Biomechanics Chapter 9

Describe the range of motion in all three planes for each vertebral region relative to the other regions.

The ROM for flexion and extension on the sagittal plane is considerable in the cervical and lumbar regions. Due to the orientation of the thoracic facets, the ROM decreases on the sagittal plane. Extension of the spine backward on the sagittal plane is called hyperextension. ROM for hyperextension is significant in the cervical and lumbar regions. Frontal plane movement away from anatomical position is termed lateral flexion. The largest ROM for lateral flexion occurs in the cervical region. Somewhat less is allowed at the thoracic, and even less in the lumbar region. Spinal rotation on the transverse plane is freest in the cervical region of the spine, and slightly less mobile in the thoracic spine. From T7-T8 down, spinal rotation and ROM drastically decreases. However, at the lumbosacral joint, there is slightly more spinal rotation allowed.

Explain proper lifting including rationale. Also, explain why twisting should be avoided when lifting.

Proper lifting rationale is to avoid lower back and trunk flexion, and maintaining their normal lumbar curve, rather than increasing lordosis or lumbar spine flexion. Maintaining normal or slightly flattened lumbar curve enables the active lumbar extensor muscle to partially offset the anterior shear produced by body weight, and uniformly loads the lumbar discs than placing posterior tensile load on the discs. Tension developed in the antagonist trunk muscles works to stabilize the spine. One should not twist when lifting because lateral and rotational movements of the spine require a more complex muscle activation than what is required for flexion and extension. This may dangerous and cause injury when carrying an external load.

Describe the most common back injury, including degree of incidence, possible causes and treatments.

Soft tissue injuries such as contusions, muscle strains, and ligament sprains collectively compose the most common injury of the back, accounting for 97% of all back pain. These types of injuries result from sustaining a blow or overloaded muscles, particularly those in the lumbar region. Painful spasms and knot-like contractions of the back muscles may develop as a sympathetic response to these injuries, and may be an underlying cause of injury. Biomechanical problems are believed to be the cause of the spasms which act to protect and immobilize the injured area. Treatments include, anti-inflammatory drugs, rest, ice, compression, and elevation.

List and discuss the primary abdominal muscles, explaining how they perform motion in all three planes.

The main abdominal muscles are the rectus abdominis, the external obliques and the internal obliques. These muscles function bilaterally, are major spinal flexors, and reduce anterior pelvic tilt. Unilateral tension developed by muscles produced lateral flexion of the spinal on the frontal plane, towards the tensed muscles. Tension development in the internal obliques causes rotation of the spine toward the same side. Tension developed in the external obliques results in rotation towards the opposite side. When the spine is fixed, the internal obliques provide rotation of the pelvis toward the same side.

List and describe the three abnormal deviations in the spinal curvature, including symptoms, possible causes, and treatment options.

Three abnormal deviations of spinal curvature are lordosis, kyphosis, and scoliosis. Lordosis is exaggeration of the lumbar curvature, and is often associated with weakened abdominal muscles and anterior pelvic tilt. Lordosis may be caused by spinal deformity, weakness of the abdominal muscles, poor posture, obesity, and repeated hyperextension in sports such as gymnastics. Lordosis places extra compressive stress on the lumbar spine and may cause low back pain. Treatments include postural alignment, back brace, and physical therapy. Kyphosis is the exaggerated curvature of the thoracic spine. Kyphosis may be caused by a congenital abnormality, osteoporosis, or Scheurermann's disease. Both genetic and biomechanics factors play a role. Kyphosis increases with age as function of degenerative changes, vertebral compression fractures, and muscular weakness. Treatment may consist of strengthening the posterior thoracic muscles, or bracing and or surgery in more severe cases. Lateral deviations in the spine or scoliosis are lateral deformities coupled with rotational deformity of the involved vertebrae. This condition ranges from mild to severe. There is structural and non-structural scoliosis. Structural is an inflexible curvature that persists with lateral bending of the spine. Non-structural curves are flexible and corrected with lateral bending. Scoliosis may be caused by congenital abnormalities, cancer, differences in leg length, and habits of carrying items lopsidedly. The cause of most scoliosis is unknown and is more common in females. Mild scoliosis can be healed on its own or treated with chiropractic care, stretching and strengthening the spinal muscles. More severe cases may need bracing and or surgery.