Lumbar Disc Injury Flashcards
Definition/Description
Lumbar disc herniation (LDH) is a common low back disorder. It is one of the most common diseases that produces low back pain and/or leg pain in adults[1]., A herniated disc is a displacement of disc material (nucleus pulposus or annulus fibrosis) beyond the intervertebral disc space.
This herniation process begins from failure in the innermost annulus rings and progresses radially outward. The damage to the annulus of the disc appears to be associated with fully flexing the spine for a repeated or prolonged period of time. The nucleus loses its hydrostatic pressure and the annulus bulges outward during disc compression.
Other names used to describe this type of pathology are: prolapsed disc, herniated nucleus pulposus and discus protrusion
Clinically Relevant Anatomy
In disc herniation, it is the intervertebral disc that causes the problem. The disc consists of the annulus fibrosus (a complex series of fibrous rings) and the nucleus pulposus (a gelatinous core containing collagen fibers, elastin fibers and a hydrated gel)[7]. The vertebral canal is formed by the vertebral bodies, intervertebral discs and ligaments on the anterior wall and by the vertebral arches and ligaments on the lateral wall. The spinal cord lies in this vertebral canal
A tear can occur within the annulus fibrosus. The material of the nucleus pulposus can track through this tear and into the intervertebral or vertebral foramen to impinge neural structure. A disc herniation can cause mechanical irritation of these structures which in turn can cause pain. This is presented as low back pain with possible radiculopathy if a nerve is affected. The disc can protrude posteriorly and impinge the roots of the lumbar nerves or it can protrude posterolaterally and impinge the descending root
A disc has few blood vessels and some nerves. These nerves are mainly restricted to the outer lamellae of the annulus fibrosus. In the lumbar region, the level at which a disc herniates does not always correlate to the level of nerve root symptoms. When the herniation is in the posterolateral direction the affected nerve root is the one that exits at the level below the disk herniation. This is because the nerve root at the hernia-level has already exited the transverse foramen. A foraminal herniation on the other hand affects the nerve root that is situated at the same level
There are four types of herniated discs
- Bulging:extension of the disc margin beyond the margins of the adjacent vertebral endplates
- Protrusion:the posterior longitudinal ligament remains intact but the nucleus pulposus impinges on the anulus fibrosus
- Extrusion:the nuclear material emerges through the annular fibers but the posterior longitudinal ligament remains intact
- Sequestration:the nuclear material emerges through the annular fibers and the posterior longitudinal ligament is disrupted. A portion of the nucleus pulposus has protruded into the epidural space
Epidemiology /Etiology
The prevalence of a symptomatic herniated lumbar disc is about 1% to 3% with the highest prevalence among people aged 30 to 50 years, with a male to female ratio of 2:1. In individuals aged 25 to 55 years, about 95% of herniated discs occur at the lower lumbar spine (L4/5 and L5/S1 level); disc herniation above this level is more common in people aged over 55 years
Tears are most frequent postero-lateral because of the absence of the anterior/posterior longitudinal ligament, where the annulus fibrosis is thin. Previously existing disc protrusion are often prior to disc herniation.
The outermost layers of the fibrous ring are still intact and none of the central portion escapes beyond the outer layers. But with the amount of pressure rising on the disc, bulging is possible. Disc herniation is also referred to as a slipped disc, but medically not accepted as spinal discs cannot “slip” out of place because they are firmly attached to the vertebrae. The most common cause is degeneration of the intervertebral disc while trauma is a less common cause of disc herniation[17]. Both degenerative disc disease and aging can result in disc degeneration[18]. Type I collagen (sp1 site), type IX collagen, Vitamin D receptor, aggrecan, asporin, MMP3, interleukin -1 and interleukin-6 polymorphisms are candidate genes that are responsible for disc degeneration[19].
Lumbar disc herniation is partly due to mutation in genes coding proteins which regulate the extracellular matrix (MMP2,THBS2)[20].Chronic or suddenly forced hyperflexion or torsion can also cause a disc hernia, but mostly there are no specific inciting events. Other possible risk factors can be a whiplash, poor posture, obesity, heavy work, gender,smoking and occupational risks such as driving for a long time
Characteristics/Clinical Presentation
In a study using provocative discography for symptom mapping, Slipman et al showed that unilateral symptoms were found just as often as bilateral symptoms
Activities that increase intradiscal pressure (eg, lifting, Valsalva manoeuvre) intensify symptoms. Conversely, lying supine provides relief by decreasing intradiscal pressure.
Vibrational stress from driving can also exacerbate discogenic pain. Yates et al showed that vibration and shock loading provided sufficient mechanical injury to exacerbate pre-existing herniation, whereas a flexed posture did not influence the distance of nucleus pulposus tracking
Lower radiculopathies (first sacral level) cause pain in the calf and bottom of the foot. Fifth lumbar radiculopathy, which occurs most commonly, causes lateral and anterior thigh and leg pain. Often, accompanying numbness or tingling occurs with a distribution similar to the pain.
Describe the Leves L1 - S1, associated areas and reflexes associated
L1 Inguinal region- Hip flexors
L2 Anterior mid-thigh -Hip flexors
L3 -Distal anterior thigh
- Hip flexors and knee extensors
- Diminished or absent patellar reflex
L4 -Medial lower leg/foot
- Knee extensors and ankle dorsiflexors
- Diminished or absent patellar reflex
L5 - Lateral leg/foot
- Hallux extension and ankle plantar flexor
- Diminished or absent achilles reflex
S1 -Lateral side of foot
- Ankle plantar flexors and evertors
- Diminished or absent achilles reflex
A study on Lateral vs Medial herniation showed -
Lateral and medial disc herniation Jung Hwan Lee etal. describes how lateral disc herniation (foraminal and extra foraminal) has clinical characteristics that are different from those of medial disc herniation (central and subarticular), including older age, more frequent radicular pain, and neurologic deficits.
This is supposedly because lateral disc herniation mechanically irritates or compresses the exiting nerve root or dorsal root ganglion inside of a narrow canal more directly than medial disc herniation. The lateral group showed significantly larger proportion of patients with radiating leg pain and multiple levels of disc herniations than the medial group. No significant differences were found in terms of gender proportions, duration of pain, pre-treatment NRS, severity of disc herniation, and presence of leg muscles’ weakness.
The proportion of patients who underwent surgery was not significantly different between both groups. However, the proportion of patients who accomplished successful pain reduction after treatment was significantly smaller in the lateral than the medial group
