Thoracic spine motion

The spine is an engine. The axial pull of the muscles on the thoracic and lumbar spine are transformed by coupled motion into axial torque, which is then applied to the pelvis. The spine is now divided into three segments the lumbar spine, which causes the pelvis to rotate the thoracic spine counter-rotates to dissipate torque and utilizes linked movements of the upper extremities in so doing. The cervical spine de-rotates in the opposite direction to allow the head, eyes and sensory organs to have a stable platform which faces the direction of travel. 

The exercises described can be used to increase regional cervical motion (muscle stretch, extensibility), to increase regional strength (muscle contractility), or to restore strucmral symmetry. Many cervical muscle fimctions and structural changes involve the thoracic region. It is suggested that the physician review the section in Chapter 9, Exercise Therapy, and Chapter 44, Exercise Therapy for the Thoracic Spine, when writing an exercise prescription for the cervical area. 

Although the thoracic spine has characteristic features that distinguish it from the cervical and lumbar spinal regions, it is mainly a transitional zone between the cervical and lumbar regions, as evidenced by the steady increase in height of the vertebral bodies from T1 to T12. Moreover, the inferior articular facets of T12 correspond to those in the lumbar area to allow proper articulation with LI. The different forms of articulation play a considerable role in the amplitude of various physiologic motions in the thoracic spine. 

Motion in the laterally flexed thoracic spine is limited by the impact of the articular processes... 

There are two mechanisms by which the ribs tend to increase the stability (and decrease the motion) of the thoracic spine. The first mechanism involves the articulation of the head of the ribs with the body and transverse processes of the vertebrae. The second mechanism increases the spine s moment of inertia via an increase in the transverse and anteroposterior dimensions of the spine structure. This results in increased resistance to motion in all directions. 

Although no studies have compared the motion of the thoracic spine with and without intact costovertebral joints. White and Panjabi et al. have determined that the costovertebral joint plays a critical role in stabilizing the thoracic spine during flexion and extension. 

Rotation is the greatest motion in the larger part of the thoracic spine (Tl-TlO). The amplitude of rotation is markedly decreased in the lower part ofthe region. The articular orientation ofthe thoracic vertebrae allows them to rotate about a point in the center of the vertebral body. The articular orientation of the lower thoracic vertebrae, however, is similar to that of the lumbar vertebrae and permits rotation only about a point near the spinous process. This rotation is greatly resisted by shearing forces in the intervertebral disk. The extent of rotation is further diminished by the resistance afforded by the intact costal cage. 

The thoracic spine should be evaluated for regional restrictions to motion. Because of the length of this region—12 vertebrae—it is helpful to divide the region into three segments upper thoracic spine (T1-T4), mid-thoracic spine (T5-T8), and lower thoracic spine (T9-T12). 

Discrepancies in findings between areas ofthe thoracic spine (T1-T12, T1-T8, orTl-T4) may indicate an area of dysfunction and should prompt the physician to examine this area more closely with the techniques of rotoscoliosis testing and intersegmental motion testing, described later. 

The methods of diagnosing intersegmental dysfunction in the lower thoracic spine are quite similar to the techniques used in the upper thoracic spine. The patient position is the same except that the patient must sit up straight. The positions of the palpating hand are the same. However, the physician is positioned differently with respect to the patient, and different techniques are used to induce motion in the lower thoracic spine. Only these differences are described. 

Patient position as for intersegmental motion testing of the upper thoracic spine. 

Gross motion of the lumbar spine is generally evaluated in conjunction with that of the thoracic spine. The patient is standing with his weight evenly distributed and his two feet are spaced 4 to 6 inches apart. The physician kneels or squats directly behind the patient his eyes are level with the lumbar spine. 

Musculoskeletal changes occur during the course of the disease. The chest assumes a barrel shape in which the anteroposterior (AP) diameter equals the transverse diameter. The accessory muscles of respiration gradually hypertrophy. Hypertrophic scalene muscles may impinge on neurovascular structures passing between or near them. Rib motion is markedly restricted and eventually contributes to the dyspnea. The thoracic spine becomes kyphotic and immobile. Motion of the diaphragm is restricted. 

The structural examination revealed marked restriction of all ribs. The first ribs were elevated bilaterally. The thoracic spine was kyphotic with restricted motion of the vertebrae. The scalene and sternocleidomastoid muscles were hypertrophied and tense. The trapezius and other scapular muscles were hypertonic. Shoulder motion was restricted bilaterally in flexion and abduction. The sternum was rigid with no flexibility at the angle of Louis. Cervical motion was restricted in all directions. The lumbar spine was flattened with hypertonic paraspinal muscles. 

After the acute asthma symptoms have abated, or in between exacerbations, manipulative treatment may include direct or indirect (including articulatory) techniques to treat motion restrictions of the clavicles, cervical and thoracic spine, ribs, thoracic inlet, sternum, and thoracoabdominal diaphragm. Treatment of these areas may improve chest wall motion, thereby diminishing the work of breathing ultimately to the benefit of the asthmatic patient. 

The design of any device to be implanted in the intervertebral space must incorporate considerations of the biomechanics of the particular spinal level to be implanted. Among other factors, the primary biomechanical factors to be considered can be characterized as the kinematics (motion), kinetics (applied forces), and load sharing (distribution of stress between anatomic components). The device should allow the expected kinematics, it should be able to withstand millions of cycles of the expected loads, and it should attempt not to disrupt the distribution of the tissue level stresses and strains experienced in a healthy intervertebral joint. The kinematics, kinetics, and load sharing of the spine vary significantly as one moves from the cervical to the thoracic to the lumbar spine. 

Coming back to the spine as an integral part of the human body and the involved, mechanical components, first we have passive elements (Fig. 3) the spinal column as the important load transferring element the hip-joint, which transfers the loads to the legs the ligaments, which control and restrict the motion of the spine the rib cage, which especially increases the rotational stiffness in the thoracic area... 

The backbone consists of seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae and three to five coccygeal vertebrae (taUbone sacrum ). The general function of the backbone is to sustain the head, torso and the arms and to make a stable posture possible. The backbone has natural curvatures in the cervical and lumbar areas of the back. Because of these curvatures the shape of the backbone is called a double-S shape . This special shape makes a straight posture possible and prevents overloads of the torso. The function of the shape is to absorb shocks that occur if you walk, run or during other movements whereby the spinal cord has to be protected. The motion in the spine can be realized because of the interaction of the intervertebral disks, joints, ligaments and muscles. 

Type I and type II dysfunctions refer only to somatic dysfunctions in the thoracic and lumbar vertebrae because Fryette s principles only apply to these areas. However, in common usage, somatic dysfunctions in the typical cervical spine are often referred to as type II, Motion characteristics of the cervical region dictate that the typical cervical vertebrae side-bend and rotate toward the same side regardless of dysfunction or normal functioning. The distinction is the involvement of a flexion or extension component in the dysfunctional unit. 

Harrison Fryette, in Principles of Osteopathic Technique, discussed specific coupled motion patterns. Of relevance here, when the spine is at rest, normal lateral flexion in one direction will cause the vertebral body to rotate in the opposite direction. (This rule apphes oidy to the thoracic and lumbar regions.) If a group of vertebrae side-bend toward the right, the vertebral bodies will... 

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