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Indications & Patient Selection
Tumor types, goals, candidacy criteria, workup
Primary Indications
- Painful osseous metastases refractory to radiation or analgesics — particularly lytic lesions from breast, lung, kidney, thyroid, and myeloma
- Sclerotic lesions (prostate, sclerotic breast): harder to ablate, but thermal ablation destroys nociceptors in the periosteum and endosteum, reducing pain
- Palliative pain relief — primary goal; NOT curative intent
- Local tumor control — secondary goal in oligometastatic disease
- Prevention of pathologic fracture — especially when combined with cement augmentation
- Combination ablation + cementoplasty — ablation destroys tumor; cement restores structural integrity
Best Candidates
- NRS pain score ≥4 at the lesion site
- Expected survival ≥3 months
- Failed or plateaued radiation therapy at the lesion site
- Lesion ≤5 cm (larger lesions require multiple overlapping probes)
- Pain localizable to the treated lesion on physical exam
- Adequate performance status for sedation/GA
Absolute Contraindications
- Uncorrectable coagulopathy
- Active infection at or adjacent to the planned probe site
- Lesion involving the spinal canal with direct cord contact — thermal injury risk; requires formal thermal protection protocol
Relative Contraindications
- >50% cortical destruction in a weight-bearing bone — fracture risk; cement augmentation mandatory or prophylactic fixation first
- Adjacent critical structure <1 cm without thermal protection capability
- Prior radiation to site (increased fracture risk post-ablation)
- SINS score ≥13 (spinal lesions) — surgical stabilization before ablation
Pre-Procedure Workup
- Plain film: assess cortical integrity, degree of destruction
- CT (axial, MPR): lesion extent, soft tissue component, probe corridor planning
- Bone scan or PET: identify additional lesions that may contribute to pain
- SINS score for spinal lesions (Spine Instability Neoplastic Score): guides cement vs. surgical stabilization decision
- Coagulation panel: INR, platelets; correct before proceeding
- Orthopedic consultation if >50% cortical destruction — prophylactic fixation may be needed before ablation
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Pre-Procedure Checklist
Equipment selection, anesthesia, antibiotic prophylaxis, consent
Guidance & Ablation Modality
- Imaging guidance: CT standard for most locations; fluoroscopy preferred for superficial or well-corticated lesions (e.g., posterior ribs, long bone cortex); real-time CT fluoroscopy for complex or deep lesions
- MRI guidance: specialized centers; superior soft tissue visualization; preferred for skull base and intracranial lesions
- RFA (monopolar cool-tip): small lesions (≤2–3 cm); monopolar cool-tip or cluster electrode
- MWA (17G antenna): most lesions; faster ablation; less susceptibility to heat sink; preferred for vascular/larger lesions
- Cryoablation: larger or irregular lesions; multiple probes for coverage; preferred near neural structures; real-time CT ice ball monitoring
Bone Access & Cement
- Bone biopsy needle: Bonopty, Ostycut, or Jamshidi 11G — for cortical access; coaxial technique allows simultaneous biopsy and ablation probe placement
- Cement kit (if augmentation planned): PMMA cement, 11G trocar, cement mixing system, cement gun
- Thermal protection equipment: D5W for epidural cooling (spinal lesions); saline hydrodissection kit; CO2 pneumodissection for spinal lesions
- Standard tray: sterile drapes, 25G/22G needles, lidocaine 1% (generous periosteal block)
Medications & Anesthesia
- General anesthesia or deep sedation required — bone ablation is significantly painful; conscious sedation alone inadequate for most patients
- Cefazolin 1g IV pre-procedure prophylaxis
- Multimodal pain plan for post-procedure pain flare: scheduled NSAIDs, acetaminophen, opioid bridge PRN
- Concurrent biopsy planned via coaxial technique — obtain informed consent for biopsy separately
Imaging reviewed. Plain film and CT reviewed; cortical integrity assessed; probe corridor identified; critical structures mapped.
SINS score calculated (spinal lesions). SINS <7 = stable; SINS 7–12 = cement augmentation; SINS ≥13 = surgical consultation before ablation.
