Anne F. Mannion

A Randomized Clinical Trial of Three Active Therapies for Chronic Low Back Pain

Study Design.A randomized clinical trial.Objectives.To examine the relative efficacy of three active therapies for chronic low back pain.Summary of Background Data.There is much evidence documenting the efficacy of exercise in the conservative management of chronic low back pain, but many questions

Active therapy for chronic low back pain part 3. factors influencing self-rated disability and its change following therapy

Design. Cross-sectional analysis of the factors influencing self-rated disability associated with chronic low back pain and prospective study of the relationship between changes in each of these factors and in disability following active therapy. Objectives. To examine the relative influences of pain, psychological factors, and physiological factors on self-rated disability. Summary of Background Data. In chronic LBP, the interrelationship between physical impairment, pain, and disability is particularly complicated, due to the influence of various psychological factors and the lack of unequivocal methods for assessing impairment. Investigations using new “belief” questionnaires and “sophisticated” performance tests, which have shown promise as discriminating measures of impairment, may assist in clarifying the situation. Previous studies have rarely investigated all these factors simultaneously. Methods. One hundred forty-eight patients with cLBP completed questionnaires and underwent tests of mobility, strength, muscle activation, and fatigability, and (in a subgroup) erector spinae size and fiber size/type distribution. All measures were repeated after 3 months active therapy. Relationships between each factor and self-rated disability (Roland and Morris questionnaire) at baseline, and between the changes in each factor and changes in disability following therapy, were examined. Results. Stepwise linear regression showed that the most significant predictors of disability at baseline were, in decreasing order of importance: pain; psychological distress; fear-avoidance beliefs; muscle activation levels; lumbar range of motion; gender. Only changes in pain, psychological distress, and fear-avoidance beliefs significantly accounted for the changes in disability following therapy. Conclusion. A combination of pain, psychological and physiological factors was best able to predict baseline disability, although its decrease following therapy was determined only by reductions in pain and psychological variables. The active therapy programm—in addition to improving physical function—appeared capable of modifying important psychological factors, possibly as a result of the positive experience of completing the prescribed exercises without undue harm.

Electromyographic median frequency changes during isometric contraction of the back extensors to fatigue.

Study Design. This was a cross‐sectional study involving 229 healthy, back pain‐free individuals. Objectives. To examine the relationship between electromyographic manifestations of fatigue and endurance time during isometric contraction of the back extensors to fatigue. Summary of Background Data. Despite the widespread use of electromyography to monitor muscle fatigue, its relationship with endurance time has not been well investigated. Methods. Using skin‐surface electrodes, electromyographic signals were recorded from thoracic (T10) and lumbar (L3) regions of erector spinae during an isometric endurance test, and the rate of change in median frequency of the electromyographic power spectrum (MFGRAD) was calculated. Results. MFGRAD was significantly higher at L3 than at T10. The best predictor of endurance time was given by the greater MFGRAD observed at either region. MFGRAD calculated over a submaximal time period (50% total time or 60 sec) also correlated significantly with endurance time. Women displayed a significantly longer endurance time and lower MFGRAD than men. Conclusions. Endurance appears to be limited by the most fatigable region of the muscle group. MFGRAD is a suitable technique for monitoring back muscle fatigue, even when it is determined over a submaximal time period. The back extensors of women are less fatigable than those of men when the same task is performed. [Key words: fatigue, electromyography, endurance, erector spinae, median frequency] Spine 1994;19:1223–1229

Active therapy for chronic low back pain part 1. Effects on back muscle activation, fatigability, and strength.

