Relationship between performance on lumbar dynamometry and Waddell score in a population with low-back pain

Human primary myoblasts derived from paraspinal muscle reflect donor age as an experimental model of sarcopenia

BACKGROUND

Low back pain is a general phenomenon of aging, and surgery is an unavoidable choice to relieve severe back pain. The discarded surgical site during surgery is of high value for muscle and muscle-related research. This study investigated the age-dependent properties of patients' paraspinal muscles at the cellular level.

METHODS

To define an association of paraspinal muscle degeneration with sarcopenia, we analyzed lumbar paraspinal muscle and myoblasts isolated from donors of various ages (25-77 years). Preoperative evaluations were performed by bioimpedance analysis using the InBody 720, magnetic resonance (MR) imaging of the lumbar spine, and lumbar extension strength using a lumbar extension dynamometer. In addition, the growth and differentiation capacity of myoblasts obtained from the donor was determined using proliferation assay and western blotting.

RESULTS

The cross-sectional area of the lumbar paraspinal muscle decreased with age and was also correlated with the appendicular skeletal muscle index (ASM/height2). Human primary myoblasts isolated from paraspinal muscle preserved their proliferative capacity in vitro, which tended to decrease with donor age. The age-dependent decline in myoblast proliferation was correlated with levels of cell cycle inhibitory proteins (p16INK4a, p21CIP1, and p27KIP1) associated with cellular senescence. Primary myoblasts isolated from younger donors differentiated into multinucleate myotubes earlier and at a higher rate than those from older donors in vitro. Age-dependent decline in myogenic potential of the isolated primary myoblasts was likely correlated with the inactivation of myogenic transcription factors such as MyoD, myogenin, and MEF2c.

CONCLUSIONS

Myoblasts isolated from human paraspinal muscle preserve myogenic potential that correlates with donor age, providing an in vitro model of sarcopenia.

Sarcopenia and Back Muscle Degeneration as Risk Factors for Back Pain: A Comparative Study

Study Design

Case-control study.

Purpose

To investigate the independent associations of back pain with sarcopenia and with back muscle degeneration, and to introduce a new risk index for back muscle degeneration.

Overview of Literature

The Asian Working Group for Sarcopenia recommends diagnosis using handgrip strength, gait speed, and skeletal muscle mass. However, these criteria do not strongly reflect back muscle degeneration.

Methods

Patients who completed a questionnaire on back-pain between October 2016 and October 2017 were enrolled in this study. Appendicular skeletal muscle index (ASMI), cross-sectional area (CSA) index, fatty infiltration (FI) rate of the paraspinal muscles, and lumbar extensor strength index (LESI) were measured and compared between no back-pain and back-pain group. Correlations between LESI and ASMI, CSA index, and FI rate were analyzed. The back-pain group was further divided according to ASMI into sarcopenia and non-sarcopenia subgroups and by our newly developed back muscle degeneration risk index based on correlation coefficients between LESI and CSA index, FI rate. Differences in ASMI, CSA index, FI rate, LESI, and Visual Analog Scale (VAS) score between subgroups were analyzed.

Results

The ASMI, CSA index, FI rate, and LESI differed significantly between back-pain and pain-free groups. The LESI demonstrated the strongest correlation with FI rate. There were no significant differences in VAS score and back muscle degeneration index in the back-pain group when divided according to the presence of sarcopenia. However, there was a significant difference in VAS score between back-pain patients when classified according to high and low back muscle degeneration risk index.

Conclusions

We suggest that the degree of back pain is more strongly associated with back muscle degeneration than with sarcopenia. This back muscle degeneration risk index, reflecting both back muscle morphology and function, could be a useful parameter for evaluation of back pain and muscle degeneration.

How does back muscle strength change after posterior lumbar interbody fusion?

OBJECTIVE There is a lack of evidence of how back muscle strength changes after lumbar fusion surgery and how exercise influences these changes. The aim of this study was to evaluate changes in back muscle strength after posterior lumbar interbody fusion (PLIF) and to measure the effects of a postoperative exercise program on muscle strength and physical and mental health outcomes. METHODS This prospective study enrolled 59 women (mean age 58 years) who underwent PLIF at 1 or 2 spinal levels. To assess the effects of a supervised lumbar stabilization exercise (LSE), the authors allocated the patients to an LSE (n = 26) or a control (n = 33) group. The patients in the LSE group performed the LSEs between 3 and 6 months postoperatively. Back extensor strength, visual analog scale (VAS) scores in back pain, and physical component summary (PCS) and mental component summary (MCS) scores on the 36-Item Short Form Health Survey were determined for the both groups. RESULTS Mean strength of the back muscles tended to slightly decrease by 7.5% from preoperatively to 3 months after PLIF (p = 0.145), but it significantly increased thereafter and was sustained until the last follow-up (38.1%, p < 0.001). The mean back muscle strength was similar in the LSE and control groups preoperatively, but it increased significantly more in the LSE group (64.2%) than in the control group (21.7%) at the last follow-up 12 months after PLIF (p = 0.012). At the last follow-up, decreases in back pain VAS scores were more significant among LSE group patients, who had a pain reduction on average of 58.2%, than among control group patients (reduction of 26.1%) (p = 0.013). The patients in the LSE group also had greater improvement in both PCS (39.9% improvement) and MCS (20.7% improvement) scores than the patients in the control group (improvement of 18.0% and 1.1%, p = 0.042 and p = 0.035, respectively). CONCLUSIONS After PLIF, strength in back muscles decreased until 3 months postoperatively but significantly increased after that period. The patients who regularly underwent postoperative LSE had significantly improved back strength, less pain, and less functional disability at 12 months postoperatively.

Characteristics of Back Muscle Strength in Patients with Scheduled for Lumbar Fusion Surgery due to Symptomatic Lumbar Degenerative Diseases

Study Design

Cross sectional study.

Purpose

To evaluate characteristics of back muscle strength in patients scheduled for lumbar fusion surgery.

Overview of Literature

Little is known regarding muscle strength in patients with symptomatic lumbar degenerative diseases who require fusion surgery.

Methods

Consecutive 354 patients scheduled for posterior lumbar interbody fusion due to symptomatic degenerative diseases were approached for participation. 316 patients were enrolled. Before surgery, muscle strength was assessed by measuring maximal isometric extension strength at seven angular positions (0°, 12°, 24°, 36°, 48°, 60°, and 72°) and mean isometric strength was calculated. The Oswestry Disability Index (0-100) and visual analogue scale (0-100) for back pain were recorded. Muscle strength was compared according to gender, age (<60, 60-70, and ≥70 years) and scheduled fusion level (short, <3; long, ≥3).

Results

Isometric strength was significantly decreased compared with previously reported results of healthy individuals, particularly at extension positions (0°-48°, p<0.05). Mean isometric strength was significantly lower in females (p<0.001) and older patients (p<0.05). Differences of isometric strength between short and long level fusion were not significantly different (p>0.05). Isometric strengths showed significant, but weak, inverse correlations with age and Oswestry Disability Index (r<0.4, p<0.05).

Conclusions

In patients with symptomatic lumbar degenerative diseases, back muscle strength significantly decreased, particularly at lumbar extension positions, and in females and older patients.

The cross-sectional construct validity of the Waddell score

BACKGROUND

In 1980 the Waddell score, consisting of 8 non-organic or behavioural signs, was developed to measure illness behaviour in patients with low back pain. There is some debate about whether the Waddell score is a valid screening instrument for illness behaviour and psychological distress, or whether it merely reflects elevated pain levels and diminished functional physical capacities.

OBJECTIVE

The purpose of this study was to examine the construct validity of the Waddell score.

METHODS

In this cross-sectional study, a total of 20 hypotheses about the associations between the Waddell score and measures from different domains were formulated a priori, based on a Medline database search (1980-2010). These hypotheses were tested in a sample of 229 patients with chronic low back pain who attended an outpatient rehabilitation centre.

RESULTS

The percentage of hypotheses that were confirmed for the association between the Waddell score and the domain pain was 100%, for the domain physical 80%, for the domain illness behaviour 80% and 50% for the domain psychological. Correlation coefficients and kappa values varied between 0.06 and 0.44 for the measures that were expected to be associated with the Waddell score.

CONCLUSION

Most of our challenging a priori hypotheses were accepted, and the Waddell score was found to have satisfactory cross-sectional construct validity. However, the presence of Waddell signs does not indicate exactly what the specific problems are and must therefore be conceptualized and understood in the total clinical picture of the patient. The association between the Waddell score and measures from different domains is weak. The Waddell score cannot be regarded as a straightforward psychological "screener".

Resistive straight leg raise test, resistive forward bend test and heel compression test: novel techniques in identifying secondary gain motives in low back pain cases

PURPOSE

'Low back pain' (LBP) is a prevalent condition with a majority showing no specific organic pathology. Distinguishing 'secondary gain motives (SGM)' from organic causes is imperative in clinical practice. We describe here, three new tests-resistive straight leg raise test (rSLRT), resistive forward bend test (rFBT) and heel compression test (HCT) to help differentiate patients with 'SGM' from those without. We conducted a prospective study to validate the above tests in predicting non-organic causes as a reason for LBP.

