Regenerative spine terminology can be confusing for patients navigating chronic disc pain. This glossary defines core concepts — from annulus fibrosus and discogenic pain to intra-annular fibrin injection and biologic disc repair — to help you have more informed conversations with your care team. Individual evaluation always determines whether any treatment is appropriate for your condition.

Spine Anatomy Terms

Annulus Fibrosus

The annulus fibrosus is the strong, fibrous outer ring of an intervertebral disc, essential for spinal stability. Composed of multiple layers of collagen, it encases the disc’s softer, gel-like center. When intact, it helps contain the nucleus pulposus and absorbs spinal loads. Tears in this outer layer — often caused by injury or age-related degeneration — are a primary source of chronic back pain. These tears can allow inflammatory chemicals to leak out and irritate nearby nerves, making them a target for regenerative treatments designed to seal and support the damaged structure.

Nucleus Pulposus

The nucleus pulposus is the soft, gel-like core at the center of each intervertebral disc. Primarily composed of water and proteoglycans, it acts as the disc’s main shock absorber, distributing pressure across the vertebrae during movement and activity. When the surrounding annulus fibrosus develops tears, the nucleus pulposus may bulge or extrude through those openings, potentially contributing to disc herniation and nerve compression — with symptoms and severity that vary by individual case.

Intervertebral Disc

An intervertebral disc is the cushion-like structure found between each vertebra in your spine, functioning as both a shock absorber and a flexible spacer. Each disc consists of the tough outer annulus fibrosus and the gel-like inner nucleus pulposus. Over time or following injury, discs can degenerate, potentially leading to tears, bulges, and herniations. Addressing disc health is central to treating many forms of chronic back pain and restoring spinal function.

Common Disc Conditions

Annular Tear

An annular tear is a rip or fissure in the annulus fibrosus — the strong outer ring of an intervertebral disc. These tears are a frequent contributor to chronic back pain, as they can expose nerve endings within the disc to inflammatory chemicals from the nucleus pulposus or allow internal disc pressure to stress surrounding structures. Because discs have a limited blood supply, annular tears often struggle to heal on their own. Biologic disc repair approaches aim to seal these tears, potentially reducing leakage and supporting the body’s natural healing response — though outcomes vary by individual case. For a detailed look at how annular tears drive chronic disc pain, see annular tears as a root cause of back pain and the role of annular tear repair.

Degenerative Disc Disease (DDD)

Despite its name, Degenerative Disc Disease (DDD) is not a disease in the traditional sense — it describes a condition in which spinal discs naturally break down over time due to aging, cumulative wear, or injury. This degeneration typically involves discs losing hydration, height, and flexibility, which can lead to annular tears, bone spurs, and instability. Many people with DDD experience no symptoms, while others may find it a significant source of chronic back pain that worsens with sitting or bending. Candidates are evaluated individually to determine whether regenerative disc repair may be an appropriate option.

Herniated Disc

A herniated disc occurs when the nucleus pulposus — the soft, gel-like center of a spinal disc — pushes through a tear in the annulus fibrosus. The displaced disc material may press on nearby spinal nerves or the spinal cord, potentially causing sharp pain, numbness, tingling, or weakness that radiates into the arms or legs. Often referred to as a ruptured or slipped disc, a herniation requires careful diagnostic evaluation to determine whether disc-level changes are the primary pain source and whether regenerative approaches may be appropriate for a given patient.

Bulging Disc

A bulging disc describes a condition in which the intervertebral disc extends beyond its normal boundaries, but the annulus fibrosus remains intact without a complete tear. The disc material spreads outward — often uniformly — rather than extruding through a localized defect. While generally considered less severe than a herniation, a bulging disc can still cause significant discomfort in some patients if it compresses spinal nerves or contributes to spinal stenosis. Whether regenerative approaches are appropriate depends on individual evaluation of disc pathology and symptom presentation.

Discogenic Pain

Discogenic pain is a specific type of chronic back pain that originates directly from a damaged intervertebral disc, rather than from nerve compression outside the disc. It often results from annular tears that allow inflammatory chemicals to escape and irritate nerve endings inside the disc or in surrounding tissues. Patients frequently describe discogenic pain as a deep, aching sensation in the lower back that worsens with sitting, bending, or lifting. Accurate diagnostic confirmation of discogenic pain is a prerequisite for evaluating candidacy for biologic disc repair.

