What Is Pseudoarthrosis? Causes, Symptoms, and Treatment

Pseudoarthrosis is the failure of a fractured bone to heal, resulting in a persistent gap or unstable connection at the fracture site that effectively behaves like a false joint. The term literally translates from Greek as “false joint,” and the condition affects roughly 10 to 15 percent of long bone fractures.¹ It can also develop after spinal fusion surgery, in congenital bone disorders, and in other skeletal sites where healing stalls for months or years. The consequences go well beyond a bone that never knits together: prolonged pain, lost mobility, repeated surgeries, and significant effects on mental health and finances.

How Pseudoarthrosis Differs from a Slow-Healing Fracture

Every broken bone takes time to heal, and the timeline varies with age, location, and overall health. A fracture that is still progressing toward union at three or four months is slow but normal. Pseudoarthrosis, by contrast, is diagnosed when the healing process has essentially stopped. Clinicians typically apply the label when a fracture shows no radiographic progress toward union over several consecutive months, often using six to nine months after injury as a rough threshold, though the exact cutoff depends on the bone involved and the clinical picture.²

Once the diagnosis is made, the nonunion is generally classified into two broad biological types. Hypertrophic pseudoarthrosis shows abundant callus formation around the fracture site, meaning the body is trying to build new bone but can’t bridge the gap, usually because the fracture is unstable or poorly aligned. Atrophic pseudoarthrosis is the opposite: the body produces little or no callus at all, suggesting a deeper biological failure in the healing response itself.³ This distinction matters for treatment. A hypertrophic nonunion often responds well to improved stabilization alone, while an atrophic one typically needs both mechanical fixation and some form of biological stimulation to restart healing.

What Causes It

Pseudoarthrosis rarely has a single cause. In most cases, several unfavorable factors converge. A study that analyzed the causes behind fracture nonunions found mechanical problems in about 59 percent of patients, dead bone and a gap at the fracture site in 47 percent, host-related factors (like nutritional deficiency or systemic illness) in 43 percent, and infection in 38 percent.⁴ Many patients had more than one factor at play simultaneously.

On the mechanical side, inadequate stabilization is the classic culprit. If a fracture is not held still enough, whether from a poorly fitting cast, loose hardware, or too much early weight-bearing, the constant micro-motion prevents the delicate new blood vessels and bone cells from doing their work. Gaps between bone fragments cause similar problems: if the fracture ends are too far apart, the body simply can’t bridge the distance. Severe open fractures, where bone is exposed through the skin, carry a particularly high risk because of combined soft-tissue damage, blood-supply disruption, and infection.

Infection deserves special attention because it is frequently underdiagnosed. Low-grade bacterial colonization can silently sabotage healing for months without causing the obvious signs of infection like fever or redness. Some research suggests that occult infection is present in a substantial portion of cases initially labeled as “aseptic” nonunions, which is why many surgeons now routinely take tissue cultures at the time of revision surgery.⁴

Congenital Pseudoarthrosis

Not all pseudoarthrosis follows a traumatic fracture. Congenital pseudoarthrosis of the tibia is a rare condition, occurring in roughly 1 in 53,000 births, where the shinbone develops an inherent weakness, often bowing before birth and fracturing in early childhood.⁵ The condition is strongly linked to neurofibromatosis type 1, a genetic disorder caused by mutations in the NF1 gene. That gene normally acts as a brake on cell-growth signals. When it is mutated, the resulting imbalance disrupts the normal activity of bone-building and bone-resorbing cells, making fractures at the affected site extremely resistant to healing.⁶

The natural history of congenital tibial pseudoarthrosis is famously difficult. Once the bone fractures, there is little or no tendency for it to heal on its own. Successful treatment generally requires surgically removing the abnormal tissue, including the diseased lining around the bone, and then stabilizing the site.⁷ Even after surgery, refracture and residual deformity are common. In one long-term follow-up series, all skeletally mature patients eventually achieved union, but nearly all required additional surgeries for refracture or deformity correction along the way, and leg-length discrepancy averaged about 4 centimeters at final follow-up.⁸

Risk Factors You Can and Cannot Control

After spinal fusion surgery, which is one of the most studied settings for pseudoarthrosis, a meta-analysis identified three standout risk factors: older age, smoking, and the number of vertebral levels fused in a single procedure.⁹ The more levels fused at once, the higher the odds of at least one segment failing to heal.

Smoking is the modifiable risk factor that gets the most attention, and for good reason. It impairs bone healing through multiple pathways, including reduced blood flow to the fracture site, lower bone mineral density, and decreased activity of the cells responsible for building new bone.¹⁰ The good news is that this risk appears to be largely reversible. A systematic review of spinal fusion outcomes found that former smokers who had quit at least a year before surgery had pseudoarthrosis rates and pain scores that were statistically indistinguishable from nonsmokers.¹¹ That makes smoking cessation one of the single most effective things a patient can do before planned surgery.

