Understanding regenerative spine terminology may help you navigate treatment conversations with greater confidence. This glossary explains key terms related to spine anatomy, common conditions, and biologic disc repair options such as intra-annular fibrin injection. Definitions are provided for educational purposes; candidacy and outcomes are always evaluated individually and vary by case.

Spine Anatomy

Annulus Fibrosus

The annulus fibrosus is the tough, fibrous outer ring of an intervertebral disc. Composed of concentric layers of collagen fibers, it encases the disc’s gel-like center (the nucleus pulposus) and provides essential structural stability to the spine. When the annulus fibrosus develops tears or fissures, it can contribute to chronic pain, inflammation, and potential disc herniation. Because the disc has a limited blood supply, these tears often struggle to resolve on their own — which is why the annulus fibrosus is a primary target of annular tear repair approaches in regenerative spine care.

Nucleus Pulposus

The nucleus pulposus is the soft, hydrated, gel-like core of each intervertebral disc. It functions as the spine’s primary shock absorber, distributing compressive loads and enabling flexible movement between vertebrae. When the surrounding annulus fibrosus is compromised by tears, the nucleus pulposus may bulge or extrude outward — a process underlying herniated disc formation. If this material contacts or compresses nearby spinal nerves, patients may experience pain, numbness, or limb weakness. Maintaining nucleus pulposus containment is a central goal of many non-surgical disc treatments.

Intervertebral Disc

An intervertebral disc is the cushion-like structure positioned between each vertebra of the spinal column. Each disc consists of a tough outer annulus fibrosus and a gel-like inner nucleus pulposus. Together, these components absorb shock, distribute spinal loads, and enable flexible movement throughout the back and neck. Damage or degeneration of these discs — from aging, injury, or repetitive stress — is among the most common sources of chronic back pain linked to damaged discs. Treatment plans for many patients center on restoring disc health and structural integrity.

Common Disc Conditions

Annular Tear

An annular tear is a rip or fissure within the annulus fibrosus, the tough outer wall of a spinal disc. These tears are a recognized source of discogenic pain — pain originating directly from the damaged disc rather than from nerve compression alone. When a tear is present, inflammatory proteins from inside the disc may leak outward and irritate adjacent nerve fibers, producing persistent discomfort. Because the disc’s blood supply is limited, annular tears frequently do not heal without intervention. Regenerative options such as intra-annular fibrin injection are specifically designed to address these tears. Learn more about annular tear causes, symptoms, and repair options.

Degenerative Disc Disease (DDD)

Degenerative Disc Disease (DDD) describes the progressive breakdown of one or more intervertebral discs, often associated with the natural aging process. Despite its name, DDD is a condition rather than a true disease. It is characterized by changes such as reduced disc height, loss of hydration, and the development of annular tears. While some degree of disc degeneration is common with age, not all individuals develop symptomatic pain. For those who do, treatment focuses on managing discomfort, improving function, and — in appropriate candidates — exploring regenerative therapies that may help slow progression and support disc health. See our overview of 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. Also called a “ruptured disc” or “slipped disc,” this condition may cause significant pain when extruded disc material compresses or irritates nearby spinal nerves. Symptoms can include localized back pain, radiating leg pain (sciatica), numbness, or limb weakness. Understanding whether a disc is bulging (still contained) versus truly herniated is important for diagnosis, as it influences which non-surgical or biologic disc repair approaches may be appropriate for a given patient.

Discogenic Pain

Discogenic pain is back or neck pain that originates directly from damage or degeneration within an intervertebral disc, rather than primarily from nerve compression. It is often felt as a deep, central ache that intensifies with activities placing pressure on the discs — such as prolonged sitting, bending, lifting, or standing. Unlike radicular pain, discogenic pain does not necessarily radiate into the arms or legs. Identifying discogenic pain typically requires specific diagnostic evaluation, including an annulargram. Treatments such as fibrin disc treatment target the disc’s structural integrity rather than solely addressing nerve inflammation.

Sciatica

Sciatica describes pain, numbness, tingling, or weakness radiating along the path of the sciatic nerve — from the lower back through the buttock and down the back of the leg. Sciatica is a symptom rather than a standalone diagnosis, most commonly caused by a herniated disc or spinal stenosis that compresses a sciatic nerve root. Identifying the underlying source of nerve compression is essential for effective treatment, which may range from physical therapy to advanced regenerative options. Our article on common sciatica myths and non-surgical relief addresses frequent patient misconceptions.

Radiculopathy

Radiculopathy refers to symptoms caused by compression, inflammation, or injury of a spinal nerve root. Depending on the location of the affected nerve root, radiculopathy may produce pain, numbness, tingling, or weakness that radiates into the arms (cervical radiculopathy) or legs (lumbar radiculopathy). Common causes include herniated discs, bone spurs, and spinal stenosis. Identifying the specific nerve root involved guides treatment planning, which may include conservative therapies, targeted injections, or regenerative disc treatments aimed at relieving the underlying source of nerve irritation.

