Understanding spine terminology helps patients participate actively in their care decisions. This glossary defines key terms in disc anatomy, common conditions such as annular tears and degenerative disc disease, and non-surgical treatment approaches including biologic disc repair and intra-annular fibrin injection. Definitions reflect general anatomy and clinical concepts; individual presentations and outcomes vary.

Annulus Fibrosus

The annulus fibrosus is the tough, fibrous outer ring of an intervertebral disc, structured from approximately 17 concentric layers of collagen fibers. Its primary role is to contain the nucleus pulposus — the gel-like center of the disc — and to provide structural integrity and resistance against twisting forces. When this outer layer sustains damage, such as an annular tear, it can compromise the disc’s shock-absorbing function and may become a significant source of chronic back pain in affected patients. Tears can also allow inflammatory chemicals from the disc’s interior to reach nearby spinal nerves, contributing to discomfort and potential progression of degenerative disc disease.

Nucleus Pulposus

The nucleus pulposus is the soft, gel-like core at the center of each intervertebral disc. Composed largely of water, it acts as the disc’s primary shock absorber, distributing pressure across the vertebrae during movement, bending, and lifting. It is encapsulated by the tougher annulus fibrosus. When an annular tear occurs, the nucleus pulposus can begin to bulge or herniate through the tear and may press on nearby spinal nerves. This compression can produce pain, numbness, or weakness in the arms or legs, depending on the location of the affected disc and nerves.

Intervertebral Disc

Intervertebral discs are the cushion-like structures located between each vertebra in the spinal column. Acting as natural shock absorbers, they protect the vertebrae from the impact of daily activities and movement. Each disc comprises two main parts: a tough outer ring called the annulus fibrosus and a soft, gel-like inner core known as the nucleus pulposus. Healthy discs allow the spine to bend, twist, and flex. Over time, discs can degenerate, lose hydration, or sustain injuries such as tears, leading to conditions including discogenic pain, herniation, or bulging discs — frequent contributors to chronic back and neck pain.

Annular Tear

An annular tear is a rip or fissure in the annulus fibrosus, the outer layer of an intervertebral disc. These tears vary in size and depth, ranging from small cracks to ruptures that extend through multiple layers. Annular tears can cause pain directly through nerve endings within the outer annulus, and they create pathways for inflammatory proteins from the nucleus pulposus to reach surrounding nerves. They are a frequent contributor to chronic low back pain and, in many cases, require specialized diagnostic testing to pinpoint the source and guide targeted care such as annular tear repair.

Degenerative Disc Disease (DDD)

Despite its name, degenerative disc disease (DDD) describes a process rather than a distinct disease — the progressive breakdown of spinal discs over time. This process involves discs losing height and hydration, becoming less flexible, and developing small tears or cracks in the annulus fibrosus. It is part of normal aging, and not everyone with DDD experiences pain. For patients who do, symptoms can include chronic back or neck pain, stiffness, or radiating pain if a disc presses on a nerve. Care at ValorSpine focuses on addressing underlying disc damage — for example, through biologic disc repair — rather than symptom management alone.

Herniated Disc

A herniated disc occurs when the soft nucleus pulposus pushes through a tear in the annulus fibrosus, extending beyond the normal disc boundary. This condition is sometimes called a ruptured disc or slipped disc. When herniated material presses on nearby spinal nerves, it can cause pain, numbness, tingling, or weakness in the areas supplied by that nerve — such as sciatica in the leg or radiculopathy in the arm. Unlike a bulging disc, where disc material remains contained, a herniation involves actual displacement of disc material outside the annular boundary. Regenerative treatments aim to repair the annular tear, support disc integrity, and reduce nerve-related symptoms in appropriate candidates; outcomes vary by case.

Bulging Disc

A bulging disc is a spinal condition in which the intervertebral disc extends beyond its normal perimeter, creating a generalized protrusion of the disc’s outer wall. Unlike a herniated disc, where the nucleus pulposus breaks through the annulus, in a bulging disc the material stays contained within the outer annular layers — though those layers may push outward. A bulging disc is not always symptomatic, but in some patients it can cause pain by pressing on adjacent nerves, the spinal cord, or other spinal structures. Symptoms may include localized back pain, radiating pain, numbness, or tingling. Non-surgical approaches focus on reducing inflammation and supporting disc health.

