Clinical Pearl about Spinal Health

Osmotic Pressure and Disk Imbibition

• When osmotic pressure within the intervertebral disk (IVD) is greater than hydrostatic pressure from axial loading, the disk imbibe fluid, causing the spine to increase in length.
• This occurs when lying in bed, and patients should avoid performing full-range spinal motions (bending) shortly after rising from bed.

Transversus Abdominis and Spinal Control

• The transversus abdominis (TrA) is the deepest abdominal muscle, which may have a presetting role in providing rotational and lateral control to the spine.
• The TrA, along with the internal oblique, maintains adequate levels of intra-abdominal pressure and imparts tension to the thoracolumbar fascia, increasing the stiffness of the lumbar spine.

Diaphragm and Abdominal Muscle Coactivation

• Coactivation of the diaphragm and abdominal muscles produces a sustained increase in intra-abdominal pressure.
• Activity of the diaphragm and TrA is initiated before rapid limb movements and is tonic during repetitive movements of the arm and walking.

Lumbar Multifidus and Dynamic Control

• The lumbar multifidus is considered to have the greatest potential to provide dynamic control to the motion segment, particularly in its neutral zone.

Intervertebral Disk Function

• The intervertebral disk (IVD) acts to provide flexibility at low loads and stability at high loads.
• The IVD distributes compressive stress evenly between adjacent vertebrae due to the nucleus pulposus and inner anulus fibrosus acting like a pressurized fluid.

Vertebral End Plates and Attachment

• The vertebral end plates are strongly bound to the IVD, whereas they are only weakly attached to the vertebral bodies.
• The end plates are considered constituents of the IVD, rather than part of the lumbar vertebral body.

Age-related Changes in Intervertebral Disk

• The IVD becomes drier, stiffer, less deformable, and less able to recover from creep with age.

Lumbar Spine Flexion and Posterior Pelvic Tilt

• Flexion of the lumbar spine can occur with a posterior pelvic tilt, which can be performed voluntarily or as a result of weak paraspinal extensor muscles or adaptively shortened hamstring and gluteal muscles.

Repetitive Contact and Periostitis

• Repetitive contact of the spinous processes during the extremes of lumbar extension can lead to a periostitis called "kissing spine", resulting in ligamentous laxity and hypermobility of the segment.

Vertebral Anatomy

• The lumbar vertebra has a massive body, pedicles, laminae, transverse process, accessory processes, and spinous process.
• The fifth lumbar vertebra is a transitional vertebra, with a wedgeshaped body and specific characteristics.

Intervertebral Disk Structure

• The intervertebral disk consists of anulus fibrosus and nucleus pulposus, with collagen fibers arranged in concentric sheets (lamellae).
• The disk resists tensile forces in nearly all directions and provides a greater cross-sectional area of anulus fibrosus posteriorly, increasing its ability to resist tension.