METHODS

200 patients presenting with low back pain at the senior author's outpatient orthopaedic clinic from Jan 2009 to Nov 2010 were studied. Patients were separated into two groups-'SGM group' (n = 100) and 'non-SGM group' (n = 100). 'SGM group' patients had a history of work-related accidents, road traffic accidents or assault, with a background of ongoing litigation issues or compensation benefits. rSLRT, rFBT, HCT, Schober's test and Waddell's five signs were performed on them. Statistical analysis was done to identify correlations between test results, MRI findings and 'SGM' status.

RESULTS

Statistically significant differences were observed between the SGM and non-SGM group (p < 0.0005) for all tests studied. In predicting SGM status, rSLRT showed highest specificity (0.94) and highest positive predictive value (0.925) while HCT showed the highest negative predictive value (0.859). Positive rSLRT was found to be strongly correlated with ≥3 positive Waddell's signs. SGM patients with positive rSLRT tended to show resistance ≤45°.

CONCLUSIONS

rSLRT, rFBT and HCT (NK triad) are highly practical tests which strongly predict SGM status in patients.

The relationship between psychological factors and performance on the Biering-Sørensen back muscle endurance test

BACKGROUND CONTEXT

Many studies report an association between low back pain (LBP) and reduced back muscle endurance and consider this to indicate muscular dysfunction. However, few have investigated the potentially confounding influence of psychological factors on performance during such endurance tests.

PURPOSE

This study examined whether psychological factors were associated with "underperformance" on the Biering-Sørensen (BS) test (ie, not performing as well as one is physiologically capable of).

STUDY DESIGN/SETTING

Cross-sectional study of the baseline data of patients with chronic (>3 months) nonspecific LBP (cLBP) before participation in a clinical trial of exercise therapy.

PATIENT SAMPLE

One hundred forty-eight patients with cLBP (43% men; age, 45±10 years).

OUTCOME MEASURES

The time for which the modified BS isometric endurance test could be performed to exhaustion minus the time that would have been predicted based on the rate of decline in median frequency of the surface electromyographic (EMG) signal recorded bilaterally from the erector spinae at L3 and L5.

METHODS

Back pain and disability, psychological disturbance, catastrophizing, fear-avoidance beliefs, back beliefs, and exercise self-efficacy were measured using validated questionnaires. Patients performed the BS test to exhaustion while physiological muscle fatigability was measured from continuous surface EMG recordings.

RESULTS

Multivariable regression analysis controlling for gender revealed that greater psychological disturbance (p=.003) and more negative back beliefs (p=.015) were unique predictors of the extent of "underperformance," accounting for 22.3% variance in expected endurance time minus actual time.

CONCLUSIONS

It is important that the underlying nature (psychological or physiological) of performance deficits be identified during such tests because this may influence the interpretation of prospective studies reporting risk factors for LBP and dictate the particular treatment or interventional approach required to remedy the situation in individuals with LBP.

Reliability and validity of a new objective tool for low back pain functional assessment

STUDY DESIGN

Classification and functional assessment model for nonspecific low back pain (LBP) patients and controls on the basis of kinematic analysis parameters.

OBJECTIVE

Develop a logistic regression model using kinematic analysis variables to (1) discriminate between LBP patients and controls and (2) obtain objective parameters for LBP functional assessment.

SUMMARY OF BACKGROUND DATA

Functional assessment of spinal disorders has been carried out traditionally by means of subjective scales. Objective functional techniques have been developed, which usually involve the application of external loads or the analysis of highly standardized trunk flexion-extension maneuvers. Few studies have used everyday activities such as sit-to-stand or lifting an object from the ground. They have shown that the motion patterns of LBP patients differ from those of healthy subjects. Nevertheless, very few studies have tried to correlate objective findings to the results of subjective scales, and no previous study has developed a LBP classification and functional assessment model on the basis of kinematic analysis of everyday activities.

METHODS

Sixteen controls and 39 LBP patients performed a sit-to-stand task, and lifted three different weights from a standing position. The vertical forces exerted and the relative positions of the lower limb and the cervical, thoracic, lumbar, and sacroiliac regions were recorded. Reliability was determined from repetitions of the tests performed by the control group. Binary logistic regression analyses were computed. The results of the selected regression equation were correlated to the Oswestry Disability Index scale results, to check the validity of the procedure for the measurement of functional disability.

RESULTS

Reliability of the parameters was good. The selected regression model used two variables, and correctly classified 97.3% of the patients. High correlations were found between the results of this regression equation and the Oswestry Disability Index scale.

CONCLUSION

It is possible to distinguish LBP patients from healthy subjects by means of the biomechanical analysis of everyday tasks. This kind of analysis can produce objective and reliable indexes about the patients' degree of functional impairment.

A comparison of a maximum exertion method and a model-based, sub-maximum exertion method for normalizing trunk EMG

The problem with normalizing EMG data from patients with painful symptoms (e.g., low back pain) is that such patients may be unwilling or unable to perform maximum exertions. Furthermore, the normalization to a reference signal, obtained from a maximal or sub-maximal task, tends to mask differences that might exist as a result of pathology. Therefore, we presented a novel method (GAIN method) for normalizing trunk EMG data that overcomes both problems. The GAIN method does not require maximal exertions (MVC) and tends to preserve distinct features in the muscle recruitment patterns for various tasks. Ten healthy subjects performed various isometric trunk exertions, while EMG data from 10 muscles were recorded and later normalized using the GAIN and MVC methods. The MVC method resulted in smaller variation between subjects when tasks were executed at the three relative force levels (10%, 20%, and 30% MVC), while the GAIN method resulted in smaller variation between subjects when the tasks were executed at the three absolute force levels (50 N, 100 N, and 145 N). This outcome implies that the MVC method provides a relative measure of muscle effort, while the GAIN-normalized data gives an estimate of the absolute muscle force. Therefore, the GAIN-normalized data tends to preserve the differences between subjects in the way they recruit their muscles to execute various tasks, while the MVC-normalized data will tend to suppress such differences. The appropriate choice of the EMG normalization method will depend on the specific question that an experimenter is attempting to answer.

Poor back muscle endurance is related to pain catastrophizing in patients with chronic low back pain

STUDY DESIGN

An experimental and comparative study of chronic low back pain (CLBP) patients and healthy controls.

OBJECTIVE

To use a motivation-independent electromyography (EMG) based test of back muscle capacity to determine whether back muscle deconditioning is present in CLBP patients and whether it is related to pain-related psychological variables.

SUMMARY OF BACKGROUND DATA

The verification of the deconditioning syndrome in CLBP patients might be biased by the use of performance-based measures to assess physical fitness, especially in patients having fear of injury. Also, the use of lumbar-specific measures of physical fitness, such as back muscle strength and endurance, might be more sensitive to physical deconditioning than more general assessments such as aerobic capacity.

METHODS

A time-limited submaximal fatigue test was performed by 27 nonspecific CLBP subjects (14 men) who had not had any surgery, and 31 healthy controls (17 men) while surface EMG signals were collected from back muscles. Motivation-independent EMG indices, which are sensitive to muscle fatigue or to activation patterns, were then computed and entered as input into previously developed regression equations to predict endurance (PTend) and strength (PStrength). Between-group comparisons were completed with patients divided in subgroups based on a median split of pain intensity, fear of movement, or pain catastrophizing scores.

RESULTS

Differences between healthy and CLBP subgroups were mainly observed when patients were divided using pain catastrophizing scores (PCS). High-PCS patients showed significantly lower PTend than low-PCS patients. Various EMG indices showed comparable results to PTend. However, some of them also pointed out that the PCS-low patients were more fatigue-resistant and showed different activation patterns comparatively to healthy subjects.

CONCLUSION

These results suggest that physical deconditioning that is specific to back muscle capacity was present in a subgroup of patients while the opposite was observed in another subgroup, pain catastrophizing being related to this outcome. These findings support previous theoretical models of pain/disability.

On the use of EMG-ratios to assess the coordination of back muscles

BACKGROUND

Electromyographic (EMG) amplitude ratios (EMG-ratios) have been proposed to assess back muscle coordination in chronic low back pain patients to avoid the normalization of EMG using maximal contractions. The aim of this study was to test the relevance of this type of EMG analysis.

METHODS

Healthy subjects (44 men and 13 women) and patients with chronic low back pain (57 men) performed three 7s static ramp extension contractions ranging from 0% to 100% of the maximal voluntary contraction while standing in a static dynamometer. A subgroup of 20 healthy men also performed 5s step contractions at 10%, 20%, 40%, 60% and 80% of the maximal voluntary contraction. Finally, to assess reliability, another subgroup (n=20 healthy and 20 men with chronic low back pain) performed the protocol three times, on different days. Surface EMG signals were collected from four pairs of back muscles and subcutaneous tissue thickness was measured at the corresponding electrode sites. EMG amplitude values were computed at each 5% force level from 10% to 80% of the maximal voluntary contraction. Then, EMG-ratios were computed between different electrode sites and averaged bilaterally.