Diabetes, particularly type 2, is another systemic factor that complicates healing. Poor blood sugar control interferes with collagen production and wound repair. Other conditions that suppress healing include malnutrition, thyroid disorders, vitamin D deficiency, and the use of certain immunosuppressive medications.

The NSAID Question

Common over-the-counter pain relievers like ibuprofen and naproxen belong to a drug class called NSAIDs, and their relationship with bone healing has been debated for years. A meta-analysis of randomized controlled trials found that NSAID use after fracture was associated with roughly triple the odds of nonunion overall. However, that elevated risk was concentrated among patients who took NSAIDs for more than four weeks; short courses of under two weeks showed no significant increase in nonunion risk. One specific NSAID, indomethacin, stood out as particularly problematic.¹²

The evidence is not perfectly consistent. Another pooled analysis found roughly doubled odds of healing complications with NSAID use in adults, though the effect was not significant in children.¹³ And when an earlier meta-analysis looked only at the highest-quality spine fusion studies, the association fell short of statistical significance.¹⁴ The practical takeaway: a few days of ibuprofen for post-fracture pain is probably fine, but prolonged use over several weeks, especially with indomethacin, is something to discuss with your surgeon.

How Pseudoarthrosis Feels

The symptoms of pseudoarthrosis depend heavily on where it occurs. In a long bone like the tibia or femur, the hallmark is persistent pain at the fracture site that does not improve or worsens with weight-bearing, often accompanied by abnormal motion at the fracture. You might feel a clicking or shifting sensation in the limb. Swelling around the site that never fully resolves is common, and in severe cases, the limb may appear visibly deformed or shortened.

In the spine, pseudoarthrosis after fusion surgery tends to present as persistent or recurrent back or neck pain that initially improved after surgery but then returned. Hardware failure, where screws loosen or rods break, can be a secondary sign that a fusion has not healed. Sometimes the pain is subtle enough that it gets dismissed as normal post-surgical discomfort for months before imaging reveals the problem.

In rarer locations, pseudoarthrosis can mimic other conditions entirely. Case reports have described foot pseudoarthrosis presenting as a painless lump that was initially suspected to be a bone tumor, underscoring the value of imaging in any case of unexplained chronic bone pain or swelling.¹⁵

Diagnosing Pseudoarthrosis

Getting the diagnosis right matters because revision surgery is a significant undertaking that you don’t want to pursue unnecessarily, nor delay when it is truly needed. No single imaging test is perfect, and each has trade-offs.

Plain X-rays are the first-line tool but have real limitations, especially in the spine. One study of lumbar pseudoarthrosis found that standard X-rays only supported the diagnosis in about 39 percent of surgically confirmed cases, though adding flexion-extension views (which show abnormal movement) pushed that to roughly 50 percent.¹⁶ CT scanning performs substantially better, demonstrating the nonunion in over 94 percent of cases in that same study. CT is considered the gold standard for evaluating bony bridging, particularly in spinal fusion, because it can show the fine detail of whether solid bone actually connects across a fusion site.

MRI adds complementary information. It doesn’t show bone architecture as crisply as CT, but it can reveal characteristic signal changes in the bone marrow adjacent to a pseudoarthrosis, which were present in about 87 percent of confirmed cases.¹⁶ A broader review of imaging across multiple studies confirmed that CT generally offers the best combination of sensitivity and specificity for assessing fusion status, with reported specificity as high as 97 percent.¹⁷

Non-Surgical Approaches

For some pseudoarthroses, particularly hypertrophic ones in accessible long bones, there is a role for non-surgical management. Bone growth stimulators, which deliver low-intensity pulsed ultrasound or electromagnetic fields through the skin, have been used for decades. A meta-analysis of randomized trials found that these devices did not significantly reduce the overall proportion of nonunions in acute fractures. However, they did accelerate the time to healing in fractures managed without surgery and in upper-limb fractures specifically.¹⁸ Their effectiveness in established pseudoarthrosis, as opposed to fresh fractures, remains less well supported by high-quality evidence, and many surgeons reserve them for patients who are poor surgical candidates or as an adjunct to other treatments.

Optimizing the patient’s overall health is a non-surgical intervention that is frequently underappreciated. Correcting nutritional deficiencies, controlling blood sugar, stopping smoking, and managing thyroid disorders can all shift the biological environment in favor of healing. Prehabilitation programs before planned spinal surgery increasingly include smoking cessation support and nutritional screening as standard components.¹⁹

Surgical Treatment

When surgery is needed, the approach is tailored to the type and location of the nonunion. The overarching principle is to address both the mechanical and biological problems simultaneously.

