Pyogenic spondylodiscitis is a bacterial infection involving the intervertebral disc and adjacent vertebral endplates. It is the most common form of spinal infection and represents a potentially serious condition that may lead to vertebral destruction, spinal instability, epidural abscess, neurological deficits, permanent disability, or death if diagnosis and treatment are delayed. Infection usually occurs through hematogenous spread but may also result from direct inoculation during spinal procedures or contiguous spread from adjacent tissues.

The most common causative organisms are Staphylococcus aureus, followed by Escherichia coli, Proteus species, and other Gram-negative bacilli.

Epidemiology

Pyogenic spondylodiscitis:

• Accounts for the majority of spinal infections

• Primarily affects adults over 50 years

• Occurs more frequently in males

• Incidence is increasing because of aging populations, diabetes mellitus, immunosuppression, spinal instrumentation, and intravenous drug use

• Lumbar spine is most commonly affected, followed by the thoracic and cervical spine

Etiology

Common causative organisms

• Staphylococcus aureus (most common)

• Methicillin-resistant Staphylococcus aureus (MRSA)

• Escherichia coli

• Proteus species

• Pseudomonas aeruginosa

• Coagulase-negative staphylococci (particularly after spinal surgery)

• Streptococcus species

Routes of infection

• Hematogenous dissemination (most common)

• Direct inoculation following spinal surgery or epidural procedures

• Contiguous spread from adjacent soft tissue infection

Risk factors

• Diabetes mellitus

• Advanced age

• Chronic kidney disease

• Immunosuppression

• HIV infection

• Intravenous drug use

• Recent bacteremia

• Urinary tract infection

• Infective endocarditis

• Spinal surgery

• Epidural injections

• Malnutrition

• Malignancy

Pathophysiology

Pyogenic spondylodiscitis usually develops after bacteria enter the bloodstream from a distant focus such as the urinary tract, skin, or respiratory tract. The organisms lodge within the highly vascular vertebral endplates where they multiply and trigger an intense inflammatory response. Infection subsequently spreads through the endplate into the relatively avascular intervertebral disc, causing disc destruction and progressive erosion of adjacent vertebral bodies.

As inflammation progresses, vertebral collapse may occur, producing spinal instability and kyphotic deformity. Extension of infection into the epidural or paravertebral spaces may result in abscess formation, compression of nerve roots or the spinal cord, and irreversible neurological injury if treatment is delayed.

Classification

According to duration

• Acute

• Subacute

• Chronic

According to route of infection

• Hematogenous

• Postoperative

• Post-traumatic

• Contiguous spread

According to anatomical involvement

• Discitis

• Vertebral osteomyelitis

• Spondylodiscitis

• Spondylodiscitis with epidural abscess

• Spondylodiscitis with paravertebral abscess

Clinical presentation

Patients commonly present with:

• Persistent back pain

• Fever

• Muscle spasms

• Local spinal tenderness

• Reduced spinal mobility

• Difficulty walking

• Night pain

• Malaise

• Weight loss (occasionally)

Neurological involvement may produce:

• Lower or upper extremity weakness

• Numbness

• Paresthesia

• Radicular pain

• Bladder or bowel dysfunction (late presentation)

• Features of spinal cord compression

Red flag features

Urgent specialist assessment is indicated in patients with:

• Progressive neurological deficit

• Suspected epidural abscess

• Sepsis

• New bowel or bladder dysfunction

• Severe spinal instability

• Persistent severe pain despite treatment

Diagnostic criteria

The diagnosis of pyogenic spondylodiscitis is established by combining:

• Compatible clinical features (persistent localized spinal pain with or without fever)

• Elevated inflammatory markers (ESR and/or CRP)

• MRI findings consistent with vertebral and disc infection

• Isolation of a causative organism from blood cultures or CT-guided biopsy

• Histopathological confirmation when microbiological diagnosis remains uncertain

Microbiological confirmation should be obtained whenever possible before prolonged antibiotic therapy, provided this does not delay treatment in critically ill patients.

Investigations

Laboratory investigations

• Complete blood count (CBC)

• Erythrocyte sedimentation rate (ESR)

• C-reactive protein (CRP)

• Blood cultures (preferably before antibiotics)

• Urine culture and sensitivity

• Renal function tests

• Liver function tests

Microbiological investigations

• CT-guided vertebral or disc biopsy for microscopy, culture, and sensitivity

• Surgical biopsy when CT-guided biopsy is non-diagnostic

• Histopathological examination when indicated

Imaging

Plain spine X-rays

May demonstrate:

• Disc space narrowing

• Endplate erosion

• Vertebral destruction

• Kyphotic deformity

Early radiographs may be normal.

MRI with contrast (investigation of choice)

Demonstrates:

• Early disc infection

• Vertebral osteomyelitis

• Epidural abscess

• Paraspinal abscess

• Neural compression

CT scan

Useful for:

• Cortical bone destruction

• Surgical planning

• Image-guided biopsy

Radionuclide bone scan

May assist diagnosis when MRI is unavailable or contraindicated.

