Residency · Residency · Physical Medicine Rehabilitation

Fluoroscopic and Ultrasound-Guided Spinal Injections

Overview

Spinal injections are core physiatric procedures for diagnosis and treatment of spinal pain. Require understanding of spinal anatomy, pain generators, image guidance, and pharmacology. Used for both diagnostic (identify pain source) and therapeutic (provide relief) purposes. Image guidance is standard of care for most spinal injections (fluoroscopy or ultrasound). Proper patient selection and interpretation of results are as important as technical skill.

Epidural Steroid Injections (ESIs)

Indications

Radicular pain (radiculopathy) from disc herniation or foraminal stenosis. Spinal stenosis with neurogenic claudication. Post-surgical epidural fibrosis. NOT indicated for axial low back pain without radicular component (limited evidence).

Mechanism of Action

Corticosteroid reduces inflammation around nerve root. Local anesthetic provides immediate diagnostic/therapeutic effect. Anti-inflammatory effects on phospholipase A2 and inflammatory cytokines. Reduces neural edema and ectopic firing of sensitized nerve fibers.

Approaches

Interlaminar ESI

Needle enters epidural space through the interlaminar window (between laminae). Loss-of-resistance (LOR) technique to identify epidural space. Fluoroscopy with contrast confirms epidural spread. Advantages: broader distribution of medication, familiar technique.

Disadvantages: less targeted, risk of dural puncture, cannot guarantee ventral spread to pathology. Most commonly performed in lumbar and cervical regions.

Transforaminal ESI (TFESI)

Needle directed into neural foramen, adjacent to the nerve root. Most targeted approach - medication delivered directly to pathology. Fluoroscopic guidance mandatory. Contrast confirms perineural spread (periradicular pattern).

Advantages: most specific, lower volume required, better ventral epidural spread. Disadvantages: higher risk of vascular injection (critical with particulate steroids). Safe triangle approach or Kambin triangle approach.

Caudal ESI

Needle enters through sacral hiatus into caudal epidural space. Advantages: lower risk of dural puncture, technically easier. Disadvantages: requires higher volume, less targeted, unpredictable cephalad spread. Useful for bilateral symptoms, post-surgical patients, multi-level pathology.

<image>Three approaches to epidural steroid injection: interlaminar, transforaminal, and caudal with fluoroscopic needle positioning</image>

Steroid Selection

Non-particulate (soluble): Dexamethasone sodium phosphate (most commonly used non-particulate). Preferred for transforaminal approach (reduced risk of particulate embolism). Shorter duration of action than particulate.

Particulate: Triamcinolone acetonide, methylprednisolone acetate, betamethasone. Larger particles - risk of arterial embolism if injected intravascularly. Longer-acting depot effect.

NEVER use particulate steroids for cervical transforaminal ESI (risk of stroke/paralysis). Acceptable for lumbar transforaminal with proper safety checks.

Safety Considerations

Cervical transforaminal ESI: highest risk procedure - vertebral artery or radicular artery injection can cause stroke, spinal cord infarction, or death. Use ONLY non-particulate dexamethasone. Real-time fluoroscopy during injection. Digital subtraction angiography (DSA) recommended.

Aspiration before injection. Frequency: limit to 3-4 injections per year (steroid-related systemic effects). Anticoagulation: hold per ASRA guidelines (procedure-specific recommendations).

Evidence

Strongest evidence: lumbar transforaminal ESI for acute radiculopathy from disc herniation. Moderate evidence: lumbar interlaminar ESI for radiculopathy. Limited evidence for spinal stenosis (short-term benefit only). Minimal evidence for axial back pain without radiculopathy. Short-term relief (2-6 weeks) is consistent; long-term benefit is debated.

Facet Joint Interventions

Facet Joint Anatomy and Pain

Zygapophyseal (facet) joints are paired synovial joints of the posterior spine. Innervated by medial branches of dorsal rami (dual innervation from level above and same level). Facet pain: axial, non-radiating, worse with extension and rotation. Prevalence as pain generator: 15-45% of chronic low back pain, 36-67% of chronic neck pain.

Medial Branch Blocks (MBBs)

Diagnostic gold standard for facet-mediated pain. Small volume (0.3-0.5 mL) of local anesthetic placed on medial branch nerves. Each facet joint requires blocks of two medial branches (level above and same level). Lumbar anatomy: medial branch crosses transverse process at junction with superior articular process.

L1-L4: medial branch at junction of transverse process and SAP. L5: dorsal ramus at junction of sacral ala and SAP of S1. Cervical anatomy: medial branch in groove on articular pillar (waist of pillar). Diagnostic criteria: ≥ 80% pain relief for duration of anesthetic (single block).

Dual diagnostic blocks recommended (second block with different duration anesthetic) to reduce false positives. False positive rate of single block: 25-40%.

Radiofrequency Ablation (RFA) / Neurotomy

Therapeutic procedure following positive diagnostic MBBs. Thermal lesion (80°C for 60-90 seconds) of medial branch nerves. Requires positive response to dual diagnostic blocks. Technique: large-bore needle (18-22G), electrode placed parallel to nerve.

