Osteomyelitis
What is Osteomyelitis?
Osteomyelitis the medical term that refers to infection in bone. This occurs when pathogens reach the bone and cause an infection. Early on this infection causes pain and may result in a collection of pus forming inside or around the bone. Theoretically if the infection can be treated at this stage before damage to the bone, it might be possible to treat with targeted antibiotics and drainage of any collections present. The infection at this early stage is termed acute osteomyelitis. However, if the infection results cause damage to the blood supply of the bone or in the presence of metalwork the infection is termed chronic osteomyelitis. This means that antibiotics alone are unlikely to cure the problem and surgery is likely to be required.
How does the infection reach the bone?
It can occur when bacteria reach the bone, either through direct contamination (often termed contiguous focus) or through the blood stream (termed haematogenous). Direct contamination of the bone can occur because of an open fracture, or by the infection getting into during an operation, often when metalwork is inserted into the bone. Haematogenous infection can result when bacteria spread into the bone via the blood stream, often because of septicaemia. Whilst now less common in the UK, haematogenous infection i still a leading cause of bone infection worldwide, particularly in children.
Once infection reaches the bone the inflammation it causes can result in damage to the bone blood supply, which kills the healthy cells living in the bone. These areas of dead bone can be invaded by the bacteria which can then produce a protecting barrier known as a biofilm that is laid down on the surface of the dead bone. This shield the bacteria for the body’s natural defences and is one of the reasons why chronic osteomyelitis cannot simply be cured with antibiotics once it is established.
What is chronic osteomyelitis?
This is a bone infection that has resulted in the formation of dead bone, known as a sequestrum. This dead bone acts as a nidus for the infection and curing the infection is almost impossible without considering surgery to remove the affected bone. Whilst the term chronic osteomyelitis implies the infection needs to have been present for some time, the formation of dead bone can occur early in a bone infection, particularly following a fracture when there is already some damage to the bone’s blood supply from the injury. Expertise is required in ensuring the diseased bone and biofilm is removed surgically that the immune defences and antibiotics are unable to reach, whilst ensuring the healthy bone is not preserved to maximise the rate of recovery following intervention. It is not uncommon we encounter people who we have successfully treated who have previously lived with infection for many years, often having been told their infection was untreatable or that nothing that could be done.
What is the difference between acute and chronic osteomyelitis?
The main difference is the presence of dead bone or biofilm in chronic osteomyelitis. This makes treatment with antibiotics alone very unlikely to eradicate the infection and the infection persists. In theory acute osteomyelitis can be successfully treated with antibiotics alone. However, biofilm may form in a few days, and dead bone may be present from the time of a fracture and so there is no time cut off that defines the difference between acute and chronic osteomyelitis.
Why don’t antibiotics work in osteomyelitis?
Antibiotics don’t penetrate well into dead bone, metal work or biofilm. This means that the concentration of antibiotics is not usually sufficiently high to kill all the bacteria and totally eradicate them. It might dampen down the infection for a period, but at some point, after the antibiotics are stopped, the infection is likely to flare up again. Furthermore, there is a risk that ongoing courses of antibiotic can select out more difficult to treat bacteria that are more resistant to the antibiotics used.
Why is surgery needed for osteomyelitis?
The aim of surgery is to remove the area of dead bone and any implants that are not contributing to the bone’s stability. At the same time samples are taken of the infected tissue to identify the organisms causing the infection, which allows the correct selection of antibiotics to be given following surgery. The operation may also involve the reconstruction of the bone if needed. We often use local antibiotic carriers that are used to fill any bone defects, and which can deliver high concentrations of antibiotic directly at the area of infection. An important part of the treatment is to ensure that the wounds are closed at the end of the procedure. We always aim to achieve this and if required will be able to achieve this with the use of plastic surgical techniques if direct closure is not possible. Unlike other centres who often perform multiple operations to treat bone infection, we always aim to deliver surgery in a single operation. This leads to faster recovery and better outcomes in the cases we treat.
Who treats osteomyelitis?
Bone infection is not a very common problem but is well known to be a challenging condition to treat. There is good evidence that outcomes are better when bone infection is treated by a multi-disciplinary team. In the Oxford Limb Reconstruction and Infection clinic we have a group if internationally recognised experts in the management of complex bone and joint infection. The team comprises orthopaedic surgeons who work together with infectious disease physicians, plastic surgeons, and musculoskeletal radiologists to successfully treat this condition. We also have dedicated physiotherapy and specialist nurse support with a focus on managing people with bone and joint infection. Each specialty brings unique skills that are needed, particularly in the complex patients.
Which bones can osteomyelitis affect?
No bone is totally resistant to infection, but the commonest bones are the long bones of the lower limb. The tibia is most often involved with serious infection and is challenging to treat due to the thin layers of protective soft tissues and relatively poor blood supply. This makes reconstruction more challenging, and this is why our team has dedicated plastic surgical expertise so that we can successfully manage these cases. After the tibia, the femur is the second most affected bone. Infection in the upper limb is also seen, particularly following fracture fixation.