Design. Randomized prospective study of the effects of three types of active therapy on back muscle function in chronic low back pain patients. Objectives. To quantify the effects of 3 months active therapy on strength, endurance, activation, and fatigability of the back entensor muscles. Summary of Background Data. Many studies have documented an association between chronic low back pain and diminished muscular performance capacity. Few studies have quantified the changes in these measures following interventions using objective measurement techniques or related them to changes in clinical outcome. Methods. A total of 148 individuals (57% women) with chronic low back pain (age, 45.0 ± 10.0 years; duration of low back pain, 10.9 ± 9.5 years) were randomized to a treatment that they attended for 3 months: active physiotherapy, muscle reconditioning on devices, or low-impact aerobics. Before and after therapy, assessments were made of the following: trunk muscle strength (in flexion, extension, lateral bending, and axial rotation), erector spinae activation (maximal, and during forward bending movements), back extensor endurance (Biering-S/orensen test), and erector spinae fatigability (determined from changes in the median frequency of the surface electromyographic signal) during isometric and dynamic tests. Results. A total of 132 of 148 patients (89%) completed the therapy. Isometric strength in each movement direction increased in all groups post-therapy (P < 0.0008), most notably in the devices group. Activation of the erector spinae during the extension tests also increased significantly in all groups and showed a weak, but significant, relationship with increased maximal strength (P = 0.01). Pretherapy 55% of the subjects showed no relaxation of the back muscles at L5 when in the fully flexed position; no changes were observed in any group post-therapy. Endurance time during the Biering-S/orensen test increased significantly post-therapy in all groups (P = 0.0001), but there were no significant changes in EMG-determined fatigability. Fatigability of the lumbar muscles at L5 (EMG median frequency changes) during the dynamic test increased post-therapy (P = 0.0001) without group differences. Conclusion. Significant changes in muscle performance were observed in all three active therapy groups post-therapy, which appeared to be mainly due to changes in neural activation of the lumbar muscles and psychological changes concerning, for example, motivation or pain tolerance.

The influence of muscle fiber size and type distribution on electromyographic measures of back muscle fatigability.

Study Design. This was a cross‐sectional study carried out on a group of 31 healthy, consenting volunteers with no history of low back pain (17 men, 14 women). Objectives. To evaluate the relationship between electromyographic measures of erector spinae fatigability and the muscles fiber type characteristics. Summary of Background Data. Using electromyographic techniques, a pronounced fatigability of the muscles of patients with low back pain has been identified. It has been postulated that this is the result of an unfavorable back muscle fiber type distribution, although an association between electromyographic measures of fatigue and the muscles fiber type characteristics has never been established. Methods. Two tests of back extensor fatigability were performed (on separate days), each to the limit of endurance: 1) maintenance of 60% total maximum voluntary contraction of the back extensors, and 2) performance of the Biering‐Sørensen test. Pairs of surface electrodes were attached to the skin overlying the belly of the erector spinae, bilaterally, at T10 and L3. The median frequency was computed from the electromyographic power spectrum, and fatigability was given by the slope of the linear regression of median frequency on time (MFgrad; %.s−1). One week later, two percutaneous erector spinae muscle biopsy samples were obtained from the same sites described for electromyography (left side only). Samples were prepared for histochemistry for the identification of muscle fiber types. Fiber sizes (cross‐sectional areas) were quantified using computerized image analysis. Results. The mean fiber size at each erector spinae region showed a significant correlation with maximum back extensor strength. In the thoracic region, the relative area of the muscle occupied by Type I fibers (which accounts for the relative size and distribution of the fiber types) showed a significant relationship with MFgrad recorded during each fatigue test. A similar relationship was observed for the lumbar region, but for the Biering‐Sørensen test only. Conclusions. The electromyographic changes recorded in back muscles during fatigue appear to be related to the underlying muscle fiber type area distribution. This confirms the usefulness of electromyography in reflecting such muscle characteristics in a noninvasive manner, when monitoring changes in function consequent to the development of, or rehabilitation from, low back pain.