Coagulopathy corrected. INR ≤1.5, platelets ≥50K.
Orthopedic consulted if >50% cortical destruction in weight-bearing bone. Prophylactic fixation plan confirmed if needed.
Anesthesia confirmed. GA or deep sedation arranged; bone ablation cannot be performed under light sedation.
Cefazolin 1g IV administered within 60 minutes of skin entry.
Thermal protection ready (if applicable): D5W for epidural cooling, hydrodissection saline, CO2 cylinder available for spinal or perineural lesions.
Cement kit available (if augmentation planned): PMMA prepared, fluoroscopy available for cement distribution confirmation.
Consent obtained. Palliative intent discussed; pain flare, nerve injury, fracture, infection, and cement risks reviewed. Biopsy consent included if coaxial biopsy planned.
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Anatomy by Location
Proximity hazards, thermal protection, and special considerations by site
| Location | Proximity Hazards | Thermal Protection | Special Consideration |
|---|---|---|---|
| Spine | Spinal cord, nerve roots | D5W epidural cooling, CO2 pneumodissection | SINS score mandatory; cement augmentation per SINS; neuro-monitoring during ablation |
| Pelvis / Acetabulum | Sciatic nerve, femoral neurovascular bundle | Hydrodissection with saline | Cement augmentation if weight-bearing; consider cryoablation if <1 cm from sciatic nerve |
| Proximal Femur | Femoral neurovascular bundle, femoral vessels | Hydrodissection | Stabilize (prophylactic nailing) if >30% cortex destruction before ablation |
| Rib | Pleura, intercostal neurovascular bundle | D5W pleural injection | Pneumothorax monitoring; avoid traversing pleural space; approach from posterior or lateral |
| Sternum | Heart, great vessels, mediastinum | Careful CT trajectory planning | Usually anterior approach only; thin cortex; beware anterior mediastinal structures; MWA preferred |
| Skull | Dura, brain, dural sinuses | CT trajectory planning | MRI guidance preferred at skull base; neurosurgery on standby for intracranial lesions; limit ablation zone at inner table |
Spinal Lesion Notes
- SINS score elements: location, pain, bone quality, spinal alignment, vertebral body collapse, posterior element involvement
- SINS <7: stable; ablation ± cement reasonable
- SINS 7–12: potentially unstable; cement augmentation mandatory
- SINS ≥13: frankly unstable; surgical stabilization before ablation
- Epidural D5W cooling (3–5 mL): reduces spinal cord temperature during ablation; confirmed on CT as low-density fluid in epidural space
Cryoablation vs. Thermal Near Neural Structures
- Cryoablation preferred when lesion is <1 cm from a motor nerve root (sciatic, femoral, brachial plexus)
- Ice ball is neuroprotective at the periphery (reversible neuropraxia) vs. RFA/MWA thermal injury (can be permanent)
- Real-time CT ice ball monitoring every 5 min during freeze cycle
- Standard cryo protocol: two 10-min freeze cycles with 5-min passive thaw between
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Step-by-Step Technique
CT- or fluoroscopy-guided percutaneous bone ablation with optional cement augmentation
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CT Planning Scan
Perform CT planning scan with patient in procedural position. Identify the lesion extent, optimal probe corridor through cortex into lesion center, and proximity to critical structures (cord, nerve roots, vessels, pleura). Confirm bone cortex entry point and trajectory angle. Plan thermal protection if any structure is within 1 cm.
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Anesthesia and Local Block
Initiate GA or deep sedation per anesthesia team. Apply generous local anesthesia (lidocaine 1%) from skin to periosteum — periosteal injection is critical as periosteum is richly innervated. Standard sterile prep and drape.
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Bone Access: 11G Coaxial Biopsy Needle
Advance 11G bone biopsy needle (Bonopty, Ostycut, or Jamshidi) through the cortex into the lesion center using the planned trajectory. Penetrate cortex using twisting/drilling motion with steady pressure; mallet advancement for hard cortex. Confirm position in lesion on CT. This coaxial trocar will serve as the access sheath for both biopsy and ablation probe.
