.(Clin.Sc.) B.App.Sc.(H.Mvt.)

BackgroundBackground There is increasing research that supports the

efficacy of muscular strengthening in neck rehabilitation programs.

The role of strengthening for chronic neck pain is The role of strengthening for chronic neck pain is still not clear from systematic reviews. still not clear from systematic reviews.

Clinically, neck strengthening is often prescribed Clinically, neck strengthening is often prescribed by manual therapists for chronic neck painby manual therapists for chronic neck pain

However is appears only 50% of patients respond However is appears only 50% of patients respond to cervical strengthening to cervical strengthening (Keating et al 2005).(Keating et al 2005).

Useful to be able to predict those that will respond Useful to be able to predict those that will respond to the intervention.to the intervention.

Just as important to be able to select out those Just as important to be able to select out those unlikely to respond.unlikely to respond.

Neck Pain and Neck Weakness Neck Pain and Neck Weakness – An Association?– An Association?

Several studies have reported an association Several studies have reported an association between neck pain and neck muscle between neck pain and neck muscle weakness.weakness.

Ylinen et al (2004) demonstrated that pain Ylinen et al (2004) demonstrated that pain and maximal strength were inversely relatedand maximal strength were inversely related– Pain prevents full effort during strength tests and Pain prevents full effort during strength tests and

hence prevents the production of maximal force.hence prevents the production of maximal force. Prushansky et al (2004) report that male Prushansky et al (2004) report that male

and female whiplash victims suffered and female whiplash victims suffered cervical strength reductions of about 80% cervical strength reductions of about 80% and 90% respectively. and 90% respectively. – Fear avoidance behaviour in these patients Fear avoidance behaviour in these patients

resulting in a reduction of maximal force.resulting in a reduction of maximal force.

Fear AvoidanceFear Avoidance

Vlaeyen et al (2000) postulate that Vlaeyen et al (2000) postulate that ‘confrontation’ and ‘avoidance’ are the ‘confrontation’ and ‘avoidance’ are the two extremes.two extremes.

‘‘Confrontation’ = reduction of fear over Confrontation’ = reduction of fear over time.time.

‘‘Avoidance’ = maintenance or Avoidance’ = maintenance or exacerbation of fear.exacerbation of fear.

Fear Avoidance may play a role in:Fear Avoidance may play a role in:– poor muscular performancepoor muscular performance– de-conditioningde-conditioning

Exercise Interventions for Exercise Interventions for Chronic Neck PainChronic Neck Pain

Verhagen et al (2004) concluded that Verhagen et al (2004) concluded that active interventions tended to be more active interventions tended to be more effective than passive interventions. effective than passive interventions.

Gross et al (2004) concluded that Gross et al (2004) concluded that mobilization and manipulation techniques mobilization and manipulation techniques are only effective when combined with are only effective when combined with exercise.exercise.

How Many People Respond to How Many People Respond to Exercise Therapy?Exercise Therapy?

Keating et al (2005) investigated three Keating et al (2005) investigated three RCTs to determine the percentage of RCTs to determine the percentage of people that changed on the NDI by more people that changed on the NDI by more than the MCID in response to exercise than the MCID in response to exercise therapy.therapy.

Three RCTs were Brontfort et al (2001), Three RCTs were Brontfort et al (2001), Korthals-de Bos et al (2003) and Ylinen et Korthals-de Bos et al (2003) and Ylinen et al (2003).al (2003).

Stratford et al (1999) propose MCID for Stratford et al (1999) propose MCID for NDI of 7/50 points (14%).NDI of 7/50 points (14%).

Authors argue that approximately 50% of Authors argue that approximately 50% of people benefit from exercise therapy.people benefit from exercise therapy.

Where to from here?Where to from here? Prescribing neck strengthening for everyone Prescribing neck strengthening for everyone

presenting with neck pain is likely to prove presenting with neck pain is likely to prove ineffective for 50% of those seeking care.ineffective for 50% of those seeking care.

Clinicians often see patients achieve Clinicians often see patients achieve significant functional improvements in significant functional improvements in response to neck strengthening programs.response to neck strengthening programs.

Challenge is in identifying those people Challenge is in identifying those people likely and unlikely to benefit from any likely and unlikely to benefit from any treatment intervention.treatment intervention.

How long should a person persist with an How long should a person persist with an exercise routine before the probability of exercise routine before the probability of response is unacceptably low?response is unacceptably low?

AimAim

To determine the efficacy of early To determine the efficacy of early change in NDI scores for predicting change in NDI scores for predicting people who are likely to respond or people who are likely to respond or not respond to an exercise program.not respond to an exercise program.