For long bone pseudoarthrosis, the typical revision involves removing the fibrous tissue and any dead bone at the nonunion site, freshening the bone ends, applying bone graft, and stabilizing the construct with updated hardware. Bone graft can come from the patient’s own body (usually the pelvis), from a donor, or from synthetic substitutes. Autograft from the patient’s own iliac crest is considered the gold standard because it provides living bone cells, growth factors, and a scaffold all in one, but harvesting it adds another surgical site and can cause pain of its own.

When the nonunion involves significant bone loss or limb-length discrepancy, more complex techniques come into play. The Ilizarov method uses a circular external fixation frame to gradually lengthen bone through a process called distraction osteogenesis. In tibial nonunions with bone loss, surgeons sometimes combine this with an internal nail: they resect the pseudoarthrosis, compress the gap until the bone ends meet, graft the site, and then perform a separate bone cut that is slowly lengthened over weeks to restore the limb to its correct length.²⁰ A similar strategy has been applied to femoral nonunions using a circular frame over a pre-existing intramedullary nail.²¹

In spinal pseudoarthrosis, revision fusion surgery aims to remove the scar tissue at the failed fusion site, add fresh bone graft and often a biologic agent like recombinant bone morphogenetic protein, and reinforce or replace the instrumentation. The use of bone morphogenetic proteins appears to reduce the risk of a second failure, and the benefit seems most pronounced in smokers and in patients undergoing multi-level cervical fusions.²²

What Recovery and Long-Term Outcomes Look Like

Recovery from revision surgery for pseudoarthrosis is typically slower and more unpredictable than the original procedure. In the spine, a study tracking patients for two years after revision fusion for lumbar pseudoarthrosis found significant improvements in pain scores, disability, and physical health. The median time to returning to work was about four months, and the median time to getting off narcotic pain medications was about a year. By the two-year mark, none of the patients in that cohort had developed a recurrent pseudoarthrosis.²³

For clavicular pseudoarthrosis, a long-term follow-up study found that fractures ultimately healed in nearly all surgically treated patients, though some required two or three procedures. Mild to moderate residual symptoms persisted in some cases even after successful bony union.²⁴ That observation reflects a broader theme in pseudoarthrosis management: achieving union is the primary goal, but it does not always equal complete symptom relief. Chronic pain patterns, muscle deconditioning, and psychological effects from months or years of disability can persist even after the bone is finally healed.

The Financial and Quality-of-Life Toll

Pseudoarthrosis carries costs that extend far beyond additional operating-room time. A study comparing cervical spine patients who developed pseudoarthrosis to those who healed normally found that the pseudoarthrosis group had significantly worse scores on measures of mobility, daily activities, and pain. About 64 percent of pseudoarthrosis patients had worsened quality-of-life scores compared with only 9 percent of controls. Mental health outcomes were also poorer. And the direct medical costs were substantially higher, driven by additional imaging, clinic visits, medications, and revision surgery.²⁵

These figures underscore why prevention and early detection matter so much. The total burden of pseudoarthrosis is not just the medical expense of a second surgery. It includes months of lost work, prolonged opioid use, strained relationships, and the psychological weight of chronic unresolved pain. For patients going into elective fusion surgery, discussing modifiable risk factors with the surgical team ahead of time is one of the most high-yield conversations available.

Stem Cells and Tissue Engineering on the Horizon

The search for better biological tools to treat atrophic pseudoarthrosis has pushed researchers toward cell-based therapies. The concept is straightforward: if the body has stopped making enough bone-forming cells at the fracture site, deliver them directly. One clinical series treated patients with long-bone pseudoarthrosis by transplanting their own bone marrow cells combined with donor bone graft. All patients achieved full consolidation within an average of about five months, and none experienced recurrence over a follow-up period averaging three years.²⁶

More recently, a pilot randomized trial compared a tissue-engineered product loaded with a patient’s own bone marrow stem cells against the standard iliac crest autograft for atrophic pseudoarthrosis. The two approaches showed no significant difference in healing rates, which the researchers framed as a positive finding: the engineered product worked just as well without requiring an additional surgical harvest from the pelvis.²⁷ This is particularly relevant for patients who have already had bone harvested from their pelvis in a prior surgery and have limited graft material remaining, or for those with conditions that make autograft harvesting risky.

A scoping review of the field noted that stem-cell-based treatment for fracture nonunion is still evolving, with researchers working to refine which cell types, delivery methods, and scaffolds produce the most reliable outcomes.²⁸ At the molecular level, the challenge is well characterized: pseudoarthrosis tissue shows suppressed bone-building signaling and elevated levels of proteins that actively block bone formation.¹ Future therapies may target those inhibitors directly, essentially removing the molecular brakes on healing rather than just adding more raw material to the site. None of these approaches have reached routine clinical use yet, but the trajectory of early results suggests that the next decade could meaningfully expand the toolkit for the most stubborn nonunions.