FINDINGS

All EMG-ratios were affected by the force level and the contraction type (ramp vs step contractions). Statistically significant Pearson's correlations (r=-0.38 to -0.57) were obtained between some EMG-ratios and their corresponding subcutaneous tissue thickness ratios. The reliability of the EMG-ratio variables ranged from moderate to excellent (intra-class correlation coefficients between 0.50 and 0.91). Comparisons between 12 men and 13 women and between 24 healthy men and 57 men with chronic low back pain showed that EMG-ratios were sensitive to sex but not to pain status. Multivariate analyses applied on the EMG-ratios identified clusters of subjects but none of the main clinical variables were able to clearly characterize these clusters.

INTERPRETATION

Overall, even though additional research is warranted to further substantiate some important psychometric characteristics of the EMG-ratios as well as their biomechanical and clinical significance, these results support their use for assessing the coordination patterns of back muscles, provided that confounding variables such as the force level, the contraction type, and subcutaneous tissue thickness are accounted for.

Reliability of electromyographic and force measures during prone isometric back extension in subjects with and without low back pain

Maximal voluntary isometric activations (MVIA) are frequently used as inputs for models attempting to predict muscle force and as normalization values in studies assessing muscle function. However, pain may adversely affect maximal muscle activation. The purpose of this study was to assess reliability of MVIA force and electromyographic (EMG) activity during prone isometric back extension in subjects with and without low back pain (LBP). A novel sub-maximal method using the percentages of the estimated mass of the head–arms–trunk (HAT) segment was also investigated. Repeated measures on 20 male volunteers divided into an LBP (n = 10) and a control group (n = 10) were made on 4 occasions. Force and EMG activity were recorded bilaterally from upper lumbar erector spinae (ULES), lower lumbar erector spinae (LLES), and biceps femoris (BF). Subjects exerted a maximal extension effort against a harness assembly that was attached to a force transducer. Submaximal exertions were also performed with an additional resistance of 100%, 110%, 120%, 130%, 140%, 150%, 160%, and 170% of HAT. Mean MVIA forces were significantly (p ≤ 0.05) lower in LBP vs. control. Intraclass correlation coefficients (ICC) for MVIA force, right and left ULES, and LLES EMG indicated high reliability in controls (R > 0.90), but were significantly less in LBP (R = 0.36–0.80). EMG of BF demonstrated excellent reliability across both groups (R > 0.90). The resistance at 100% HAT demonstrated the highest reliability for LBP patients, whereas higher percentages of HAT showed either similar or higher reliability for controls. Force output and back EMG activity are less reliable with LBP individuals and should be taken into consideration when testing.

Pain-Related Factors Contributing to Muscle Inhibition in Patients With Chronic Low Back Pain

OBJECTIVE

To evaluate muscle strength, as a component of physical deconditioning, and central activation ratio, representing the performance level during testing, in patients with chronic low back pain as compared to healthy controls, and to evaluate the contribution of cognitive-behavioral and pain-related factors to the central activation ration of patients with chronic low back pain.

METHODS

Twenty-five patients with chronic low back pain and 25 age and gender-matched controls participated. Muscle strength, that is, peak torque of the quadriceps muscle, was measured on a Cybex dynamometer. During peak torque, the quadriceps muscle was percutaneously stimulated using superimposed electrical stimulation, generating an additional twitch torque in case of submaximal performance. The central activation ratio was calculated as peak torque/(peak torque + additional twitch torque). To evaluate cognitive-behavioral and pain-related factors influencing the central activation ratio, measures of fear of injury, pain catastrophizing, psychologic distress, and pain intensity were used. Differences between groups were tested using either T tests or Mann-Whitney U tests. Associations were tested by partial correlation coefficients controlling for gender.

RESULTS

The male:female ratio was 15:10. Mean age and chronic low back pain duration were 42.7 (+/-9.5) and 9.9 (+/-8.3) years, respectively. Mean muscle torque (per kg lean body mass) in patients (1.95 Nm/kg +/-0.8) was less than in controls (3.16 Nm/kg +/-0.7) (P < 0.01). Median central activation ratio was lower in patients (P < 0.05). Patients experiencing increased psychologic distress and patients with a higher current pain level showed a lower central activation ratio (P < 0.05).

CONCLUSIONS

When interpreting decreased muscle strength in terms of physical deconditioning in patients with chronic low back pain, submaximal performance has to be taken into account. The results suggest that patients with chronic low back pain who report increased psychologic distress and a higher level of current pain tend to show increased inhibition of muscle activity, leading to submaximal performance.

Back muscle strength and fatigue in healthy and chronic low back pain subjects: A comparative study of 3 assessment protocols

OBJECTIVE

To compare the sensitivity of 3 different back test protocols in measuring differences in strength and fatigue between subjects with and without chronic low back pain (CLBP).

DESIGN

Descriptive study using a repeated-measures design.

SETTING

A research laboratory within a rehabilitation center.

PARTICIPANTS

Eighteen healthy subjects and 13 subjects with CLBP were assessed in a single session to compare the 3 protocols. The protocols were an upright position test (UPP), a semicrouched lifting test (LIF), and the Sorensen fatigue test.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Moments of force and surface electromyography were recorded bilaterally from 4 homologous back muscles while the subjects performed static trunk extension efforts for each protocol. Fatigue was quantified by the slopes of the linear regression of electromyography time-series.

RESULTS

The back muscle fatigue and strength scores did not differ significantly for the 2 subject groups for any of the 3 protocols. The electromyography fatigue indices revealed that the Sorensen fatigue test and UPP produced more fatigue in the back muscles than the LIF.

CONCLUSIONS

It was impossible to specify which protocol is more sensitive to low back status because no between-group difference was observed for any of the 3 tests.

Critical issues in the use of muscle testing for the determination of sincerity of effort

Over the past 20 years, there have been numerous attempts to identify methodologies that are capable of the determination of sincerity of effort during muscle testing. The ensuing paper reviewed this literature and drew several conclusions. Injured patients and healthy volunteers do produce less force and more variable force while performing submaximal contractions than maximal contractions. However, submaximal efforts during strength testing can be reproduced and the use of force variability is not adequate to distinguish sincerity of effort. Visual examination of the shape of force output curves is also not adequate for distinguishing sincerity of effort. Furthermore, much of the research using strength ratios, difference scores, and an assortment of different parameters derived during strength testing has not established reliable and clinically useful methods of differentiating effort levels. Methods examining motion variability, radial/ulnar force output ratios, difference scores of eccentric-concentric ratios, and electromyography offer some promise, but numerous critical issues need to addressed. The use of the coefficient of variation, for example, is statistically untenable given the number of trials appropriate for clinical samples. Several studies have inadequate sample size to number of variable ratios. Many studies have questionable or at least unknown generalizability to patient samples and actual functional capacity. It is critical that other explanatory variables such as fear of injury, pain, medications, work satisfaction, and other motivational factors be considered. It is our opinion that there is not sufficient empirical evidence to support the clinical application of muscle testing to determine sincerity of effort.

Testing lifting capacity: validity of determining effort level by means of observation

STUDY DESIGN

Video observation study.

OBJECTIVES

To establish the validity of determining effort level by visual observation of a lifting test.

SUMMARY OF BACKGROUND DATA

Determining effort level during a lifting test is critical for interpretation of test performance, yet the validity of these determinations has not been established in patients with chronic nonspecific low back pain.

METHODS

Fifteen healthy subjects and 16 patients with chronic nonspecific low back pain performed a standardized lifting test as outlined in the Isernhagen Work System Functional Capacity Evaluation. The lifts were videotaped and independently observed by 9 trained observers, who rated effort levels using an Isernhagen Work System categorical scale and a Borg Category Ratio scale. External effort indexes were established to control for effort at group level. Validity of the observer ratings was analyzed by means of a sensitivity and specificity analysis and correlations between performances and observer ratings. Interrater reliability was analyzed by means of intraclass correlation coefficients and Cohen kappa.

RESULTS

External indexes differ significantly between patients with chronic low back pain and healthy subjects, indicating that at group level, patients did not perform maximally. Submaximal performances were correctly rated in 85% to 90% (healthy subjects) and in 100% (patients with chronic nonspecific low back pain) of the cases. "Maximal" performances were correctly rated in 46% to 53% (healthy subjects) and in 5% to 7% (patients with chronic nonspecific low back pain) of the cases. Correlations between performances and observer ratings were r = 0.90 to r = 0.92 (healthy subjects) and r = 0.82 (patients with chronic nonspecific low back pain). Reliability: intraclass correlation coefficient, r = 0.76 (patients with chronic nonspecific low back pain) to r = 0.87 (healthy), Kappa K = 0.50 (patients with chronic nonspecific low back pain) to r = 0.58 (healthy subjects).

CONCLUSIONS

Effort level can be determined validly by means of visual observation.