Pain measurement in patients with low back pain

Pain is a multidimensional experience that is a prominent feature of many musculoskeletal disorders. Despite its subjective nature, pain is a highly relevant complaint; hence, nothing should deter physicians from attempting to formally assess it. This Review summarizes the main aspects of pain measurement from a practical standpoint, with a specific focus on low back pain. On balance, for the assessment of pain intensity, categorical scales with verbal descriptors or numerical rating scales seem to be preferable to traditional visual analogue scales, although no single best measure can be recommended. Pain per se should be assessed, rather than surrogate measures such as analgesic use. Back and leg pain should be evaluated separately in patients in whom these conditions coexist. For assessing change, prospective measurements are preferable to retrospective reports. Pain is not synonymous with function or quality of life, and other tools covering these important outcome dimensions should complement the assessment of pain, especially in patients with chronic symptoms. Clinicians should be aware of the psychometric properties of the tool to be used, including its level of imprecision (random measurement error) and its minimum clinically important difference (score difference indicating meaningful change in clinical status).

Fatigue of the erector spinae muscles : a quantitative assessment using frequency banding of the surface electromyography signal

Study Design The authors investigated fatigue-induced changes in the frequency content of the surface electromyographic (EMG) signal from the erector spinae muscles. Objectives The objective of the study was to understand the EMG changes in fatiguing muscle and to obtain a rellable index of fatigue. Summary of Background Data Power spectral analysis has been used increasingly in recent years to monitor muscle fatigue, but parameters other than the mean or median frequency have received little attention. Methods Thirty-five healthy volunteers participated. They pulled upward with constant force on a handlebar attached to a floor-mounted load cell while the EMG signal from the erector spinae was recorded at the levels of T10 and L3 at 1024 Hz; 1.0-sec “windows” of the signal were analyzed using fast Fourier transforms, and the resulting power spectra were divided into 10 frequency bands between 5 Hz and 300 Hz. The median frequency, total power, and peak amplitude of the spectra were also calculated. Changes in the frequency content of the EMG signal were examined during submaximal contractions of different intensity and duration. Results Median frequency decreased steadily during the contractions, whereas total power and peak amplitude increased. The most repeatable and linear index of change was the increase in the EMG signal in the 5–30 Hz frequency band. The middle-to-high frequency component of the EMG signal increased during the early stages of the contractions, but decreased as the endurance limit was approached. Conclusions Changes in the 5–30 Hz band of the EMG power spectrum provide a more reliable and linear index of fatigue in the erector spinae muscles than do changes in median frequency. In the erector spinae, the early effects of fatigue appear to be delayed by the recruitment of additional motor units.

Predictors of surgical outcome and their assessment

The relatively high rate of failed back surgery has prompted the search for “risk factors” to predict the result of spinal surgery in a given individual. However, the literature reveals few unequivocal predictors and they often explain a relatively low proportion of variance in outcome. This suggests that we have a long way to go before being able to rest easily, having refused someone surgery on the basis of unfavourable baseline characteristics. The best recommendation is to ensure, firstly, that the indication for surgery is absolutely clear-cut (i.e. that surgically remediable pathology exists) and then to consider the various factors that may influence the “typical” outcome. Consistent risk factors for a poor outcome regarding return-to-work include long-term sick leave/receipt of disability benefit. Hence, every effort should be made to keep the individual in the workforce, despite the ongoing symptoms and plans for surgery. In patients with a particularly heavy job, consultation with occupational physicians might later ease the patient’s way back into the workplace. Patients with degenerative disorders and/or comorbidity should be counselled that few of them will have complete/lasting pain relief or a complete return to pre-morbid function. Patients with a high level of distress may benefit from psychological treatment, before and/or accompanying the surgical treatment. The opportunity (time), encouragement (education and positive messages), and resources (referral to appropriate support services) to modify risk factors that are indeed modifiable should be offered, and realistic expectations should be discussed with the patient before the decision to operate is made.

