What is Bone Nonunion?
Nonunion of bone is when the body can’t heal a broken bone. The U.S. Food and Drug Administration (FDA) defines it as a fracture that has not shown any signs of healing for three months after being present for at least nine months. However, it’s worth noting that this definition isn’t strict and that not all bones heal at the same rate. Certain medications, such as bisphosphonates, can also affect how long it takes a bone to heal.
For instance, one study found that delay in bone healing (also known as delayed unions), particularly in unusual fractures of the thigh bone (femur), occurred more often with long-term use of bisphosphonates. Nonunion of bone is a complex issue that can be influenced by many factors, and doctors must consider various treatment approaches.
To determine if a fracture is healing, doctors look at medical imaging such as X-rays to see if new bone is growing across the fracture line. They also assess other signs of healing, like the absence of pain when putting weight on the affected area, and no movement at the fracture site. Patients’ other health conditions must also be considered to evaluate any risk factors that could hinder bone healing. These factors need to be managed properly to allow the fracture to heal.
What Causes Bone Nonunion?
When it comes to treating situations where a broken bone doesn’t heal correctly (which we call a nonunion), understanding why this happened is key in deciding the best treatment. The reason behind the nonunion is a complex process that depends on a few factors. These include the patient’s physical condition, type of injury, medical history, lifestyle habits, and how the treatment was conducted.
Blood supply to the bone is an important aspect when considering healing; if it gets reduced, the bone might not recover properly. This could be due to bad lifestyle choices like poor diet or smoking; medical conditions like diabetes, blood vessel diseases, low vitamin D, compromised kidney function, or certain medications can also play a role.
The method of treatment can also impact recovery – if the break isn’t properly stabilized, healing becomes challenging. Sometimes, the type of bone fracture makes it hard to heal. These specific situations may include bone loss with fracture gaps larger than 3 mm, lack of cortical (bone outer layer) continuity, highly comminuted (broken into many pieces), and butterfly fragments.
According to Steen et al., smoking and diabetes are the most significant risk factors causing nonunion. Identifying these individualized risk factors can help predict the likelihood of nonunion and assist doctors in deciding the best surgical treatment.
Nonunion of the bone can be grouped into four categories:
1. Hypertrophic Nonunion: Here, the x-ray shows a lot of callus (extra bone-like tissue) formation, but the bone ends are not connected. This indicates there’s enough blood supply, but the bone is not stable enough.
2. Atrophic Nonunion: In this type, there’s very little or no callus visible in x-rays, suggesting poor blood supply and other issues mentioned earlier, and inadequate fixation.
3. Oligotrophic: This is a blend of Hypertrophic and Atrophic nonunion, with incomplete callus formation, indicating improper alignment of the bone.
4. Septic Nonunion: Here, the organisms consume the nutrition necessary for bone health, reducing blood flow, decreasing new bone formation.
Risk Factors and Frequency for Bone Nonunion
In the United States, approximately 100,000 fractures do not heal properly each year. This issue, known as nonunion, affects between 1.9% and 10% of all fractures. The likelihood of nonunion can vary based on the area of the body that’s fractured. For example, about 8% of femur (thigh bone) fractures and 4.6% of tibia (shin bone) fractures that are treated with a special type of surgery called intramedullary nailing end up in nonunion. However, some studies suggest that the nonunion rate for tibia fractures could be as high as 10% to 12%.
Certain factors can increase the risk of nonunion. For instance, extensive damage to the soft tissues surrounding the fracture can raise the nonunion rate to as high as 16%. It has also been suggested that being male might increase the risk of nonunion, potentially due to differences in activity types and injury patterns between genders. However, this claim should be regarded with caution, as other studies have not been able to confirm these findings. In fact, a study by Brown and colleagues found equal nonunion rates of 12% in both males and females.
Signs and Symptoms of Bone Nonunion
If a patient’s bone isn’t healing properly, doctors have to consider many factors. They’ll ask about how the injury occurred, like whether it was from an open or closed wound. They’ll also evaluate what kind of surgery was done, like whether it involved plates and screws or a procedure known as intramedullary nailing. The patient’s health history is important, too. Doctors look at things like how well the patient is eating, if they have diabetes, smoke, suffer from vascular disease, how much vitamin D they have, if their kidneys are functioning well, and if they’re taking nonsteroidal anti-inflammatory drugs (NSAIDs) or steroids. Doctors also need to study x-rays or CT scans to find out what kind of fracture it is, like whether it’s comminuted, segmental, or infected. Clinically, doctors will ask the patient if they feel pain at the fracture site when they put weight on it or walk. They’ll also physically check for signs of infection, like if there’s pus or draining tracts at the wound. They’ll also check for any neural or vascular issues, how well the soft tissues are doing, and whether the fracture site is still mobile.