Differences in outcome of a multidisciplinary treatment between subgroups of chronic low back pain patients defined using two multiaxial assessment instruments: the multidimensional pain inventory and lumbar dynamometry

OBJECTIVE

To investigate the effects of a multidisciplinary back school programme (Roessingh Back Rehabilitation Programme, RRP) compared with usual care, as well as differences in treatment outcome between subgroups defined using two multiaxial assessment instruments: the Multidimensional Pain Inventory (MPI-DLV) and lumbar dynamometry.

DESIGN

Randomized controlled trial.

SETTING

Rehabilitation.

SUBJECTS

One hundred and sixty-three patients with chronic, aspecific low back pain.

INTERVENTION

All subjects were randomly assigned either to a multidisciplinary, physically oriented group treatment or to their usual care.

MAIN OUTCOME MEASURES

The Roland Disability Questionnaire and health-related quality of life (EuroQol, EQ5-D) were measured as primary outcomes before randomization and after eight weeks and six months follow-up.

RESULT

Only 30-50% of the patients in the RRP group showed improvement and this number is not significantly different from the control group. Subgroup analyses give some first indications that multiaxial measurement instruments can be used to identify subgroups with differences in treatment effects.

CONCLUSION

The overall effect of a multidisciplinary treatment is disappointing, however multiaxial assessment before admission might be valuable in clinical practice, resulting in more effective treatments for patients with chronic low back pain.

Trunk muscle strength and disability level of low back pain in collegiate wrestlers

INTRODUCTION/PURPOSE

Low back pain (LBP) is a frequent injury in athletes. This study examined the relationship between isokinetic trunk muscle strength and the functional disability level of chronic LBP. We particularly focused on the existence of radiological abnormalities (RA) in the lumbar region.

METHODS

Subjects were 53 collegiate wrestlers. Trunk extensor and flexor muscle strength was measured at three angular velocities (60, 90, and 120degrees x s(-1)). The examined parameters for trunk muscle strength were peak torque, work, average torque, and average power. The disability level of LBP was estimated by using two questionnaires. Based on the RA evaluation with x-ray and MRI, all 53 wrestlers were assigned to two groups as the RA group (N = 35, 66%) and the non-RA group (N = 18, 34%). Correlations between trunk muscle strength and the disability level of LBP in each group were analyzed with Spearman's rank test.

RESULTS

Without considering the disability level, there were 14 subjects with LBP (40%) in the RA group and 8 (44%) in the non-RA. Significantly correlated parameters with the disability level of LBP could be observed only when the subjects were restricted to the non-RA group. The correlated parameters with the two questionnaires were peak torque at 120degrees x s(-1), work at 60degrees x s(-1) and 90degrees x s(-1), and average torque at 90degrees x s(-1) and 120degrees x s(-1). There were no significantly correlated parameters in the RA group. None of the trunk flexor parameters were significantly correlated with the disability level of LBP.

CONCLUSION

The relatively low strength of trunk extensors may be one of the factors related to nonspecific chronic low back pain in collegiate wrestlers.

Surface electromyography assessment of back muscle intrinsic properties

The purpose of this study was to assess (1) the reliability and (2) the sensitivity to low back pain status and gender of different EMG indices developed for the assessment of back muscle weakness, muscle fiber composition and fatigability. Healthy subjects (men and women) and chronic low back pain patients (men only) performed, in a static dynamometer, maximal and submaximal static trunk extension tasks (short and long duration) to assess weakness, fiber composition and fatigue. Surface EMG signals were recorded from four (bilateral) pairs of back muscles and three pairs of abdominal muscles. To assess reliability of the different EMG parameters, 40 male volunteers (20 controls and 20 chronic low back pain patients) were assessed on three occasions. Reliable EMG indices were achieved for both healthy and chronic low back pain subjects when specific measurement strategies were applied. The EMG parameters used to quantify weakness and fiber composition were insensitive to low back status and gender. The EMG fatigue parameters did not detect differences between genders but unexpectedly, healthy men showed higher fatigability than back pain patients. This result was attributed to the smaller absolute load that was attributed to the patients, a load that was defined relative to their maximal strength, a problematic measure with this population. An attempt was made to predict maximal back strength from anthropometric measurements but this prediction was prone to errors. The main difficulties and some potential solutions related to the assessment of back muscle intrinsic properties were discussed.

Back strength cannot be predicted accurately from anthropometric measures in subjects with and without chronic low back pain

OBJECTIVES

(1) To develop a multiple regression equation using anthropometric measurements to predict back strength and (2) to estimate the effect of practice on the back strength results and back strength predictions.

DESIGN

Comparative study with repeated measures performed on three days.

BACKGROUND

The assessment of back muscle relative endurance (% maximal strength) requires the measurement of maximal back strength which is problematic with low back pain patients.

METHODS

The back strength (L5/S1 static extension moment), age and 26 anthropometric parameters were obtained from 83 male volunteers [42 healthy subjects and 41 chronic low back pain patients] aged between 20 and 60 years. A subsample of 20 healthy subjects and 20 patients were assessed through three days of testing to evaluate the variations of back strength with practice.

RESULTS

The final regression model (n=42 healthy subjects) explained 39% of the variance in back strength. Back strength increased with practice (Day1<Day2 & 3) for both healthy and patients groups. However, the error of prediction of back strength derived from the regression model showed a significant improvement with practice for the patients only.

CONCLUSIONS

Back strength cannot be predicted from simple anthropometric measures without important errors. The decrease of the error of prediction obtained for the patient group is indicative of a decreasing influence of psychological factors that are independent of motor learning because the effect of motor learning would have occurred on both groups if present.

RELEVANCE

The prediction of back strength would be useful to determine (1) the relative force level of a given exercise or (2) the preinjury back strength. Unfortunately, anthropometric measurements are not enough good predictors of back strength.

A structured evidence-based review on the meaning of nonorganic physical signs: Waddell signs

STUDY DESIGN

This is a structured, evidence-based review of all available studies addressing the concept of nonorganic findings: Waddell signs (WSs).

OBJECTIVES

To determine what evidence, if any, exists for the various interpretations for the presence of WSs on physical examination.

SUMMARY OF BACKGROUND DATA

WSs are a group of eight physical findings divided into five categories, the presence of which has been alleged at times to have the following interpretations: Malingering/secondary gain, hysteria, psychological distress, magnified presentation, abnormal illness behavior, abnormal pain behavior, and somatic amplification. At the present time, there is, therefore, significant confusion as to what these findings mean.

METHODS

A computer and manual literature search produced 61 studies and case series reports relating to WSs. These references were reviewed in detail, sorted, and placed into tabular form according to the following subject areas: 1) Reliability (test-retest); 2) Reliability (inter-rater); 3) Reliability (factor analysis); 4) Validity, psychological distress; 5) Validity, correlation Minnesota Multiphasic Pain Inventory (MMPI); 6) Validity, correlation abnormal illness behavior; 7) Validity, other behaviors; 8) Validity, as a nonorganic phenomenon; 9) Validity, correlation pain drawing; 10) Validity, functional performance; 11) Validity, treatment outcome; 12) Validity, predicting surgical treatment outcome; 13) Validity, return to work outcome; 14) Validity, secondary gain correlation; and 15) Validity, pain correlation. Each study in each topic area was classified according to the type of study it represented according to the type of evidence guidelines developed by the Agency for Health Care Policy and Research (AHCPR). In addition, a list of 14 study quality criteria was used to measure the quality of each study. Each study was categorized for each criterion as positive, (criterion filled), negative (criterion not filled), or not applicable independently by two of the authors. A percent quality score was obtained for each study by counting the total number of positives obtained, dividing by 14 minus the total number of not applicables, and multiplying by 100. Only studies having a quality score of 75% or greater were used to formulate the conclusions of this review. The strength and consistency of the evidence represented by the remaining studies in each topic area (above) was then categorized according to the strength and consistency AHCPR guidelines. Conclusions of this review for each topic area are based on these results.

RESULTS OF DATA SYNTHESIS

Of the 61 studies, four had quality scores below 75% and were not used to generate the results of this review. According to the AHCPR guidelines for strength and consistency of the reviewed data, the following results were obtained: 1) There was consistent evidence for WSs being associated with decreased functional performance, poor nonsurgical treatment outcome, and greater levels of pain; 2) There was generally consistent evidence for WSs not being associated with psychological distress, abnormal illness behavior, or secondary gain; 3) There was also generally consistent evidence that WSs are an organic phenomenon and that they cannot be used to discriminate organic from nonorganic problems; 4) There was inconsistent evidence that WSs do demonstrate inter-rater reliability, do not correlate with the neurotic triad of the MMPI, are associated with poorer surgical treatment outcome, and are associated with nonreturn to work; 5) There was little or no evidence that WSs demonstrate test-retest reliability, or reliable factors, and are associated with self-esteem problems, catastrophizing, or the nonorganic pain drawing.

