Author and medical reviewer: Serhii Horbenko, orthopedic trauma surgeon of the highest qualification category, Medical Director of biodrook. 15 years of clinical practice, retired Major of the Medical Service. Responsible for the medical accuracy of biodrook materials and reviews them before publication.
Contact:
sgorbenko@biodrook.com
Updated: 13 September 2026. This material is for informational purposes only and does not replace consultation with a physician.
Key points at a glance
- Delayed union — bone healing is progressing more slowly than expected, but the process is continuing. NICE benchmark for long bones: no radiographic signs of union after 3 months.
- Nonunion (pseudarthrosis) — the healing process has stopped. NICE benchmark and FDA labeling: at least 9 months have elapsed, with no visible progression of healing during the last 3 months.
- The strongest evidence-based risk factor is infection (the odds of nonunion are 7 times higher). This is followed by open fracture, smoking, diabetes mellitus, and obesity.
- Symptoms that should raise concern: pain that does not decrease; pain with weight-bearing; abnormal mobility; failure of fixation hardware.
- The diagnosis is made by a physician based on examination and serial radiographs or CT — not on timelines found on the internet.
- For established pseudarthrosis, treatment is usually surgical: revision osteosynthesis, infection debridement, and bone grafting. In complex cases, patient-specific 3D-printed implants may be considered — an approach with a currently limited evidence base.
What are delayed union and nonunion (pseudarthrosis)?
When a bone breaks, the body initiates fracture healing. Normally, the process occurs in stages: a bone callus forms, the fragments gradually unite, and after a certain period the fracture heals.
In some cases, the process slows down or stops.
Delayed union is a condition in which healing occurs more slowly than expected for the specific bone and type of fracture, but the process is still ongoing. The bone continues to form callus, although with a delay.
Fracture nonunion (nonunion, pseudarthrosis) is a condition in which healing has stopped and spontaneous union is unlikely without intervention. A false joint may form at the fracture site, with persistent abnormal mobility between the bone fragments.
How does delayed union differ from nonunion?
| Feature |
Delayed union |
Nonunion (pseudarthrosis) |
| Status of the process |
Ongoing, but slow |
Stopped |
| Approximate timeframe (long bones) |
No signs of union after ~3 months |
≥9 months since injury, with no progress during the last 3 months |
| Serial radiographs |
Callus formation is delayed |
No change between radiographs |
| Prognosis without intervention |
Union is possible |
Spontaneous union is unlikely |
| Main management approach |
Correction of risk factors, optimization of fixation and loading; observation |
Usually surgical treatment |
These timeframes are not universal. They vary depending on the bone, type of fracture, treatment method, and local clinical protocols. The final diagnosis is established by a physician based on clinical examination, changes in symptoms over time, and imaging findings.
Why does a fracture fail to heal?
The causes are divided into two groups: systemic factors, related to the overall condition of the body, and local factors, directly related to the fracture and its treatment. A combination of several factors is often involved, and the more factors that are present simultaneously, the higher the risk.
How strong is each risk factor?
A systematic review and meta-analysis of 30 studies (Jensen et al., EFORT Open Reviews, 2022) assessed risk factors for nonunion after surgically treated diaphyseal fractures:
| Risk factor |
Odds ratio (OR) |
95% CI |
| Infection |
7,0 |
3,2–15,0 |
| Open fracture |
2,6 |
1,8–3,9 |
| Severity according to the AO classification |
2,4 |
1,5–3,7 |
| Severity according to the Gustilo classification |
2,2 |
1,4–3,7 |
| Smoking |
1,7 |
1,2–2,4 |
| Diabetes mellitus |
1,6 |
1,3–2,0 |
| Obesity |
1,5 |
1,1–1,9 |
The authors specifically emphasize that the included studies were observational and carried a risk of bias; therefore, these figures demonstrate an association rather than proven causation.
Systemic factors
Smoking and nicotine exposure. A separate systematic review and meta-analysis (122 studies, 417 767 patients; Xu et al., EClinicalMedicine, 2021) showed that smokers had a higher rate of nonunion — OR 2,50 (95% CI 1,73–3,61). Nicotine impairs tissue blood supply and reduces oxygenation. An important practical detail: smoking cessation at least 4 weeks before surgery was associated with a lower rate of postoperative wound infection (OR 0,37).
