Sports Medicine: Just the Facts

CHAPTER 42 • THORACIC AND LUMBAR SPINE 249

• There are five lumbar vertebral bodies.


• Being the largest vertebrae in the spine, they consti-
  tute 25% of the height of the entire vertebral column.

INTERVERTEBRALDISC

• The function of the disc is for weight bearing and load
  transfer.


• The outer portion of the disc is the annulus fibrosis,
  composed of concentric rings of fibrocartilaginous
  tissue.


• The anterior portion is thicker than the posterior.


• The outer one-third of the disc is innervated by the
  vertebral and sinuvertebral nerve.


• The inner portion of the disc is the nucleus pulposus
  and is a gelatinous material of loose, nonoriented, col-
  lagen embedded in a matrix of glucosaminoglycans,
  water, and salt.
  •With age, the amount of water within the disc decreases
  and therefore the height of the disc decreases.


• The vertebral endplate is composed of two layers of
  cartilage that cover the top and the bottom of each
  disc.


• The blood supply to the disc is obliterated within the
  first three decades of life, and therefore nutritional
  support is disrupted.


• The discs must then rely on diffusion from the end-
  plate and the annulus for its nutrients.


• The thoracic disc is thinner, but has a stronger annu-
  lus than the cervical and lumbar discs.

COSTOVERTEBRALJOINTS OF THETHORACICSPINE

• These joints are synovial joints located between the
  vertebral bodies and the ribs.


• There are four articulations/joints (two pairs) on each
  vertebral body, with the exception of T1 and T10–T12
  which have only one pair each.


• This joint is strengthened by the radiate ligament.

COSTOTRANSVERSEJOINTS OF THETHORACICSPINE

• These joints are also synovial joints located between
  ribs 1 and 10, and the transverse processes of the ver-
  tebra of the same level.


• The ribs for T11 and T12 do not articulate with the
  transverse processes and therefore this joint does not
  exist there.


• This joint is strengthened by the costotransverse liga-
  ment.

PEDICLES

• The pedicle channels forces between the zygopophy-
  seal joint, the transverse process and the spinous
  process.

POSTERIOR ELEMENTS

• The posterior elements are composed of the lamina,
  transverse processes, zygopophyseal/facet joint (supe-
  rior and inferior), and a spinal process.


• The lamina channels forces from the spinous and infe-
  rior processes.


• The zygapophyseal joint resists sliding and twisting
  of the vertebral bodies.


• The superior facet of the inferior vertebral body artic-
  ulates with the inferior facet of the superior vertebral
  body.


• This joint is a synovial joint and is subject to inflam-
  mation.
  •With respect to the facets from T2 to T11 the superior
  facets face up, back, and slightly laterally, while the
  inferior facets face down, forward, and slightly medi-
  ally.


• The positioning of these facets allows for the slight
  rotation that occurs in the thoracic spine.


• The facets for T1 and T12 are considered transitional
  since they are situated similar to that of the cervical
  and lumbar spine facets respectively.
  •With respect to the lumbar spine facets, L1–L4 are
  oriented in a sagittal plane which is conducive to flex-
  ion and extension.


• L4–L5 and L5–S1 facets are oriented in the coronal
  plane which is conducive to lateral bending and rota-
  tion.


• The pars interarticularis is a portion of the lamina that
  intervenes between the superior and inferior
  zygopophyseal joints.


• The spinous processes of the thoracic spine face
  obliquely downward.


• The area of greatest angulation is at T7.


• T1–T3 spinous processes project posteriorly and are
  on the same plane as their transverse process of the
  same vertebrae.


• T4–T6 spinous processes project slightly downward
  and therefore they are on the plane halfway between
  their own transverse process and that of the vertebral
  body below.


• T7–T9 spinous processes project downward and there-
  fore the tip is at the level of the transverse process of
  the vertebrae below.


• T10 spinous process is at the level of the transverse
  process of the vertebra below, like that of T9.


• T11 spinous process is halfway between the two
  transverse processes, like that of T6.


• T12 spinous process is on the same plane as its trans-
  verse process of the same vertebrae, like that of T3.


• This spinous process arrangement of the thoracic
  spine is sometimes referred to as the rule of 3s
  (Greenman, 1996).