CONCLUSIONS

Based on the above results, the following conclusions were made: 1) WSs do not correlate with psychological distress; 2) WSs do not discriminate organic from nonorganic problems; 3) WSs may represent an organic phenomenon; 4) WSs are associated with poorer treatment outcome; 5) WSs are associated with greater pain levels; 6) WSs are not associated with secondary gain; and 7) As a group, WS studies demonstrate some methodological problems.

A new sign of inappropriate lower back pain

The treatment of lower back pain constitutes a major problem for orthopaedic surgeons. Identifying the patients who have a non-organic component to their lower back pain is often difficult. Waddell et al. (Waddell G, McCulloch HA, Kummel E, Venner RM. Non-organic physical signs in low-back pain. Spine 1980; 5: 117-25) devised a set of five physical signs to assist in determining this. These signs are time consuming and can be difficult to interpret. We have developed a sign that is simple, quick and easy to perform. In a set of 94 patients, we have compared our sign with Waddell's signs. Our sign has a highly significant correlation with Waddell's signs (chi2 = 55.093, P < 0.001), and thus we would suggest it as an accurate alternative to Waddell's signs.

Electromyographic assessment of back muscle weakness and muscle composition: reliability and validity issues

OBJECTIVE

To assess the reliability and construct validity of various electromyographic indices developed to assess back muscle weakness and muscle fiber composition.

DESIGN

A prospective study with repeated measures performed on 3 days along with comparisons of groups presenting different back strength and/or back muscle fiber composition.

SETTING

A biomechanics laboratory within a rehabilitation center.

PARTICIPANTS

Forty male volunteers (20 healthy, 20 with chronic low back pain) were assessed on 3 different days to assess reliability and to make group comparisons. Thirteen healthy women were also assessed once to obtain a third group with known lower strength and different back muscle fiber composition.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Surface electromyography was recorded for 4 pairs of homologous back muscles while the subjects performed, on a dynamometer, static trunk extension efforts. Electromyographic parameters were computed to assess muscle weakness and muscle fiber composition. The reliability of the data collected across the 3 sessions and comparisons between groups were determined.

RESULTS

Electromyographic parameters generally showed good to excellent reliability, but were insensitive to differences in back muscle strength and did not appear to be related to muscle composition. Some trends were observed in the electromyographic parameters across the force levels, but the large interindividual variability impeded statistical comparisons.

CONCLUSIONS

The assessment of muscle weakness and muscle fiber composition through electromyographic analysis does not appear feasible, at least on an individual basis, for the muscles of the back.

Evaluation of measurement strategies to increase the reliability of EMG indices to assess back muscle fatigue and recovery

The purpose of this study was to assess different measurement strategies to increase the reliability of different electromyographic (EMG) indices developed for the assessment of back muscle impairments. Forty male volunteers (20 controls and 20 chronic low back pain patients) were assessed on three sessions at least 2 days apart within 2 weeks. Surface EMG signals were recorded from four pairs (bilaterally) of back muscles (multifidus at the L5 level, iliocostalis lumborum at L3, and longissimus at L1 and T10) while the subjects performed, in a static dynamometer, two static trunk extension tasks at 75% of the maximal voluntary contraction separated by a 60 s rest period: (1) a 30 s fatigue task and (2) a 5 s recovery task. Different EMG indices (based on individual muscles or averaged across bilateral homologous muscles or across all muscles) were computed to evaluate muscular fatigue and recovery. Intra-class correlation coefficient (ICC) and standard error of measurement (SEM) in percentage of the grand mean were calculated for each EMG variable. Reliable EMG indices are achieved for both healthy and chronic low back pain subjects when (1) electrodes are positioned on medial back muscles (multifidus at the L5 level and longissimus at L1) and (2) measures are averaged across bilateral muscles and/or across two fatigue tests performed within a session. The most reliable EMG indices were the bilateral average of medial back muscles (ICC range: 0.68-0.91; SEM range: 5-35%) and the average of all back muscles (ICC range: 0.77-0.91; SEM range: 5-30%). The averaging of measures across two fatigue tests is predicted to increase the reliability by about 13%. With regards to EMG indices of fatigue, the identification of the most fatigable muscle also lead to satisfactory results (ICC range: 0.74-0.79; SEM range: 21-26%). The assessment of back muscle impairments through EMG analysis necessitates the use of multiple electrodes to achieve reliable results.

Estimated moments at L5/S1 level and muscular activation of back extensors for six prone back extension exercises in healthy individuals

The purpose of this study was to identify the prone back extension (PBE) exercises that offer the most resistance to the back extensor muscles. Twenty males with no previous history of low back injury performed two repetitions of eight exercises. These consisted of two maximal isometric voluntary activations (MVA) and six different PBE exercises. The participants, while lying prone on a bench, were asked to raise either their trunk or legs to the horizontal position and hold for one second (static phase) before returning to the original position. The exercises differed according to the particular segments that were raised into extension. To assess the PBE exercises, a biomechanical model was used to estimate the level of load resistance (%MVA) relative to the maximum voluntary activation strength (MVA). In addition, electromyography (EMG) was included to measure the level of muscle activity (%MVE) relative to the maximum voluntary activation EMG (MVE) value reached during the MVA. A significant relationship of 0.86 was found between the mass of the subject and the peak reaction moment during the MVA. Peak level of load resistance averaged around 50% MVA with the exception of exercise no. 5 where the subject had to raise in extension his trunk, legs and arms (65% MVA). The erector spinae (ES) activity level reached a peak value of 61% MVE for exercise no. 5. In the exercises where only the trunk was lifted, the peak level of ES was below 47% MVE and the average activity during the static phase reached approximately 26% MVE. For healthy individuals PBE exercises can be considered low intensity exercises (< 50% MVA; except exercise no. 5) and can be used to improve the endurance of the back muscles.

Differences in treatment outcome between subgroups of patients with chronic low back pain using lumbar dynamometry and psychological aspects

OBJECTIVE

To investigate whether subgroups of patients with chronic low back pain show differences in treatment outcome, measured with the Roland Disability Questionnaire. (RDQ).

SETTING

The study was carried out in a rehabilitation centre.

SUBJECTS

Eighty-four patients with chronic low back pain participated in this study.

INTERVENTION

Patients followed a multidisciplinary treatment programme that primarily targets physical aspects. DESIGN AND MAIN OUTCOME MEASURE: Based on pretreatment lumbar dynamometry results and Symptom Checklist (SCL-90) scores, patients were divided into subgroups. The dynamometry subgroups were: performances lower than healthy subjects (expected performance), performances comparable with those of healthy subjects (normal performance) and inconsistent performances (submaximal performance). The SCL-90 subgroups were: a total score of 'average' or lower compared with a population of chronic pain patients (low psychological score) and a total score of 'above average' or higher compared with this population (high psychological score). Patients answered the RDQ in the week before (RDQ1; n = 84) and after treatment (RDQ2; n = 78) to investigate whether the subgroups show differences in outcome expressed as the percentage change between RDQ2 and RDQ1, (%RDQ2-1). A %RDQ2-1 > or = 20% was classified as an improvement.

RESULTS

Improvement on disability level > or = 20% is shown in 64% and 55% of the patients with 'normal' and 'expected' lumbar dynamometry performances and low psychological scores compared with only 33% and 25% of those with high psychological scores. Patients with submaximal performances show hardly any changes in disability level and there are no differences betweenthose with low psychological scores (14%) and those reporting high scores (0%).

CONCLUSION

The fact that patient subgroups with differences in treatment outcome can be defined using lumbar dynamometry and psychological questionnaires suggests that these instruments might facilitate treatment indication in clinical practice.

Radiofrequency facet joint denervation in the treatment of low back pain: a placebo-controlled clinical trial to assess efficacy

STUDY DESIGN

A prospective double-blind randomized controlled trial was performed.

OBJECTIVE

To assess the efficacy of percutaneous radiofrequency articular facet denervation for low back pain.

SUMMARY OF BACKGROUND DATA

Uncontrolled observational studies in patients with low back pain have reported some benefits from the use of facet joint radiofrequency denervation. Because the efficacy of percutaneous radiofrequency had not been clearly shown in previous studies, a randomized controlled trial was conducted to assess the efficacy of the technique for improving functional disabilities and reduce pain.

METHODS

For this study, 70 patients with low back pain lasting of more than 3 months duration and a good response after intraarticular facet injections under fluoroscopy were assigned randomly to receive percutaneous radiofrequency articular facet denervation under fluoroscopic guidance or the same procedure without effective denervation (sham therapy). The primary outcomes were functional disabilities, as assessed by the Oswestry and Roland-Morris scales, and pain indicated on a visual analog scale. Secondary outcomes included spinal mobility and strength.

RESULTS

At 4 weeks, the Roland-Morris score had improved by a mean of 8.4% in the neurotomy group and 2.2% in the placebo group, showing a treatment effect of 6.2% (P = 0.05). At 4 weeks, no significant treatment effect was reflected in the Oswestry score (0.6% change) or the visual analog pain score (4.2% change). At 12 weeks, neither functional disability, as assessed by the Roland-Morris scale (2.6% change) and Oswestry scale (1.9% change), nor the pain level, as assessed by the visual analog scale (-7.6% change), showed any treatment effect.

