Pseudoarthrosis is a term used to describe what happens when a spinal fusion is unsuccessful. Spinal fusion is a type of back surgery given for a variety of problems including but not limited to scoliosis curve correction, disc problems, and/or instability in the spine (which can be due to an infection or tumor). The ultimate goal of a spinal fusion is to reduce pain and improve function. For spinal stenosis and/or radiculopathy, the goal is also to decompress, or make room for, nerves and/or the spinal cord as they pass through spaces in the spinal column.

According to the American Academy of Orthopedic Surgeons (AAOS), spinal fusion is essentially a welding process. The idea is to join neighboring, painful vertebrae together and, with time, allow them to fuse into one single, solid bone. This increases stability and can reduce painful movement at that joint.

The AAOS says that (often along with instrumentation such as rods, screws, and/or wires) all spinal fusions involve placing some type of bone material into the space between the vertebrae that will eventually grow together as a solid unit. This material is called a bone graft; the graft increases bone production and stimulates healing and fusing.

Causes

But what happens if the spinal fusion doesn’t take? Healthcare providers refer to this as a “non-union” or pseudoarthrosis. In cases of non-unions, not enough bone formation occurs during the mending period immediately following the procedure.

In general, poor bone healing is what leads to pseudoarthrosis. Sometimes this is due to planning and/or what goes on during surgery; other times it’s based on lifestyle habits, such as being a smoker, or due to medications you may take, such as steroids.

Pseudoarthrosis and Smoking

Being a smoker dramatically increases your risk of psuedoarthrosis. In fact, some spine surgeons won’t even operate on smokers (except in cases where your life would be in danger without it).

Smoking can lead to a 33% decrease in the rate of fusion, according to surgeons Steven Ondra and Shaden Marzouk in their article “Revision Strategies for Lumbar Pseudarthrosis.” They say the reason is that smoking constricts your blood vessels as well as reduces the amount of blood vessel growth into the site of the fusion. To be successful, fusions need the blood supply that new and existing blood vessels (with normal diameters) can deliver.

Other factors that increase your risk of pseudoarthrosis include:

  • ObesityChronic steroid useOsteoporosisDiabetesMalnutritionInflammatory arthritisPrevious pseudoarthrosisOther chronic illnesses

On the surgical side, the Scoliosis Research Society says that even in the best of surgical hands, the risk for pseudoarthrosis is at a minimum of 5% to 15%. Surgeons must take into consideration specific and overall biomechanics, the condition of the grafted “environment” and other factors.

Pseudoarthrosis and Bone Graft Material

As far as what to use for a bone graft is concerned, while numerous possibilities exist, including manufactured bone graft, experts agree that using the patient’s own bone (called autograft) is best. 

Surgical factors that can increase risk of pseudoarthrosis

  • Numbers of levels fusedType of fusion performedChoice of graft material (with autograft perferrred)Condition and preparation of the graftPlacement of graftUse of surgical instrumentation to keep the spine aligned and immobile after the surgery (called internal fixation)Whether it is a revision graft

But this is not always possible. It depends on things like your underlying health, what the graft site (i.e., your hip, spine or another area from which the bone is taken) is like, if the use of instrumentation (i.e., rods, screws and/or wires) is planned and if the fusion will be done in front or in back.

Diagnosis

Pseudoarthrosis is sometimes difficult to diagnose. One reason for this is that you may or may not notice symptoms. Another reason is that no one can say for sure how long after your spinal fusion surgery any related pain or other symptoms may occur. You may feel pain from pseudoarthrosis months or even years after your spinal fusion surgery.

Finally, sometimes a pseudoarthrosis is not always visible, making spotting it on a film difficult, if not impossible, for the reading radiologist. However, other types of studies can be helpful in this setting.

Treatment

Treatment for pseudoarthrosis will likely start conservatively with medication, physical therapy, or pain management, especially in cases where it is important to rule out other sources of back or neck pain. If that fails to satisfactorily relieve your symptoms, your healthcare provider may suggest revision surgery.