Diabetes mellitus. Impaired microcirculation and altered collagen synthesis reduce the body’s ability to restore bone structure. Glycemic control is an important component of preparation for treatment.
Infection at the fracture site. According to available data, this is the strongest risk factor for nonunion. The infectious process damages tissues and sustains chronic inflammation, which interferes with bone healing.
Obesity. It places additional mechanical stress on the bone and is often accompanied by metabolic disturbances that affect healing.
Vitamin D, calcium, and protein deficiency. These nutrients are necessary for bone tissue formation. Correction should be prescribed by a physician based on laboratory findings, rather than “just in case.”
Osteoporosis. Reduced bone mineral density may make the formation of a strong callus more difficult, although direct evidence of this association remains limited.
Age. In older patients, regenerative processes occur more slowly, while comorbidities may further complicate healing.
Use of certain medications. The EAST/OTA clinical guideline on pain management after orthopedic trauma states that the evidence regarding NSAIDs and nonunion is conflicting. Intravenous ketorolac during the acute period improved pain control and reduced opioid requirements without increasing the rate of nonunion. At the same time, prolonged use of high-dose NSAIDs should be discussed with a physician.
Local factors
Type and severity of injury. Open fractures, comminuted fractures, fractures with major displacement, or fractures with bone loss carry a higher risk. Soft tissue and vascular damage complicates healing.
Impaired blood supply to the fragments. Loss of normal blood supply to one or both bone fragments slows or stops callus formation.
Insufficient or unstable fixation. Mobility of the fragments interferes with the formation of a strong callus. Stable fixation is one of the main prerequisites for successful union.
Soft tissue interposition. Entrapment of muscles, tendons, or other tissues between bone fragments mechanically prevents union.
Large bone defect. A substantial defect may exceed the body’s biological capacity for spontaneous repair.
Which symptoms should raise concern?
- Persistent pain at the fracture site — pain that does not decrease over time or becomes more severe.
- Pain with weight-bearing — attempting to bear weight on the limb or perform movement causes pain at the fracture site.
- Persistent swelling or deformity — swelling that does not resolve or a visible change in the shape of the limb.
- Abnormal mobility — a feeling of instability where the bone should already have healed.
- Grinding or clicking during movement.
- Lack of functional improvement — the ability to move normally or bear weight on the limb does not recover within the expected timeframe.
- Breakage or loosening of fixation hardware. If a metal implant breaks, this may indicate that the bone has not united and the entire load is being carried by the hardware.
These symptoms are not a basis for self-diagnosis. They are a reason to consult an orthopedic trauma surgeon.
How does a physician diagnose impaired fracture healing?
Clinical examination. The physician evaluates symptoms, limb function, pain, swelling, deformity, and abnormal mobility. It is important to assess how the symptoms have changed over time.
Serial radiography. Radiographs are obtained at specific intervals. The physician assesses whether signs of callus formation are appearing and whether the fracture line is becoming less visible. If the appearance remains unchanged for several months, this indicates nonunion.
Computed tomography (CT). Provides more detailed information about callus quality, persistence of the fracture line, the condition of the fixation, and bone defects. It is particularly useful for surgical planning.
Evaluation for infection. If an infectious process is suspected, laboratory tests, tissue cultures, or other studies are performed to identify the causative pathogen.
Hypertrophic or atrophic: why does it matter?
| Hypertrophic nonunion |
Atrophic nonunion |
| Radiographic appearance |
Excessive bone formation around the fracture line, but without union |
No bone formation; the ends of the fragments are “smoothed” |
| Primary cause |
Mechanical: excessive mobility, unstable fixation |
Biological: impaired blood supply, cellular deficiency |
| What this means |
The biology is functioning, but the mechanics are interfering |
The mechanics may be adequate, but the biology is not functioning |
| Main treatment approach |
Improving fixation stability |
Biological stimulation: bone grafting, restoration of blood supply |
Distinguishing between these types directly determines the choice of surgical procedure.
What treatment options are available?
The choice depends on the type of fracture, type of nonunion, fixation stability, presence of infection, size of the bone defect, and the patient’s overall condition.
Can nonunion be treated without surgery?
