Ch. 9 Biomechanics of the Spine

How do we help to prevent lower back pain?

Lower back pain is an extremely preventable problem. The incidence of low back pain has been increasing due to a huge increase of overweight and obesity. Back pain could be prevented in this case by eating a healthy diet. Another way to prevent the pain is to teach workers who have to handle heavy materials how to properly lift heavy objects. Men under the age of 50 experience low back pain about four times more frequently than do women because of their predominance in occupations with heavy materials. It is also more common for athletes to encounter lower back pain compared to nonathletes. It is advocated to train the trunk muscles for endurance rather than for strength as a prophylactic for low back injury. Fatigue of the spinal extensor muscles with concomitantly reduced force output has been shown to increase the bending moment on the lumbar spine and also to reduce the ability of these muscles to protect the spine. It is also said to do abdominal exercises, such as partial curl-up, so that abdominal muscle strength is sufficient enough to contribute to spinal stability.

How can we properly breathe (and brace) while lifting?.

One should breathe from their diaphragm when lifting. When bracing to lift, one should inhale in this eccentric phase. The diaphragm contracts during this phase, which stabilizes the core. Breathing in also creates intraabdominal pressure in the abdominal cavity which helps stiffen the lumbar spine against buckling. One should also stabilize their trunk in a neutral position to avoid sternal elevation. During the hardest part of lifting, one should exhale in the concentric phase.

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

The cervical region has triplanar movement. Flexion and extension are as high as 17 degrees in the C5-C6 vertebral joint which takes place in the sagittal plane. ROM for hyperextension in the cervical spine is also allowed which takes place in the sagittal plane as well. Lateral and medial rotation of the cervical spine is also allowed, where there is up to 12 degrees of motion allowed at C1-C2 which occurs in the transverse plane. The largest lateral flexion in the spine occurs at the cervical spine where it is about 9-10 degrees of motion at C4-C5 which occurs in the frontal plane. The thoracic region allows lateral flexion with a ROM of about 6 to 8-9 degrees depending on the height of the segments. This takes place in the frontal plane. The thoracic region also contains lateral and medial rotation. Here, there is 9 degrees of rotation in the upper motion segments, but ROM seems to decrease in rotational capability from T7-T8 downward. This takes place in the transverse plane. ROM for flexion and extension is only in 4 degrees at T1-T2 and 10 degrees at T11-T12 which is in the sagittal plane. The lumbar regions allows extension and flexion. There is a ROM of about 20 degrees from the L5-S1. This takes place in the sagittal axis. Hyperextension also takes place in this plane. Lateral flexion of the lumbar spine is 6 degrees, but is only about 3 degrees at the L5-S1. Lateral flexion takes place in the frontal plane. There is limited rotation in the lumbar, where there is only about 5 degrees allowed at the lumbosacral joint which is in the transverse plane. In the sacral region, movement is fixed due to the fact that the vertebrae are fused to the pelvic girdle.In the coccygeal region is fixed due to the fact that the vertebrae are fused together.

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

The primary abdominal muscles are the rectus abdominis, external obliques, and the internal obliques. The rectus abdominis allows spinal flexion in the sagittal plane when functioning bilaterally. It also allows lateral flexion of the spine when there is unilateral tension development which occurs in the frontal plane. The external obliques allow spinal flexion when they function bilaterally in the sagittal plane. They also allow lateral flexion of the spine when there is unilateral tension in the frontal plane. Rotation of the spine toward the opposite side also occurs in the transverse plane from unilateral tension development. The internal obliques produce sagittal plane movement through spinal flexion when it functions bilaterally. Lateral flexion of the spine also takes places in the frontal plane when there is unilateral tension development. Rotation of the spine toward the same side occurs in the transverse plane from unilateral tension development.

List and describe the three abnormal deviations in the spinal curvature.

Three abnormal deviations in the spinal curvature are lordosis, kyphosis, and scoliosis. Lordosis is extreme lumbar curvature. It is associated with weak abdominal muscles and anterior pelvic tilt. It also places added compressive stress on the posterior elements of the spine. A risk factor for lordosis is obesity where there is reduced ROM of the entire spine and pelvis. Causes of lordosis are congenital spinal deformity, weakness of the abdominal muscles, poor postural habits, and overtraining in sports that require repeated lumbar hyperextension. Kyphosis is extreme thoracic curvature. Its causes are congenital abnormality, a pathology such as osteoporosis, or Scheuermann's disease where abnormal epiphyseal plate behavior leads to one or more wedge-shaped vertebrae. In milder cases, it appears that an individual's posture is slouching. It may be treated by exercises that strengthen the posterior thoracic muscles as well as bracing or surgical corrections, depending on the severity of the condition. Scoliosis is lateral spinal curvature/ lateral deviation in spinal curvature. It is coupled with deformity of the involved vertebrae. It can have a C- or S- curve in either the thoracic or lumbar spine, or both. There are two forms of scoliosis: structural scoliosis and nonstructural scoliosis. Structural scoliosis has inflexible curvature that persists even with lateral bending of the spine that can be caused by congenital abnormalities and selected cancers. Nonstructural scoliosis is flexible and are corrected with lateral bending. This type of scoliosis may be secondary to leg length discrepancy or local inflammation.

Lumbar spondylolysis is more prevalent in men than women. True False

True

Obese individuals typically display increased anterior pelvic tilt and lumbar lordosis. True False

True

Explain proper spinal position while lifting. Also, explain why twisting should be avoided when lifting.

