Spine Anatomy
The spine is a complex structure that provides structural support, protects the spinal cord, and enables movement. Understanding spine anatomy is essential for comprehending spinal conditions and treatment options. The spine is divided into four main regions: cervical, thoracic, lumbar, and sacral.
Vertebral Segments
The spine consists of 33 vertebrae (bones) arranged in a column:
- Cervical Spine (C1-C7) - The seven vertebrae that form the neck, supporting the head and enabling head movement
- Thoracic Spine (T1-T12) - The twelve mid-back vertebrae that attach to the rib cage and protect vital organs
- Lumbar Spine (L1-L5) - The five largest vertebrae in the lower back, bearing most of the body's weight
- Sacral Spine (S1-S5) - Five fused vertebrae forming the sacrum, connecting the spine to the pelvis
- Coccyx (Tailbone) - The small, fused vertebrae at the base of the spine
Each vertebra consists of a vertebral body (anterior) and a posterior arch that encloses the spinal canal.
Intervertebral Discs
Between each vertebra sits an intervertebral disc that acts as a shock absorber:
- Nucleus Pulposus - The gel-like center of the disc containing water and proteins
- Annulus Fibrosus - The tough outer layer of fibrous tissue surrounding the nucleus
These discs allow movement, absorb impact, and maintain proper spacing between vertebrae. They can degenerate, bulge, or herniate with age or injury.
Spinal Cord and Nerves
The spinal cord runs through the spinal canal (vertebral foramen) inside each vertebra:
- Spinal Cord - The bundle of nerves extending from the brain down through the vertebral column
- Nerve Roots - Nerves exit the spinal canal through openings (intervertebral foramina) between vertebrae
- Cauda Equina - The bundle of nerve roots below the lumbar spine
Compression or injury to these structures can cause pain, numbness, tingling, and weakness in various parts of the body.
Ligaments and Supporting Structures
Multiple ligaments provide stability and support to the spine:
- Anterior Longitudinal Ligament - Runs along the front of the vertebral bodies
- Posterior Longitudinal Ligament - Runs along the back of the vertebral bodies inside the spinal canal
- Facet Joint Capsules - Encapsulate the small joints between vertebrae
- Ligamentum Flavum - Yellow ligament connecting the posterior arches of adjacent vertebrae
Muscles of the Spine
Deep and superficial muscles support spinal movement and stability:
- Erector Spinae - Extends the spine and maintains posture
- Multifidus - Stabilizes individual vertebrae
- Transverse Abdominis - Deep abdominal muscle providing core stability
- Rectus Abdominis - Front abdominal muscle
- Latissimus Dorsi - Large back muscle aiding movement
Common Spine Conditions
Cervical Spondylosis
Age-related degeneration of cervical vertebrae and discs causing pain, stiffness, and sometimes nerve compression with radiating pain into the arms.
Lumbar Disc Herniation
Rupture or protrusion of intervertebral disc material compressing nerve roots, causing lower back pain and possible leg pain (sciatica), numbness, or weakness.
Spinal Stenosis
Narrowing of the spinal canal or intervertebral foramina, restricting space for the spinal cord and nerve roots. Results in pain, numbness, and weakness, particularly with walking.
Spondylolisthesis
Forward displacement of one vertebra over another, often causing lower back and leg pain, instability, and potential nerve compression.
Degenerative Disc Disease
Progressive degeneration of intervertebral discs leading to loss of height, flexibility, and increased wear on surrounding structures. Causes chronic pain and stiffness.
Facet Joint Syndrome
Arthritis or inflammation of the small facet joints between vertebrae, causing localized back pain that may radiate to the buttocks or legs.
Spinal Fractures
Breaks in vertebral bodies, typically from trauma or osteoporosis. Can range from compression fractures to unstable fractures requiring urgent treatment.
Scoliosis
Abnormal sideways curvature of the spine, which can be idiopathic, congenital, or degenerative. May cause cosmetic concerns, pain, and breathing difficulties if severe.
Whiplash Injury
Cervical spine injury from sudden head movement, commonly from motor vehicle accidents. Causes neck pain, stiffness, and headaches.
Spine Treatments & Procedures
Physical Therapy & Rehabilitation
Conservative first-line treatment focusing on strengthening core muscles, improving flexibility, correcting posture, and managing pain. Often combined with activity modification and ergonomic advice.
Epidural Steroid Injection
Injection of corticosteroid medication around the spinal nerves to reduce inflammation and provide pain relief. Often used for disc herniation and stenosis-related symptoms.
Facet Joint Injection
Targeted injection of local anesthetic and steroid into facet joints to reduce inflammation and pain. Useful for facet-mediated back pain.
Discography
Diagnostic procedure injecting contrast dye into discs to identify painful or degenerative discs, helping guide treatment decisions and rule out other causes of pain.
Microdiscectomy
Minimally invasive surgical procedure removing a portion of herniated disc material pressing on nerve roots. Provides relief from leg pain and radiculopathy.
Laminectomy / Decompression
Surgical removal of the lamina (roof) of a vertebra or ligaments to widen the spinal canal and relieve compression. Addresses spinal stenosis and improves pain and mobility.
Anterior Cervical Discectomy and Fusion (ACDF)
Surgical approach from the front of the neck to remove a damaged disc and fuse adjacent vertebrae. Stabilizes the cervical spine and relieves nerve compression.
Posterolateral Fusion
Spinal fusion procedure from the posterior approach combining decompression with bone graft to fuse unstable segments. Restores stability for spondylolisthesis or severe degeneration.
Artificial Disc Replacement
Replacement of a degenerative disc with a prosthetic device that preserves motion and function. An alternative to fusion in select candidates.
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