Current Concepts in the Diagnosis and Treatment of Lumbar Degenerative Disc Disease
Pathogenesis: There is a strong genetic component to degenerative disc disease (DDD), with studies identifying the following genes as involved in the pathogenesis of DDD: genes that code for collagens I, IX, and XI, interleukin 1, aggrecan, the vitamin D receptor, matrix metalloproteinase 3, and other proteins.
Aging and environmental factors also are components in the pathogenesis of DDD. With aging, the process of DDD starts with a decrease in intervertebral disc and fissures in the nucleus pulposus that may extend into the annulus fibrosus. Environmental factors that appear to be risk factors for DDD include smoking and manual jobs that require frequent bending, twisting, and whole-body vibration.
Clinical Presentation: Patients with DDD of the lumbar spine typically present with symptoms of pain, radiculopathy, and weakness. Symptoms often worsen with flexion of the spine and are relieved with extension. The differential diagnosis should include exclusion of abdominal pathology (eg, aortic aneurysms, pancreatic disease, and renal calculi) as well as checking for such symptoms as fevers, chills, fatigue, and weight loss, which are suggestive of other pathology.
Diagnosis: Initially, upright plain radiographs in two planes are used to rule out other potential causes of back pain (eg, deformity, fracture, or metastatic cancer). These radiographs are typically used in combination with other imaging modalities to look for signs of degeneration.
Magnetic resonance imaging (MRI) is more sensitive than radiography for diagnosis of DDD. However, findings on both plain radiographs and MRI may not be associated with clinical symptoms. Thus, discography has been used to identify degenerated discs as the cause of pain symptoms; however, this technique has been shown to have a high false-positive rate (up to 25%) and may accelerate disc degeneration.
Treatment: While spinal fusion surgery is a treatment for low back pain, the efficacy of this procedure is controversial. Fusions do not address the cause of DDD, but are used to alleviate discogenic pain. Studies suggest that fusions may lead to changes in motion in adjacent segments and eventually degeneration. Thus, motion preserving procedures to prevent changes in adjacent segments are now used including disc arthroplasty and posterior dynamic stabilization; however, longer-term results showing the efficacy of these motion-preserving techniques are needed.
Long-term studies are also needed for noninvasive options directed at reversing disc degeneration, including biologic growth factors, stem cells, and gene transplant.
This is an excellent review article on the state of lumbar disc disease, including pathogenesis, clinical presentation, diagnosis, and treatment options.
The authors discussed the role that aging, as well as genetic and environmental factors, plays in disc degeneration, including the genes that code for collagens 1, IX, XI. The authors compare and contrast the various treatment options, including disc regeneration therapy, whether it be cell based, growth factor, or gene therapy.
This article is helpful in defining the current state of disc degeneration and regeneration.