CONCLUSIONS

Although radiofrequency facet joint denervation may provide some short-term improvement in functional disability among patients with chronic low back pain, the efficacy of this treatment has not been established.

The role of the motor system in spinal pain: implications for rehabilitation of the athlete following lower back pain

The purpose of this review is to consider the role of the motor system in spinal pain. It is well accepted that spinal stability is dependent on the contribution of the muscular system. However, the ability of this system to satisfy the requirements of stability is dependent on its controller--the central nervous system (CNS). The CNS must predict the outcome of movements to plan appropriate strategies of muscle activity to meet the demands of internal and external forces, and initiate appropriate responses to unexpected disturbances. In addition, this complex control of stability must occur in conjunction with control of the trunk muscles for other functions, such as respiration. For the CNS to cope with athletic performance the coordination of these parameters must be streamlined. Yet evidence suggests that when spinal pain is present the strategies used by the CNS to control trunk muscles may be altered. The mechanism for these changes is poorly understood but may be due to changes at many levels of the CNS. For rehabilitation of the athlete with spinal pain it is critical that the motor control of stability is optimised. Furthermore, this must be coordinated with the multiple other functions of trunk muscles, including respiration.

Minimal influence of facet joint anesthesia on isokinetic muscle performance in patients with chronic degenerative low back disorders

STUDY DESIGN

Experimental design.

OBJECTIVES

To examine the influence of pain reduction after facet joint injections on isokinetic back muscle performance.

SUMMARY OF BACKGROUND DATA

Methods for evaluating the effect of facet joint injections vary. Recent studies base their results solely on the patient's subjective opinion and suggest a need for more objective, concrete, and reliable measurements.

METHODS

Eighty-seven patients with a degenerative low back disorder (49 women and 38 men; mean age, 48 years; range, 22-79) who had facet joint injections as a part of preoperative evaluation participated. The mean duration of symptoms was 12.3 years (range, 1-45). The patients underwent isokinetic trunk flexor and extensor muscle strength testing at angular velocities of 60 deg/sec and 120 deg/sec. They performed two tests before the facet joint injections (to eliminate learning effect). All patients had bilateral facet joint injections at L5-S1. Those who did not report pain relief had additional injections at L4-L5. The flexion-extension test was repeated 15 minutes after each injection. Pain and fear were registered on visual analog scales.

RESULTS

All 87 patients could perform the isokinetic tests. For extension at 60 deg/sec, a significant improvement was found between the two pretests (P < 0.05). Pain increased significantly from the first to the second pretest (P = 0.02), and a significant decrease in pain was found after the first injection (P = 0.0001). Fear decreased between each test, with a significant decrease after the first injection. No significant change was found for the muscle strength measurements after facet joint anesthesia. There were only weak correlations between decrease in pain and alteration in muscle performance, ranging from 0.06 to 0.37.

CONCLUSION

Pain reduction after facet joint injections did not influence isokinetic muscle performance in patients with degenerative low back disorders.

Relationship between functional evaluation measures and self-assessment in nonacute low back pain

STUDY DESIGN

The correlations between objective biomechanical indicators of function and self-assessment scores were examined retrospectively for 91 subjects with nonacute low back pain.

OBJECTIVES

To examine the correlation between self-assessment, trunk range of motion (ROM), velocity, and complex mechanical coordination patterns of the spine in nonacute low back pain.

SUMMARY OF BACKGROUND DATA

In low back pain, there is often little concordance between pain, physical impairment, and disability. Use of range of motion and velocity to enhance objectivity in impairment evaluations has been ineffectual. In this study, two hypotheses were examined: range of motion and velocity are controllable and inherently correlated with self-assessment; complex spinal coordination patterns such as range of lordosis cannot be controlled and are independent of self-assessment.

METHODS

Self-assessment questionnaires were administered, and indexes of spinal motion and coordination were measured through skin marker kinematics. The correlation between self-assessments and biomechanical measures was determined.

RESULTS

Self-assessments of function were significantly correlated with parameters prone to regulation: range of motion, velocity, and load lifted. In contrast, little correlation was found with measures of complex spinal coordination less susceptible to conscious or affective regulation, namely, range of lordosis and estimated segmental mobility. This effect was magnified with increased load. Self-assessment scores were significantly poorer among insurance referrals, regardless of functional status.

CONCLUSIONS

Simple parameters of the functional examination, such as range of motion and velocity, are strongly correlated with cognitive state, and thus the information they supply is less than ideal. Complex spinal coordination is a better indicator of the degree of spinal dysfunction and enhances the process of differentiating between pain, disability, and functional impairment.

The effect of load on the coordination of the trunk for subjects with and without chronic low back pain during flexion-extension and lateral bending tasks

OBJECTIVE

To evaluate if patients move their trunk sections differently than normal subjects and to determine if these differences increase when lifting a load.

DESIGN

Comparative study using a repeated measures design.

BACKGROUND

Many studies demonstrate a modification of the lumbar-pelvic rhythm for chronic low back pain patients but the large variability of the results impair the discrimination power. It was hypothesized that the lifting of a load would magnify the manifestation of lumbar impairments.

METHODS

Fifteen chronic low back pain patients and 18 normal subjects performed maximal flexion-extension and lateral bending of the trunk with and without a 12 kg load. The pelvic, lumbar and thoracic motions were measured with a motion analysis system.

RESULTS

During flexion-extension tasks, a significant decrease in lumbar flexion and increase in thoracic flexion were observed for the patients. The load effect was significant for all trunk sections but did not allow a better discrimination between groups.

CONCLUSIONS

Lifting a 12 kg load during flexion-extension of the trunk did confirm alteration in trunk section coordination but did not help to better discriminate patients from normal subjects. However, it was demonstrated for the first time that chronic low back pain patients compensate for a loss of lumbar flexion by increasing their thoracic flexion.

RELEVANCE

The lumbar-pelvic rhythm is routinely used to evaluate low back impairments. The use of kinematic measures enhance the objectivity of the examination but the large variability of the results impair the discrimination power. Lifting a load during such an evaluation might magnify the low back impairments and increase the discrimination power of this measure.

The comparison of trunk muscles EMG activation between subjects with and without chronic low back pain during flexion-extension and lateral bending tasks

The purpose of the study was to compare the electromyographic (EMG) activity of the trunk muscles between normal subjects and chronic low back pain (CLBP) patients during standardized trunk movements. Thirty-three male subjects (18 normals, 15 suffering from non specific CLBP) aged between 35 and 45 yr participated. A biomechanical analysis involving the recording of EMG signals from 12 trunk muscles, the kinematics of trunk segments and the computation of L5/S1 moments was performed. The subjects performed flexion-extension and lateral bending (left and right) tasks (three complete cycles) with and without a 12 kg load. Between group comparisons were performed on the full cycle average pattern of all biomechanical variables for each task. The reliability of EMG variables was evaluated for 10 subjects (5 normals and 5 CLBP) who performed the tasks on three different days. The reliability of EMG amplitude values was generally excellent for agonist muscles but poor to moderate for antagonists. The EMG amplitude analysis revealed significant differences between groups for some muscles (left lumbar and thoracic erector spinae). The abnormal (asymmetric) EMG patterns detected among CLBP patients were not explained by postural asymmetries.

Cervical nonorganic signs: a new clinical tool to assess abnormal illness behavior in neck pain patients: a pilot study

OBJECTIVE

To develop and assess the reliability of a group of cervical nonorganic physical signs to be used as a simple screening tool for identifying patients with low neck pain who exhibit abnormal illness behavior.

DESIGN

Survey, consecutive sample.

DATA SET

Double masked.

SETTING

Functional restoration program.

PATIENTS

Twenty-six consecutive patients with complaints of chronic neck pain (greater than 4 months duration). Each patient was evaluated by a physician and then again by either a physical or occupational therapist, for the presence of specific cervical nonorganic signs. Both of the evaluations occurred on the same day.

MAIN OUTCOME MEASURES

Five categories consisting of eight tests were appraised: (1) tenderness, (2) simulation, (3) range of motion, (4) regional disturbance, and (5) overreaction.

RESULTS

The percent agreement between raters ranged from a high of 100% for regional sensory disturbance, to a low of 68% for one of the simulation tests. The average agreement between raters across all of the nonorganic test signs was 84.6%. Likewise, kappa coefficients ranged from 1.00 to .16, reflecting differences in strength of agreement.

CONCLUSION

For many years, the lumbar nonorganic signs (developed by Waddell and colleagues) have been a useful screening tool in the assessment of abnormal illness behavior in the low back pain population. For the first time, a group of cervical nonorganic signs have been developed, standardized, and proven reliable.

Chronic pain disability exaggeration/malingering and submaximal effort research

OBJECTIVE

This is the first review of chronic pain (CP) malingering/disease simulation research. The purpose of this review was to determine the prevalence of malingering within CP patients (CPPs), whether evidence exists that malingering can be detected within CPPs, and to suggest some avenues of research for this topic.

