Understanding Primary Spinal Infection (PSI)

Primary spinal infection (PSI) refers to infections affecting any part of the spine—including the intervertebral disc, vertebral body, spinal canal, or nearby paraspinal tissues—without prior surgical intervention. PSI frequently involves multiple spinal compartments and can present as anything from isolated discitis to extensive epidural or subdural abscesses. The primary cause is usually bacterial, often originating from a distant site through hematogenous spread.

A Diagnostic Challenge

PSI manifests with a wide range of clinical symptoms, from mild, progressive back pain to severe, unrelenting pain, neurologic deficits, and spinal deformity. Due to this broad spectrum, diagnosis is often delayed, leading to worsened outcomes including higher mortality rates and severely reduced quality of life.

• Rising Global Incidence.

Despite improvements in hygiene and socioeconomic factors, the global rate of PSI continues to climb. Contributing factors include aging populations, increased numbers of immunocompromised individuals, and the widespread use of intravenous drugs. This trend is reflected in clinical practice, where the number of spinal infection cases is rising.

• Inconsistent Treatment Practices.

Treatment strategies for PSI vary significantly—even among patients with similar presentations. Approaches range from conservative antibiotic management to complex surgical intervention. A major barrier to improving patient outcomes is the absence of universally accepted treatment algorithms.

• Global and Regional Variability.

Variations in treatment approaches are common between countries and even among providers within the same region. These differences arise from diverse pathogen profiles, resource availability, and physician training or preferences. This lack of consistency underscores the need for more standardized and evidence-based protocols.

• Nonoperative Treatment Dilemmas.

Nonoperative management, typically involving a minimum of four weeks of antibiotics, is the most common initial approach. However, the choice of antibiotics and treatment duration vary widely. The success of identifying the bacteria causing Primary Spinal Infection (PSI) can vary a lot—lab tests (called cultures) only detect the infection in about 24% to 93% of cases. This wide range makes it hard for doctors to choose antibiotics that target the exact bacteria. As a result, they often have to use broad-spectrum antibiotics that work against many types of bacteria. The length of antibiotic treatment also varies, usually lasting between 4 to 12 weeks, depending on the patient’s condition and how severe or complex the infection is.

When Should Surgery Be Considered?

Failure of conservative (nonoperative) treatment is also widely cited as a surgical indication. However, many studies do not provide clear benchmarks for what constitutes “failure.” This could range from persistent or worsening pain, lack of improvement in infection markers (like CRP or ESR), or radiographic evidence of disease progression despite adequate antibiotic therapy. The ambiguity in these criteria makes it difficult to establish standardized surgical thresholds or timing.

When surgery is warranted, several types of procedures may be required depending on the severity and extent of the infection. Debridement is often performed to remove infected or necrotic tissue. This can be done through anterior, posterior, or combined approaches depending on the infection’s location. In cases where the spinal cord or nerve roots are compressed by infected tissue or abscess, decompression surgery, such as a laminectomy or discectomy, may be necessary.

If there is structural compromise leading to instability, spinal stabilization and fusion are often required. This involves instrumentation (e.g., rods, screws) and sometimes bone grafts or cages to restore the spine’s integrity. For patients with large abscesses, surgical or percutaneous drainage may also be necessary to control the spread of infection and reduce inflammation.

Surgical intervention decisions are inconsistently defined in current literature. Common indications include:

• Neurological deficits (especially progressive ones), though definitions vary (e.g., presence vs. ASIA scale).
• Spinal instability, which lacks clear radiographic criteria and is largely based on clinical judgment.
• Failure of conservative treatment, though many studies fail to define what constitutes “failure.”

Unfortunately, the ambiguity in these indications makes it difficult to determine optimal surgical timing or approach.

Complexities in Surgical Management.

Surgical treatment of PSI is often high-risk due to:

• Infections located in difficult-to-access regions (e.g., ventral to the spinal cord).
• The need for extensive decompression, debridement, and spinal fusion.
• Increased likelihood of blood loss, postoperative complications, and lengthy recovery.

Surgical challenges are especially pronounced in the thoracic spine due to its anatomical complexity. Furthermore, PSI often affects medically complex patients—many of whom are elderly, immunocompromised, or affected by substance use—which can complicate both surgical and nonsurgical outcomes.

Urgency of Standardization and Research.

Delayed surgery, when needed, can lead to devastating consequences including permanent neurological impairment, disability, or death. Yet, despite the increasing prevalence of PSI, treatment remains highly variable due to a lack of high-quality, prospective studies and standardized outcome definitions.

To address this gap, the AO Spine Knowledge Forum Trauma & Infection is actively developing a comprehensive classification system and planning a multicenter observational study to refine diagnostic and therapeutic strategies for PSI.

Conclusion: A Call for Collaborative Action.

PSI presents a growing clinical challenge globally. Its rising incidence, combined with a lack of standardized treatment pathways, calls for urgent, collaborative efforts to create evidence-based algorithms. Such initiatives will ensure more consistent care, reduce preventable complications, and ultimately improve the quality of life for patients worldwide.

Frequently Asked Questions