In an attempt to explain how and why some individuals with musculoskeletal pain develop a chronic pain syndrome, Lethem et al. (Lethem J, Slade PD, Troup JDG, Bentley G. Outline of fear-avoidance model of exaggerated pain perceptions. Behav Res Ther 1983; 21: 401-408).ntroduced a so-called 'fear-avoidance' model. The central concept of their model is fear of pain. 'Confrontation' and 'avoidance' are postulated as the two extreme responses to this fear, of which the former leads to the reduction of fear over time. The latter, however, leads to the maintenance or exacerbation of fear, possibly generating a phobic state. In the last decade, an increasing number of investigations have corroborated and refined the fear-avoidance model. The aim of this paper is to review the existing evidence for the mediating role of pain-related fear, and its immediate and long-term consequences in the initiation and maintenance of chronic pain disability. We first highlight possible precursors of pain-related fear including the role negative appraisal of internal and external stimuli, negative affectivity and anxiety sensitivity may play. Subsequently, a number of fear-related processes will be discussed including escape and avoidance behaviors resulting in poor behavioral performance, hypervigilance to internal and external illness information, muscular reactivity, and physical disuse in terms of deconditioning and guarded movement. We also review the available assessment methods for the quantification of pain-related fear and avoidance. Finally, we discuss the implications of the recent findings for the prevention and treatment of chronic musculoskeletal pain. Although there are still a number of unresolved issues which merit future research attention, pain-related fear and avoidance appear to be an essential feature of the development of a chronic problem for a substantial number of patients with musculoskeletal pain.

/pdf/fear-avoidance-and-its-consequences-in-chronic-25jwj42o35.pdf

Fear-avoidance and its consequences in chronic musculoskeletal pain: a state of the art

&NA; In an attempt to explain how and why some individuals with musculoskeletal pain develop a chronic pain syndrome, Lethem et al.(Lethem J, Slade PD, Troup JDG, Bentley G. Outline of fear‐avoidance model of exaggerated pain perceptions. Behav Res Ther 1983; 21: 401‐408).ntroduced a so‐called ‘fear‐avoidance’ model. The central concept of their model is fear of pain. ‘Confrontation’ and ‘avoidance’ are postulated as the two extreme responses to this fear, of which the former leads to the reduction of fear over time. The latter, however, leads to the maintenance or exacerbation of fear, possibly generating a phobic state. In the last decade, an increasing number of investigations have corroborated and refined the fear‐avoidance model. The aim of this paper is to review the existing evidence for the mediating role of pain‐related fear, and its immediate and long‐term consequences in the initiation and maintenance of chronic pain disability. We first highlight possible precursors of pain‐related fear including the role negative appraisal of internal and external stimuli, negative affectivity and anxiety sensitivity may play. Subsequently, a number of fear‐related processes will be discussed including escape and avoidance behaviors resulting in poor behavioral performance, hypervigilance to internal and external illness information, muscular reactivity, and physical disuse in terms of deconditioning and guarded movement. We also review the available assessment methods for the quantification of pain‐related fear and avoidance. Finally, we discuss the implications of the recent findings for the prevention and treatment of chronic musculoskeletal pain. Although there are still a number of unresolved issues which merit future research attention, pain‐related fear and avoidance appear to be an essential feature of the development of a chronic problem for a substantial number of patients with musculoskeletal pain.

Fear-avoidance and its consequences in chronic musculoskeletal pain: a state of the art.

Retrospective study: The diagnostic accuracy of conventional forceps biopsy of gastric epithelial compared to endoscopic submucosal dissection (STROBE compliant).

STUDY DESIGN: The literature on psychological factors in neck and back pain was systematically searched and reviewed.

OBJECTIVES: To summarize current knowledge concerning the role of psychological variables in the etiology and development of neck and back pain.

SUMMARY OF BACKGROUND DATA: Recent conceptions of spinal pain, especially chronic back pain, have highlighted the role of psychological factors. Numerous studies subsequently have examined the effects of various psychological factors in neck and back pain. There is a need to review this material to ascertain what conclusions may be drawn.

METHODS: Medical and psychological databases and cross-referencing were used to locate 913 potentially relevant articles. A table of 37 studies was constructed, consisting only of studies with prospective designs to ensure quality. Each study was reviewed for the population studied, the psychological predictor variables, and the outcome.

RESULTS: The available literature indicated a clear link between psychological variables and neck and back pain. The prospective studies indicated that psychological variables were related to the onset of pain, and to acute, subacute, and chronic pain. Stress, distress, or anxiety as well as mood and emotions, cognitive functioning, and pain behavior all were found to be significant factors. Personality factors produced mixed results. Although the level of evidence was low, abuse also was found to be a potentially significant factor.

CONCLUSIONS: Psychological factors play a significant role not only in chronic pain, but also in the etiology of acute pain, particularly in the transition to chronic problems. Specific types of psychological variables emerge and may be important in distinct developmental time frames, also implying that assessment and intervention need to reflect these variables. Still, psychological factors account for only a portion of the variance, thereby highlighting the multidimensional view. Because the methodologic quality of the studies varied considerably, future research should focus on improving quality and addressing new questions such as the mechanism, the developmental time factor, and the relevance that these risk factors have for intervention.

A review of psychological risk factors in back and neck pain.