DESIGN

A computer and manual literature search produced 328 references related to malingering, disease simulation, dissimulation, symptom magnification syndrome, and submaximal effort. Of these, 68 related to one of these topics and to pain. The references were reviewed in detail, sorted into 12 topic areas, and placed into tabular form. These 12 topic areas addressed the following: existence of malingering within the CP setting; dissimulation, identification simulated (faked) facial expressions of pain; identification of malingering by questionnaire; identification of malingered sensory impairment; identification of malingered loss of hand grip strength; identification of submaximal effort by isometric strength testing; identification of submaximal or malingered effort by isokinetic strength testing; identification of submaximal or malingered effort by the method of coefficient of variation; self-deception; symptom magnification syndrome; and miscellaneous malingering identification studies. Each report, in each topic area, was rated for scientific quality according to guidelines developed by the Agency for Health Care, Policy and Research (AHCPR) for rating the level of evidence presented in the reviewed study. The AHCPR guidelines were then used to rate the strength and consistency of the research evidence in each topic area based on the type of evidence the reports represented. All review conclusions were based on the results of these ratings.

SETTING

Any medical setting reporting on either malingering or disease simulation, or dissimulation, or submaximal effort and pain.

PATIENTS

Normal volunteers, CPPs, or any group asked to produce a submaximal or malingered effort or a malingered test profile.

RESULTS

The reviewed studies indicated that malingering and dissimulation do occur within the CP setting. Malingering may be present in 1.25-10.4% of CPPs. However, because of poor study quality, these prevalence percentages are not reliable. The study evidence also indicated that malingering cannot be reliably identified by facial expression testing, questionnaire, sensory testing, or clinical examination. There was no acceptable scientific information on symptom magnification syndrome. Hand grip testing using the Jamar dynamometer and other types of isometric strength testing did not reliably discriminate between a submaximal/malingering effort and a maximal/best effort. However, isokinetic strength testing appeared to have potential for discriminating between maximal and submaximal effort and between best and malingered efforts. Repetitive testing with the coefficient of variation was not a reliable method for discriminating a real/best effort from a malingered effort.

CONCLUSIONS

Current data on the prevalence of malingering within CPPs is not consistent, and no conclusions can be drawn from these data. As yet, there is no reliable method for detecting malingering within CPPs, although isokinetic testing shows promise. Claims by professionals that such a determination can be made should be viewed with caution.

Effectiveness of Waddell's nonorganic signs in predicting a delayed return to regular work in patients experiencing acute occupational low back pain

STUDY DESIGN

Consecutive case series.

OBJECTIVE

To determine whether the presence of Waddell's nonorganic signs in occupational, acute low back pain patients predicts a longer time before return to unrestricted regular work.

SUMMARY OF BACKGROUND DATA

Waddell's nonorganic signs identify patients with chronic low back pain with a poor prognosis; however, they have not been used as an outcome predictor in patients with occupational, acute low back pain.

METHODS

Standardized histories and physical examinations, including Waddell's signs were recorded at the first clinic visit (n = 143) by a single physician who was not blinded to the study's goals or methods. Those with chronic low back pain or complicating medical conditions (n = 88) were excluded. Data from patients exhibiting the nonorganic signs were compared with those from patients without the signs for time to return to regular work without restrictions and medical resource use.

RESULTS

Fifty-five patients with acute work-related low back pain were included. One or more of the nonorganic signs were seen in 14 patients (25.5%) at the first appointment. The most common signs were simulated axial loading (78.6%) and simulated rotation (71.4%). Those with any nonorganic sign required a median 58.5 days to return to regular work compared with 15.0 days for those without (P < 0.0001). Patients exhibiting any nonorganic sign compared with those without used more physical therapy (50.0% vs. 12.2%; P < 0.01) and lumbar computed axial tomography (21.4% vs. 0.0%; P = 0.01).

CONCLUSIONS

Patients with acute, occupational low back pain exhibiting Waddell's nonorganic signs had a four times lengthier time for return to unrestricted, regular work and a greater use of physical therapy and lumbar computed tomographic scans.

Predictors of isokinetic back muscle strength in patients with low back pain

STUDY DESIGN

Testing for trunk muscle strength was performed on 105 patients with chronic low back pain.

OBJECTIVES

To investigate prediction of isokinetic back muscle strength in patients with low back pain.

SUMMARY OF BACKGROUND DATA

The clinical evaluation of patients with chronic low back pain often in difficult because of discrepancy between disability and impairment. The isokinetic trunk device was developed as a tool for objective assessment of back muscle strength. However, the performance of patients depends on radiologic abnormalities of the spine, conditions of the back muscles, and various psychosocial factors. Studies are warranted that address how these variables influence back muscle strength.

METHODS

The patients with chronic low back pain were tested by an isokinetic trunk muscle strength test (Cybex TEF, Ronkonkoma, NY). In addition, the following variables were recorded: gender, age, body mass index, emotional distress, pain on exertion, self-efficacy for pain, degenerative changes of the lumbar spine, cross-sectional area, and density of the erector spinae muscles. The three latter variables were estimated by computed tomography scans. The sum of the total work performed during isokinetic extension strength test was the dependent variable in a multiple regression analysis, and anthropometric, demographic, psychological, and radiologic factors were independent variables.

RESULTS

Gender, cross-sectional muscle area, and pain on exertion were the most powerful predictors of isokinetic back muscle strength. The final regression model, which included these variables, could account for approximately 40% of the variability in back muscle strength.

CONCLUSION

For assessing the results of an isokinetic trunk muscle strength test, cross-sectional muscle area, gender, and pain on exertion should be taken into account.

Assessment of spinal musculature using surface electromyographic spectral color mapping

STUDY DESIGN

A technique is described for analyzing electromyogram data from lumbar spinal muscles, with special reference to discrimination of people with back pain. The ability to discriminate was evaluated in 99 people (61 healthy and 38 with chronic or acute back pain), and the influence of load was assessed.

OBJECTIVES

To evaluate methods of analysis of complex electromyogram data and to assess correlation of electromyogram information with clinical condition in people with and without back pain.

SUMMARY OF BACKGROUND INFORMATION

In previous analyses of electromyogram data, only a small part of the data have been used. Spinal muscular decompensation has been postulated in chronic low back pain, but there has been no direct demonstration of this phenomenon. Objective measures are still elusive.

METHODS

Lumbar spinal surface electromyograms were recorded during an isometric lifting task. The data were represented graphically as color-coded plots of electromyogram frequency, time, and electromyogram amplitude. Spectral width at half-peak amplitude (spectral half width) was calculated from the digitized, summed data. Ninety-nine people were tested: 48 men (29 with no recent [in the past 2 years] history of back pain, 16 with chronic back pain, 3 with acute back pain) and 51 women (32 with no recent back pain and 19 with chronic back pain).

RESULTS

Spectral color maps in people with chronic back pain were markedly different from those in healthy people. Spectral half width was greater in people with chronic back pain than in healthy people (P < 0.01). Blinded analysis of spectral color maps allowed discrimination of people with back pain from healthy people with a sensitivity of 76% and a specificity of 81%. People with a history of back pain had markedly variable half widths.

CONCLUSIONS

A new method of analysis of electromyogram data from lumbar spinal muscles has allowed discrimination between people with back pain and healthy people. This provides direct evidence of a correlation between muscular electrical function, measured by electromyogram, and low back pain. This technique may have potential as an objective measurement tool.

Assessment of chronic back pain patient characteristics using factor analysis of the MMPI-2: which dimensions are actually assessed?

Guided by the study of Deardorff et al. (Pain, 54 (1993) 153-158), the MMPI-2 data from 240 chronic back pain patients were factor-analyzed in an attempt to discern the most important dimensions for this patient population. Principal components analysis with an oblique rotation revealed four underlying factors: Psychological disturbances, Extraversion-introversion, Passivity, and Somatic complaints. The factor structure reported by Deardorff et al. was thus successfully replicated. The stability of the factors was also supported using random split subsamples. External measures relevant to pain were used to investigate the external validity of Somatic complaints in a subsample of patients (n=93). Relations were found to number of painful sites, Waddell signs, fear of movement (maximal isometric flexion and extension performance by dynamometry, and cardiovascular fitness (VO2-max). Substantial differences emerged across genders. The derived MMPI-2 dimensions appear to constitute important characteristics associated with chronic pain. It is concluded that MMPI-2 research into chronic pain may become more productive when the instrument and its clinical correlates are examined within a clear conceptual framework of distress and personality relevant for chronic pain and its treatment.

A prospective study of Waddell signs in patients with chronic low back pain. When they may not be predictive

STUDY DESIGN

Analysis of the treatment-outcome predictive power of Waddell signs by evaluating them before and after functional restoration, with assessment of 1-year socioeconomic outcomes.

OBJECTIVE

To evaluate the presence of Waddell nonorganic signs in a group of patients with chronic low back pain presenting for functional restoration, and to determine whether they were predictive of treatment success of failure.