Conservative treatment may be appropriate for delayed union when there are signs that the healing process is continuing. In such cases, the physician may recommend:
Correction of modifiable risk factors. Smoking cessation, glycemic control in diabetes, correction of laboratory-confirmed vitamin D and calcium deficiency, and optimization of nutrition.
Optimization of immobilization and weight-bearing. The physician may adjust the weight-bearing regimen or method of fixation.
Biostimulatory methods. In the NICE MTG12 guidance, low-intensity pulsed ultrasound therapy (LIPUS, EXOGEN system) is considered an option for nonunion and delayed healing of long bones when appropriate indications are present. It is prescribed individually by a physician; it does not replace surgical intervention in established pseudarthrosis.
Limitations of the approach. In established pseudarthrosis, when the healing process has stopped, conservative methods are usually insufficient.
Surgical approaches to nonunion
Surgical treatment is based on two principles: stable fixation and biological stimulation of union. If infection is present, controlling it is a mandatory prerequisite.
Revision osteosynthesis. If insufficient stability is the cause, revision surgery is performed: replacement or reinforcement of fixation devices, or a change in the type of fixation (for example, switching from a plate to an intramedullary nail or vice versa).
Infection management. Removal of infected tissue, debridement of the fracture site, and, if necessary, antibacterial therapy. The infection must be controlled before or during reconstructive surgery.
Bone grafting. Addition of bone tissue to the fracture site to stimulate union.
Autograft, allograft, or synthetic material?
| Autograft |
Allograft |
Synthetic substitutes |
| Source |
The patient’s own bone (most commonly the iliac crest) |
Donor bone |
Artificial materials |
| Living cells and growth factors |
Yes |
No |
No |
| Biological potential |
Highest |
Lower |
Primarily provides a scaffold |
| Amount of material |
Limited |
Practically unlimited |
Unlimited |
| Main disadvantage |
Additional incision, pain at the donor site |
Lower biological activity |
Requires the patient’s own biological healing potential |
In a retrospective study of 182 patients with long-bone nonunion (Flierl et al., Journal of Orthopaedic Surgery and Research, 2013), autologous bone grafting showed a shorter time to union (an average of 198 days versus 416 days for allograft) and a lower rate of repeat surgery (17% versus 47%). This was an observational rather than randomized study, so the results should be interpreted with caution. In practice, synthetic materials are often used in combination with autologous bone rather than as a replacement for it.
Correction of deformities. If nonunion is accompanied by limb deformity, the intervention may include correction of the bone axis.
Surgical treatment of nonunion is a complex procedure that requires careful planning. Even after surgery, there remains a risk of recurrent nonunion and other complications; the physician discusses expectations, risks, and the postoperative management plan with the patient.
When are patient-specific 3D implants considered?
In complex clinical cases, standard reconstruction methods may be insufficient or technically difficult. Patient-specific 3D-printed implants may be considered, in particular, for:
- Large bone defects, when standard bone grafting does not provide sufficient volume or stability.
- Complex anatomy — in joint regions or in the presence of deformities where off-the-shelf implants do not match the patient’s anatomy.
- Repeated fixation failures, when previous attempts have not resulted in union.
- The need for precise anatomical reconstruction rather than merely restoration of bone continuity.
How such an implant is created: CT of the affected area → three-dimensional digital model → design based on the patient’s anatomy → 3D printing using biocompatible materials (most commonly titanium or specialized polymers) → surgical implantation.
Advantages: precise anatomical fit, the ability to reconstruct complex defects, and potentially improved fixation stability.
What is important to know about the evidence. The evidence base for patient-specific 3D implants is currently limited mainly to small retrospective studies and case series. There are no randomized or multicenter studies, so the role of these implants compared with standard techniques has not yet been definitively established.
Risks and limitations: infection, nonunion, and the need for revision procedures. The method requires precise preoperative planning, is highly dependent on local anatomy and the nature of the defect, is not available at all medical centers, and is not suitable for every case. The decision to use it is made by a multidisciplinary team.
Who should you consult and how should you prepare for the appointment?
The appropriate specialist is an orthopedic trauma surgeon. If necessary, the physician may refer you to a center experienced in treating complex nonunions and with access to modern reconstruction technologies.
What to bring with you:
- All radiographs and CT discs obtained since the fracture, as well as physicians’ reports — this will make it possible to assess the progression of the healing process.
