Spondylodiscitis – Causes, Symptoms, Diagnosis, Treatment

Spondylodiscitis, (rare plural: spondylodiscitis) also referred to as discitis-osteomyelitis, is characterized by an infection involving the intervertebral disc and adjacent vertebrae. Facet arthropathy is a degenerative condition that affects the spine. The spine is made up of segments of vertebrae running along the spinal column. Between each vertebra are two facet joints. The facet joints along the posterior of the spine help align the vertebrae and limit motion. Facet joints are made up of two bony surfaces cushioned by cartilage and lubricated by synovial fluid. Facet arthropathy occurs when the facet joints begin to wear down and put pressure on the spinal cord, resulting in pain.

The lumbar zygapophysial joint, otherwise known as facet joint, is a common generator of lower back pain. The facet joint is formed via the posterolateral articulation connecting the inferior articular process of a given vertebra with the superior articular process of the below adjacent vertebra. The facet joint is a true synovial joint, containing a synovial membrane, hyaline cartilage surfaces, and surrounded by a fibrous joint capsule. There is a meniscoid structure formed within the intra-articular folds. The facet joint is dually innervated by the medial branches arising from the posterior ramus at the same level and one level above the joint. This activity describes the pathophysiology, evaluation, and management of lumbar facet arthropathy and highlights the role of the interprofessional team in improving care for affected patients.

Anatomy of facet joints (FJs)

Each spinal segment consists of an intervertebral disc and posterior paired synovial joints (FJ) comprising a “three-joint complex”, where each component influences the other two, with degenerative changes in one joint affecting the biomechanics of the whole complex. FJs constitute the posterolateral articulation connecting the posterior arch between vertebral levels. They are a paired and diarthrodial joints and are the only synovial joints in the spine, with hyaline cartilage overlying subchondral bone, a synovial membrane, and a joint capsule []. The joint space presents a capacity of 1–2 mL []. Each joint comprises an anteriorly and laterally facing inferior articular process from the superior vertebral level and reciprocally a larger, posteriorly, and medially facing concave superior, the articular process from the inferior vertebral level. Morphological variations may occur within the lumbar spine, as lumbosacral transitional vertebra (defined as either sacralization of the lowest lumbar segment or lumbarization of the most superior sacral segment of the spine). They are common in the general population, with a reported prevalence of 4–30%, with varying morphology, ranging from broadened transverse processes to complete fusion (Castellvi classification) []. Knowledge of such variations is essential to avoid an intervention at an incorrect level (see below). The axial morphology of the lumbar FJ from L3 to S1 has been shown to assume a gradually more coronal orientation compared to proximal lumbar levels, with a maximal transverse articular dimension to the distal end. The orientation of the lumbar FJ in the sagittal plane allows for a greater range of flexion motion and prevents gross rotatory instability []. Facet joint tropism has been defined as an asymmetry between right and left FJ angles, with one joint having more of a sagittal orientation than the other. Some studies found a relationship among patients who had a symptomatic disc herniation or degenerative spondylolisthesis at L4–5 or L5–1 levels, and an increased severity of facet joint tropism []. FJs play an important role in load transmission, providing a posterior load-bearing helper, stabilizing the motion segment in flexion and extension. They are also involved in the mechanism of rotational kinematics by restricting the axial rotation []. This is achieved through a collagenous tissue of the fibrous capsule played in a transverse plane providing resistance to flexion motions [].