Failed Back Surgery Syndrome (FBSS)

Failed Back Surgery Syndrome (FBSS) is characterized by persistent or recurring chronic pain following one or more spine surgeries. Despite surgical intervention, patients with FBSS continue to experience significant discomfort — often from scar tissue formation, residual nerve compression, spinal instability, or ongoing disc degeneration. FBSS can be particularly challenging because repeat surgery may carry compounding risks. For patients in this situation, non-surgical alternatives such as biologic disc repair after failed back surgery may offer a pathway worth evaluating, with candidacy assessed on an individual basis.

Regenerative Treatment Terms

Fibrin

Fibrin is a naturally occurring protein produced by the body during the clotting and wound-healing process. When injury occurs, fibrin molecules cross-link to form a mesh-like scaffold that stops bleeding and provides a structural framework for new tissue growth. In regenerative disc treatment, fibrin is precisely delivered into a damaged disc during intra-annular fibrin injection. Within the disc, it acts as a biologic sealant for annular tears and creates a natural scaffold intended to support the disc’s own repair cells — potentially promoting healing of the fibrous outer wall and reducing the escape of inflammatory proteins.

Annulargram

An annulargram (also called a discogram) is a diagnostic procedure used to identify and characterize tears within the annulus fibrosus. During the procedure, contrast dye is injected directly into the suspected disc under fluoroscopic (live X-ray) guidance. If a tear is present, the dye escapes the disc and outlines the damage on imaging. Critically, clinicians also monitor whether the injection reproduces the patient’s familiar pain — a key indicator that the disc is a primary pain generator. This information is vital for determining candidacy for targeted treatments such as fibrin disc treatment, as it reveals structural damage that may not be fully apparent on MRI alone. See our glossary of key terms in diagnosing disc conditions for related definitions.

Intradiscal Injection

An intradiscal injection delivers therapeutic substances directly into the nucleus pulposus or annulus fibrosus of an intervertebral disc. This differs from epidural steroid injections, which deliver medication around the spinal nerves or outside the disc. Intradiscal injection allows highly targeted delivery of regenerative agents — such as fibrin — precisely to the site of structural damage. For patients with discogenic pain or annular tears, this approach provides a direct route for biologic therapies intended to support disc repair and may be evaluated as part of a comprehensive non-surgical treatment plan.

Regenerative Medicine

Regenerative medicine focuses on developing treatments that harness the body’s natural healing capabilities to repair or restore damaged tissues. In spine care, this approach aims to rebuild structural integrity and function of injured or degenerated discs, rather than solely managing symptoms or removing damaged tissue surgically. Intra-annular fibrin injection falls within regenerative medicine, introducing biologic agents into the disc to support cellular repair and fibrous tissue regeneration. For patients exploring alternatives to traditional surgery, regenerative medicine may offer a pathway oriented toward addressing underlying disc pathology rather than symptom suppression alone. Our resource on non-surgical disc treatments for chronic back pain provides broader context.

Intra-Annular Fibrin Injection

Intra-annular fibrin injection is a minimally invasive regenerative procedure designed to address chronic back pain caused by annular tears in the intervertebral discs. During treatment, a specialized fibrin preparation — derived from natural blood proteins — is injected directly into the damaged annulus fibrosus under fluoroscopic guidance. The fibrin serves as a biologic sealant and scaffold, supporting the disc’s natural repair processes, reducing the leakage of inflammatory chemicals onto adjacent nerves, and promoting regeneration of the disc’s outer wall. For patients with discogenic pain arising from unhealed annular tears, this targeted approach may provide meaningful relief; outcomes vary and candidacy is determined through individual evaluation. Explore our detailed overview of annular tears and the role of annular tear repair.

Biologic Disc Repair

Biologic disc repair is a broad term encompassing non-surgical regenerative treatments that introduce biologic materials — such as fibrin — into damaged intervertebral discs to support healing and restore function. Unlike surgical approaches that remove or fuse disc tissue, biologic disc repair aims to work with the body’s own healing mechanisms. It is considered a potential alternative for candidates who have not responded adequately to conservative care and wish to explore options before or instead of surgery. Our team evaluates each patient individually to determine whether biologic disc repair as a modern alternative to spinal fusion may be appropriate for their specific condition.

Expert Take

Our clinical team emphasizes that understanding these foundational terms is a meaningful first step in any spine care journey. Conditions such as annular tears and degenerative disc disease vary considerably in severity and presentation across patients, which is why diagnostic precision — including tools like the annulargram — informs every treatment recommendation we make. Regenerative options such as intra-annular fibrin injection may benefit many patients with discogenic pain; however, outcomes depend on individual anatomy, condition severity, and overall health. We encourage patients to use this glossary as a starting point for informed conversations during their evaluation.

For related terminology, explore our companion resource: A Glossary of Key Terms in Regenerative Spine Treatment.