- History: Type of injury (open or closed), type of surgery (plates and screws or intramedullary nailing), patient’s health risk factors (dietary health, diabetes, smoking, vascular disease, vitamin D levels, kidney function, use of NSAIDs, use of steroids)
- X-rays or CT scans: Type of fracture (comminuted, segmental, infected)
- Physical exam: Pain when putting weight on it or walking, presence of pus or draining tracts at the wound, neural or vascular conditions, state of the soft tissues, mobility of the fracture site
Testing for Bone Nonunion
If your doctor suspects you have a nonunion, which is when a broken bone doesn’t heal, they will need to perform several tests for a thorough evaluation. The first test they’ll use is a plain radiograph, which is an X-ray image. For broken tibia (the shin bone), doctors can use something called a RUST (radiographic union score for tibia) score. This is a way for them to objectively assess the state of healing of a broken leg using X-ray images.
The RUST score ranges from 4 to 16 — a score of four implies no healing has taken place in any of the four sections (cortices) of the bone, while a score of 16 shows full healing of all four sections. Each of the four sections of the bone are scored separately. A score of 1 for a section indicates no sign of healing. A score of 2 shows the presence of callus, which is new bone tissue that forms on the bone’s surface when it’s healing. A score of 3 reveals that the callus is bridging or connecting the broken parts of the bone. And finally, a score of 4 for a section signifies the bone has healed completely and the fracture can no longer be seen. The final RUST score is then calculated by adding up the scores for all four sections.
Additionally, if your doctor is uncertain about how well the bone is healing, they might recommend a CT scan. They can also do some blood investigations like checking the levels of C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood cell count (WBC) to rule out any infection that might interfere with the healing process. These test results will be interpreted in connection with your physical examination.
Treatment Options for Bone Nonunion
When a person’s bone doesn’t heal properly after a fracture, it’s a condition referred to as ‘nonunion’. The treatment for this issue requires several steps and depends on the specific condition of the nonunion.
At first, doctors may try non-surgical treatments. This could consist of using a special brace or cast for a while after surgery, or therapies using devices that stimulate bone healing externally, like pulsed low-intensity ultrasound.
If non-surgical treatments don’t work, surgery might be required. The type of surgery depends on the specific type of nonunion.
In case of hypertrophic nonunion, which happens when the body tries to heal the bone but fails due to instability, surgeries aim to improve stability. The techniques include the use of compression plates, exchange nailing (replacing a bone’s metal rod), and augmented plating with open reduction and internal fixation (a procedure to put the pieces of bone back together).
Atrophic nonunion indicates a failure in the bone healing process itself. In such cases, surgeons aim to address both the biological failure and mechanical instability. Techniques include a combination of fixing the bone in place and procedures to stimulate bone growth. Bone grafts or certain approved biological substances like Bone morphogenetic proteins (BMP) can be used for this.
Oligotrophic nonunion is when there is potential for healing but it’s insufficient due to instability and lack of growth stimulation. Here, both stability enhancement and growth stimulation methods are used depending on the situation.
If infection is involved, doctors order specific tests and follow a 2-stage surgical protocol. The first stage includes removing any infected hardware, cleaning the area, revising the unstable bone fragment, and starting a course of antibiotics. The specific method to provide initial stability in case of infection could include the use of antibiotic beads, antibiotic nails, or antibiotic cement spacers, among other techniques.
Once infection signs have disappeared after a course of antibiotics, the second stage begins. It involves definitive fixation, which progresses to bone grafting, biological treatment, or bone transport depending on the specific fracture.
What else can Bone Nonunion be?
If you’re healing slower than expected from a fracture, doctors may suspect a ‘delayed union’. This situation demands a detailed examination as it could alter the healing process and treatment method. If there’s suspicion of a delayed union, health professionals might first opt for less invasive treatments. These could include external stimulation techniques like ultrasound, or nail dynamization. These techniques are preferred before considering any major surgery.
- Infection
It’s a condition that also needs to be considered if your healing process is slower than expected.
What to expect with Bone Nonunion
Non-surgical treatment options for bone healing complications can be quite effective. Using ultrasound, success rates can reach between 70% and 93%. This typically involves the use of ultrasound therapy within three months after the last operation. Importantly, it seems to work best when used less than six months after surgery.
Surgical treatments for these bone healing complications also have high success rates. For instance, a technique called nail dynamization has an 83% success rate. While, another method used in upper arm fractures, known as exchange nailing, has shown a 95.6% success rate.
However, complication associated with infections portrays a poor prognosis. Studies have shown low success rates after surgical treatments for this particular complication.
Possible Complications When Diagnosed with Bone Nonunion
Some potential complications you might experience with humeral shaft fractures could include:
- Nerve damage, mainly to the radial nerve
- Nonunion, where the bones do not grow back together
- A requirement for amputation
- Infection causing more damage to nearby body parts
- Use of BMP-2 (a bone growth protein) causing potential side effects like bone weakening, abnormal bone growth, issues with ejaculation during spine surgery, and complications with the wound healing process
Preventing Bone Nonunion
It’s crucial to talk with patients about what could happen after a procedure, particularly if their injury didn’t heal completely, and there’s a chance of infection. Letting patients know that their broken bone may not heal completely, even with the best treatment, helps them understand their options moving forward. This can empower patients in their own care, minimize confusion, and create a better doctor-patient relationship.
Explaining all possible outcomes, including the chance that they might need an amputation in certain circumstances, can prepare patients for what could happen and make it less likely for them to file a lawsuit. It’s important not to catch patients by surprise with their treatment and recovery process.