What are the symptoms of osteomyelitis?
Bone infection can have a range of symptoms including pain, swelling and redness at the site of infection. A draining wound over the affected bone may develop and can spontaneously dry up or persist for years. A collection of pus under pressure can cause severe pain and make the patient unwell with fevers and temperatures. If the infection occurs following a fracture, then the risk is the infection prevents the bone from healing resulting in a non-union. Furthermore, the metalwork place to support bone healing can itself become loose or fail over time.
Who is at risk of developing osteomyelitis?
Although anyone can develop osteomyelitis, there are certain risk factors that make it more likely to occur. Some of these risk factors include:
- Those with chronic health conditions, such as poorly controlled diabetes or kidney disease.
- Those who smoke.
- Those who have had surgery to fix a fracture. The risk is significantly higher with open fractures, particularly when there is more severe soft tissue injury
- Those who have immunosuppression, such as those taking steroids, or receiving chemotherapy.
Supportive Care
Generally, osteomyelitis is a persistent problem, but not dangerous and cannot be spread between people. Whilst the problems its cause vary between cases it principally causes pain or requires dressings to manage discharge from leaking sinuses in the skin.
There are three times when osteomyelitis can worsen to cause serious complications. Firstly, the infection can spread around the body to make the patient septic and if untreated this can result in a life-threatening infection. This is less common when there is a discharging sinus present. The early administration of antibiotics is required in this situation to treat the sepsis. Secondly, over time the infection may weaken the infected bone which can occasionally cause the bone to break. This infected fracture is more difficult to treat. Finally, a chronic wound or scar for many years has a very small chance of developing a cancerous growth.
How is the diagnosis of osteomyelitis made?
Most commonly a history and examination along with plain film xrays can diagnose osteomyelitis. An MRI scan is very helpful in demonstrating the extent of infection, which aids surgical planning. In the context of fracture related infection, serial xrays, along with clinical review is often sufficient to raises the suspicion of infection. Occasionally more specialist scans are needed to stage the disease and help plan treatments. However, the gold standard for diagnosis of osteomyelitis remains the culture of infecting organisms from the bone itself or pathological analysis of the bone tissue form surgical samples.
What investigations are used for osteomyelitis?
Xray and MRI are the most commonly used investigations for the diagnosis and assessment of bone infection. Blood tests such are C-reactive protein are rarely useful. CT or PET-CT also have a role. Bone biopsy can be useful to diagnose infection. Culture of the infecting organism from a representative section of bone is used in the diagnosis and to guide antibiotic treatment. Wound swabs are not used at they do not represent the microbiology of the bone but rather the surface wound only.
Is MRI useful in bone infection?
Magnetic resonance imagining is often the best investigation to obtain for a bone infection. It is used for assessment of the infection in the bone and surrounding soft tissues and useful to guide the surgery required. However, MRI is impaired by the presence of metal work which makes it less useful in cases with implants in place. Newer scanners can use sequences that are able to reduce this image disruption to a minimum. Interpretation of these scans can be challenging, and this is why it is important that they are reviewed in a multi-disciplinary team which includes radiologists and surgeons with expertise in treating bone infection cases.
Which antibiotics are used in bone infection?
The choice of antibiotics is best determined following identification of the infecting organism and guided by a specialist infectious disease physician. Careful and diligent sampling by the surgical team is required to ensure the best chance of identifying the organism(s) causing the infection. Oxford have developed protocols to ensure the highest chance of identifying the cause of the infection. Through further research work at the Oxford Bone Infection Unit, it has been demonstrated that oral antibiotics can be equally as effective as intravenous. One antibiotic is not ‘stronger’ than another but has a different mechanism of action and kills specific bacteria. The decision about which antibiotics to use in managing infection can be complex and out team includes infectious disease physicians who can help make the best choices for each case we treat.
What is the success of surgery?
Although osteomyelitis is perceived to be a difficult problem to address, through the protocols developed in Oxford we have very good outcomes following surgery. By undertaking surgery through a multidisciplinary team that includes accurate bone sampling, excision of infected bone, delivery of local antibiotics, and bone and soft tissue reconstruction we can achieve successful outcomes in a single operation in around 90-95% of cases.
Is amputation needed for osteomyelitis?
With the modern multidisciplinary approaches to bone infection in our unit, amputation is rarely part of the treatment. Many of the cases we successfully treat for infection have previously been told that there is no surgical treatment available, or that amputation is the only option. We would rarely recommend amputation as a treatment, although something the individual with the infection is keen to explore this as an option. We recognise that these sorts of decisions can be difficult, and it is important that each individual is aware of all the options for treatment before making a decision. We are very happy to offer a second opinion or discuss potential surgical options with individuals in this situation.
Contact Us
If you’re concerned about symptoms or need more information, please don’t hesitate to contact the Oxford Limb Reconstruction and Infection Clinic. We’re here to help you understand your condition and explore the best treatment options.