remodelling of articular surfaces → instability → forward slippage of upper on lower vertebra.
synovial cysts are frequently solid (cartilaginous or myxomatous) - can be confused with migratory disc fragments or intraspinal tumor; attachment to joint space is characteristic.
bulging of disc annulus; osteophytes converge on protruded annulus, and may convert it into bony ridge (transverse bar) that protrudes posteriorly (compromising spinal canal); protrusion laterally compromises foramina.
laxity of ligaments + increased load / traction on ligaments → infolding (hypertrophy) of ligamentum flavum, ossification of posterior longitudinal ligament (see below)
These changes narrow spinal canal* & intervertebral foramina
*acquired spinal stenosis- may form subarachnoid block (with CSF protein content↑ below block).
N.B. patients with congenitally narrow spinal canal are at increased risk!
Central canal stenosis can cause myelopathy (cervical) or cauda equina syndrome (lumbar)
Lateral recess stenosis can cause radiculopathy.
Intervertebral foramenstenosis can cause radiculopathy.
Sources of osteophytes compromising intervertebral foramen:
edges of vertebral bodies.
facet (interpedicular, zygapophyseal) joints
uncovertebral (Luschka) joints (only in cervical vertebrae).
on sagittal MRI or reformatted CT, foramina appear as comma-shaped, fat-filled spacesjust above disc level; roots exit via bulbous upper portion (just below pedicles) - early degeneration of disc and facet joints effaces only fat inferior to nerve roots.