Differential diagnosis

• Degenerative disc disease

• Vertebral compression fracture

• Tuberculous spondylitis

• Metastatic spinal disease

• Multiple myeloma

• Epidural hematoma

• Mechanical low back pain

• Ankylosing spondylitis

Management

Management should involve early antimicrobial therapy, adequate pain control, spinal stabilization where necessary, and prompt surgical intervention in selected patients.

Non-pharmacological treatment

• Bed rest during the acute painful phase

• External spinal immobilization using appropriate spinal orthoses

• Gradual mobilisation after pain improves

• Adequate nutritional support

• Optimisation of diabetes and other comorbidities

• Physiotherapy following infection control

• Close neurological monitoring

Pharmacological treatment

General principles

• Obtain microbiological diagnosis whenever feasible before starting antibiotics.

• Initiate empirical intravenous antibiotics while awaiting culture and sensitivity results in clinically suspected cases.

• Modify antibiotic therapy according to culture and sensitivity findings.

• Continue treatment until clinical improvement and normalization of inflammatory markers, particularly CRP.

Pain management

Ibuprofen (PO) 400 mg stat then 200 mg every 8 hours

OR

Diclofenac sodium (PO) 50 mg every 8 hours

OR

Meloxicam (PO) 7.5–15 mg every 12–24 hours for 7–14 days

Severe pain

Diclofenac (IM) 75 mg every 12 hours by deep IM injection for 1–3 days

±

Tramadol (IM) 100 mg every 12 hours by deep IM injection for 1–3 days

THEN

Diclofenac (PO) 50 mg every 8 hours for 14 days

±

Tramadol (PO) 50 mg every 8 hours for up to 14 days

Topical analgesics

Diclofenac gel applied every 12 hours

OR

Ketoprofen gel applied every 12 hours

Gastroprotection

Consider gastroprotective therapy in patients with previous peptic ulcer disease or when NSAIDs are prescribed for two weeks or longer.

Omeprazole (PO) 20 mg once daily for 2–4 weeks

OR

Pantoprazole (PO) 40 mg once daily for 2–4 weeks

OR

Esomeprazole (PO) 40 mg once daily for 2–4 weeks

OR

Lansoprazole (PO) 30 mg once daily for 2–4 weeks

For radicular symptoms add

Pregabalin (PO) 75–150 mg once daily for 4 weeks (dose may be escalated according to response)

AND

Vitamin B1 + Vitamin B6 + Vitamin B12 (PO) once daily for 4 weeks

AND

Baclofen (PO) 5 mg every 8 hours initially, increasing by 5 mg per dose every 3 days up to 20 mg every 8 hours for up to 2 weeks

OR

Tizanidine (PO) 2 mg every 8 hours initially, increasing gradually to 4 mg daily after 1–4 days. Therapy may continue for 4 weeks or longer. Taper gradually when discontinuing by reducing 2–4 mg daily.

Antibiotic treatment

Ceftriaxone (IV) 2 g every 12 hours for 4–6 weeks

OR

Amoxicillin + clavulanate (IV) 1.2 g every 12 hours

AND

Metronidazole (IV) 500 mg every 8 hours for 4–6 weeks

Switch to organism-specific antimicrobial therapy once culture and sensitivity results become available.

Surgical management

Surgical debridement of infected disc and vertebral tissue with reconstruction and stabilization is indicated when conservative treatment is unsuccessful or complications develop.

Surgical intervention is recommended for patients with:

• Failure to respond to appropriate conservative therapy

• Progressive or significant neurological deficits

• Large paraspinal or epidural abscess causing neurological compression or septic embolization

• Progressive spinal deformity

• Mechanical spinal instability

• Persistent severe pain despite adequate treatment

• Extensive vertebral body destruction

Procedures may include:

• Surgical debridement

• Epidural abscess drainage

• Vertebral reconstruction

• Autologous bone grafting

• Instrumented spinal stabilization when indicated

The surgical approach should minimize disruption of normal spinal stabilizing structures while achieving adequate debridement and decompression.

Rehabilitation

Following infection control:

• Progressive physiotherapy

• Core muscle strengthening

• Gait training

• Gradual return to activities

• Occupational rehabilitation where appropriate

Complications

• Vertebral collapse

• Kyphotic deformity

• Chronic pain

• Epidural abscess

• Paravertebral abscess

• Sepsis

• Spinal instability

• Permanent neurological deficit

• Paralysis

• Recurrent infection

• Death

Prognosis

Early diagnosis and prompt treatment result in favourable outcomes for most patients. Delayed diagnosis increases the risk of neurological impairment, spinal deformity, chronic pain, and recurrent infection. Prognosis is poorer in elderly patients, immunocompromised individuals, and those presenting with neurological deficits or extensive vertebral destruction.

Prevention

• Prompt treatment of bloodstream and urinary tract infections

• Strict aseptic technique during spinal procedures

• Good glycaemic control in patients with diabetes

• Appropriate perioperative antibiotic prophylaxis

• Early investigation of persistent back pain associated with fever or elevated inflammatory markers

• Early treatment of spinal infections to prevent neurological complications