Causes of Spondylodiscitis

  • Lumbar herniated disc
  • Discogenic pain syndrome
  • Lumbosacral radiculopathy
  • Piriformis syndrome
  • Paraspinal muscle/ligament sprain/strain
  • Lumbar spondylosis/spondylolysis/spondylolisthesis
  • Rheumatoid arthritis (more common in cervical)
  • Seronegative spondyloarthritis (most commonly ankylosing spondylitis, psoriatic arthritis, reactive arthritis)
  • Gout, pseudogout
  • Diffuse idiopathic skeletal hyperostosis
  • Sacroiliac joint dysfunction
  • Thoracolumbar fascia dysfunction
  • Infection
  • Neoplasm
  • Fibromyalgia
  • remote infection (present in ~25%)
  • ascending infection, e.g. from urogenital tract instrumentation
  • spinal instrumentation or trauma
  • intravenous drug use
  • immunosuppression
  • long-term systemic administration of steroids
  • advanced age
  • diabetes mellitus
  • organ transplantation
  • malnutrition
  • cancer
  • Staphylococcus aureus (most common; 60%)
  • Streptococcus viridans (IVDU, immunocompromised)
  • gram-negative organisms, e.g. Enterobacter spp., E. coli
  • Mycobacterium tuberculosis (Pott disease)
  • less common organisms
    • fungal
      • Cryptococcus neoformans,
      • Candida spp.
      • Histoplasma capsulatum
      • Coccidioides immitis
    • Burkholderia pseudomallei (i.e. melioidosis): diabetic patients from northern Australia and parts of Southeast Asia
    • Brucella spp.
  • in patients with sickle cell disease consider Salmonella spp.
  • can occur anywhere in the vertebral column but more commonly involves lumbar spine
  • single level involvement (65%)
  • multiple contiguous levels (20%)
  • multiple non-contiguous levels (10%)

The typical presentation is back pain (over 90% of patients) and less common fever (under 20% of patients). Patients are often bacteremic from sources such as endocarditis and intravenous drug use.

Symptoms of facet arthropathy include

  • Pain is the most common and noticeable symptom of facet arthropathy is pain. Features of pain caused by facet arthropathy include:
  • Pain that is worse following sleep or rest
  • Lower back pain that worsens when twisting, bending backward, and standing
  • Pain centered to one specific area of the spine
  • A dull ache on one or both sides of the lower back
  • Unlike the pain caused by sciatica, or a slipped disc, facet arthropathy pain doesn’t typically extend down the legs
  • Development of other conditions including bone spurs, and spinal stenosis

Diagnosis of Spondylodiscitis

Diagnostic
method		 Key message (year of publication) Evidence
level*
Patient history The direct link between previous spinal surgery and pyogenic spondylodiscitis (32.9% of patients
with pyogenic spondylodiscitis) (2010) ()		 IV
Patient history Spondylodiscitis following conservative (22.2 %) and invasive intervention such as catheterization,
surgery, or fine-needle aspiration (50.4%) (2010) ()		 IV
Laboratory parameter (CRP) High CRP (56 days shorter) or positive blood culture (60 days shorter) are
associated with a shorter diagnostic delay (2017) ()		 III
Patient history Diabetes as a predisposing factor (2009) () III
Laboratory parameter (PCT) PCT is not suitable as a diagnostic parameter or for monitoring
spondylodiscitis (2009) ()		 III
Microbiology (PCR) Using species-specific PCR, spondylodiscitis was detected in 46.7% of patients treated
with antibiotics; using conventional PCR, pathogen detection was possible
in only 26.7% (2014) ()		 II
Imaging (X-ray) Conventional X-ray as the first imaging technique, but not particularly helpful
in the early phase (2015) ()		 V
Biopsy (CT) Low pathogen detection rate using CT-guided fine-needle aspiration in patients with high
radiological and clinical likelihood of infection (30.4%) (2012) ()		 III
Biopsy (MRI and CT) Fine needle aspiration using combined MRI/CT data increases the pathogen
detection rate (36%) (2016) ()		 III
Biopsy (MRI and CT) Combined MRI/CT data increases the detection rate
(100% sensitivity, 50% specificity) (2016) ()		 III
Biopsy (tissue) In the case of suspected adjacent soft tissue abscess formation, soft tissue is
superior to bone tissue for pathogen detection
(odds ratio: 2.28; 95% CI: [1.08; 4.78]) (2015) ()		 III
Biopsy (tissue) There is no statistically significant difference (p<0.05) in specificity and sensitivity
according to biopsy tissue (sensitivity/specificity end plate vs. paravertebral
soft tissue 38%/86% vs. 68%/92%, p = 0.09; disc vs. end plate:
57%/89% vs. 38%/86%; p = 0.05) (2015) ()		 IV
Imaging (MRI) MRI remains the gold standard (2012) () V
Imaging (PET-CT) High specificity (88%; 95% CI: [0.74; 0.95]) and sensitivity (97%; 95% CI: [0.83; 1.00])
to detect spondylodiszitis (2014) ()		 I
Imaging (PET-CT) MRI (98%) with better sensitivity than PET-CT (95%); but PET-CT has better specificity
(86% vs. 67%), particularly in the differentiation between postoperative/severe degenerative
changes and spondylodiscitis (2014) ()		 III
Imaging (PET-CT) PET-CT as a helpful diagnostic tool if concomitant degenerative changes are present
(Modic I); differentiation between Modic I changes and spondylodiscitis
simplified by PET-CT (2010) ()

Elevated serum CRP and/or ESR.