Hypothesis: The probability of Hypothesis: The probability of responding to a course of neck responding to a course of neck strengthening treatment is greater in strengthening treatment is greater in those that respond in the first 3 those that respond in the first 3 weeks.weeks.

MethodsMethods Between 2000 and 2003, three hundred and nine Between 2000 and 2003, three hundred and nine

(309) patients were referred to a Clinic in Australia (309) patients were referred to a Clinic in Australia for treatment of chronic neck painfor treatment of chronic neck pain..

Two hundred and forty one started treatment (241).Two hundred and forty one started treatment (241). Reasons for not starting treatment included:Reasons for not starting treatment included:

Personal reasons (n = 53) – time, funds, locationPersonal reasons (n = 53) – time, funds, location Aggravated symptoms after initial evaluation (n = 6)Aggravated symptoms after initial evaluation (n = 6) Did not meet inclusion criteria (n = 4)Did not meet inclusion criteria (n = 4) Not approved for treatment from third party payer (n = Not approved for treatment from third party payer (n =

2)2) Waiting on legal proceedings (n = 1)Waiting on legal proceedings (n = 1) Referred to interstate Centers (n = 1)Referred to interstate Centers (n = 1) Advised against the program by a doctor (n = 1)Advised against the program by a doctor (n = 1)

MethodsMethods

Twenty seven (27) patients dropped Twenty seven (27) patients dropped out before first re-evaluation:out before first re-evaluation:– Personal reasons (n = 12)Personal reasons (n = 12)– Flared symptoms (n = 5)Flared symptoms (n = 5)– Dissatisfaction with results (n = 8)Dissatisfaction with results (n = 8)– Unknown (n = 2)Unknown (n = 2)

Two hundred and fourteen (214) Two hundred and fourteen (214) completed > than a 3 week completed > than a 3 week strengthening program.strengthening program.

EquipmentEquipment Multi-Cervical Unit (BTE Multi-Cervical Unit (BTE

Technologies Inc.) “MCU”Technologies Inc.) “MCU” Used to measure maximal Used to measure maximal

isometric strength of isometric strength of flexors, extensors and flexors, extensors and lateral flexors in:lateral flexors in:– in neutral in neutral – 2525° rotation left and right ° rotation left and right – 45° rotation left and right45° rotation left and right

Excellent reliability in Excellent reliability in isometric strength isometric strength measurement with ICCs measurement with ICCs ranging from 0.92 – 0.99ranging from 0.92 – 0.99 (Chui et al 2002).(Chui et al 2002).

Exclusion CriteriaExclusion Criteria

Unable to initiate 3 lbs (1.36kgs) of Unable to initiate 3 lbs (1.36kgs) of force for isometric testing.force for isometric testing.

Flare-up post-evaluation that lasted Flare-up post-evaluation that lasted for longer than 36 hours.for longer than 36 hours.

Significant exacerbation of peripheral Significant exacerbation of peripheral symptoms.symptoms.

The Initial EvaluationThe Initial Evaluation

History and duration of complaintHistory and duration of complaint AgeAge GenderGender Compensation status (Private or Compensation status (Private or

Compensable)Compensable) Neck Disability IndexNeck Disability Index VBI screeningVBI screening Evaluated on the MCU for Maximal Evaluated on the MCU for Maximal

Isometric StrengthIsometric Strength

Maximal isometric strength Maximal isometric strength testingtesting

Participants were allowed familiarizationParticipants were allowed familiarization ““Push as hard and as fast as you can”Push as hard and as fast as you can” Hold maximal isometric contraction for 3 Hold maximal isometric contraction for 3

seconds.seconds. 3 trials with 10 second rest period between 3 trials with 10 second rest period between

trialstrials Trials were averaged to obtain maximal Trials were averaged to obtain maximal

isometric strength in lbs.isometric strength in lbs. Trials were repeated if an effort was not Trials were repeated if an effort was not

within COV of 15%.within COV of 15%.

Treatment ProgramTreatment Program

The exercise program was designed to achieve The exercise program was designed to achieve strength scores comparable to isometric strength strength scores comparable to isometric strength measurements of 100 healthy subjects (Jordan et measurements of 100 healthy subjects (Jordan et al 1995).al 1995).

