Standard descriptions of the lumbar spine refer to the healthy, young, adult spine. There is also variation to what is "normal" for the lumbar spine. With aging you see fairly uniform changes in the lumbar spine, and so normality changes with advancing age. Many changes in the lumbar spine are not associated with symptoms and are therefore not pathological, but rather part of the normal ageing process.
Biochemical Changes
The changes in collagen, proteoglycans, and elastic fibres have major biomechanical effects on the disc. With age they become drier, and with an increase in collagen and reduction of elastin, they become more fibrous and less resilient. The increased collagen and collagen-proteoglycan binding leads the disc to become stiffer (more resistant to deformation), and the decreased water-binding capacity means they are less able to recover from creep deformation. This can lead to a change in mobility.
| Area of Change |
Biochemical Changes
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| Metabolism |
In childhood, the disc adapts to anaerobic metabolism after the regression in infancy of the meagre blood supply to the disc.
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| Proteoglycans |
- synthesis, size, and the concentration in the nucleus pulposis (NP) decreases with age.
- Proteoglycans account for 65% of the dry weight in early adult life, decreasing to 30% by age 60.
- There is a reduction in large proteoglycan aggregates by adolescence
- The concentration of chondroitin sulphate falls, with keratan sulphate remaining constant. This means a rise in the keratan sulphate/chondroitin sulphate ratio.
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| Collagen |
- Collagen content increases, with an increase in collagen-proteoglycan binding, in both the anulus fibrosis (AF) and NP.
- Fibril diameter in the NP increases, so that the type II collagen of the NP resembles the type I collagen of the AF. Reciprocally, the average fibril diameter in the AF decreases. Overall, there is less distinction between the collagen of the NP and the AF
- Increase in the amount of type I collagen in the outermost laminae of the posterior quadrant of the AF, and a decrease in the type II collagen. This suggests some changes are not age related but related to internal stresses related to location.
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| Elastic fibres |
Reduction in the AP from 13% at age 26 to 8% at age 62
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| Non-collagenous proteins |
Increase in concentration, with the appearance of distinctive non-collagenous proteins. Their function is unknown.
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| Water content |
- Decrease in water content with age from 88% at birth, to 65-72% by age 75.
- Most of the dehydration occurs during childhood and adolescence, with a final reduction of AP water content by 6% from early adulthood to old age
- Factors leading to reduced water content: loss of proteoglycans, change in KS/CS ratio, increased collagen and collagen-proteoglycan binding leaving fewer polar groups of the PGs to bind water
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