Sciatica

Sciatica is a type of radiating pain that follows the path of the sciatic nerve — the longest nerve in the body. Originating in the lower back, the pain travels through the buttock and down the back of one leg. Sciatica is a symptom rather than a standalone condition, most commonly arising from a herniated disc, bulging disc, or bone spur compressing part of the sciatic nerve. Patients describe the pain as shooting, sharp, or burning, and it may be accompanied by numbness, tingling, or weakness in the affected leg or foot. Non-surgical treatments are evaluated individually, aiming to relieve nerve pressure and reduce inflammation. For more context, see our overview of common myths about sciatica and non-surgical relief.

Radiculopathy

Radiculopathy describes a condition in which a spinal nerve root is compressed or irritated, producing symptoms that radiate along the nerve’s pathway. These can include pain, numbness, tingling, or weakness in the limb or area served by the affected nerve. Compression in the neck (cervical spine) causes cervical radiculopathy, affecting the arms and hands; compression in the lower back (lumbar spine) causes lumbar radiculopathy, affecting the legs and feet. Common causes include herniated discs, bulging discs, bone spurs, or spinal stenosis. Addressing the root structural cause — such as an underlying annular tear — is a key focus for achieving lasting relief, though outcomes vary by patient.

Discogenic Pain

Discogenic pain refers to pain that originates directly from a damaged or degenerated intervertebral disc, rather than from nerve compression. This type of pain is felt in the lower back or neck and is aggravated in many patients by activities that increase disc pressure — sitting, bending, lifting, or prolonged standing. The pain stems from internal disc disruption or tears within the annulus fibrosus, which contains nerve endings that can become sensitized. Diagnosing discogenic pain involves a process of clinical exclusion and sometimes specialized testing to confirm the disc as the primary pain source, making it a candidate for targeted treatments such as fibrin disc treatment.

Fibrin

Fibrin is a naturally occurring protein in the blood that plays a central role in wound healing and tissue repair. When an injury occurs, fibrin polymerizes to form a mesh-like scaffold that helps stop bleeding and provides a structural framework for cell growth and tissue repair. In the context of regenerative disc treatment — such as intra-annular fibrin injection — fibrin is prepared and delivered directly into annular tears within the spinal disc. Its adhesive and biologic properties help seal the tear, limit further leakage of disc material, and create a supportive environment that may encourage the disc’s natural healing response.

Intra-annular Fibrin Injection

Intra-annular fibrin injection is a minimally invasive regenerative treatment for chronic back pain caused by annular tears in the intervertebral discs. The procedure involves injecting fibrin — a natural blood protein involved in healing — directly into the damaged annulus fibrosus. The fibrin functions as a biologic seal for the tear, limiting the leakage of inflammatory chemicals and providing a scaffold that may support tissue regeneration within the disc. This treatment aims to restore disc structural integrity and reduce discogenic pain in suitable candidates. For veterans with service-connected back injuries, it may represent an alternative path to surgery; candidacy is assessed individually.

Expert Take

When our clinical team evaluates candidates for intra-annular fibrin injection, imaging findings are one piece of a larger clinical picture. A confirmatory annulargram that reproduces the patient’s familiar pain pattern is a critical step — it helps ensure treatment targets the actual pain source rather than an incidental imaging finding. Candidacy is assessed individually; not every disc abnormality on imaging corresponds to a patient’s primary pain generator.

Annulargram

An annulargram — also referred to as a discogram — is a specialized diagnostic procedure used to confirm the presence of annular tears and determine whether a specific disc is the source of a patient’s pain. During the procedure, contrast dye is injected directly into the disc under fluoroscopic (live X-ray) guidance. If the dye leaks from the nucleus into the annulus, it reveals the location and extent of a tear. When the injection reproduces the patient’s familiar pain, it identifies that disc as a likely pain generator. This test supports candidacy evaluation for biologic disc repair and guides precise treatment delivery.

Intradiscal Injection

An intradiscal injection is any procedure in which substances are injected directly into the intervertebral disc. This targeted approach differs from epidural injections, which deliver medication into the space surrounding the nerves. Intradiscal injections serve both diagnostic purposes — such as the annulargram, which helps confirm whether a specific disc is the pain source — and therapeutic purposes, such as intra-annular fibrin injection, where biologic materials are delivered to the damaged disc to support healing. Direct delivery helps ensure the therapeutic agent reaches the site of injury.

Regenerative Medicine

Regenerative medicine is a field of healthcare focused on treatments that stimulate the body’s natural healing processes to repair or regenerate damaged tissues. Rather than managing symptoms or removing damaged structures, regenerative therapies aim to address the underlying cause of tissue damage. In spine care, this includes treatments such as fibrin disc treatment, which leverages the body’s own biologic resources to support repair of torn or degenerated intervertebral discs. These approaches represent an evolving area of non-surgical care; outcomes vary by patient and condition. For a broader look at these options, see our disc conditions glossary for patients.