SUMMARY OF BACKGROUND DATA

Waddell has described "nonorganic" physical signs in patients with chronic low back pain indicative of somatization. Other researchers have correlated high Waddell scores with psychosocial barriers that required additional consultation, and have suggested that diminution of a Waddell score during physical rehabilitation is predictive of subsequent therapeutic success.

METHODS

Total positive Waddell signs score and individual sign scores were assessed at initial presentation for functional restoration treatment and at discharge in a group of 50 patients with chronic low back pain (average length of disability = 17.9 months; average age = 38.5 years). Patients were then tracked and assessed with a 1-year follow-up structured interview to evaluate outcome variables such as return to work, work retention, re-injury rate, health utilization, and subsequent surgery.

RESULTS

Statistical analyses of these data revealed no significant associations between Waddell total positive score or changes in score and therapeutic success as measured by any of the behavioral outcomes such as return to work. Also, no predictive value was found for the individual positive signs of their changes and therapeutic success.

CONCLUSIONS

Although positive Waddell signs have been found to be predictive in patients with short-term chronic low back pain, the current results suggest that, in patients who have longer duration of pain and who undergo a comprehensive functional restoration program, these signs are not significantly prognostic. Because functional restoration is an interdiscipilinary approach that effectively manages somatization complaints in a consistent manner by all treatment personnel, such complaints do not create any major barriers to recovery. Therefore, although Waddell signs may be predictive of treatment outcome in less intensive rehabilitation programs, they do not provide any predictive power in a comprehensive functional restoration program, which has a basic goal of managing barriers to recovery in a clinically efficacious manner.

Low synthesis rate of type I procollagen is normalized during active back rehabilitation

STUDY DESIGN

Open, prospective trial with patients participating in an active back restoration program.

OBJECTIVES

To compare the concentrations of biochemical indicators of Type I and III collagen synthesis and Type I collagen degradation in the serum of patients with chronic low back pain and healthy control subjects and to evaluate the effect of active back rehabilitation based on vigorous exercise on collagen metabolism.

SUMMARY OF BACKGROUND DATA

The aim of active back rehabilitation is to restore the physical function of low back pain patients falling into the so-called "deconditioning syndrome." The changes in functional muscle strength measurements during the restoration rehabilitation program always depend on motivation, learning phenomena, and fear of pain and injury, so that even more objective ways of showing changes in physical activity are needed.

METHODS

Specific radioimmunoassays for the amino-terminal (PINP) and carboxy-terminal (PICP) propeptides of Type I procollagen, the amino-terminal propeptide of Type III procollagen (PIIINP), and the cross-linked carboxy-terminal telopeptide of Type I collagen (ICTP) were used for serum samples obtained from 41 patients before, during, and after an active back restoration program and from 16 age- and sex-matched healthy control subjects.

RESULTS

The circulating concentrations of PINP and PICP were initially lower in the patients ([mean +/- SD] 35.3 +/- 12.5 micrograms/L and 119.0 +/- 32.6 micrograms/L, respectively) than in the control subjects (47.9 +/- 18.0 micrograms/L and 136.7 +/- 47.7 micrograms/L, respectively; P < 0.05 for PINP). Toward the end of the active back rehabilitation program, both PINP and PICP increased in the patients (P < 0.001 for the increase between the initial level and the end of rehabilitation). There was a significant difference in the time courses of these changes, with the circulating PICP concentration increasing earlier than that of PINP. In the intervention group, the PIIINP concentration also increased (P < 0.01), whereas the ICTP concentration remained unchanged, with a tendency to decrease. No changes occurred in the control subjects.

CONCLUSIONS

Active back rehabilitation based on vigorous exercise increases. Type I collagen synthesis in patients with chronic low back pain; this may provide a means of objectively verifying the effects of such rehabilitation.

Compensation neurosis: financial reward for illness as nocebo

Results of medical treatment are notoriously poor in patients with pending litigation after personal injury or disability claims, and for those covered by workers' compensation programs. Although some instances of overt malingering are documented by surveillance videos, most exaggerated illness behavior in compensation situations takes place because of a combination of suggestion, somatization, and rationalization. A distorted sense of justice, victim status, and entitlement may further the exaggerated sick role. Adversarial administrative and legal systems challenging the claimant to prove repeatedly he or she is permanently ill harden the conviction of illness and the individual's defense of the claim. Unfortunately, after advocating for one's injury before a sometimes doubting public for the several years required to resolve such claims, care eliciting behavior too often remains permanent. Because any improvement in the claimant's health condition may result in denial of disability status in the future, the claimant is compelled to guard against getting well and is left with no honorable way to recover from illness. Financial reward for illness thus functions as a powerful nocebo, a nonspecific force creating and exacerbating illness. Solutions require recognition that judging disability and work incapacity in others is an unscientific process and that adversarial systems rewarding permanent illness or injury, particularly self reported pain, are often permanently harmful. The remainder of the solution must be political.

The reliability and validity of a measure of perceived functional capacity for work in chronic back pain

Psychosocial factors, including perceived disability and self-efficacy, are important determinants of outcome for individuals with chronic back pain. Consequently, there is a need for an evaluation and consideration of such factors in occupational rehabilitation. This study evaluated the reliability and validity of a tool, the Spinal Function Sort, as a measure of perceived capacity for work-related tasks with 42 rehabilitation clients with chronic back pain. Results provided support for the internal consistency (Cronbach's alpha of 0.97), test-rest reliability (ICC of 0.89) and construct validity of the Spinal Function Sort as a measure of perceived capacity for work-related tasks in persons with chronic back pain. Measures of similar constructs were significantly correlated with the Spinal Function Sort and were highly predictive of the Spinal Function Sort on multiple regression. Relationships between perceived work capacity and pain intensity and gender are discussed. The need for the consideration of perceived capacity in the evaluation and rehabilitation of persons with chronic back pain is highlighted.

Objective evaluation of functional capacity: medical, occupational, and legal settings

Clinicians are called upon to perform objective evaluation of functional capacity in a variety of treatment and evaluation settings. To assist the clinician in selecting the appropriate testing methods for assessment of functional capacity in different settings, a survey of available techniques is presented. It is structured around the goals of treatment as the patient progresses from the stage of acute injury or disease through early postacute care to long-term rehabilitation. The role of the clinician in treatment of the patient is contrasted to the role of the clinician in evaluation of the patient for reasons other than making clinical decisions. In particular, the specific demands of workers fitness and risk evaluation are described. The goal-related differences in the design and the correct use of clinical dynamometers vs. work simulators are presented. The key concepts are the professional role of the clinician, reliability of measurements, and validity in the sense of the decisions one is justified in making based on the results of these measurements in a particular context.

Symmetry of lumbar rotation and lateral flexion range of motion and isometric strength in subjects with and without low back pain

There is substantial reason to believe that asymmetry of trunk motion plays a significant role in the development and presentation of low back pain. However, there has been little review of objective measurements of low back pain and asymptomatic populations to support these assumptions or the related clinical models. In order to study asymmetry of trunk function and its relationship to the presence of low back pain and laterality of symptoms, 120 subjects with low back pain (LBP) and 168 subjects without low back pain (NLBP) were tested for rotation and lateral flexion, active range of motion (ROM), and isometric strength using the B-200 Lumbar Dynamometer. A similar pattern of asymmetry was found in both NLBP and LBP populations; however, the magnitude of ROM asymmetry was significantly greater for the LBP subjects (p < .005). There was also a positive relationship between ROM magnitude of asymmetry and intratest variance in LBP subjects that was not evident in NLBP subjects. No relationships were found between isometric strength measures and LBP nor between laterality of asymmetric function and laterality of radiating symptoms. The asymmetry observed in the LBP population may be an augmented expression of normal asymmetrical performance, and behavioral factors may play a role in this expression. These observations may influence our use of lumbar function asymmetry as an objective clinical sign relating to specific pathological processes.

Effect of instructions to simulate a back injury on torque reproducibility in an isometric lumbar extension task

The purpose of this study was to investigate the differences in test-retest reliability between maximal and "simulated back injury" efforts in an isometric lumbar extension task and to test the hypothesis that voluntary attempts to "simulate" a back injury would yield less consistent torque production than maximal efforts. Twenty subjects were asked to undergo lumbar extensor testing at seven different positions in a lumbar extension machine. Each subject was tested twice in a maximal effort condition and twice with instructions to "simulate" a back injury. The order of the conditions was counterbalanced across subjects so that half of the subjects performed the maximal effort tests first and half performed the "simulated" effort first. Results indicated high test-retest correlations at all angles in both conditions. There were no differences in test-retest reliability between effort conditions. Therapist ratings of consistency did not differ between conditions and therapists could not discriminate between conditions on the basis of effort consistency. In the "simulated" condition subjects produced reliable, submaximal torque plots consistent with previous data indicating similar reliability at submaximal levels. It was concluded that use of test-retest torque consistency as a measure of sincerity of effort is premature and may be misleading.