DISC DEGENERATION and SPINAL STENOSIS
Ageing or degeneration of the spine otherwise referred to as lumbar spondylosis is commonly as the direct result of disc ageing or degeneration. This process will usually begin in the 3rd decade and by the age of 50 years 95% of the population will have disc degeneration.
As intervertebral discs degenerate they depressurize and abnormal shear forces are generated across the bone endplates. This leads to development of traction osteophytes and encroachment into the spinal canal.
The disc also loses height, this causes undue stress over the facet joints with resultant facet degeneration and hypertrophy due to a combination of facet osteophyte formation and facet capsular hypertrophy.
The end result is loss of vertical height and loss of canal dimensions most severe over the lateral part of the canal otherwise known as the subarticular region. This causes the most usual form of canal stenosis (lateral canal stenosis).
In a proportion of symptomatic individuals the role of developmental (congenital) canal stenosis and a trefoil shaped spinal canal also contributes significantly to the development of symptomatic stenosis. In those with trefoil shaped canals from L3 to L5 vertebral levels there is an increased tendency to develop symptomatic stenosis from facet degeneration and arthropathy.