Initial resistance = 25-40% of the maximum Initial resistance = 25-40% of the maximum isometric score achieved during testingisometric score achieved during testing

2-3 times per week2-3 times per week 30 minute supervised session30 minute supervised session 3 sets of 10 repetitions for each of 6-8 exercises3 sets of 10 repetitions for each of 6-8 exercises Participants were re-evaluated for strength and Participants were re-evaluated for strength and

NDI scores after every 9 sessions until discharge.NDI scores after every 9 sessions until discharge.

Length of ProgramLength of Program

Time period between initial and final Time period between initial and final evaluation dependent upon:evaluation dependent upon:– How quickly a person responded to How quickly a person responded to

therapytherapy– How long the person took to complete How long the person took to complete

each 9 sessionseach 9 sessions

RespondersResponders

The MCID (minimum clinically The MCID (minimum clinically important difference) for the NDI is 7 important difference) for the NDI is 7 points points (Stratford 1999).(Stratford 1999).

Participants were considered Participants were considered responders if their NDI scores had responders if their NDI scores had changed by 7 points or more, or as changed by 7 points or more, or as non-responders if the NDI score did non-responders if the NDI score did not change by 7 points or more.not change by 7 points or more.

Analysis of DataAnalysis of Data

Linear Regression analysis was used to Linear Regression analysis was used to study the relationship between final NDI study the relationship between final NDI scores and 3 week NDI change scores. scores and 3 week NDI change scores.

Odd ratios were used to describe the Odd ratios were used to describe the relationship between 3 week and relationship between 3 week and discharge NDI scores.discharge NDI scores.

Other analyses included positive and Other analyses included positive and negative predictive scores, and sensitivity negative predictive scores, and sensitivity and specificity. Unable to report all due to and specificity. Unable to report all due to time restraints.time restraints.

DemographicsDemographics

80/115 were female (70%)80/115 were female (70%) Average age - 41 years (SD 12)Average age - 41 years (SD 12) 67 private (58%); 48 compensable (42%)67 private (58%); 48 compensable (42%) Median duration of symptoms – 60 months Median duration of symptoms – 60 months

(inter-quartile range 19 – 120)(inter-quartile range 19 – 120) Median initial NDI scores – 18 points (36%) Median initial NDI scores – 18 points (36%)

(inter-quartile range 14 – 25 points)(inter-quartile range 14 – 25 points) Median length of treatment – 10 weeks Median length of treatment – 10 weeks

(inter-quartile range 7 – 14 weeks)(inter-quartile range 7 – 14 weeks)

Results of Regression Results of Regression AnalysisAnalysis

A positive A positive change in the 3 week NDI change in the 3 week NDI score explained 47% of the variance score explained 47% of the variance in the final NDI in the final NDI positive change positive change (F = (F = 97.36; p = 0.00).97.36; p = 0.00).

Significant association between 3 week Significant association between 3 week and discharge NDI scores (r = 0.69; p = and discharge NDI scores (r = 0.69; p = 0.00)0.00)

Regression Line of Best FitRegression Line of Best Fit

Contingency TableContingency Table

Improved Improved at Finalat Final

Not Not Improved Improved at Finalat Final

TotalTotal

Improved Improved at 3 at 3

weeksweeks

41 3 4444

Not Not Improved Improved

at 3 at 3 WeeksWeeks

25 46 7171

TotalTotal 66 (57%)66 (57%) 4949 115115

Results of Odds Ratio Results of Odds Ratio AnalysisAnalysis

Odds ratio = 25.15 (95% confidence Odds ratio = 25.15 (95% confidence interval 7.07 – 89.49)interval 7.07 – 89.49)

If a patient demonstrated a positive If a patient demonstrated a positive improvement after 3 weeks of improvement after 3 weeks of therapy, then the patient has a 25 x therapy, then the patient has a 25 x greater (25.15) odds of responding greater (25.15) odds of responding overall to the course of neck overall to the course of neck strengthening therapy.strengthening therapy.

Possible Mechanisms of Possible Mechanisms of EffectEffect

Fear Avoidance ModelFear Avoidance Model– Fear avoidance has been proposed to play a Fear avoidance has been proposed to play a

role in “de-conditioning” (Vlaeyen 2000).role in “de-conditioning” (Vlaeyen 2000).– Neck strengthening pushes these patients into Neck strengthening pushes these patients into

the confrontation extreme of the fear the confrontation extreme of the fear avoidance model which can result in a avoidance model which can result in a reduction in fear and therefore a reduction in reduction in fear and therefore a reduction in self perceived disability.self perceived disability.

Increase in muscle fibre size (hypertrophy)Increase in muscle fibre size (hypertrophy) Motor Skill Acquisition Motor Skill Acquisition

– CNS harnesses existing resources to perform CNS harnesses existing resources to perform activities more efficiently.activities more efficiently.

