Pseudoarthrosis, or bone nonunion, occurs when bones do not fuse as they should after an injury or surgery. For example, it can occur if surgeons attempt spinal fusion surgery, but the spine’s bones do not successfully join together.

Not everyone with pseudarthrosis has symptoms, but if they do, they can include pain, clicking joints, and reduced mobility.

Moving too quickly after surgery can result in pseudarthrosis. There are also some forms of congenital pseudarthrosis people can have from birth.

Read on to learn more about pseudarthrosis, its causes, symptoms, and treatment.

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Pseudarthrosis occurs when two bones fail to fuse as they should. This could occur after an injury or following a surgery that aims to fuse bones.

For instance, surgeons sometimes use spinal fusion surgery to resolve problems with the bones of the spine, or vertebrae. It involves fusing the vertebrae into one solid bone, which may help increase stability, repair fractures, or improve scoliosis. If the bones do not successfully fuse, the individual has pseudarthrosis.

An older 2016 study reported that as many as 50% of spinal fusion surgeries fail and that surgeons are performing more of these operations annually.

Pseudarthrosis can be serious, depending on which bones it affects and the reasons for the surgery. For example, if a person has broken bones in the neck that do not heal, this may cause significant pain, difficulty moving the neck, or other complications.

Pseudarthrosis is one of the main causes of pain after surgery. However, in around 30% of cases, people with this condition have no symptoms.

Several factors can cause pseudarthrosis. They include:

  • Moving after surgery: If a person moves too soon following fusion surgery and before their bones have started the fusion process, this can result in pseudarthrosis.
  • Medical conditions: Some medical conditions can cause pseudarthrosis. For example, anklylosing spondylitis is an inflammatory condition that causes the bones of the spine to fuse. Pseudarthrosis is a potential complication, occurring when bones almost fuse but do not.
  • Congenital conditions: In rare cases, pseudoarthrosis may be a congenital condition a person has from birth. For instance, someone can have congenital pseudarthrosis of the clavicle, or collarbone. Congenital pseudarthrosis of the tibia in the lower leg is also possible.
  • Surgical techniques: A 2021 study concluded that, regarding adults undergoing spinal fusion, pseudarthrosis often occurs due to the risks of certain surgical approaches doctors use.

Of the surgical approaches the researchers assessed, techniques that had an increased risk of pseudarthrosis included:

  • long fusions, which involve fusing the spine beyond the upper-end vertebra at the top of the spine
  • osteotomies, which involve cutting or reshaping bone
  • pelvic fixation, which involves immobilizing the base of the spine using rods and screws

In contrast, procedures involving going through the front of the body reduced pseudarthrosis rates by 30%.

Certain lifestyle factors, health conditions, and medications elevate the risk of a person getting pseudarthrosis. They include:

Additionally, a study from 2019 reviewed data from people who had developed surgical site infections of the spine. The researchers found that the number of spine levels undergoing fusion was the main predictor for a person developing pseudarthrosis.

Some people with pseudarthrosis may not have any symptoms. Others may experience one or more of the following:

  • reduced mobility
  • persistent pain
  • clicking joints
  • fever

Doctors order imaging tests, such as X-rays or CT scans, to check for pseudarthrosis. This gives them a detailed picture of the skeleton from which to make a diagnosis.

The treatment for pseudarthrosis is often surgery. In cases where bone fusion surgeries have previously failed, surgery focuses on trying to repair the bone a second time.

Surgeons can treat pseudarthrosis affecting the spine by:

  • replacing loose implants or devices
  • using stronger tissue replacements
  • interbody fusion, which involves removing the spongy disc between the vertebrae

The authors of a 2021 study also recommend surgery for treating congenital pseudarthrosis of the clavicle. This involves resectioning the clavicle using a bone graft from the iliac crest, in the pelvis.

Congenital pseudarthrosis of the tibia can be challenging to treat. A study from 2021 states that, on average, only 50% of surgical procedures for the condition resulted in healing without refracturing.

However, a surgical technique known as intentional cross-union between the tibia and fibula increased the success rate to 100% healing without refracture.

Electrical stimulation therapy is another possible treatment option. A study from 2020 found that electrical stimulation devices may significantly increase bone fusion rates in people undergoing spinal fusion.

Pseudarthrosis occurs when two bones do not fuse successfully. This can happen after an injury or after bone fusion surgery. It is a common complication of such procedures, particularly those fusing bones in the spine.

Some people with pseudarthrosis have no symptoms, but if they do, they may experience a loss of mobility, pain, and clicking sounds when they move. Surgeons may perform additional surgical procedures to treat it.