Part II – Chronic Pain Conditions Impact on Future Care: Failed Back Syndrome

Failed back syndrome (also known as Failed Back Surgery Syndrome or FBSS) is not considered a diagnosis in itself, but rather a term often used to describe patients who have undergone lumbar surgery and continue to experience chronic and persistent pain syndromes with unsatisfactory outcomes. This condition it is characterized by severe, disabling chronic pain that is generally resistant to physiotherapy, pharmacological treatment and is associated with various degrees of functional disability.  It is estimated that this complication occurs in 5% to 10% of patients after spinal surgeries.

Failed back syndrome has many causes.  If surgery fails to adequately relieve pressure on the nerve or disc herniation recurs, ongoing pain can result.   What if the nerve sustained serious injury?  Full nerve recovery may not be possible, regardless of surgical intervention.  If spinal fusion was performed, incomplete healing of the bone graft and/or hardware failure (i.e. breakage) can lead to persistent instability of the spinal segments requiring additional treatment. The formation of scar tissue at the surgical site also presents challenges which need to be taken into consideration when addressing short-term and long-term future care.

Fibrosis and Adhesions

The formation of scar tissue is a normal part of the healing process.  When we are injured, our bodies launch a complex rescue mission, mobilizing specialized cells to stop the bleeding and lay down a matrix of collagen¹.  Other cells (fibroblasts) reorganize these fibers eventually anchoring themselves into the matrix and pulling the wound edges together.  Every wound results in some form of scarring but we all scar differently. In some of us, scars are barely noticeable while in others the fibroblasts are overzealous, laying down excessive amounts of collagen which results in large raised (hypertrophic or keloid) scars.

Internal scar tissue also reflects the body’s natural healing abilities, repairing muscles and tissues injured or cut during a surgical procedure. Internal scar tissue differs from “normal” scar tissue in that it can create tethers, barriers and adhesions to internal body structures, pulling them out of place.

Epidural fibrosis occurs when fibrous tissue replaces the normal epidural fat adjacent to the dura  in the spinal canal. This tissue binds the dura² and nerve roots to the surrounding structures.  Dense epidural fibrosis can cause nerve root irritation, entrapment, compression and restrict nerve root mobility. When encased in scar tissue, nerve fibers are subject to increased tension, impaired blood supply and a reduced capacity to transport substances along its length. Epidural fibrosis has been reported to be the cause of symptoms in 8-14% of patients with failed back surgery syndrome (FBSS) and is related to a poorer surgical outcome and increased complication rates in patients requiring reoperation.

Multiple treatment strategies have been researched in hopes of finding a way to prevent scar tissue from forming without compromising the wound healing process. A variety of materials have been implanted on top of the dura such as absorbable gelatin sponges and Gore-Tex membranes.  Chemical agents aimed at reducing scar formation suppress fibroblast proliferation after surgery.   Although some methods show promising results, researchers are calling for further studies to determine short- and long-term complications as well as the efficacy of these methods in clinical practice.

Scar tissue (fibrosis) generally forms between 6 weeks and 6 months after surgery, which may be why some individuals experience initial improvement of their symptoms, followed by a gradual return of back and/or leg pain. Undergoing additional surgery to remove scar tissue is not always recommended as the scarring tends to reform and can ultimately leave the patient worse off than they were before.

Some suggest that stretching the nerve root while the body is healing after back surgery can help limit epidural fibrosis from becoming a clinical problem.  The theory is that if the nerve is kept mobile while the wound heals, the nerve will not be bound down by adhesions and the scar tissue that does develop should be less problematic.

Spinal Instability

It is estimated that more than 300,000 spine fusions are performed annually in the United States which reflects a 76% increase in this procedure between 1996 and 2001.  The reasons for spinal instability are numerous and can be related to injury or disease of the bones, discs, joints or ligamentous support structures.