Changes in co-activation of antagonistsChanges in co-activation of antagonists

Early Change to Early Change to StrengtheningStrengthening

Hypertrophy does not occur until Hypertrophy does not occur until after 3 weeksafter 3 weeks

Sub-group of patients (35.7%) who Sub-group of patients (35.7%) who respond favorably in the first 3 weeksrespond favorably in the first 3 weeks

Change is likely motor skill acquisitionChange is likely motor skill acquisition

Later Change to Later Change to StrengtheningStrengthening

Combination of motor skill acquisition Combination of motor skill acquisition and muscle hypertrophy?and muscle hypertrophy?

Additionally there may have been Additionally there may have been changes in the co-activation of the changes in the co-activation of the antagonistsantagonists

Hakkinen et al (1998) demonstrated Hakkinen et al (1998) demonstrated that progressive strength training leads that progressive strength training leads to significant decreases in the co-to significant decreases in the co-activation of the antagonists recorded activation of the antagonists recorded during maximal isometric action.during maximal isometric action.

Role of Further Strengthening Role of Further Strengthening in Early Respondersin Early Responders

Why continue with strengthening in the Why continue with strengthening in the early responders?early responders?

Average additional improvement is only 2 Average additional improvement is only 2 NDI points.NDI points.

Still a role for continued strengthening in Still a role for continued strengthening in early responders for early responders for protective/maintenance effects rather than protective/maintenance effects rather than discharging patients after 3 weeks.discharging patients after 3 weeks.

Six month or two year follow up would be Six month or two year follow up would be useful to compare outcome differences useful to compare outcome differences between early responders discharged at 3 between early responders discharged at 3 weeks and early responders discharged at 6 weeks and early responders discharged at 6 or 9 weeks.or 9 weeks.

Collected but not yet analyzed.Collected but not yet analyzed.

Future Research DirectionsFuture Research Directions Use of EMG and MVC to further study the Use of EMG and MVC to further study the

mechanism of effect for early and late mechanism of effect for early and late responders responders

Could more specifically define the Could more specifically define the contributions of motor skill acquisition and contributions of motor skill acquisition and muscle hypertrophymuscle hypertrophy

Investigate other factors that may have Investigate other factors that may have contributed to a reduction in self perceived contributed to a reduction in self perceived disabilitydisability– Fear avoidance questionnairesFear avoidance questionnaires– Joint ROMJoint ROM– Measure both agonists and antagonists via EMGMeasure both agonists and antagonists via EMG

Future Research DirectionsFuture Research Directions

Six month follow up comparing the Six month follow up comparing the outcomes of early responders discharged outcomes of early responders discharged after 3 weeks and early responders who after 3 weeks and early responders who continued for further therapycontinued for further therapy

Predictor variables for late responders (n Predictor variables for late responders (n = 25)= 25)

Correlate increase in strength with a Correlate increase in strength with a decrease in self perceived disability decrease in self perceived disability (functional questionnaire such as NDI)(functional questionnaire such as NDI)

Implications for Clinicians, Implications for Clinicians, Patients and Third Party PayersPatients and Third Party Payers Neck strengthening programs do not provide Neck strengthening programs do not provide

hypertrophy benefits alone.hypertrophy benefits alone. Clinicians can provide a probability for Clinicians can provide a probability for

response based on early change (as early as 3 response based on early change (as early as 3 weeks). weeks). – For responders, this can aid in further third party For responders, this can aid in further third party

approval or encourage patients to continue for the approval or encourage patients to continue for the protective or maintenance effects (based on the protective or maintenance effects (based on the clinical premise that further rehabilitation will clinical premise that further rehabilitation will improve longer term outcome).improve longer term outcome).

– For non-responders at 3 weeks, clinicians can For non-responders at 3 weeks, clinicians can provide patients with a probability for longer term provide patients with a probability for longer term change and the patient, clinician or third party can change and the patient, clinician or third party can decide if the odds warrant continued investment in decide if the odds warrant continued investment in the program.the program.

AcknowledgementsAcknowledgements

BTE Technologies, Colorado BTE Technologies, Colorado www.btetech.comwww.btetech.com

Melbourne Whiplash Centre Melbourne Whiplash Centre www.whiplashcentre.comwww.whiplashcentre.com

Professor Jenny Keating, Monash Professor Jenny Keating, Monash University, Melbourne, AUSTRALIA.University, Melbourne, AUSTRALIA.

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