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Concurrent Biopsy via Coaxial Technique
Pass inner biopsy stylet through the coaxial needle to obtain core tissue sample. Send for permanent histologic section. Coaxial technique avoids a second access and reduces procedure time. Withdraw inner needle; leave coaxial trocar in place for ablation probe placement.
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Place Ablation Probe Through Coaxial Access
Advance ablation probe (MWA 17G antenna, RFA cool-tip, or cryo probe) through the coaxial trocar into the center of the lesion. Confirm probe tip position on CT. For lesions >3 cm or irregular shape, plan multiple overlapping probe positions prior to initiating ablation.
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Thermal Protection (Spinal / Perineural Lesions)
For spinal lesions: inject D5W 3–5 mL into the epidural space under CT fluoroscopy before initiating ablation; D5W appears as low-density fluid separating the ablation zone from the spinal cord; confirm adequate distribution. CO2 pneumodissection is an alternative for displacing the cord. For lesions near peripheral nerves: inject 5–10 mL saline hydrodissection to create thermal buffer.
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Ablation
MWA: 65W × 5–10 min (adjust per probe manufacturer and lesion size); obtain mid-procedure CT at 5 min to assess ablation zone extent. RFA: ramp to target temperature per manufacturer protocol; impedance rollback indicates adequate tissue desiccation. Cryoablation: two 10-min freeze cycles with 5-min passive thaw; CT every 5 min during freeze to monitor ice ball; ice ball must cover entire lesion with margin. Perform neuro-checks every 5 min for spinal lesions during ablation.
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Cement Augmentation (If Planned)
Withdraw ablation probe, leaving coaxial trocar in place. Mix PMMA cement to a toothpaste-like consistency. Inject through the 11G coaxial trocar using the cement gun under intermittent CT fluoroscopy. Inject until the ablation cavity is filled. Avoid epidural, foraminal, or venous extravasation — stop injection if cement approaches these structures. Confirm adequate distribution and no extravasation on fluoroscopy and CT.
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Post-Procedure CT and Needle Removal
Final CT to confirm: (1) ablation zone covers the entire lesion; (2) no extra-osseous cement extravasation; (3) no new fracture; (4) no pneumothorax (rib/lung cases). Remove trocar and ablation probe. Apply pressure at skin entry site. Perform immediate post-procedure neuro assessment for spinal lesions.
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CT Landmarks
Imaging findings during and after bone ablation
Ablation Zone on CT
- Low-density zone within bone: tumor replaced by ablation necrosis; appears as geographic hypodensity replacing the lesion on post-ablation CT
- Gas bubbles within ablation zone: normal post-ablation finding representing nitrogen from tissue boiling; do not mistake for infection
- Perilesional sclerosis: thin rim of reactive sclerosis at ablation margin suggests adequate treatment; develops over weeks to months on follow-up imaging
- Ice ball (cryo): homogeneous hypodense zone corresponding to frozen tissue; outer margin = −20°C isotherm (cell death); inner margin = −40°C isotherm; must cover entire lesion with 5–10 mm margin
Cement Distribution
- Adequate fill: cement should fill the ablation cavity; appears as hyperdense PMMA conforming to the bone defect
- Venous extravasation: small amounts common and usually benign; linear hyperdensity tracking along venous channels; monitor for pulmonary cement embolism
- Epidural/foraminal extravasation: cement tracking toward spinal canal; stop injection immediately; obtain emergent neuro exam; surgical consultation if neurologic change
- Cortical breach: >50% cortex destruction on planning CT = structural compromise; augmentation or fixation required; do not ablate weight-bearing bone without structural plan
Follow-Up Imaging Findings
- 6–8 weeks post-procedure CT: adequate response = stable or decreasing lesion size, persistent ablation zone hypodensity, reactive sclerotic rim
- Local recurrence CT pattern: nodular enhancement at the margin of the ablation zone on contrast CT; indicates viable residual tumor
- MRI follow-up: superior for soft tissue component assessment; ablated zone shows T2 hypointensity and lack of enhancement on contrast sequences
- PET/CT: decreased FDG uptake in successfully ablated lesion; new uptake at margin suggests recurrence or residual disease
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Troubleshooting
Intraoperative problems and solutions
Sclerotic Lesion — Probe Won't Advance
Bone Needle Cannot Penetrate Densely Sclerotic Cortex or Tumor
Switch to a diamond-tip drill bit attachment for the biopsy needle system. Manually tap needle through dense cortex using a mallet. Alternatively, consider switching to cryoablation — ice nucleation propagates better through sclerotic bone than RFA/MWA thermal diffusion. Applying steady rotational pressure with the 11G needle while intermittently imaging on CT is often effective.
