Bony Structure of the Lumbar Spine - Essay Example

Chronic lower back pain negatively affects the daily lives of the majority of working Americans. This pain is categorized as a chronic condition persisting for longer than a twelve week period cause by either a degenerative disorder or a traumatic exterior influence to the spine. The pressures of the modern world are faceted firmly upon the human body’s lumbar spine, which supports significant weight loads during physical activity. The lumbar spine supports the cranial structure, the upper extremities (the arms and shoulders) and provides protection for major internal organs when the body is postured as a bipedal stance. The bony structure of the lumbar spine, unlike the body’s thoracic spine, lacks lateral support but is a specialized structure designed to distribute the weight of heavy loads throughout the back. It consists primarily of trabeculae, a highly vascularized cancellous bone, which is organized in a fashion to redistribute stress throughout the spine. The size of these vertebral bodies progressively increases in direct relation to the augmentation of gravitational loads from the cephalic to the caudal segments of the spine. These segments are connected with ligaments and muscular tissue to each concurring segment located above or below the bony structure. The composition of the body’s intervertebral disc consists primarily of outer annulus fibrosis, which holds the transmitting nociceptors and proprioceptive nerve endings, and the inner nucleus pulposus. Nociception is the process whereby chemical responses to interpret pain or sensation and illicit physical reactions from the brain to the central nervous system, including basic movement. The signals are sent through peripheral neural pathways and are received by the outer annulus fibrosis, posterior longitudinal ligament, facet capsule and the associated muscle groups located in the particular segment of the spine. The composition of the inner annulus, which holds the nucleus, provides the spinal disc with supplemental support during instances of compression. A healthy nucleus pulposus consists of the majority of the surface area of each spinal disc, supporting seven-tenths of the compression against each disc. During the course of adolescence, bone growth balances the proportionate decrease of disc height and loading pressure shifts posteriorly. Over the course of an individual’s development, the overgrowth of bone structures and the inherent hypertrophy of facets lead to the narrowing of central canals and progressive foraminal. Coinciding with herniated discs and the condensing of flavum, these structural changes diminish the diameter of the antiposterior canal and foraminal patency. The stenosis of the spine climaxes during later periods in one’s life and possess the potential to result in vascular, myelopathic and radicular syndromes including spinal cord ischemia and pseudoclaudication. Lower back pain can emerge during the earliest stages of disc degeneration, which generally occurs in the latter stages of an individual’s lifespan. This is referred to as the stabilization phase (Kirkaldy-Willis). A decreasing blood supply delivered strictly to the external third layer of the outer annulus inhibits the healing of intervertebral discs, leading to a condition of chronic nociception. Several previous neurophysiologic studies have found direct correlation between the introduction of lumbar region back pain with the damage and weakening of the superior proprioception centres, directly afflicting the motor control of the individual. These previous studies failed to determine whether the pain directly causes the inhibition of motor control and/or if the lacking motor control causes the pain. Studies conducted by Farfan (1973) and Panjabi (1992) concluded that diminished motor control results in the reduction of an individual’s joint control, leading to pain. Janda (1978) concurred with Farfan’s model, determining that younger individuals with poor motor control are more likely to experience joint related pain as adults. Numerous other studies have concluded that the introduction of chronic pain for an extended period of time results in significant changes of motor control for an individual. Hodges and Moseley (2003) proposed several consequences which pain has upon motor control, including changes in stimulation to spinal responsiveness and proprioception, and common tension upon the central nervous system, such as fear and stress. Several studies also determined that distress and anxiety have been linked to negative adjustments in muscle activity, without intensified pain present. The presence of emotional anguish, including depression, coincides heavily with physical pain, as depression can emerge from an individual bearing the pain. Also, the biochemical processes of the human body for depression and the transmission of pain are similar and can possibly lead to an increased intensification of pain symptoms. Another aspect of human emotion, fear, may also affect motor control. Fear avoidance mechanisms inherent in human activity subconsciously forces individuals to avoid normally performing activities which had previously caused pain or injury. Also, it has been proposed that a lower back pain patient’s exposure to stressors personally relevant to their lives increases muscle activity around the spine more than exposure to generalized stressors. Hodges and Moseley (2003) also noted that an individual’s fear of experiencing pain can inhibit the complete control of the trunk muscles, possibly connecting physiological alterations and psychosocial factors which result in pain. Human conditioning to prevent recurrence of pain and limit the weight of preconceived loads resulting in pain can be interpreted through changes in an individual’s motor control. Another element to this study is that an individual’s ability to control body movement relies upon the motor system’s cognitive sensory detection. Basic reflex responses and complex body movements which are dependent upon accurate body control can be affected by inaccurate afferent input. Patients suffering from lower back pain have been shown in several studies to posses diminished perspicacity to move the spine, along with a weakened ability to reposition the spine. Physical impairment of motor control is common in lower back pain patients, including affected balance control and aspects of sensory cognition. Impaired balance when standing on one or both legs is evident in lower back pain patients, and individuals displaying poor balance when standing have an increased risk of experiencing lower back pain. Observing the changes in individual sensory input when conducting a study on lower back pain is essential to ensure accurate results in which feed-forward and feedback components are necessary to gather data. Several prior studies noted decreased acuity coinciding with the inability to perform repositioning tasks for patients suffering from lower back pain. Another noteworthy factor in the reduction of sensory acuity is muscle endurance related to fatigue, especially with patients experiencing chronic pain. Read More