As a Sacramento Motorcycle Accident Attorney, and Sacramento Brain Injury Lawyer, I have represented many people over the years who have suffered horrible spine injuries. Injures to the spinal cord can be devastating both to those who have suffered the trauma, as well as their loved ones.
Next Generation Wheelchairs Helps People with Spinal Cord Injuries
I am thrilled to learn that the next generation in wheelchairs is helping people stand up whenever they want, thanks to a new robotic device called Tek RMD. The new technology is a Segway-like device which allows people with spinal cord injuries to stand and move upright.
Spinal Mechanical Structure
The spine is a mechanical structure. The vertebrae articulate with each other in a controlled manner through a complex of levers (vertebrae), pivots (facets and discs), passive restraints (ligaments), and activations (muscles).The long, slender, ligamentous bony structure is markedly stiffened by the rib cage. Although the spine has some inherent ligamentous stability, the major portion of the me chanical stability is due to the highly developed, dynamic neuromuscular control system. The spine structure is designed to protect the spinal cord, which lies at its center.
The spine has three fundamental biomechanical functions. First, it transfers the weights and the resultant bending moments of the head, trunk, and any weights being lifted to the pelvis. Second, it allows sufficient physiologic motions between these three body parts. Finally, and most important. it protects the delicate spinal cord from potentially damaging forces and motions produced by both physiologic movements and trauma. These functions are accomplished through the highly specialized mechanical properties of the normal spinal anatomy.
Biomechanically Relevant Anatomy
The spine consists of seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae, five fused sacral vertebrae, and three to four fused coccygeal segments. As the spine is viewed in the frontal plane, it generally appears straight and symmetrical. In some individuals there may be a slight right thoracic curve, which may be due to either the position of the aorta or the increased use of the right hand. In the lateral or sagittal plane there are four normal curves. These curves are convex anteriorly in the cervical and lumbar regions and convex pasteriorly in the thoracic and sacral regions. There is a mechanical basis for these normal analomic curves; they give the spinal column increased flexibility and augmented, shock-absorbing capacity, while at the same time maintaining adequate stiffness and stability at the intervertebral joint level.
The thoracic curve is structural and is due to the lesser vertical heights of the anterior thoracic vertebral borders, as opposed to the posterior borders. This is also true of the sacral curve. Curvatures of the cervical and lumbar regions are largely due to the wedge-shaped intervertebral discs. Consequently, when distracting forces are applied to tho entire spine, there is a greater flattening of the cervical and lumbar lordosis as compared with the thoracic kyphosis.
The intervertebral disc, which has many functions, is subjected to a considerable variety of forces and moments. Along with the facet joints, it is responsible for carrying all the compressive loading to which the trunk is subjected. When a person is standing erect, the forces to which a disc is subjected are much greater than the weight of the portion of the body above it. In fact, some researchers have determined that the force on a lumbar disc in a sitting position is more than three times the weight predicted by mathematical models. In addition, with any activity where dynamic loads are involved (e.g., jumping and trauma),the actual loads on the vertebral disc are much higher, perhaps up to twice as high as those in the static positions. These are mainly compressive loads.
The disc is also subjected to other types of loads and stresses. Tensile stresses are produced in certain portions of the disc during physiologic motions of flexion, extension, and lateral bending. Axial rotation of the torso with respect to tho pelvis causes torsional loads that result in shear stresses in the lumbar discs. Combined rotation and bending result in stresses in the disc that are a combination of tensile, compressive, and shear stresses.
The loads to which the disc is subjected may be divided into two main categories according to the duration of application: short duration-high Amplitude loads (e.g., jerk lifting) and long duration-low magnitude loads due to more normal physical activity. This division is important, because the disc exhibits time-dependent properties such as viscoelasticity characterized by load-rate sensitivity, hysteresis, creep, and relaxation.
Short-duration, high-level Loads cause irreparable structural damage of the intervertebral disc when a stress of higher value than the ultimate failure stress is generated at a given point. The mechanism of failure during long-duration, low-level, repetitive loading of relatively low magnitude is entirely different and is due to fatigue failure. A tear develops at a point where the nominal stress is relatively high (but much less than the ultimate or even yield stress), and it eventually enlarges and results in complete disc failure.
Biomechanical behavior of the disc is dependent upon its state of degeneration, which in turn is frequently age dependent. Discs are also damaged when subjected to trauma, as with the forces involved in motorcycle and automobile accidents.
If you or a loved one has suffered a spine injury caused by another’s negligence, please call my law firm, the Edward A Smith Law Offices, a Sacramento Personal Injury Attorney, immediately at (916) 694-0002 locally or (800) 404-5400 toll-free for advice.