Back Pain Causes of mechanical back pain (BP) generally are attributed to an acute traumatic event, but they may also include cumulative trauma. The severity of an acute traumatic event varies widely, from twisting one's back to being involved in a motor vehicle collision. Mechanical BP due to cumulative trauma tends to occur more commonly in the workplace.
The pathophysiology of mechanical BP remains complex and multifaceted. Multiple anatomic structures and elements of the spine (eg, bones, ligaments, tendons, disks, muscle) are all suspected to have a role. Many of these components of the spine have sensory innervation that can generate nociceptive (a sensory receptor that responds to pain) signals representing responses to tissue-damaging stimuli. Other causes could be neuropathic (dysfunction of the nervous system--e.g, sciatica). Most chronic BP cases most likely involve mixed nociceptive and neuropathic etiologies.
The concept of a biomechanical degenerative spiral has an appealing quality and is gaining wider acceptance. This concept postulates the breakdown of the annular fibers and allows PLA2 and glutamate, and possibly other as-yet unknown compounds, to leak into the epidural space. The weakened vertebra and disk segment become more susceptible to vibration and physical overload, resulting in compression and stimulating release of substance P. Substance P, in turn, stimulates histamine and leukotriene release, leading to an altering of nerve impulse transmission. The neurons become sensitized further to mechanical stimulation, possibly causing ischemia, which attracts polymorphonuclear cells and monocytes to areas that facilitate further disk degeneration and produce more pain.
The National Pain Foundation – http://www.nationalpainfoundation.org/cat/862/back-and-neck