Disc herniation is a broad term referring to a tear in the outer ring (annulus, thus allowing the soft gelatinous matter to leak out through the tear.
The intervertebral disc is responsible for the attachment of vertebral bodies to each other, providing flexibility and absorbing and distributing the loads applied to the spinal column. With aging, the disc undergoes significant changes in volume and shape as well as in biochemical composition and properties. Lumbar disc herniations are believed to result from anular degeneration that leads to a weakening of the anulus fibrosus, leaving the disc susceptible to annular fissuring and tearing.
Disc herniation is an important cause of back pain and leg pain. Most patients with a herniated disc can be managed conservatively, though some cases may need interventional treatments including injections and surgery for improvement in pain and preservation or restoration of neurological function.
Several factors, including genetic factors and changes in hydration and collagen play a role in the development of degenerative disc disease. It is widely accepted that the water-binding capability of the nucleus plays an integral role in the physical properties of the disc. In the healthy disc, the nucleus distributes the applied forces equally throughout the annulus. Decreased hydration of the disc can reduce the cushioning effect, thus transmitting a greater portion of the applied loads to the annulus in an asymmetric distribution, which could lead to injury.
The most common levels for a herniated disc are L4-5 and L5-S1. The onset of symptoms is characterized by a sharp, burning, stabbing pain radiating down the posterior or lateral aspect of the leg, to below the knee. Pain is generally superficial and localized, and is often associated with numbness or tingling. In more advanced cases, motor deficit, diminished reflexes or weakness may occur. Low back pain is a commonly present in addition to leg pain.
Specific movements and positions that reproduce the symptoms should be investigated during the examination to help determine the source of the pain. Motor, sensory and reflex function should be assessed to determine the affected nerve root level.
Nerve root tension signs are often used in the evaluation of patients suspected of having a herniated disc. The straight-leg raising test is performed with the patient in the supine position. The physician raises the patient’s legs to approximately 90 degrees. Normally, this position results in only minor tightness in the hamstrings. If nerve root compression is present, this test causes severe pain in the back of the affected leg and can reveal a disorder of the L5 or S1 nerve root.
A crossed straight-leg raising test may also suggest nerve root compression. In this test, straight-leg raising of the contralateral limb reproduces more specific but less intense pain on the affected side. In addition, the femoral stretch test can be used to evaluate the reproducibility of pain. In this test, the patient lies in either the prone or the lateral decubitus position. The thigh is extended at the hip, and the knee is flexed. Reproduction of pain suggests upper nerve root (L2, L3 and L4) disorders.
Red flags are features, signs and symptoms in a patient with back pain which indicate serious spinal pathology. It is important to rule out red flags while evaluating a patient with back pain. Red flags include:
The major finding on plain radiographs of patients with a herniated disc is decreased disc height. Radiographs have limited diagnostic value for herniated disc because degenerative changes are age-related and are equally present in asymptomatic and symptomatic persons.
The gold standard modality for visualizing the herniated disc is magnetic resonance imaging (MRI). As with plain radiographs, MRI can reveal bulging and degenerative discs in asymptomatic persons; therefore, any management decisions should be based on the clinical findings corroborated by diagnostic test results.
While low back pain and radiculopathy can cause significant disability, the majority of patients experience resolution of their symptoms regardless of the treatment method. Most patients with low back pain respond well to conservative therapy, including remaining active, gentle exercise and, in selected cases, injections. Excessive bed rest can result in deconditioning, bone mineral loss and economic loss.
While most patients with a herniated disc may be effectively treated conservatively, some do not respond to conservative treatment or have symptoms that necessitate referral to a surgical specialist. Any surgical decisions should be firmly based on the clinical symptoms and corroborating results of diagnostic testing. Indications for referral include: