The Lumbar Spine And Associated Disorders Flashcards
Vertebral Column
The vertebral column extends from the skull to the apex of the coccyx.
Approximately a quarter of the length is derived from the intervertebral discs, with remainder from the vertebrae and sacrum.
In total there are seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae, five sacral vertebrae and four coccygeal vertebrae.
5 lumbar, 5 sacral, 4 coccygeal - All capable of individual movement - Mobile Lumbar
Fused Vertebrae - 9 vertebrae fused to give 2 innominate
structures - Sacrum (fusion of 5 vertebrae) and Coccyx (fusion of 4 vertebrae)
Functions of the vertebral column
The vertebral column provides several functions:
Structure of lumbar vertebra - anterior region
Kidney-shaped Vertebral Body
Largest part of the vertebra
End Plates: superiorly and inferiorly covered with hyaline cartilage
Main weight bearing part of the vertebra ( 80%)
• 10% Cortical bone good
• 90% Cancellous bone - good at resisting compression + lightweight + haemonpoeisis
Linked to adjacent vertebral bodies by intervertebral discs
(IVD good for shock absorbing)
The size of the vertebrae increases from superior to inferior in order to resist the increasing compressive load from the structures above.
Structure of a lumbar vertebra - posterior
The vertebral arch provides a protective tunnel in which the spinal cord runs
Gap that spinal cord runs in is called the vertebral foramen - also contains conus medulla is, cauda equina, meninges, epidural veins and spinal arteries
Vertebral arch is formed of two pedicles and two laminae. The lamina (plural laminae) connects the transverse process to the spinous process.
The pedicle connects the transverse process to the vertebral body.
The transverse and spinous processes provide attachment points for muscles and ligaments to control the position of the vertebral bodies. Their shape provides an arm to provide system with mech adv
The inferior articular processes (or inferior articular facets) project caudally, and the superior articular processes (or superior articular facets) project in a cephalic direction.
These articulate with the adjacent vertebrae and therefore provide a mobile joint that contributes to the overall movement of the spine.
When two adjacent vertebrae are in their normal anatomical alignment, the space created on each side is referred to as the intervertebral foramen. This foramen allows passage of the spinal nerves from the spinal canal to the periphery.
The zygapophyseal (or facet) joint formed between adjacent superior and inferior articular processes is a synovial joint, lined with hyaline cartilage
Orientation, movements and joints of the Lumbar spine
The amount of fuel ion and rotation permissible at the facet joints is determined by the inclination of the articulating surfaces
Perpendicular to axial (transverse) plane
At 45° to coronal plane, therefore flexion and extension are possible
Superior articular facet faces posteromedially
Inferior articular facet faces anterolaterally
This allows for a limited range of - Flexion and Lateral flexion, extension and Rotation
Fibrous: Non-mobile e.g. sacroiliac joint Secondary cartilaginous (symphyses): Partially mobile e.g. intervertebral discs Synovial Joints: Highly mobile e.g. facet joints
Intervertebral discs
Account for 25% of the length of the vertebral column
Disc height changes throughout day
Disc height changes with age
70% water, 20% collagen, 10% proteoglycans
Consist of two regions:
Ligaments of the vertebral column
The major ligaments are the anterior longitudinal and posterior longitudinal ligaments.
These lie immediately anterior and posterior to the vertebral bodies (not the spinous processes!).
The anterior longitudinal ligament is stronger than the posterior longitudinal ligament, runs from C1 to sacrum - over the IVD it’s loosely attached - function - prevent hyper extension of vertebral column
The posterior longitudinal ligament runs from the C2 vertebra to the sacral canal. It prevents hyperflexion of the vertebral column. Its main relevance clinically is that it reinforces the annulus fibrosus centrally so that intervertebral disc prolapse tends to occur lateral to the posterior longitudinal ligament (paracentral disc prolapse)
The ligamentum flavum has a high elastin content and appears yellow to the naked eye. It is situated between the laminae of adjacent vertebrae and becomes stretched during flexion of the spine.
The interspinous ligaments are relatively weak sheets of fibrous tissue that unite the spinous processes along their adjacent borders. They are most highly developed in the lumbar region, where they increase the stability of the vertebral column by resisting hyperflexion. They fuse posteriorly with the supraspinous ligament which runs along the tips of the adjacent spinous processes.
The supraspinous ligament is a strong band of fibrous tissue. It is lax in extension and taught in flexion, further increasing the stability of the vertebral column.
Change in force transmission with age
As we flex the spine, the posterior longitudinal ligament, ligamentum flavum, interspinous ligament and supraspinous ligament are all under tension.
The vertebral bodies, intervertebral discs and anterior longitudinal ligament are under compression.
When we are young, 80% of our body weight is transmitted through the vertebral bodies and 20% through the facet joints.
As we age, the nucleus pulposus dehydrates and decreases in size. A greater proportion of the load is therefore borne through the facet joints e.g. 65% vertebral bodies, 35% facet joints.