Radiculopathy

Radiculopathy refers to symptoms caused by compression or irritation of a spinal nerve root as it exits the spinal column. Depending on the level affected, symptoms may include pain, numbness, tingling, or weakness radiating along the nerve’s pathway — into the arms (cervical radiculopathy) or legs (lumbar radiculopathy). Common causes include herniated discs, bulging discs, bone spurs, and spinal stenosis. When disc pathology is identified as the source, intra-annular fibrin injection may be evaluated as a potential treatment option during individual consultation.

Sciatica

Sciatica is a form of radiculopathy characterized by pain that radiates along the path of the sciatic nerve — from the lower back through the buttocks and down one leg. It typically affects one side of the body. Symptoms can range from a mild ache to a sharp, burning sensation, often accompanied by numbness, tingling, or muscle weakness in the affected leg. A common disc-related cause is a herniated or bulging lumbar disc pressing on the nerve roots that form the sciatic nerve. Regenerative disc treatment may address the underlying disc problem in suitable candidates; outcomes are evaluated individually. See also: 10 myths about sciatica and non-surgical relief.

Failed Back Surgery Syndrome (FBSS)

Failed Back Surgery Syndrome (FBSS) describes chronic back or leg pain that persists or recurs after one or more lumbar spine surgeries. This condition may arise from continued disc degeneration, scar tissue formation, or incomplete resolution of the original problem. Patients with FBSS are evaluated individually to determine whether non-surgical regenerative alternatives — such as biologic disc repair — may offer a viable path forward for their specific situation. For more context, see 5 things to know about avoiding failed back surgery by considering regenerative disc repair first.

Regenerative Treatment Terms

Fibrin

Fibrin is a naturally occurring protein in blood that plays a central role in clotting and wound healing throughout the body. When tissue is injured, fibrin forms a mesh-like scaffold that helps stop bleeding and supports new cell growth and repair. In biologic disc repair, purified fibrin is precisely injected into annular tears to act as a biologic seal and healing scaffold. This may support the disc’s natural repair mechanisms and help restore disc integrity in appropriate candidates — though individual responses vary and outcomes are not guaranteed.

Intra-annular Fibrin Injection

An intra-annular fibrin injection is a minimally invasive regenerative procedure in which fibrin — a natural healing protein — is injected directly into tears within the annulus fibrosus under advanced imaging guidance. The goal is to seal annular tears that contribute to chronic discogenic pain. By creating a biologic scaffold, the fibrin may support the body’s natural healing processes and help restore disc integrity in appropriate candidates. This procedure may offer a non-surgical alternative for patients who meet evaluation criteria; individual outcomes vary by case.

Expert Take

Intra-annular fibrin injection is not appropriate for every presentation of back pain. Our clinical team evaluates each patient’s disc pathology, symptom history, and prior treatment responses before considering this approach. The fibrin procedure targets the disc structure directly — not just the nerve — which is why diagnostic confirmation of true discogenic pain is a required step before any candidacy determination is made.

Annulargram (Discogram)

An annulargram, also known as a discogram, is a specialized diagnostic procedure used to identify and precisely locate tears within the annulus fibrosus. During the procedure, a small amount of contrast dye is injected directly into the disc under fluoroscopic (live X-ray) guidance. If an annular tear is present, the dye outlines its location and extent on imaging. This test is important for confirming whether a patient’s back pain is truly discogenic in origin and whether they may be a suitable candidate for biologic disc repair evaluation.

Regenerative Medicine

Regenerative medicine is a field focused on treatments that support the body’s natural ability to repair or regenerate damaged cells, tissues, or organs. Rather than managing symptoms in isolation or removing damaged structures, regenerative approaches aim to address underlying causes of chronic pain. In spine care, techniques like intra-annular fibrin injection target disc damage at its source. Our clinical team applies these principles to offer non-surgical options for patients who qualify — with candidacy determined through thorough individual evaluation.

Intradiscal Injection

An intradiscal injection is any medical procedure in which a therapeutic substance is delivered directly into the nucleus pulposus or annulus fibrosus of an intervertebral disc. Unlike epidural injections, which deliver medication around the nerve space, intradiscal injections target the disc itself. This precise delivery method is central to intra-annular fibrin injection, allowing therapeutic agents to reach internal disc damage directly. Accuracy in intradiscal procedures is critical to their potential effectiveness in regenerative disc repair applications.

Explore More

For additional terminology, explore our companion glossaries: spine anatomy and disc conditions, diagnostic imaging and evaluation, spinal surgery and its alternatives, and pain management and rehabilitation terminology.