Lumbar Spine Age Changes: Difference between revisions
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| Metabolism ||<ul><li>In childhood, the disc adapts to anaerobic metabolism after the regression in infancy of the meagre blood supply to the disc.</li></ul> | | Metabolism ||<ul><li>In childhood, the disc adapts to anaerobic metabolism after the regression in infancy of the meagre blood supply to the disc.</li></ul> | ||
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| Proteoglycans || <ul><li>synthesis, size, and the concentration in the nucleus pulposis ( | | Proteoglycans || <ul><li>synthesis, size, and the concentration in the nucleus pulposis (NP) decreases with age.</li><li>Proteoglycans account for 65% of the dry weight in early adult life, decreasing to 30% by age 60.</li><li>There is a reduction in large proteoglycan aggregates by adolescence</li><li>The concentration of chondroitin sulphate falls, with keratan sulphate remaining constant. This means a rise in the keratan sulphate/chondroitin sulphate ratio.</li></ul> | ||
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| Collagen || <ul><li>Collagen content increases, with an increase in collagen-proteoglycan binding, in both the anulus fibrosis ( | | Collagen || <ul><li>Collagen content increases, with an increase in collagen-proteoglycan binding, in both the anulus fibrosis (AF) and NP.</li><li>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</li><li>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.</li></ul> | ||
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| Elastic fibres ||<ul><li>Reduction of elastic fibres in the AP from 13% at age 26 to 8% at age 62.</li></ul> | | Elastic fibres ||<ul><li>Reduction of elastic fibres in the AP from 13% at age 26 to 8% at age 62.</li></ul> | ||
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! Feature !! Change | ! Feature !! Change | ||
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| Viable cells ||<ul><li>Viable cells decrease in the | | Viable cells ||<ul><li>Viable cells decrease in the NP.</li><li>Proportion of cells that exhibit necrosis rises from 2% in infancy, to 50% in young adults, to 80% in old age. Lipofuscin granules accumulate</li></ul> | ||
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| NP and AF distinction ||<ul><li>There is less distinction between the NP and AF as the disc becomes more fibrous.</li><li>They coalesce, and the NP becomes encroached by the AF.</li></ul> | |||
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| NP changes ||<ul><li>The NP becomes more solid, dry, and granular after middle age. There is less ability to exert fluid pressure with a drier more fibrous NP, with it being less able ot transmit weight directly, and less able to exert radial pressure on the AF. There is therefore a greater vertical load borne by the AF.</li></ul> | |||
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| Collagen lamellae ||<ul><li>Collagen lamellae of the | | Collagen lamellae ||<ul><li>Collagen lamellae of the AF increases in thickness, and becomes more fibrillated, and cracks and cavities may develop.</li><li>These can enlarge and become clefts and fissures. There is an increase in incomplete lamellae</li><li>These changes can occur due to repeated minor insults with an overloaded AF during trunk movements over the course of activities of daily living.</li></ul> | ||
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| Tensile strength ||<ul><li>Reduction in the tensile strength of the | | Tensile strength ||<ul><li>Reduction in the tensile strength of the AF, but no simple relationship between age and tensile properties.</li></ul> | ||
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| Intervertebral disc height ||<ul><li>Intervertebral disc height ''increases'' with age.</li><li>There is an increase in AP diameter by 10% in females, and 2% in males, and a 10% increase in height of most discs. The upper and lower surfaces of the discs increase in convexity.</li><li>Disc height maintenance with age is "normal."</li><li>Any loss of trunk stature is due to decreases in vertebral body height.</li><li>Disc narrowing is due to a process other than ageing.</li></ul> | | Intervertebral disc height ||<ul><li>Intervertebral disc height ''increases'' with age.</li><li>There is an increase in AP diameter by 10% in females, and 2% in males, and a 10% increase in height of most discs. The upper and lower surfaces of the discs increase in convexity.</li><li>Disc height maintenance with age is "normal."</li><li>Any loss of trunk stature is due to decreases in vertebral body height.</li><li>Disc narrowing is due to a process other than ageing.</li></ul> | ||
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| Vertical trabeculae || <ul><li>Slowly absorbed, but those that persist are thickened</li></ul> | | Vertical trabeculae || <ul><li>Slowly absorbed, but those that persist are thickened</li></ul> | ||
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| Horizontal trabeculae || <ul><li>Absorbed and not replaced.</li><li>Therefore ageing is characterised by the loss of horizontal trabeculae, most marked in the central vertebral body (the part overlying the | | Horizontal trabeculae || <ul><li>Absorbed and not replaced.</li><li>Therefore ageing is characterised by the loss of horizontal trabeculae, most marked in the central vertebral body (the part overlying the NP).</li><li>This removes weakens their bracing effect on the vertical trabeculae, and the loadbearing capacity of the central vertebral body decreases.</li></ul> | ||
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| Cortical bone || <ul><li>With the weakening of the trabecular system, a greater proportion of the compressive load on the vertebral bodies is borne by the cortical bone.</li><li>Over the age of 40, trabecular bone bears only 35% of the load, but cortical bone fails at only 2% deformation, while trabecular bone fails at 9.5% deformation.</li><li>The vertebral body is less resistant to deformation and injury with greater reliance on the cortical bone.</li></ul> | | Cortical bone || <ul><li>With the weakening of the trabecular system, a greater proportion of the compressive load on the vertebral bodies is borne by the cortical bone.</li><li>Over the age of 40, trabecular bone bears only 35% of the load, but cortical bone fails at only 2% deformation, while trabecular bone fails at 9.5% deformation.</li><li>The vertebral body is less resistant to deformation and injury with greater reliance on the cortical bone.</li></ul> | ||
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Spondylosis refers to the development of osteophytes along the junction of vertebral bodies and their intervertebral discs. Spondylosis is not a disease but a natural consequence of the stresses applied to the spine throughout life. They are reactive and adaptive changes that are due to compensation of biomechanical aberrations. It is an active and purposeful process, not a degenerative one. | Spondylosis refers to the development of osteophytes along the junction of vertebral bodies and their intervertebral discs. Spondylosis is not a disease but a natural consequence of the stresses applied to the spine throughout life. They are reactive and adaptive changes that are due to compensation of biomechanical aberrations. It is an active and purposeful process, not a degenerative one. | ||