White and Panjabi described spinal stability as the ability of the spine, under physiological loads, to limit patterns of displacement so as to not damage or irritate the spinal cord and nerve roots and, in addition, to prevent incapacitating deformity or pain due to structural changes.  Conversely, instability refers to excessive displacement of the spine that would result in neurological deficit, deformity, or pain.  Instability can have an acute onset, as with spinal fractures or dislocations, or present as chronic conditions (i.e. spondyolisthesis³).

Depending on the circumstances, stabilization can be achieved externally or internally.  Chronic instability (and acute stable injuries such as fractures without displacement and/or nerve compression) can be stabilized with external bracing such as a cervical collar, halo brace or Thoracic lumbo-Sacral Orthosis⁴ (TLSO).  When applied, external bracing provides support which can improve posture and facilitate unloading of the compressive forces on the spine.  Bracing can also be used as a temporary means of stabilization, before fusion is undertaken or after surgery, until healing occurs.

Spinal fusion is an example of internal stabilization. This can be accomplished with bone grafting, hardware or a combination of both.  Many factors can adversely affect healing after fusion.  According to Pakzaban, these can include malnutrition, cortisteroid use, irradiation, cancer, diabetes, infection, osteoporosis and smoking. Of these, smoking is the most prevalent correctable risk factor.  There is growing evidence that cigarette smoking adversely affects fusion and disrupts the normal function of basic body systems that contribute to bone formation and growth.  In a study of patients undergoing lumbar fusion, the patients who smoked experienced failed fusions in up to 40% of cases, compared to only 8% among non-smokers.

Postoperatively, early mobilization is recommended as it expedites rehabilitation and can prevent complications associated with immobility (deep vein thrombosis, pneumonia etc).  If fusion is performed without instrumentation (hardware) an external support brace or orthosis is utilized until the fusion has matured.  If hardware has been used, an external orthosis may still be applied during healing to provide additional supplemental support for the hardware especially with more extensive procedures.  Although exercise therapy is often delayed several months, some studies suggest that an early home program focused on pain-contingent training for functional strength and endurance of back, abdominal and leg muscles, as well as stretching and cardiovascular fitness is beneficial.

As we all know, surgical fusion of the spine does not always result in relief of pain and FBSS often becomes a chronic condition. Conservative management includes the use of analgesics, anti-inflammatory drugs and physical therapy.  When depression is a factor, psychological intervention may be indicated.  Some physicians also advocate behavioral modification to address smoking cessation, weight loss or other lifestyle changes. Periodic epidural steroid injections or facet injections may be used to provide pain relief and increase functional activities.

Achieving the goal of improved function often involves a patient-centered, multidisciplinary approach.  Treatment planning and future care considerations need to address a biopsychosocial factors as well as spiritual and cultural issues.  With an emphasis on patient education, empowerment, self-management skills and lifestyle changes, the chronic pain sufferer is in a better position to regain control of their life.

In Part III of this series, Chronic Pain Conditions and their Impact on Future Care, we will explore the world of implantable devices used in the treatment of chronic pain conditions.  These include Spinal Cord Stimulators (aka Dorsal Column Stimulators) and Intrathecal Pain Pumps that deliver medication directly to the spinal fluid.

¹Collagen is any of various tough, fibrous proteins found in bone, cartilage, skin and other connective tissue.  Collagens have great tensile strength, and provide these body structures with the ability to withstand forces that stretch them.

²The dura mater or simply dura is the outermost membrane which envelopes and protects the spinal cord
³Spondylolisthesis is a descriptive term referring to slippage of a vertebra (usually forward) relative to another vertebra.  Spondylolisthesis is graded according to the percent of displacement
⁴The Thoracic Lumbo-Sacral Orthosis or TLSO brace stabilizes the spine with circumferential pressure. Whereas a Halo brace stabilizes the cervical spine with rigid hardware attached to the skull on one end and fixed to a vest (made of plaster or molded plastic) on the upper body.

References:

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