This increased stress on facet joints leads to OS changes - similar to in the knee
Sacrum and Coccyx
Sacrum consists of 5 fused vertebrae
Articulates with L5 superiorly, ilium laterally, and coccyx inferiorly
Spinal nerves exit spinal canal via the sacral foramina and sacral hiatus
Coccyx consists of 4 fused vertebrae
Evolutionary remnant of the
Patterns of spinal curvature
Different types of spinal curvature - also seen in fetus
Pregnant woman
The vertebral column in the fetus is C-shaped, concave anteriorly (kyphosis). This is known as the primary curvature and is retained throughout life in the thoracic, sacral and coccygeal regions.
When the young child begins to lift its head the cervical spine develops a posterior concavity (lordosis).
During crawling, the lumbar spine loses its primary kyphosis and straightens out. When the child begins to stand up and walk, a lumbar lordosis develops (figure 2.38).
The cervical and lumbar lordosis are the secondary curvatures. These secondary curvatures develop primarily due to the intervertebral discs becoming more wedge-shaped.
In the young adult, there are therefore two kyphoses (thoracic and sacrococcygeal) and two lordoses (cervical and lumbar).This sinusoidal profile confers great flexibility and resilience to the spine.
During pregnancy, the additional abdominal mass leads to an exaggeration of the normal lumbar lordosis.
With increasing age, the annulus fibrosis of the intervertebral discs begins to undergo degeneration (because of wear and tear). The nucleus pulposus loses its turgor and becomes thinner because of dehydration and degeneration.
These degenerative processes account for some loss of height. In addition, patients commonly experience osteoporotic vertebral compression fractures, resulting in wedge-shaped vertebrae.
Disc atrophy, with or without accompanying osteoporotic fractures, means that the secondary curvatures start to disappear, and a continuous primary curvature is re- established. This is the ‘senile kyphosis’.
Centre of gravity
The centre of gravity of the body is projected into the lower limbs through a line that passes centrally through the natural curvatures of the vertebral column.
The sacral vertebrae are fused, widened and concave anteriorly to transmit the weight of the body through the pelvis to the lower limbs. The curvatures of the spine are balanced to aid walking and to prevent falling.
In an adult standing erect, the centre of gravity of the body passes through the vertebral column at four sites C1/2, C7/T1, T12/L1 and L5/S1.
These are the ‘weak points’ of the vertebral column at which pathology tends to develop.
Investigations
The X-ray below shows features consistent with ageing, such as loss of disc height and the formation of osteophytes (bony spurs) on the margin of the vertebral end-plates
CT scan gives a more detailed image of the bony structures than a plain X-ray. It can also produce images in multiple planes.
Magnetic resonance imaging (MRI) makes it possible to see many abnormalities in the spine that cannot easily be seen using other modalities e.g. tumours, infections, disc herniations and narrowing of the spinal canal (which is called stenosis)
Finally, isotope bone scans can be used to identify an inflammatory process (such as a spinal tumour or infection) or an occult fracture (small fracture not visible on X- ray) as the cause of back pain. They can also be used to identify sites where a primary tumour has metastasised to bone.
Mechanical back pain
Mechanical back pain is extremely common.
50% of the UK population report lumbar back pain for at least 24 hours in any one year; half of those episodes last > 4 weeks.
80% of the UK population will experience lumbar back pain lasting >24 hours in their lifetime. It is characterised by pain when the spine is loaded, that worsens with exercise and is relieved by rest.
Risk factors include obesity, poor posture, a sedentary lifestyle with deconditioning of the paraspinal (core) muscles, poorly-designed seating and incorrect manual handling (bending and lifting) techniques.
Degeneration changes in the vertebral column - disc degeneration and marginal osteophytosis
The nucleus pulposus of the intervertebral discs dehydrates with age. This leads to a decrease in the height of the discs, bulging of the discs and alteration of the load stresses on the joints.
Osteophytes (bony spurs) develop adjacent to the end plates of the discs. This is known as marginal osteophytosis.
Increased stress is also placed on the facet joints, which also develop osteoarthritic changes.
The facet joints are innervated by the meningeal branch of the spinal nerve, so arthritis in these joints is perceived as painful.
As the disc height decreases and arthritis develops in the facet joints and vertebral bodies, the intervertebral foramina decrease in size. This can lead to compression of the spinal nerves and is perceived as radicular or nerve pain.
Herniation of an IVD i.e. slipped disc
‘Slipped disc’ is common. Pain occurs due to herniated disc material pressing on a spinal nerve. The most common age group is 30-50 years and 90% of cases resolve by 3 months.
There are four stages of disc herniation that you need to be aware of
- Disc degeneration: chemical changes associated with ageing cause discs to dehydrate and bulge
- Prolapse: Protrusion of the nucleus pulposus occurs with slight impingement into the spinal canal. The nucleus pulposus is contained within a rim of annulus fibrosus
- Extrusion: The nucleus pulposus breaks through the annulus fibrosus but is still contained within the disc space
- Sequestration: The nucleus pulposus separates from the main body of the disc and enters the spinal canal.