Incomplete Ablation Zone
Ablation Zone Does Not Cover Entire Lesion on Mid-Procedure CT
Reposition probe to untreated portion of lesion and perform additional ablation cycle. For MWA, simultaneous dual-probe application is possible with appropriate spacing (1.5–2 cm between antenna tips) for overlapping zones. For large lesions (>4 cm), plan multiple overlapping positions before starting. Do not proceed to cement until full lesion coverage is confirmed on CT.
Thermal Injury to Adjacent Nerve
Patient Reports Numbness, Weakness, or Paresthesias During or After Ablation
Stop ablation immediately. For spinal lesions: inject additional D5W into epidural space if not already done. For peripheral nerve proximity: flush with saline hydrodissection to cool the adjacent tissue. Monitor for neurologic recovery. Most thermal neuropraxia from RFA/MWA resolves over 6–12 weeks. Cryoablation-related nerve injury (neuropraxia) is almost always fully reversible.
Cement Extravasation — Epidural
PMMA Tracks Toward Spinal Canal or Neural Foramen
Stop cement injection immediately upon detection. Obtain immediate post-injection CT to characterize extent. Perform emergent neurologic assessment. Small epidural extravasation without neurologic symptoms: monitor closely with serial exams. Neurologic change (weakness, bowel/bladder dysfunction): emergent surgical consultation for decompression. Do not continue injecting once epidural tracking is identified.
Pneumothorax (Rib / Chest Wall Lesions)
Pleural Violation During Rib Ablation
Small asymptomatic pneumothorax (<20%): observe; supplemental oxygen; repeat CT at 2h. Symptomatic or enlarging: chest tube or pigtail catheter placement. Prevent by planning approach to avoid traversing the pleural space; use D5W pleural injection to displace lung away from rib lesion before ablation.
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Complications
Rates, presentation, and management
Expected / Common
- Pain flare (virtually universal, 24–72h): inflammatory response to ablation; manage with scheduled NSAIDs + acetaminophen; opioid bridge if needed; warn patient pre-procedure that pain will worsen before it improves
- Local swelling and soft tissue edema: expected at ablation site; resolves over 1–2 weeks
- Low-grade fever (<38.5°C, post-ablation syndrome): systemic inflammatory response to ablated tissue; self-limited 24–48h; no antibiotic escalation unless infection suspected
Serious Complications
- Pathologic fracture (≤5% with augmentation): higher risk in weight-bearing bones with >30% cortex destruction; cement augmentation significantly reduces risk; orthopedic consultation if fracture risk high
- Nerve injury (2–5%): thermal injury to adjacent nerves; reversible with cryoablation (neuropraxia); more permanent risk with RFA/MWA; spinal cord injury is catastrophic
- Infection / osteomyelitis (<1%): cefazolin prophylaxis reduces risk; presents as escalating pain + fever >72h post-procedure; CT shows periosteal gas, soft tissue gas outside the ablation zone
- Cement embolism / PVE (rare): avoid excessive cement volume; monitor fluoroscopically during injection; pulmonary cement embolism usually asymptomatic; symptomatic PVE requires respiratory support
Local Recurrence
- Rate: 15–30% at 12 months for lesions >3 cm; lower for smaller lesions with adequate ablation margins
- Recurrence does not preclude repeat ablation — repeat ablation is safe and effective in appropriately selected patients
- Pain relief remains durable even with imaging evidence of local recurrence in some cases (nociceptor destruction persists)
- Follow up with CT or MRI at 6–8 weeks, then every 3 months for 1 year
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Critical Pearls
High-yield clinical pearls and landmark evidence
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Goal is palliation, not cure — set expectations accordingly. Pain relief occurs in 70–85% of patients with at least a 2-point NRS reduction. The primary endpoint is pain reduction, not radiographic tumor eradication. Communicate this clearly with patients and referring oncologists before the procedure.
