The lumbar spine refers to the lower back, where the spine curves inward toward the abdomen. It starts about five or six inches below the shoulder blades, and connects with the thoracic spine at the top and extends downward to the sacral spine.The lumbar vertebrae are the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column. They are designated L1 to L5, starting at the top. The lumbar vertebrae help support the weight of the body, and permit movement.
Discs form the main connection between vertebrae. They bear loading during axial compression and allow movement between the vertebrae. Their size varies depending on the adjacent vertebrae size and comprises approximately one quarter the length of the vertebral column.
Each disc consists of the nucleus pulposus, a central but slightly posterior mucoid substance embedded with reticular and collagenous fibers, surrounded by the annulus fibrosus, a fibrocartilaginous lamina. The annulus fibrosus can be divided into the outermost, middle, and innermost fibers. The anterior fibers are strengthened by the powerful anterior longitudinal ligament (ALL). The posterior longitudinal ligament (PLL) affords only weak midline reinforcement, especially at L4-5 and L5-S1, as it is a narrow structure attached to the annulus. The anterior and middle fibers of the annulus are most numerous anteriorly and laterally but deficient posteriorly, where most of the fibers are attached to the cartilage plate. The annular fibers are firmly attached to the vertebral bodies and are arranged in lamellae. This annular arrangement permits limiting vertebral movements, reinforced by investing ligaments.
Common conditions of lumbar disc include:
- Lumbar Degenerative Disc Disease
- Lumbar Disc Herniation
- Lumbar Disc Prolapse
- Lumbar Disc Injury
Four functional groups of muscles govern the lumbar spine and can be divided into extensors, flexors, lateral flexors, and rotators. Synergistic muscle action from both the left and right side muscle groups exist during flexion and extension of the L-spine.
The anterior longitudinal ligament covers the ventral surfaces of lumbar vertebral bodies and discs. It is intimately attached to the anterior annular disc fibers and widens as it descends the vertebral column. The anterior longitudinal ligament maintains the stability of the joints and limits extension.
The posterior longitudinal ligament is located within the vertebral canal over the posterior surface of the vertebral bodies and discs. It functions to limit flexion of the vertebral column, except at the lower L-spine, where it is narrow and weak.
The supraspinous ligament joins the tips of the spinous processes of adjacent vertebrae from L1-L3. The interspinous ligament interconnects the spinous processes, from root to apex of adjacent processes. Sometimes described together as the interspinous/supraspinous ligament complex, they weakly resist spinal separation and flexion.
The ligamentum flavum (LF) bridges the interlaminar interval, attaching to the interspinous ligament medially and the facet capsule laterally, forming the posterior wall of the vertebral canal. It has a broad attachment to the undersurface of the superior lamina and inserts onto the leading edge of the inferior lamina. Normally, the ligament is taut, stretching for flexion and contracting its elastin fibers in neutral or extension. It maintains constant disc tension.
The intertransverse ligament joins the transverse processes of adjacent vertebrae and resists lateral bending of the trunk.
The iliolumbar ligament arises from the tip of the L5 transverse process and connects to the posterior part of the inner lip of the iliac crest. It helps the lateral lumbosacral ligament and the ligaments mentioned above stabilize the lumbosacral joint.
Common conditions of lumbar muscles and ligaments include:
- Lumbar Strain
- Iliolumbar Ligament Syndrome
There are two types of joint in the lumbar spine. Both of these articulations are not unique to the lumbar vertebrae, and are present throughout the vertebral column.
- Between vertebral bodies – adjacent vertebral bodies are joined by intervertebral discs, made of fibrocartilage. This is a type of cartilaginous joint, known as a symphysis.
- Between vertebral arches – formed by the articulation of superior and inferior articular processes from adjacent vertebrae. It is a synovial type joint.
The lumbosacral joint is a joint of the body, between the last lumbar vertebra and the first sacral segment of the vertebral column.
Common conditions of lumbar joints include:
- Lumbar Osteoarthritis
- Facet Joint Disorders
All lumbar spinal nerve roots originate at the T10 to L1 vertebral level, where the spinal cord ends as the conus medullaris. A dorsal or posterior (somatic sensory) root from the posterolateral aspect of the spinal cord and a ventral or anterior (somatic motor) root from the anterolateral aspect of the cord join in the spinal canal to form the spinal nerve root. The roots then course down through the spinal canal, forming the cauda equina, until they exit at their respective neural (intervertebral) foramina as a single pair of spinal nerves. Thus, the lumbar nerve roots exit the spinal canal at a lower level than where they arise.
Common conditions of lumbar nerves include:
- Lumbar Nerve Injuries
- Lumbar Spinal Stenosis
- Lumbar Radiculopathy
For approximately the first 72 hours following an injury, the RICE regime should be followed to ensure control of inflammation and pain relief.
R – Rest
I – Ice
C – Compression
E – Elevation
Rest from aggravating activity.
Ice should be applied in the first 72 hours or when inflammation persists. Ice should be applied for 15 to 20 minutes at a time. Ice should not be applied directly to the skin, but through a wet towel or cloth.
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