Influence of age and duration of symptoms on fibre type distribution and size of the back muscles in chronic low back pain patients

Abstract Many studies have documented an association between chronic low back pain (LBP) and deficits in back muscle strength and endurance. The sub-optimal performance is believed to be the result of alterations in the size and structure of the muscle, although the long-standing issue of whether the observed changes precede or are a consequence of the pain remains unresolved. If consequent to the problem, and predominantly related to disuse of the muscles, then it may be expected that a relationship between muscle structure and symptom duration would exist. Lumbar paraspinal muscle samples were obtained from 59 chronic LBP patients using the percutaneous biopsy technique. The samples were subject to routine histochemical analysis for the examination of muscle fibre type characteristics and cytochemical architectural changes. In 55 of the patients, the gross cross-sectional areas of magnetic resonance images of the trunk muscles were also measured. Multivariate analysis showed that symptom duration was the strongest predictor of the individual proportions of the fast-fatigable type IIX fibres; with age and gender included in the model, nearly 30% of the variance in fibre type distribution could be accounted for. Duration of pain had no influence on fibre size. Gross muscle cross-sectional area correlated directly with lean body mass and inversely with age, but showed no relationship with symptom duration. Pathological changes in the internal fibre structure were more frequently encountered in older patients, and were independent of symptom duration. The results suggest that, over the long term, fibre type transformations rather than alterations in fibre size are the predominant changes to be found in the muscles of chronic LBP patients. The direction of change supports the results of many previous studies that have demonstrated corresponding differences in the fatigability of the muscles. There is a strong case for the early implementation of active measures to attempt to offset the development of these changes in back pain patients.

Psychological questionnaires: do "abnormal" scores precede or follow first-time low back pain?

Study Design A prospective study of psychological risk factors for first‐time low back pain with repeated use of psychological questionnaires. Objectives To measure the reproducibility of scores from psychological questionnaires, and to compare this with changes that follow an individuals first attack of back pain. Secondly, to determine which scores predict first‐time back pain. Summary of Background Data “Abnormal” psychometric scores are associated with several aspects of back pain behavior. Little is known, however, about their reproducibility or long‐term stability, and there has been no definitive answer to the question: which comes first, “abnormal” scores or low back pain? Methods 403 volunteers with no history of “serious” low back pain (defined as pain requiring medical attention or absence from work) participated in a functional spinal assessment. At the time of initial assessment and at 6‐month intervals thereafter, the volunteers completed the following questionnaires: the Health Locus of Control, which was subdivided into three sections labelled “Internal,” “Powerful others,” and “Chance”; the Modified Somatic Perception Questionnaire; and the Zung depression scale. Scores from the Modified Somatic Perception Questionnaire and from the Zung depression scale were added to form a measure of psychological distress. Additional questionnaires inquired about any back pain experienced in the previous 6 months. Only three volunteers had left the study at the 18‐month follow‐up. At that time 162 participants had reported “any” low back pain, of which 79 were “serious.” Results Intraclass correlation coefficients for scores repeated after 6 months ranged from 0.67‐0.80, and reproducibility of scores was equally high between the 0‐, 6‐, 12‐ and 18‐month assessments. None of the scores were affected by “any” low back pain, and only the Modified Somatic Perception Questionnaire scores changed after “serious” back pain was reported. In a multivariate analysis, the most significant predictor of first time “serious” or “any” back pain was a history of non‐“serious” back pain (P < 0.001). Of the psychological factors, the sum of Modified Somatic Perception Questionnaire scores and Zung questionnaire scores was the best predictor of “serious” back pain (P = 0.037), and the Modified Somatic Perception Questionnaire score was the best predictor of “any” back pain (P = 0.002). The 25% of participants with the highest sum of scores from the Modified Somatic Perception Questionnaire and Zung questionnaire was 2.7 times more likely to develop “serious” back pain than the 25% with the lowest sum of these scores. Nevertheless, after accounting for the effects of a history of non‐“serious” back pain, psychometric scores predicted less than an additional 3% of reported back pain. Conclusions The scores from the Modified Somatic Perception Questionnaire and Zung questionnaire were reproducible over 18 months and were affected little by first episodes of back pain; yet these scores were significant predictors of it. “Abnormal” scores from these questionnaires precede back pain in a small number of people.