Non-specific low back pain

volves gross structural disruption as well as cell-mediated changes in matrix composition, but there is little evidence concerning which comes first. Comparatively minor damage to a vertebral body is known to decompress the adjacent discs, and this may adversely affect both structure and cell function in the disc. Methods. In this study, 38 cadaveric lumbar motion segments (mean age, 51 years) were subjected to complex mechanical loading to simulate typical activities in vivo while the distribution of compressive stress in the disc matrix was measured using a pressure transducer mounted in a needle 1.3 mm in diameter. “Stress profiles” were repeated after a controlled compressive overload injury had reduced motion segment height by approximately 1%. Moderate repetitive loading, appropriate for the simulation of light manual labor, then was applied to the damaged specimens for approximately 4 hours, and stress profilometry was repeated a third time. Discs then were sectioned and photographed. Results. Endplate damage reduced pressure in the adjacent nucleus pulposus by 25% 6 27% and generated peaks of compressive stress in the anulus, usually posteriorly to the nucleus. Discs 50 to 70 years of age were affected the most. Repetitive loading further decompressed the nucleus and intensified stress concentrations in the anulus, especially in simulated lordotic postures. Sagittal plane sections of 15 of the discs showed an inwardly collapsing anulus in 9 discs, extreme outward bulging of the anulus in 11 discs, and complete radial fissures in 2 discs, 1 of which allowed posterior migration of nucleus pulposus. Comparisons with the results from tissue culture experiments indicated that the observed changes in matrix compressive stress would inhibit disc cell metabolism throughout the disc, and could lead to progressive deterioration of the matrix. Conclusions. Minor damage to a vertebral body end

Mechanical Initiation of Intervertebral Disc Degeneration

We investigated the distribution of compressive 'stress' within cadaver intervertebral discs, using a pressure transducer mounted in a 13 mm diameter needle The needle was pulled along the midsagittal diameter of a lumbar disc with the face of the transducer either vertical or horizontal while the disc was subjected to a constant compressive force The resulting 'stress profiles' were analysed in order to characterise the distribution of vertical and horizontal compressive stress within each disc A total of 87 discs from subjects aged between 16 and 87 years was examined Our results showed that age-related degenerative changes reduced the diameter of the central hydrostatic region of each disc (the 'functional nucleus') by approximately 50%, and the pressure within this region fell by 30% The width of the functional annulus increased by 80% and the height of compressive 'stress peaks' within it by 160% The effects of age and degeneration were greater at L4/L5 than at L2/L3, and the posterior annulus was affected more than the anterior Age and degeneration were themselves closely related, but the stage of degeneration had the greater effect on stress distributions We suggest that structural changes within the annulus and endplate lead to a transfer of load from the nucleus to the posterior annulus High 'stress' concentrations within the annulus may cause pain, and lead to further disruption

‘stress’ distributions inside intervertebral discs: the effects of age and degeneration

STUDY DESIGN: A prospective study of personal risk factors for first-time low back pain

OBJECTIVES: To construct and validate a multivariate model to predict low back pain

SUMMARY OF BACKGROUND DATA: Various physical and psychological factors have been reported to increase the risk of low back pain, but conflicting results may be attributable to inaccurate "clinical" measures and to poorly validated statistical models

METHODS: A total of 403 health care workers aged 18-40 years volunteered for the study None had any history of "serious" back pain requiring medical attention or time off work The volunteers completed the following questionnaires: the modified somatic perception questionnaire, the Zung depression scale, and the Health Locus of Control Anthropometric factors were quantified using standard techniques The 3Space Isotrak device (Polhemus, VT) was used to measure lumbar curvature and hip and lumbar spine mobility Leg and back strength and back muscle fatiguability were measured in functional postures Postal follow-up questionnaires, sent after 6, 12, 18, 24, 30, and 36 months, inquired about back pain, and multivariate logistic regression was used to identify risk factors at each follow-up

RESULTS: The response rate fell from 99% at 12 months to 90% at 36 months, at which time 90 volunteers reported "serious" back pain and 266 reported "any" back pain The following were consistent predictors of serious back pain: reduced range of lumbar lateral bending, a long back, reduced lumbar lordosis, increased psychological distress, and previous nonserious low back pain Only the latter three were consistent predictors of "any" back pain Physical factors had the most influence in a sub-population of volunteers who were new to the job

CONCLUSIONS: Personal risk factors explained up to 12% of first-time low back pain

Personal risk factors for first-time low back pain.

STUDY DESIGN: Cadaveric motion segment experiment. Measurements on each specimen were compared before and after creep loading.

OBJECTIVES: To show how sustained "creep" loading affects stress distributions inside intervertebral discs.

SUMMARY OF BACKGROUND DATA: The central region of an intervertebral disc acts like a hydrostatic "cushion" between adjacent vertebrae. However, this property depends on the water content of the tissues and may be lost or diminished after creep.

METHODS: Twenty-seven lumbar motion segments consisting of two vertebrae and the intervening disc and ligaments were loaded to simulate erect standing postures in life. The distribution of compressive stress in the disc matrix was measured by pulling a miniature pressure transducer through the disc in the midsagittal plane. Profiles of vertical and horizontal compressive stress were repeated after each specimen had been creep loaded in compression for 2-6 hours.

RESULTS: Creep reduced the hydrostatic pressure in the nucleus by 13-36%. Compressive stresses in the anulus were little affected when the profiles were measured at 1 kN, but at 2 kN, localized peaks of compressive stress appeared (or grew in size) in the posterior anulus after creep.

CONCLUSIONS: Increased loading of the apophysial joints causes an overall reduction in intradiscal stresses after creep. In addition, water loss from the nucleus causes a transfer of load from nucleus to anulus. Stress concentrations may lead to pain, structural disruption, and alterations in chondrocyte metabolism. Disc mechanics depend on loading history as well as applied load.

Sustained loading generates stress concentrations in lumbar intervertebral discs.

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 wide-spread 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.

Patricia Dolan

Papers

Mechanical Initiation of Intervertebral Disc Degeneration

‘stress’ distributions inside intervertebral discs: the effects of age and degeneration

Personal risk factors for first-time low back pain.

Sustained loading generates stress concentrations in lumbar intervertebral discs.

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