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SINS score governs spinal ablation safety. Always calculate the Spine Instability Neoplastic Score before spinal bone ablation. SINS ≥7 = cement augmentation mandatory. SINS ≥13 = surgical stabilization required before ablation. Ablating a frankly unstable spine without fixation risks catastrophic collapse.
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Ablation + cement is more durable than either alone. Ablation destroys tumor and nociceptors; cement restores structural integrity and further destroys residual tumor via exothermic polymerization of PMMA (cement reaches 70–90°C during hardening). The combination is the gold standard for weight-bearing bone metastases.
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Cryoablation is preferred near motor nerves. Creates a well-defined, CT-visible ice ball with predictable margins. Reversible neuropraxia at the ice ball periphery vs. potentially permanent RFA/MWA thermal injury. Use cryoablation for spine and pelvis lesions when the lesion is within 1 cm of a major nerve root. Two 10-min freeze / 5-min thaw cycles standard.
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Monitor ice ball in real-time on CT every 5 minutes during cryo. This is cryoablation's unique advantage in bone. The ice ball must cover the entire lesion with margin. Unlike RFA/MWA where the ablation zone is inferred from temperature and impedance, cryo allows direct visualization of the treatment zone — use it. CT every 5 min during freeze is the standard of care.
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Callstrom et al. (JCO 2006) — landmark RCT establishing bone metastasis ablation. Cryoablation reduced worst pain score by 3.0 points (NRS) vs. sham control in 32 patients (p < 0.001). This was the first randomized controlled trial demonstrating efficacy of ablation for radiation-refractory bone pain and established percutaneous ablation as standard of care for this indication.
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References & Resources
Primary sources and related procedures
Ablation Modality Quick Reference
- MWA: fastest ablation; 65W × 5–10 min; less heat sink susceptibility; first choice for most lesions
- RFA: monopolar cool-tip; smaller lesions (≤2–3 cm); established track record; more heat sink effect near vessels
- Cryo: larger/irregular lesions; multiple probes; preferred near nerves; real-time CT monitoring; 2 freeze / 1 thaw cycles; longer procedure time
Primary References
- Faintuch S, Salazar GM (Callstrom MR, Kurup AN chapter authors). In: Interventional Radiology: A Practical Approach. Thieme; 2016. Chapter 11: Bone Tumor Ablation.
- Callstrom MR, Dupuy DE, Solomon SB, et al. Percutaneous image-guided cryoablation of painful metastases involving bone: multicenter trial. Cancer. 2013;119(5):1033–1041.
- Callstrom MR, Atwell TD, Charboneau JW, et al. Painful metastases involving bone: percutaneous image-guided cryoablation — prospective trial interim analysis. Radiology. 2006;241(2):572–580.
- Callstrom MR, Charboneau JW, Goetz MP, et al. Image-guided ablation of painful metastatic bone tumors: a new and effective approach to a difficult problem. Skeletal Radiol. 2006;35(1):1–15.
- Callstrom MR, Dupuy DE, Solomon SB, et al. Percutaneous image-guided cryoablation of painful metastases (landmark RCT). J Clin Oncol. 2006;24(34):5403–5409.
- Thacker PG, Callstrom MR, Curry TB, et al. Palliation of painful metastatic disease involving bone with imaging-guided treatment: comparison of patients’ immediate response to ablation and cementoplasty. AJR Am J Roentgenol. 2011;197(2):510–515.
- Prologo JD, Ray CE Jr., eds. Advanced Pain Management in Interventional Radiology: A Case-Based Approach. Thieme; 2024. DOI: 10.1055/b000000387