Pathophysiology
- Definition of Spondylosis - It is a degenerative condition of vertebral column involving intervertebral (facetal) joints, intervertebral disc & bodies of vertebrae.
- The vertebral column is a weight bearing structure. 75% of weight is borne by bodies of vertebrae & remaining is shared by intervertebral disc & intervertebral joints. The weight needs to be transferred along the line of gravity (LOG) This happens if the vertebral column has its curvatures in normal range & with proper alignment of all vertebrae. 3. This weight bearing function leads to compressive load on these three structures. The compressive load in course time in years is responsible for changes in them.
- These changes may occur early for age, if the vertebral column is subjected to long hours of sitting, standing, travelling or weightlifting. 5. Changes in bodies of vertebrae - Excessive or imbalanced weight bearing leads to excessive bone formation at margins of body of
vertebrae. This is called osteophytes.
- These osteophytes may protrude in intervertebral foramen, putting pressure on spinal nerve.
- Changes in the Intervertebral Disc-Prolonged compressive load leads to escaping of water molecules from Annulus Fibrosus & Annulus Pulposus making them dry & thin
- This reduces the height of IVD, which may narrow the intervertebral foramen through which the spinal nerve comes out. However, this is a long duration (chronic) process which may lead to nerve compression. 9. Unequal pressure on disc, mainly in its posterior region, may lead to
bulging of Annulus Fibrosus posteriorly or laterally.
- Persistent pressure may lead to tear of Annulus Fibrosus posteriorly (Central, Paracentral or lateral - foraminal). 11. Herniation of Nucleus Pulposus through this tear is called Prolapsed Intervertebral Disc(PID) also called as herniation of disc or slip disc
- This PID may press the nerve in the intervertebral foramen (foraminal - exiting nerve) or posteriorly (central or paracentral - traversing nerve) .
- There may be a precipitating cause like lifting eight, straining at stool coughing, sudden bending, kick of vehicle or obesity etc. The pressure on the nerve gives rise to its' irritation. This gives rise to sharp pain in the
region of its distribution. This commonly occurs at intervertebral foramen between L5
& S1 affecting L5 nerve. Other common site being IVF between L4 & L5 affecting L4.(Both exiting nerves) However let us remember the posterocentral disc bulge or
prolapse may compress L5/ S1 Traversing nerves depending on the level. This is
called Radiculopathy of L4/L5/S1.( In layman’s term it is called Sciatica)
- Changes in the Intervertebral joint-Excessive
load/compression leads to thinning of articular cartilage, ligamental laxity & osteophyte formation.
Osteophytes may protrude in the intervertebral foramen (posterior boundary) compressing the nerve. Ligamental laxity may lead to anterior or posterior listhesis of one vertebra over other. 15. Thus, lumbar Spondylosis is the wear & tear of vertebral column in lumbar region. It can be prevented by sufficient sleep, postural awareness, optimum,strength in muscles supporting the lumbar spine, stretching the shortened erector spinae & mental peace.( Disturbed mind may increase the tone of
erector spinae muscle)
Complications of Spondylosis
Spondylolysis- is a break at pars interarticularis, I.e. the part between superior and
interior articulating processes. This part is a weight bearing part of vertebra as weight
of HAT (Head + Arms + Trunk) is shared with intervertebral joints passing through
this portion of vertebra. This break is called stress or fatigue fracture. If it occurs
bilaterally, the front (anterior) portion of vertebra slips forward leading to anterior
listhesis of one vertebra over other.
Spondylolisthesis- is slipping of one vertebra over other. It can be anterior (front) or
posterior (back). It can occur due to ligamentous laxity or spondylolysis. As long
term degenerative changes in intervertebral disc leads to its desiccation, thinning, the
intervertebral space reduces. The ligaments holding the vertebrae snuggly with each
other become loose. The degenerative changes at intervertebral joints add to this
situation leading to anterior or posterior slipping of vertebra over other. The effect of
spondylolisthesis can be narrowing of intervertebral foramen leading to nerve
compression at that level