Spinal scar tissue, formally known as epidural fibrosis, is an abnormal accumulation of fibrous tissue that develops around the nerve roots or the protective covering of the spinal cord. This tissue collects in the epidural space, the narrow area located just outside the dura mater, which is the membrane surrounding the spinal cord. The presence of this dense, non-elastic material often leads to persistent or recurrent pain. While scar tissue is a natural part of the body’s healing process, its excessive formation following trauma, especially after spine procedures, is a common reason for chronic back complaints.
The Body’s Response: Biological Mechanism of Spinal Scarring
The formation of scar tissue in the spine begins with the universal process of tissue repair following any injury or trauma. The initial event, whether a surgical incision or a physical blow, triggers an immediate inflammatory response. This reaction brings specialized immune cells to the site of damage to remove damaged cells and debris.
The inflammation then activates local cells called fibroblasts, which are the primary scar-forming cells in the body. These fibroblasts migrate to the injury site and begin to produce and deposit a large amount of extracellular matrix, predominantly made of collagen. This collagen framework is intended to bridge and reinforce the damaged tissue. In the confined space of the spinal canal, this process becomes problematic if it is excessive. The resulting epidural fibrosis is a disorganized and dense collection of collagen fibers that replaces the normal, delicate fat and connective tissue surrounding the nerves. The degree of scarring is directly proportional to the intensity and duration of the initial inflammatory signal.
Primary Trigger: Fibrosis Following Spinal Surgery
Spinal surgery is the most frequent cause of epidural fibrosis, a condition often associated with Failed Back Surgery Syndrome. Procedures that require the removal of bone or disc material, such as a laminectomy or discectomy, cause substantial disruption to the anatomy of the epidural space. This surgical trauma initiates the inflammatory cascade that leads to the deposition of scar tissue.
The extent of the fibrosis is often influenced by several factors that increase local inflammation and tissue disruption. The fibrosis typically matures into a dense mass over a period of six weeks to six months post-operation. Factors that promote scar formation include:
- The presence of a blood clot, or hematoma, in the epidural space immediately after surgery. If this blood is not completely reabsorbed, it acts as a scaffold that directs the growth of the fibrous tissue.
- The size of the bone defect created during the operation. Larger defects expose more tissue surfaces, encouraging a broader area for fibroblasts to anchor and deposit collagen.
- Residual disc material left behind after the procedure.
- Irritation caused by an accidental dural tear, which can prolong the inflammatory environment.
Non-Surgical Causes of Spinal Scar Tissue
While surgery is the leading cause, spinal scar tissue can also form as the body’s response to non-surgical forms of trauma and chronic disease. Severe physical trauma to the spine, such as fractures or dislocations, can cause significant hemorrhage and tissue damage within the spinal canal. The resulting hematoma and inflammatory response lead to the formation of dense, localized fibrosis as the body attempts to heal.
Infections of the spine are another cause, particularly a spinal epidural abscess, which is a collection of inflammatory material in the epidural space. The body’s attempt to wall off and contain this infection involves a large inflammatory reaction and the creation of granulation tissue. Once the active infection is resolved, this site often remains as a patch of dense, constrictive scar tissue.
Certain chronic inflammatory conditions, such as ankylosing spondylitis, can also lead to excessive fibrous tissue formation. In this disease, persistent inflammation where ligaments attach to bone causes a destructive and reparative cycle. Over time, this chronic process results in the buildup of fibrous tissue and subsequent calcification, which can stiffen the spine and encroach upon the spinal canal.
How Spinal Scar Tissue Causes Pain and Symptoms
Spinal scar tissue causes pain not merely by its presence, but by its mechanical interaction with the sensitive nerves and spinal cord structures. This fibrous material lacks the elasticity of the surrounding healthy tissue and tends to adhere tightly to the nerve roots and the dura mater. This process is known as nerve root tethering or entrapment.
When the patient moves, the scar tissue physically restricts the nerve’s normal gliding and sliding motion within the spinal canal. This restriction causes mechanical irritation and undue tension on the nerve, which the body interprets as pain. This pain often manifests as radiculopathy, a sharp or burning sensation that radiates down the leg.
The constrictive nature of the scar tissue can also cause symptoms like numbness, tingling, or muscle weakness in the extremities. Even if the original problem was successfully treated, the new scar tissue can create a state of relative spinal stenosis. This means that minor movements or small bone spurs can compress the already restricted nerve, leading to chronic or recurrent neurological symptoms.