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.

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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

We review the evidence that there are two types of disc degeneration. 'Endplate-driven' disc degeneration involves endplate defects and inwards collapse of the annulus, has a high heritability, mostly affects discs in the upper lumbar and thoracic spine, often starts to develop before age 30 years, usually leads to moderate back pain, and is associated with compressive injuries such as a fall on the buttocks. 'Annulus-driven' disc degeneration involves a radial fissure and/or a disc prolapse, has a low heritability, mostly affects discs in the lower lumbar spine, develops progressively after age 30 years, usually leads to severe back pain and sciatica, and is associated with repetitive bending and lifting. The structural defects which initiate the two processes both act to decompress the disc nucleus, making it less likely that the other defect could occur subsequently, and in this sense the two disc degeneration phenotypes can be viewed as distinct.

Intervertebral disc degeneration: evidence for two distinct phenotypes

Diurnal changes in the loads acting on the spine affect the water content and height of the intervertebral discs. We have reviewed the effects of these changes on spinal mechanics, and their possible clinical significance. Cadaveric lumbar spines subjected to periods of creep loading show a disc height change similar to the physiological change. As a result intervertebral discs bulge more, become stiffer in compression and more flexible in bending. Disc tissue becomes more elastic as its water content falls, and its affinity for water increases. Disc prolapse becomes more difficult. The neural arch and associated ligaments resist an increasing proportion of the compressive and bending stresses acting on the spine. Observations on living people show that these changes are not fully compensated for by modified muscle activity. We conclude that different spinal structures are more heavily loaded at different times of the day. Therefore, the time of onset of symptoms and signs, and any diurnal variation in their severity, may help us understand more about the pathophysiology of low back pain and sciatica.

Diurnal changes in spinal mechanics and their clinical significance

Repetitive lifting tasks fatigue the back muscles and increase the bending moment acting on the lumbar spine

The Relationship Between EMG Activity and Extensor Moment Generation in the Erector Spinae Muscles During Bending and Lifting Activities

STUDY DESIGN Mechanical testing of cadaveric lumbar motion segments. OBJECTIVES To test the hypothesis that degenerative changes in the intervertebral discs can influence loading of the anterior vertebral body in a manner that makes it vulnerable to fracture. SUMMARY OF BACKGROUND DATA Measurements of systemic bone loss do not fully explain the patterns of osteoporotic vertebral fractures. METHODS Thirty-three cadaveric lumbar motion segments (aged 19-82 years) were subjected to 2 kN of compressive loading while positioned to simulate habitual erect standing postures and forwards bending. Intradiscal stresses were measured in each posture by pulling a miniature pressure transducer along the midsagittal diameter of the disc. "Stress profiles" were then integrated over area to calculate the force acting on the anterior and posterior halves of the vertebral body. These forces were subtracted from the applied 2 kN to determine the compressive force on the neural arch. RESULTS In motion segments with nondegenerated discs, <5% of the compressive force was resisted by the neural arch, and forces on the vertebral body were always distributed evenly, irrespective of posture. However, with severely degenerated discs, neural arch load-bearing increased to 40% in the erect posture, and the compressive force on the vertebral body was concentrated anteriorly in forwards bending, and posteriorly in erect posture. CONCLUSIONS Severe disc degeneration causes the anterior vertebral body to be stress-shielded during the usual erect posture, and yet severely loaded whenever the spine is flexed. This could help to explain why this region is frequently the site of osteoporotic fracture, and why forward bending movements often precipitate the injury.

Patricia Dolan

Papers

Intervertebral disc degeneration: evidence for two distinct phenotypes

Diurnal changes in spinal mechanics and their clinical significance

Repetitive lifting tasks fatigue the back muscles and increase the bending moment acting on the lumbar spine

The Relationship Between EMG Activity and Extensor Moment Generation in the Erector Spinae Muscles During Bending and Lifting Activities

Intervertebral disc degeneration can lead to "stress-shielding" of the anterior vertebral body: a cause of osteoporotic vertebral fracture?