In the pediatric age group infection often starts in the intervertebral disc itself (direct blood supply still present) whereas in adult infection is thought to begin at the vertebral body endplate, extending into the intervertebral disc space and then into the adjacent vertebral body endplate.

Plain radiography is insensitive to the early changes of discitis/osteomyelitis, with normal appearances being maintained for up to 2-4 weeks. Thereafter disc space narrowing and irregularity or ill definition of the vertebral endplates can be seen. In untreated cases, bony sclerosis may begin to appear in 10-12 weeks.

CT findings are similar to plain film but are more sensitive to earlier changes. Additionally, surrounding soft tissue swelling, intervertebral disc enhancement with contrast, collections (e.g. paraspinal and psoas muscle abscesses), and even epidural abscesses may be evident.

MRI is the imaging modality of choice due to its very high sensitivity and specificity. It is also useful in differentiating between pyogenic, tuberculous, and fungal infections, and a neoplastic process.

Signal characteristics include:

  • T1
    • low signal in disc space (fluid)
    • low signal in adjacent endplates (bone marrow edema)
  • T2: (fat saturated or STIR especially useful)
    • high signal in disc space (fluid)
    • high signal in adjacent endplates (bone marrow edema)
    • loss of low signal cortex at endplates
    • high signal in paravertebral soft tissues
    • hyperintensity within the psoas muscle (imaging psoas sign): this finding is ~92% sensitive and ~92% specific for spondylodiscitis
  • T1 C+ (Gd)
    • peripheral enhancement around fluid collection(s)
    • enhancement of vertebral endplates
    • enhancement of paravertebral soft tissues
    • enhancement around the low-density center indicates abscess formation (hard to distinguish inflammatory phlegmon from abscess without contrast)
  • DWI
    • hyperintense in the acute stage
    • hypointense in the chronic stage

The DWI sequence can help to distinguish between the acute and chronic stages of the disease.

A bone scan and white cell (WBC) scan may be used to demonstrate increased uptake at the site of infection, and are more sensitive than plain film and CT, but lack specificity. Not infrequently, a WBC scan demonstrates cold spots, a non-specific finding. The classic appearance on multiphase bone scans is increased blood flow and pool activity and associated increased uptake on the standard delayed static images. Gallium-67 citrate has been used with some success but is hampered by higher dosimetry and inferior imaging characteristics (high effective dose, long half-life time, poor spatial resolution).

F-18-FDG PET has been demonstrated to possess high sensitivity in detecting spondylodiscitis. As such, infectious spondylodiscitis can virtually be excluded by a negative scan. Dual imaging with PET/CT may thus become the imaging modality of choice, especially in patients with prior surgery and/or implants, where MRI is contraindicated or hampered by artifact. Specificity is not as high but monitoring of treatment results is possible.

Non-FDG PET/CT with Ga-68 citrate (an emerging, generator-based tracer) has shown promising results in pilot studies/small series.