- A list of medications and supplements, including vitamins and dietary supplements.
- Information about comorbidities: diabetes mellitus, osteoporosis, vascular diseases, and other chronic conditions.
- Notes on symptoms and timing: when they appeared, how they changed, and what makes the pain better or worse.
Do not delay evaluation: the earlier the diagnosis is established and treatment is started, the better the chances of successful recovery. Do not rely solely on traditional remedies — fracture nonunion requires professional medical care.
Frequently asked questions
How long should a fracture take to heal?
Healing time depends on the bone, type of fracture, and treatment method, so there is no single timeframe. For long bones, the NICE benchmark is as follows: if there are no radiographic signs of union after approximately 3 months, this is considered delayed union. The expected timeframe for your specific case should be determined by your physician.
After how many months is a fracture considered a nonunion?
According to the NICE benchmark and FDA labeling — when at least 9 months have elapsed since the injury and there have been no visible signs of healing progression during the last 3 months. This is a benchmark, not an automatic diagnosis: the decision is made by a physician based on the clinical picture and imaging findings.
Can pseudarthrosis heal on its own?
Once pseudarthrosis is established, spontaneous union is unlikely — the healing process has already stopped. This is why surgical intervention is required in most cases.
Does smoking affect fracture healing?
Yes. According to meta-analyses, the rate of nonunion is significantly higher among smokers. Smoking cessation at least 4 weeks before surgery was also associated with a lower rate of postoperative wound infection.
Can painkillers be taken for a fracture?
The evidence regarding NSAIDs is conflicting. Intravenous ketorolac during the acute period did not show an increased risk of nonunion in the EAST/OTA guideline. Prolonged use of high-dose NSAIDs should be discussed with a physician — they should not be taken independently for months.
How does hypertrophic nonunion differ from atrophic nonunion?
In hypertrophic nonunion, the bone is attempting to heal, but excessive mobility interferes with union — treatment is aimed at improving fixation stability. In atrophic nonunion, bone formation is absent because of a biological problem — stimulation is required, most commonly bone grafting.
Does ultrasound therapy (EXOGEN, LIPUS) help?
NICE considers LIPUS an option for nonunion and delayed healing of long bones when appropriate indications are present. It is an adjunctive method: it does not replace surgery in established pseudarthrosis and is prescribed individually by a physician.
Are vitamin D and calcium necessary for fracture healing?
These nutrients are necessary for bone tissue formation, and their deficiency may slow healing. However, supplementation is prescribed based on laboratory test results rather than prophylactically “just in case.”
Conclusion
Fracture nonunion is a serious complication that requires careful diagnosis and, in most cases, surgical treatment. The choice of method depends on the type of nonunion, presence of infection, size of the bone defect, and the patient’s overall condition. Modern orthopedics offers a wide range of approaches — from revision osteosynthesis and bone grafting to patient-specific 3D-printed implants in complex cases. Timely consultation with an orthopedic trauma surgeon and adherence to the physician’s recommendations are key factors for successful recovery.
Sources
- National Institute for Health and Care Excellence. EXOGEN ultrasound bone healing system for long bone fractures with non-union or delayed healing (MTG12). 2013, updated 2019. https://www.nice.org.uk/guidance/mtg12
- Jensen SS, Jensen NM, Gundtoft PH, Kold S, Zura R, Viberg B. Risk factors for nonunion following surgically managed, traumatic, diaphyseal fractures: a systematic review and meta-analysis. EFORT Open Reviews. 2022;7(7):516–525. https://doi.org/10.1530/EOR-21-0137
- Xu B, et al. The influence of smoking and alcohol on bone healing: systematic review and meta-analysis of non-pathological fractures. EClinicalMedicine. 2021. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8571530/
- Eastern Association for the Surgery of Trauma (EAST) / Orthopaedic Trauma Association (OTA). Pain Management After Orthopedic Trauma: Guidelines. Summary: https://www.aafp.org/afp/2024/0400/practice-guidelines-pain-management-orthopedic-trauma
- Flierl MA, et al. Outcomes and complication rates of different bone grafting modalities in long bone fracture nonunions: a retrospective cohort study in 182 patients. Journal of Orthopaedic Surgery and Research. 2013. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3847297/
