Pyogenic spondylitis is relatively uncommon and includes two clinical types: vertebral pyogenic osteomyelitis and disc space infection.
Vertebral Pyogenic Osteomyelitis
The most common causative pathogen is Staphylococcus aureus. The pathogenic bacteria reach the vertebral body through three main routes:
- Hematogenous dissemination, where bacteria from pre-existing purulent infections of the skin or mucosa spread to the vertebrae via the bloodstream.
- Direct spread from soft tissue infections adjacent to the spine.
- Lymphatic dissemination to the vertebrae.
This condition is more commonly seen in adults, with the lumbar spine being the most frequently affected, followed by the thoracic spine, while involvement of the cervical spine is rare. The lesions are typically limited to the vertebral body but may extend into intervertebral discs or adjacent vertebrae. In rare cases, the infection can spread through the vertebral arch into the spinal canal. Most cases result in paravertebral abscess formation, such as psoas abscesses in the lumbar spine or retropharyngeal abscesses in the upper cervical spine. The condition progresses rapidly, with the development of sclerosis and the fusion of adjacent vertebrae, sometimes leading to intervertebral fusion. The onset is often abrupt, characterized by chills, shivering, high fever, and marked symptoms of sepsis. Patients experience severe pain in the lumbar, thoracic, or cervical regions, which may render them bedridden, unable to turn or move their neck. Paraspinal muscle spasms, localized tenderness, and percussion pain are frequently observed.
Treatment primarily focuses on systemic anti-infective therapy, with sufficient and effective antibiotic administration. Blood cultures can help identify the pathogen, and sensitivity testing guides the selection of appropriate antibiotics. Strict bed rest may relieve pain and facilitate tissue repair. Surgical debridement is indicated for cases with paravertebral abscesses or significant vertebral destruction.
Disc Space Infection
The most common causative pathogens are Staphylococcus aureus and Staphylococcus epidermidis. Bacteria can reach the disc space via two main routes:
- Direct introduction into the disc space through surgical instruments, such as post-discectomy infections.
- Hematogenous dissemination from remote infections, such as those in the skin, mucosa, or urinary tract, with urinary tract infections being the most common source.
Postoperative infections of the disc space may have a sudden or gradual onset. Infections caused by Staphylococcus aureus often present acutely, with chills, high fever, severe back pain, and significant nerve root irritation symptoms. Patients may avoid turning their body, as even minor movements can trigger muscle spasms and pain. Symptoms and signs of the primary nerve root involvement often worsen. Infections caused by less virulent bacteria, such as Staphylococcus epidermidis, typically have a more insidious onset with milder systemic symptoms and a tendency to become chronic.
Hematogenous disc space infection is more common in young and middle-aged adults and is rare in children. The lumbar spine is the most commonly affected site. The typical onset is insidious, with symptoms such as fever and loss of appetite. Patients may experience lumbar back pain and sciatica. Common physical signs include localized tenderness, lumbar muscle spasm, and restricted movement. Symptoms generally improve with antibiotic therapy but can recur with excessive activity or interruption of treatment. During periods of active infection, leukocytosis and an elevated erythrocyte sedimentation rate (ESR) are often observed.
Treatment emphasizes systemic anti-infective and supportive therapy. Delayed diagnosis is common, particularly in hematogenous disc space infections, making early diagnosis challenging. In later stages, local tissue adhesions may become significant, complicating surgical procedures and increasing the risk of complications. As such, surgery is only indicated in the following situations:
- Progressive neurological deficits.
- Significant bone destruction, spinal deformity, or spinal instability.
- Large paravertebral abscess formation.
- Recurrent infections.
- Failure of conservative treatment.
Surgical procedures may include debridement and removal of the affected intervertebral disc, decompression of the spinal canal and neural structures, and bone graft fusion with internal fixation.