Treatment of Spondylodiscitis

Antibiotic treatment (according to IDSA guidelines 
Pathogen First-line treatment Alternative treatment
Staphylococci,
oxacillin-susceptible		 – Flucloxacillin 1.5–2 g i. v.
(3–4 × d)
– Cefazolin 1–2 g i. v. (3 × d)
– Ceftriaxone 2 g i. v. (1 × d)		 – Vancomycin i. v. 15–20 mg/kg (2 × d)
(monitor serum levels)
– Daptomycin 6–8 mg/kg i. v. (1 × d)
– Linezolid 600 mg p. o./i. v. (2 × d)
– Levofloxacin p. o. 500–750 mg (1 × d) and rifampin p. o. 600 mg/d or clindamycin i. v. 600–900 mg (3 × d)
Staphylococci,
oxacillin-resistant		 – Vancomycin i. v. 15–20 mg/kg (2 × d)
(monitor serum levels)		 – Daptomycin 6–8 mg/kg i. v. (1 × d)
– Linezolid 600 mg p. o./i. v. (2 × d)
– Levofloxacin p. o. 500–750 mg (1 × d) and rifampin p. o. 600 mg/d
Enterococcus spp.,
penicillin-susceptible		 – Penicillin G 20–24 million IU i. v.
continuously over 24 h or in 6 partial doses
– Ampicillin 12 g i. v. continuously over 24 h or in 6 partial doses		 – Vancomycin 15–20 mg/kg i. v. (2 × d)
(monitor serum levels)
– Daptomycin 6 mg/kg i. v. (1 × d)
– Linezolid 600 mg p. o. or i. v. (2 × d)
Enterococcus spp.,
penicillin-resistant		 – Vancomycin i. v. 15–20 mg/kg (2 × d)
(monitor serum levels)		 – Daptomycin 6 mg/kg i. v. (1 × d)
– Linezolid 600 mg p. o. or i. v. (2 × d)
β-Hemolytic
streptococci		 – Penicillin G 20–24 million IU i. v.
continuously over 24 h or in 6 partial doses
– Ceftriaxone 2 g i. v. (1 × d)		 – Vancomycin 15–20 mg/kg i. v. (2 × d)
(monitor serum levels)
Enterobacteriaceae – Cefepime 2 g i. v. (2 × d)
– Ertapenem 1 g i. v. (1 × d)		 – Ciprofloxacin 500–750 mg p. o. (2 × d)
– Ciprofloxacin 400 mg i. v. (2 × d)
  • Medications – Such as NSAIDs, Aspirin, Ibuprofen, Naproxen, and Toradol are helpful to reduce pain as are cyclo-oxygenase-2 Inhibitors such as Celecoxib, and analgesics Acetomenophen, known as Paracetamol or Tylenol.
  • Non-surgical treatments – Physical therapy, strengthening exercises, avoiding movements that aggravate the symptoms, and medications such as NSAIDs like ibuprofen and naproxen can be used.
  • Intra-joint injections – and medial branch blocks of steroids/numbing medication under radiographic guidance and radiofrequency (RF) ablation to block the sensation of pain are two standard therapies. It appears that medial branch blocks and RF ablation are the best options with the lowest complication rates.
  • Shockwave therapy – is another therapy that appears to be better than steroid injections and as effective as RF ablation with better long-term outcomes. Shockwave therapy uses the same technology that breaks up kidney stones. The idea of this therapy
  • Stem Cell Regeneration – Stem cell regeneration is a non-invasive and experimental treatment for damaged and painful facet joints. For many years patients have achieved promising results from targeted stem cell treatments of the hip and knee joints, and in the facet joint, this is also possible. During the treatment, stem cells are carefully injected into the facet joints under CT imaging guidance by an orthopedic specialist. The cells respond to inflammatory signals from the arthritic joint and start working to repair and regenerate the joint. This can be assisted with shockwave therapy (mentioned above) and other supportive therapies.
  • Spine Surgery – For patients who have exhausted conservative therapies, surgery may be an option to relieve the pain of facet arthropathy – in cases of nerve compression, spinal stenosis, spinal instability and associated motor or sensory symptoms. Total Lumbar Facet Replacement”, which is a new motion-preserving solution where the facet joints are removed and replaced with artificial joints. This restores healthy height and movement to the damaged part of the spine.
  • For mild to moderate Facet Arthropathy presenting with a degenerative spinal disc at the same level, Artificial Disc Replacement is also an option. The controlled movement of the New-Generation ESP & M6 Artificial Discs protects the facet joints, and when natural height and movement is re-introduced to the damaged spinal level with ADR, then we observe cases where Facet Joint rehabilitation is possible.
  • If the patient is not a candidate for a motion-preserving solution, then a spinal fusion can be offered as a ‘last line of defense’. In most forms of a spinal fusion, the surgeon removes the facet joints between the levels of the spine that are to be fused together, which effectively eliminates the facet joints as a source of future symptoms.

References