The lumbar spine is the third region of the vertebral column, located in the lower back between the thoracic and sacral vertebral segments. It is made up of five distinct vertebrae, which are the largest of the vertebral column, and it supports the lumbar spine in its main function as a weight bearing structure. This article is going to explore the features, joints and clinical correlations of lumbar vertebrae in more detail.
The lumbar vertebrae may lack some of the more distinguishable features of other vertebrae, but there are some characteristics that help to differentiate them. The vertebral bodies are large and kidney-shaped and they are deeper anteriorly than posteriorly, which results in the lumbosacral angle (the angle between the long axis of the lumbar region and that of the sacrum). The vertebral foramen is triangular in shape, and the transverse processes are long and slender. The articular processes have nearly vertical facets, while the spinous processes are short and broad. There are also accessory processes at the posterior aspect of the base of each transverse process, which act as the sites of attachment for deep back muscles. Additionally, the fifth lumbar vertebrae, L5, has some distinctive features of its own such as a notably large vertebral body and transverse processes as it carries the weight of the entire upper body.
The lumbar spine has two types of joint, which are present throughout the entire vertebral column. The first type of joint is between adjacent vertebral bodies and is known as intervertebral discs, which are made of fibrocartilage and is a type of cartilaginous joint, known as a symphysis. The second type is the joint between vertebral arches formed by the articulation of superior and inferior articular processes of adjacent vertebrae. This is a synovial type joint.
The joints of the lumbar vertebrae are supported by several ligaments, which can be divided into two main groups, those present throughout the vertebral column and those unique to the lumbar spine. The ligaments that occur in the vertebral column include the anterior and posterior longitudinal ligaments, ligamentum flavum, interspinous ligament, and supraspinous ligament. In the cervical spine, these ligaments thicken and combine to form the nuchal ligament. Unique to the lumbar spine are the iliolumbar ligaments which are fan-like ligaments radiating from the transverse processes of the L5 vertebra to the ilia of the pelvis.
Throughout the vertebral column, the spinal cord travels through the vertebral canal (made up by the foramina of all vertebrae). At around the level of L1, the spinal cord terminates and the cauda equina begins, and this is a bundle of lumbar, sacral and coccygeal nerve roots. Additionally, spinal nerves exit the vertebral canal through the intervertebral foramina.
Lumbar spinal stenosis is an abnormality of the lumbar spine which is thought to be hereditary and is characterised by a stenotic (narrow) vertebral foramen in one or several lumbar vertebrae. The effects of this condition vary depending upon the severity of the narrowing, which can lead to symptoms such as pain, tingling, numbness and weakness in the lower limbs.
The lumbar spine is an important part of the vertebral column, made up of five distinct vertebrae. This article has explored the characteristic features, joints and their clinical correlations in more detail. Also, it is important to note and be aware of any abnormal features of the lumbar spine, such as lumbar spinal stenosis, and the effects of this condition.
The vertebral foramen is triangular in structure. It is the opening in the vertebral arch through which the spinal cord passes, forming part of the vertebral canal.
Further to this, the fifth lumbar vertebra, L5, has some distinctive characteristics of its own. It has a notably large vertebral body and transverse processes due to the weight of the entire upper body being carried on it.
The lumbar vertebrae possess two types of joint. These are common to other areas of the vertebral column as well.
The joints of the lumbar vertebrae are supported by several ligaments. These can be divided into two groups; ligaments common throughout the vertebral column, and those unique to the lumbar spine.
The lumbosacral joint (between the L5 and S1 vertebrae) is strengthened by the iliolumbar ligaments. These are fan-like ligaments radiating from the transverse processes of the L5 vertebra, attaching to the ilia of the pelvis.
The spinal cord travels through the vertebral canal from the top of the vertebral column and terminates at around the level of L1. Beyond this, a bundle of lumbar, sacral and coccygeal nerve roots, known as the cauda equina, continues through the vertebral canal. These spinal nerves exit the vertebral canal through the intervertebral foramina.
Lumbar spinal stenosis is thought to be hereditary and results in a stenotic (narrow) vertebral foramen in one or several lumbar vertebrae. This can compress the spinal cord and exiting nerves, and is often worsened by age-related degenerative changes, such as bulging of the intervertebral discs. Treatment of lumbar spinal stenosis sometimes necessitates decompressive laminectomy surgery.
Excessive lumbar lordosis is an abnormal anterior curvature of the vertebral column in the lumbar region, characterised by anterior tilting of the pelvis. Temporary excessive lumbar lordosis can occur in late pregnancy in women, but this resolves after childbirth. Similarly, obesity can cause lordosis due to the increased weight of the abdomen. Both cases can cause back pain as a result of an altered line of gravity.