Duration of relief: 6-12 months (nerve regeneration occurs). Can be repeated when pain recurs. Cooled radiofrequency: larger lesion size, may improve capture rate.

Intra-Articular Facet Joint Injections

Injection of corticosteroid directly into the facet joint capsule. Less evidence than medial branch blocks/RFA pathway. May provide short-term relief. Not predictive of RFA outcome. Some guidelines recommend against routine use.

<image>Facet joint anatomy with medial branch nerve targets for diagnostic blocks and radiofrequency ablation at lumbar and cervical levels</image>

Sacroiliac Joint Interventions

SI Joint Pain

Accounts for 15-30% of chronic low back pain. Pain typically in buttock, may refer to groin, posterior thigh (rarely below knee). Provocation tests: distraction, compression, thigh thrust, sacral thrust, Gaenslen, FABER. ≥ 3 positive provocation tests = high likelihood of SI joint pain source. Fluoroscopic or US-guided diagnostic injection confirms the diagnosis.

SI Joint Injection

Fluoroscopic guidance: needle directed into inferior aspect of joint. Confirm intra-articular placement with contrast (arthrogram). Local anesthetic ± corticosteroid. Diagnostic: ≥ 75% pain relief = positive. Therapeutic: short-term relief with corticosteroid.

SI Joint Radiofrequency Ablation

Lateral branch neurotomy (S1-S3 lateral branches, L5 dorsal ramus). Cooled RF or conventional RF with bipolar strip lesioning. Requires positive diagnostic blocks. Evidence: moderate for short-to-medium term relief.

Technical Safety Principles

Fluoroscopic Safety

ALARA principle: As Low As Reasonably Achievable (radiation exposure). Minimize fluoroscopy time (intermittent, not continuous). Collimate to area of interest. Maximum distance from radiation source. Lead shielding for patient and operator. Monitor cumulative dose.

Contrast Injection

Live/real-time fluoroscopy during contrast injection for transforaminal ESI. Confirm epidural spread pattern before injecting medication. Identify intravascular uptake (washout of contrast = vascular). Digital subtraction angiography for cervical transforaminal ESI.

Infection Prevention

Sterile technique throughout. Chlorhexidine or povidone-iodine skin prep. No clear evidence for prophylactic antibiotics for spinal injections. Steroids from single-dose vials (avoid multi-dose vials).

Anticoagulation Management (ASRA Guidelines)

Procedure-risk stratification (intermediate vs. high risk). Hold anticoagulants per ASRA recommendations: Warfarin: hold 5 days, INR < 1.5. DOACs (apixaban, rivaroxaban): hold 3-5 days.

Clopidogrel: hold 5-7 days. Aspirin (low-dose): generally continue for most procedures. Enoxaparin: hold 12-24 hours depending on dose.

<image>Fluoroscopic views showing proper needle placement for lumbar transforaminal epidural, medial branch block, and sacroiliac joint injection</image>

Interpreting Results

Diagnostic vs. Therapeutic Response

Diagnostic blocks: assess percent pain relief during anesthetic duration. Document pre-procedure pain level, pain relief during block, return of pain when anesthetic wears off. Pain diary for patients to track response. Concordant relief (matches expected anesthetic duration) supports the diagnosis. Discordant relief (too long or too short) raises questions about placebo or alternate diagnosis.

Red Flags Requiring Urgent Evaluation

New neurological deficit after injection. Severe headache after dural puncture (post-dural puncture headache). Fever, increasing back pain after procedure (epidural abscess). Bilateral lower extremity weakness (epidural hematoma).

Clinical Pearls

The single most important aspect of spinal injections is patient selection - the best technique cannot compensate for injecting the wrong structure. NEVER use particulate steroids for cervical transforaminal ESI - dexamethasone only (catastrophic stroke risk). Dual diagnostic medial branch blocks with ≥ 80% relief are required before radiofrequency ablation to reduce false-positive treatment. If an epidural steroid injection provides only 1-2 weeks of relief, the diagnosis is likely correct but the treatment needs adjustment; if it provides zero relief, reconsider the pain generator. Three or more positive SI joint provocation tests have a sensitivity > 90% for SI joint pain - this clinical examination can guide injection decisions.

References

• Manchikanti L, et al. Comprehensive evidence-based guidelines for interventional techniques in the management of chronic spinal pain. Pain Physician. 2009;12(4):699-802.
• Rathmell JP. Atlas of Image-Guided Intervention in Regional Anesthesia and Pain Medicine. 2nd ed. Lippincott Williams & Wilkins; 2012.
• Cohen SP, et al. Epidural steroids: a comprehensive, evidence-based review. Reg Anesth Pain Med. 2013;38(3):175-200.
• Narouze SN, et al. Interventional spine and pain procedures in patients on antiplatelet and anticoagulant medications (second edition). Reg Anesth Pain Med. 2018;43(3):225-262.
• Manchikanti L, et al. An update of comprehensive evidence-based guidelines for interventional techniques in chronic spinal pain. Pain Physician. 2013;16(2 Suppl):S1-S106.

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