When lifting, one must maintain normal lumbar curvature by lifting this the legs. This is thought to minimize trunk flexion which minimizes the torque generated on the spine by body weight. This allows the active lumbar extensor muscles to partially offset the anterior shear produced by body weight as well as uniformly load the lumbar discs rather than place a tensile load on the posterior annulus of the discs. Lordotic lumbar posture must be eliminated in lifting because it increases the loading of the posterior annulus and the fact joints. Full lumbar flexion also must be diminished because it changes the line of action of the lumbar extensor muscles in which they cannot counteract the anterior shear. Twisting should be avoided when lifting because it places about three times more stress on the back than lifting in the sagittal plane.

A typical geriatric disc has a fluid content that is reduced by approximately how much? a. 5% b. 35% c. 50% d. 85%

b. 35%

Contraction of the rectus abdominis causes __________ flexion of the spine. a. unilateral b. bilateral c. eccentric d. isometric

b. bilateral

What causes the pumping action (influx and outflux of water containing nutrients and waste) of the intervertebral discs in adults? a. blood supply b. body motion c. neural activity d. both A and B e. all of the above

b. body motion

Which of the following is not true about lordosis? a. often accompanied by anterior pelvic tilt b. can be caused by poor abdominal flexibility c. often a result of weight gain and/or pregnancy d. all of the above are true

b. can be caused by poor abdominal flexibility

The condition of exaggerated thoracic curvature is known as which of the following? a. lordosis b. kyphosis c. scoliosis d. none of the above

b. kyphosis

What is the most common type of vertebral fracture? a. fracture to the coccyx b. stress fracture of the pars interarticularis c. cervical fracture d. none of the above

b. stress fracture of the pars interarticularis

Which of the following spinal curves are present at birth? a. the cervical and sacral curves b. the thoracic and sacral curves c. the cervical and lumbar curves d. the thoracic and cervical curves

b. the thoracic and sacral curves

Attachment to the ribs limits range of motion in which vertebrae? a. sacral b. thoracic c. lumbar d. cervical

b. thoracic

How many pairs of ribs do humans have? Does this differ from the number of thoracic vertebrae? a. 7 pairs of ribs; Yes it differs - we have 10 thoracic vertebrae b. 24 pairs of ribs; Yes it differs - we have 12 thoracic vertebrae c. 12 pairs of ribs; No it does not differ - we have 12 thoracic vertebrae d. 6 pairs of ribs; No it does not differ - we have 6 thoracic vertebrae

c. 12 pairs of ribs; No it does not differ - we have 12 thoracic vertebrae

In anatomical position, where is the center of gravity located relative to the spine? a. inferior b. posterior c. anterior d. lateral

c. anterior

Transverse or spinous process fractures may result from which of the following? a. extremely forceful contraction of the attached muscles b. the sustenance of a hard blow to the back of the spine c. both A and B d. none of the above

c. both A and B

Which of the following are potential consequences of spinal fractures? a. paralysis b. death c. both A and B d. none of the above

c. both A and B

What is the result when part of the nucleus pulposus of the disc protrudes and presses on a nerve? a. stress fracture b. contusion c. herniated disc d. stress fracture

c. herniated disc

What action(s) do posterior trunk muscles cause when they contract unilaterally? a. extension b. hyperextension c. lateral flexion d. medial rotation

c. lateral flexion

Lateral deviations in spinal curvature are called what? a. lordosis b. kyphosis c. scoliosis d. all of the above

c. scoliosis

The articulations between adjacent vertebral bodies are which of the following types of joints? a. pivot joints (synovial) b. hinge joints (synovial) c. symphysis joints (cartilaginous) d. none of the above

c. symphysis joints (cartilaginous)

Which of the following vertebral regions has the best range of motion? a. cervical b. thoracic c. sacral d. lumbar

cervical

Lack of flexibility in which of the following muscle groups can cause anterior pelvic tilt? a. hip flexors b. erector spinae c. quadratus lumborum d. all of the above e. none of the above

d. all of the above

Movement of the spine occurs in which plane(s)? a. sagittal b. frontal c. transverse d. all of the above

d. all of the above

Unusually high incidences of pars interarticularis fractures have been documented in which of the following groups of athletes? a. female gymnasts b. interior football linemen c. weight lifters d. all of the above

d. all of the above

Which statement is not true about the intervertebral discs? a. act as cushions between the vertebrae b. account for approximately 1/4 of the height of the spine c. are responsible for spinal movement due to compression d. all of the above are true e. all of the above are false

d. all of the above are true

Which part of the vertebrae bears the most weight? a. superior articulating facet b. lamina c. inferior articulating facet d. body

d. body

Which muscle(s) cause spinal rotation to the left (i.e. left lateral rotation)? a. left internal oblique b. right external oblique c. left rectus abdominis d. both A and B e. all of the above

d. both A and B

Which of the following helps the spine absorb shock? a. spinal curves b. intervertebral discs c. ligaments d. both A and B e. all of the above

d. both A and B

What type of joint occurs between the superior and inferior articulating facets of adjacent vertebrae? a. hinge (synovial) b. cartilaginous c. fibrous d. gliding (synovial)

d. gliding (synovial)

What musculoskeletal problem causes the most absences from work? a. medial tibial stress syndrome b. ankle sprain c. carpal tunnel syndrome d. low back pain

d. low back pain

Which vertebrae are the largest? a. sacral b. thoracic c. cervical d. lumbar

d. lumbar

The most superior cervical vertebrae is called what? a. atlas b. atlanto-axial c. cephalo-axial d. axis

a. atlas

What is the most common type of spinal loading during daily activities? a. compression b. tension c. shear d. torsion

a. compression

The spinous processes of the thoracic vertebrae limit movement in which plane? a. sagittal b. frontal c. transverse d. all of the above

a. sagittal

To minimize postural adaptations, a back pack load should be as high as possible near the shoulders. True False

False