Postoperative Spinal Infections - Classifications and Management

Introduction:

Spinal infections following spinal surgeries are painful and serious complications that can prolong the treatment and reduce the prognosis. The patient may experience pseudoarthrosis, long-standing pain that may need additional surgery, and severe neurological damage that may even cause death. The severity and incidence of infection vary according to the type of spine surgery performed and the surgical approach used.

What Are the Problems of Postoperative Spinal Infections?

Postoperative spinal infections pose a number of problems. Acute conditions not only prolong the treatment time it also reduces the outcome of the treatment. Infections can cause pain to patients and can be a financial burden. The presence of infections also affects imaging techniques and can cause artifacts, making diagnosis difficult. In these cases, hematoma and edema may be difficult to differentiate in an MRI (magnetic resonance imaging) scan after the procedure. It is also difficult to detect an infection as not all cases are associated with pain. Therefore the diagnosis and treatment of postoperative spinal infections are often delicate and problematic.

What Are the Risk Factors for Spinal Infections?

There are a plethora of conditions that can be a risk factor for spinal infection, and out of these risk factors, some are not modifiable.

Modifiable risk factors include:

• Smoking.

• Obesity.

• Malnutrition.

• Extended hospitalization.

• Inadvertent use of antibiotics, be it orally, intravenously, or directly at the site of surgery.

Nonmodifiable risk factors include:

• Advanced age.

• Urgent need for surgery such as in spinal trauma.

• Presence of diabetes mellitus.

• Decreased immunity.

• Spinal injury.

• Neuromuscular disorders.

Procedure-related risk factors:

• Duration of surgery.

• Blood transfusion.

• Blood loss.

• Intervention in multiple stages.

What Are the Clinical Symptoms?

A patient who has undergone spinal surgery should be monitored regularly. Some symptoms include:

• Back pain at the site of a wound.

• Fever.

• Increased white blood cells in the blood.

• Increased erythrocyte sedimentation rate.

• Fever can not be a reliable symptom as most patients experience after a procedure.

How Are Spinal Infections Classified?

There are a number of criteria by which spinal infections can be classified.

1. Depending on the size of the infection, it can be classified as deep or superficial.

• Deep Infections: These are those that extend beyond the fascia.

• Superficial Infections: These are those limited to the skin and subcutaneous tissues. Superficial infections are accompanied by inflammatory signs such as pain, swelling, redness, and a rise in temperature. Infections are generally localized.

2. Depending on proximity to surgery, it can be classified as:

• Acute Infection: Within three weeks of the procedure.

• Delayed Infection: If it occurs after more than three weeks of the procedure.

3. Depending on the pathogen present, it can be:

• Presence of a single type of microorganism.

• Presence of multiple types of organisms.

• Presence of myonecrosis (necrosis of muscles) along with multiple microorganisms.

How Are Spinal Infections Managed?

Treatment can be described as early recognition, debridement, and administration of culture-specific antibiotics.

Initial Management:

• Managing postsurgical spinal infections may be difficult, requiring multiple debridements and antibiotic administration for a prolonged period. Initial management is focused on stabilizing the patient’s condition.

• The first step after a suspected infection is blood tests and blood cultures to confirm the diagnosis.

• After the blood test results are obtained, broad-spectrum antibiotics are administered. An infectious disease specialist can be consulted to guide antibiotic therapy.

• If the patient is stable, additional diagnostic modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) can be held off until bacterial culture results are obtained.

• If the patient undergoes sepsis or shock due to sepsis, emergency surgery and administration of antibiotics should be started immediately, without waiting for culture results.

• If the patient has neurological symptoms, the patient should be taken urgently to the operating room for debridement and irrigation to reduce compression of neurologic structures.

Surgical Management:

• Surgical debridement is done based on the determination of whether the wound is deep or superficial. Once this is determined, thorough debridement of necrotic tissue is done. It is important to remove the infected tissue.

• If the local blood supply is insufficient, multiple debridements may be necessary.

• Administration of antibiotic beads at the site of the wound ensures that adequate antibiotic coverage is available at the wound. This is to combat the decreased perfusion of antibiotics due to infection present at the site.

• In cases of postsurgical complications involving spinal instrumentation, it is treated based on whether the infection is acute or delayed.

• In the case of acute infections, hardware is not removed to prevent destabilization of the spine; however, the loose bone graft is removed during debridement.

• In the case of late infections, hardware is removed. This is done so because proper anchorage should be achieved by this point. Likewise, if proper bone fusion has been achieved, hardware can be removed.

Antibiotic Management:

• Antibiotic therapy should be continued in addition to debridement. But antibiotic therapy should only be started after culture results, provided the patient is stable.

• If the patient is septic, antibiotics should be started before culture results to prevent further worsening of the situation.

• Postoperative osteomyelitis is treated with more than three months of antibiotics.

• For deep infections, antibiotics are continued for four to six weeks.

• Duration and type of antibiotic therapy are decided based on culture results, inflammatory markers, and blood tests.

Additional Therapy:

Hyperbaric oxygen is used as an adjunct for the treatment of spinal infections. Hyperbaric oxygen is used as it is believed that it is beneficial in reducing infection by restoring oxygen tension in the intramedullary bone. It also reduces phagocyte reduction and brings it to normal levels, and stimulates the blood supply or neovascularization of healing wound edges. It also increases blood supply, which helps in the healing of the tissues. There are no side effects that have been reported for hyperbaric oxygen therapy. Whether hyperbaric oxygen therapy reduces the number of revision surgeries in comparison with standard therapy options is under research.

How to Prevent Postoperative Spinal Infection?

Reduction of Risk Factors:

• By reducing modifiable risk factors, spinal infections can be decreased to an extent. The choice of proper surgical intervention can also reduce postoperative infections.

• To avoid postoperative infections, infections that are present at distant places must be treated before the surgery.

• Maintaining sterile working conditions is of paramount importance in reducing spinal infections, as studies have suggested that most infections may be due to direct inoculation.

Chemical Agents and Physical Drains:

• Adjuvant measures can be undertaken to reduce the incidence of postoperative infections. Chemical agents can be used as disinfectants, and antibiotic and physical agents can be used as prophylactic drains.

• Powdered Vancomycin can be administered locally during surgery to prevent direct inoculation.

• Betadine solution irrigation has been found to reduce infections.

• Prophylactic drains are used widely in orthopedic cases. This helps to drain out the blood and inflammatory byproducts, thereby reducing the incidence of infection.

Prophylactic Antibiotics:

It has been found that the use of antibiotics before the procedure has significantly decreased infections post-surgery. Cephalosporin is usually used for this purpose.

Conclusion:

In spite of the evolution of modern medicine and the accessibility of antibiotics, infections are a potential and dangerous complication of spinal surgeries. This can negatively affect the treatment outcome, prolong the duration of treatment, and even lead to sepsis and death. But proper monitoring of symptoms and preventing the risk factors for infections can reduce the incidence of the infection. If it arises, a blood culture is done, antibiotics are prescribed to reduce microorganism load, and debridement is done to enhance healing.