Understanding spine terminology may help you have more informed conversations with your care team and evaluate treatment options more confidently. This glossary defines key terms in spinal anatomy, common disc conditions, and regenerative therapies—including biologic disc repair approaches—in clear, patient-friendly language. Outcomes and candidacy vary by individual, so each term is framed accordingly.
Spine Anatomy Terms
Annulus Fibrosus
The annulus fibrosus is the tough, fibrous outer ring of each intervertebral disc. Composed of layered collagen fibers, it surrounds and contains the softer, gel-like nucleus pulposus within. This structure provides critical disc stability and helps withstand the mechanical forces of daily movement. When the annulus fibrosus sustains a tear, inflammatory substances from the disc’s interior may leak out and irritate nearby nerves—often contributing to chronic pain. Repairing these annular tears is a primary focus of advanced biologic disc repair treatments, with the goal of restoring structural integrity and slowing further degeneration.
Nucleus Pulposus
The nucleus pulposus is the soft, gel-like center of each intervertebral disc. Its high water content allows it to distribute pressure evenly across the disc during movement, helping protect the vertebrae from impact. When the annulus fibrosus develops a tear, the nucleus pulposus may begin to bulge or extrude through that opening—potentially pressing on nearby spinal nerves. This extrusion is a hallmark of disc herniation and can lead to pain, numbness, or weakness in some patients. Maintaining the nucleus pulposus within its annular boundaries is important for healthy disc function.
Intervertebral Disc
An intervertebral disc sits between each pair of vertebrae from the neck to the lower back. These structures serve as shock absorbers, cushioning daily activities and enabling spinal flexibility. Each disc is made up of two primary components: the tough outer annulus fibrosus and the gel-like inner nucleus pulposus. Damage or degeneration of these discs—whether from injury, aging, or repetitive stress—is among the most common sources of chronic back and neck pain, making disc health a central focus of both non-surgical and regenerative spine care. Learn more about common lumbar spine conditions causing low back pain.
Foramen (Neural Foramen)
The neural foramen refers to the natural openings on each side of the spinal column through which spinal nerves exit to travel to the limbs and torso. These nerves transmit sensory and motor signals throughout the body. When discs bulge, herniate, or bone spurs develop, these passageways can narrow—a condition called foraminal stenosis. Nerve compression within a narrowed foramen may produce pain, tingling, numbness, or weakness in the areas supplied by the affected nerve. Addressing the underlying disc or structural problem may help relieve this compression in appropriate candidates.
Common Disc Conditions
Annular Tear
An annular tear is a fissure or rip in the annulus fibrosus—the tough outer ring of an intervertebral disc. These tears range from small surface fissures to deeper radial tears that extend into the disc’s interior. Annular tears are a frequent contributor to chronic back pain because they may allow inflammatory chemicals from inside the disc to leak out and irritate spinal nerves. They can also weaken disc structure, potentially predisposing the disc to bulging or herniation. Because discs have a limited blood supply, natural healing of annular tears is often limited. Treatments such as intra-annular fibrin injection are specifically designed to seal and support repair of these tears in suitable candidates. See also: annular tears: causes, symptoms, and regenerative repair options.
Degenerative Disc Disease (DDD)
Degenerative disc disease (DDD) describes a condition in which one or more intervertebral discs break down over time—commonly due to aging, prior injury, or cumulative wear. Despite the name, it is not strictly a disease but a progressive condition characterized by discs losing height, hydration, and elasticity. This degeneration may contribute to discogenic pain, disc bulging, herniation, bone spur formation, and—in advanced cases—spinal stenosis. Some degree of disc degeneration is a natural part of aging; however, for many patients it becomes a significant source of chronic pain and reduced function. Regenerative approaches focus on slowing or addressing aspects of disc degeneration in appropriate candidates. Explore non-surgical options for degenerative disc disease.
Herniated Disc
A herniated disc occurs when the nucleus pulposus pushes through a tear in the annulus fibrosus, extending beyond the disc’s normal boundaries. The extruded material may compress or irritate nearby spinal nerves, potentially causing sharp pain, numbness, tingling, or weakness that radiates into an arm or leg—patterns often called radiculopathy or sciatica. Also referred to as a ruptured or slipped disc, a herniation represents significant structural disruption. Treatment goals typically include reducing nerve compression and supporting healing of the underlying annular tear. See bulging disc vs. herniated disc: understanding your pain.
Bulging Disc
A bulging disc occurs when the intervertebral disc extends beyond its normal perimeter, but the annulus fibrosus remains intact without a full tear that allows the nucleus pulposus to extrude. The disc wall stretches outward, creating a bulge. While generally considered less structurally severe than a herniation, a bulging disc may still cause significant pain in some patients—particularly if it presses on nearby nerves or the spinal cord. It often represents an early stage of disc degeneration and may predispose the disc to future herniation. Regenerative approaches aim to strengthen disc integrity and reduce the bulge in appropriate candidates.