With age, the | With age, the NP becomes less resilient and stiffer, and the AF bears more of the compressive loads applied to the disc. Adaption occurs with the greater loads. Excessive compression can result in ossification of the terminal ends of the collagen fibres of the AF. This ossification can occur in the anterior and posterior margins of the disc where compressive strains are focused during flexion and extension. Excessive vertical load-bearing can result in the development of osteophytes along the entire margin of the vertebral body. This is the vertebral body trying to expand its articular surface area in order to distribute axial loads over a wider area, and therefore lessening the stress applied to the AF during load. In other words, osteophytosis is a natural response to the altered biomechanics of the lumbar spine that are itself due to biochemical changes in the disc. It is not a disease but rather an expected morphological change with age. | ||
The terms osteoarthrosis and degenerative joint disease refer to changes seen in the facet joints. However again, these are morphological consequences of stresses applied to the facet joints over time. The changes are found in regions of greatest and repeated stresses. These are adaptive changes, the structure remodels to account for the applied stresses. However, with severe or repeated stresses, destructive features may occur. | The terms osteoarthrosis and degenerative joint disease refer to changes seen in the facet joints. However again, these are morphological consequences of stresses applied to the facet joints over time. The changes are found in regions of greatest and repeated stresses. These are adaptive changes, the structure remodels to account for the applied stresses. However, with severe or repeated stresses, destructive features may occur. |
Revision as of 17:59, 26 April 2021
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 |
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Proteoglycans |
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Collagen |
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Elastic fibres |
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Non-collagenous proteins |
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Water content |
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Structural Changes
Feature | Change |
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Viable cells |
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NP and AF distinction |
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NP changes |
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Collagen lamellae |
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Tensile strength |
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Intervertebral disc height |
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Vertebral Endplate Changes
Age | Changes |
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Newborn |
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Age 10-15 |
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Age 17-20 |
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Age 20-65 |
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Vertebral Body Changes
Feature | Change |
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Bone Density |
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Vertical trabeculae |
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Horizontal trabeculae |
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Cortical bone |
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Microfractures |
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(Schmorl's nodes) |
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Facet Joint Changes
Header text | Header text |
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Subchondral bone |
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Articular cartilage |
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Posterior joint |
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Cell hypertrophy |
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Osteophytes |
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Movement Changes
The biochemical and structure changes that occur have an effect on the mechanical properties and movements of the spine.
Changes | |
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Creep and hysteresis |
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Range of motion |
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Spondylosis and Degenerative Joint Disease
Spondylosis refers to the development of osteophytes along the junction of vertebral bodies and their intervertebral discs. Spondylosis is not a disease but a natural consequence of the stresses applied to the spine throughout life. They are reactive and adaptive changes that are due to compensation of biomechanical aberrations. It is an active and purposeful process, not a degenerative one.
With age, the NP becomes less resilient and stiffer, and the AF bears more of the compressive loads applied to the disc. Adaption occurs with the greater loads. Excessive compression can result in ossification of the terminal ends of the collagen fibres of the AF. This ossification can occur in the anterior and posterior margins of the disc where compressive strains are focused during flexion and extension. Excessive vertical load-bearing can result in the development of osteophytes along the entire margin of the vertebral body. This is the vertebral body trying to expand its articular surface area in order to distribute axial loads over a wider area, and therefore lessening the stress applied to the AF during load. In other words, osteophytosis is a natural response to the altered biomechanics of the lumbar spine that are itself due to biochemical changes in the disc. It is not a disease but rather an expected morphological change with age.
The terms osteoarthrosis and degenerative joint disease refer to changes seen in the facet joints. However again, these are morphological consequences of stresses applied to the facet joints over time. The changes are found in regions of greatest and repeated stresses. These are adaptive changes, the structure remodels to account for the applied stresses. However, with severe or repeated stresses, destructive features may occur.
The most pivotal reason that all these changes are not diseases, is the fact that they are irregularly associated with pain and disability. There is no correlation between spondylosis and osteoarthrosis in patients with or without symptoms. There is some additional factor that must be the cause of pain.
References
These are study notes taken from Chapter 13 of:
- Bogduk, Nikolai. Clinical and radiological anatomy of the lumbar spine. Edinburgh: Elsevier/Churchill Livingstone, 2012.