Sciatica
Sciatica is a specific type of radiculopathy characterized by pain that travels along the sciatic nerve’s path—from the lower back through the buttock and down the back of the leg. It is typically caused by compression or irritation of the nerve roots forming the sciatic nerve, most often from a herniated disc, spinal stenosis, or bone spurs. Symptoms may include sharp or shooting pain, numbness, tingling, or muscle weakness in the affected leg. Investigating the root cause of sciatica is essential for selecting an appropriate treatment that addresses the underlying disc or structural issue. Learn more at 10 myths about sciatica and non-surgical relief.
Discogenic Pain
Discogenic pain refers to chronic back or neck pain originating directly from a damaged or degenerated intervertebral disc—from the disc structures themselves rather than from external nerve compression. This type of pain often intensifies with sitting, bending, or lifting, which increase intradiscal pressure. It is frequently associated with annular tears and disc-level inflammation, even when significant nerve impingement is not present on imaging. Confirming a discogenic pain source often involves specialized diagnostic tests such as an annulargram. Regenerative disc treatments are designed to address the internal disc pathology underlying this pain pattern in suitable candidates. See: glossary of key terms in diagnosing disc conditions.
Failed Back Surgery Syndrome (FBSS)
Failed back surgery syndrome (FBSS) describes persistent or recurring chronic back pain—with or without leg pain—that continues after one or more lumbar spine surgeries. This complex condition may arise from scar tissue formation, continued disc degeneration, adjacent segment disease, or an initial diagnosis that did not fully account for all pain generators. For patients experiencing FBSS, advanced non-surgical and regenerative options—including biologic disc repair—may offer a path forward by focusing on tissue healing rather than further invasive procedures. Candidacy is evaluated individually. Explore 5 things to know about avoiding failed back surgery and whether biologic disc repair may be a next step after failed back surgery.
Regenerative Treatment Terms
Fibrin
Fibrin is a natural protein found in the blood that plays a central role in the body’s healing response. When tissue is injured, fibrin forms a mesh-like scaffold that traps blood cells and platelets, creating a clot and initiating repair. In regenerative spine care, fibrin is used for its adhesive and scaffolding properties. In intra-annular fibrin injection procedures, a concentrated fibrin sealant is delivered into a damaged disc to seal annular tears, provide structural support, and encourage the disc’s natural healing processes. This approach draws on the body’s own biology rather than introducing synthetic materials.
Annulargram
An annulargram—sometimes called a discogram or provocative discography—is a specialized diagnostic procedure used to identify whether a specific intervertebral disc is the source of a patient’s chronic back pain, particularly when annular tears are suspected. Under fluoroscopic (live X-ray) guidance, a contrast dye is injected into the center of the disc. If the injection reproduces the patient’s familiar pain and the dye reveals leakage through an annular tear, that disc is confirmed as the likely pain generator. This diagnostic precision is important for determining which patients may be appropriate candidates for targeted interventions such as intra-annular fibrin injection. See diagnostic imaging and evaluation terms for spinal health.
Intra-Annular Fibrin Injection
Intra-annular fibrin injection is a minimally invasive biologic disc repair treatment evaluated for patients with chronic low back pain attributed to symptomatic annular tears or degenerative disc disease. During the procedure, a specialized fibrin sealant is precisely injected into the damaged annulus fibrosus under image guidance. The fibrin acts as a biological scaffold—sealing tears and reinforcing the disc’s structure—while supporting the body’s natural tissue repair processes. Unlike traditional surgical approaches that remove disc material, this treatment aims to restore disc integrity rather than eliminate it. Outcomes vary by patient and candidacy is assessed individually. Learn more: 7 ways biologic disc repair may help chronic back pain and 5 non-surgical disc treatments for chronic back pain.
Regenerative Medicine
Regenerative medicine is a field of healthcare focused on treatments that stimulate the body’s own healing mechanisms to repair or regenerate damaged tissues. Rather than managing symptoms alone or surgically removing affected structures, regenerative therapies aim to restore normal tissue function. In spine care, this approach targets conditions such as degenerative disc disease and annular tears by supporting repair within the intervertebral discs themselves. Approaches such as intra-annular fibrin injection represent an application of regenerative principles—leveraging the body’s biology to address root causes of chronic discogenic pain in appropriate candidates, potentially without invasive surgery. Explore why many patients choose regenerative spine care over traditional operations.
Expert Take
Familiarity with these terms can make a meaningful difference when reviewing imaging reports, discussing diagnoses, or evaluating treatment options. Our clinical team recommends bringing a written list of questions to consultations—knowing the vocabulary helps patients engage more actively in shared decision-making. Candidacy for any treatment discussed here is determined through individual evaluation, and outcomes vary depending on each patient’s anatomy, history, and goals.
For further reading, visit our related glossary resources: key terms in regenerative spine treatment, essential spine anatomy terms for understanding back pain, and spine anatomy and conditions explained for patients.
