Radiofrequency ablation of spinal tumors: temperature distribution in the spinal canal

Percutaneous Spinal Ablation in a Sheep Model: Protective Capacity of an Intact Cortex, Correlation of Ablation Parameters with Ablation Zone Size, and Correlation of Postablation MRI and Pathologic Findings

BACKGROUND AND PURPOSE

Despite the growing use of percutaneous ablation therapy for the treatment of metastatic spine disease, several issues have yet to be fully addressed. Our aims were to determine whether the vertebral body cortex protects against ablation-induced spinal cord injury; correlate radiofrequency, cryo-, and microwave ablation parameters with resulting spinal ablation zone dimensions and describe normal spinal marrow postablation changes on MR imaging.

MATERIALS AND METHODS

Ten thoracolumbar vertebrae in 3 sheep were treated with radiofrequency ablation, cryoablation, or microwave ablation under fluoroscopic guidance. Technique parameters were chosen to produce ablation zones that exceeded the volume of the vertebral bodies in sheep 1 and were confined to the vertebrae in sheep 2 and 3. Expected ablation zone dimensions were based on data provided by the device manufacturers. Postablation MR imaging was performed at 48 hours (sheep 1) or 7 days (sheep 2 and 3).

RESULTS

In sheep 1, cryoablation and microwave ablations extended into the spinal canal and caused histologically confirmed neurologic injury, but radiofrequency ablation did not. The mean difference between the lengths of the radiofrequency ablation zone dimensions measured on gross pathology compared with those expected was 9.6 ± 4.1 mm. The gross pathologic cryo- and microwave ablation zone dimensions were within 1 mm of those expected. All modalities produced a nonenhancing ablation zone with a rim of enhancement, corresponding histologically to marrow necrosis and hemorrhagic congestion.

CONCLUSIONS

An intact cortex appears to protect against radiofrequency ablation-induced spinal cord injury, but not against non-impedance-based modalities. Ablation dimensions produced by microwave and cryoablation are similar to those expected, while radiofrequency ablation dimensions are smaller. Ablation of normal marrow produces a rim of enhancement at the margin of the ablation zone on MR imaging.

Decision Making: Osteoplasty, Ablation, or Combined Therapy for Spinal Metastases

Metastatic disease involving the spine and pelvis is common, often resulting in significant pain and disability. Several percutaneous interventions have been described, including osteoplasty, ablation, and screw fixation, that when used alone or in combination can significantly reduce pain and disability from metastatic bone disease. Although it is possible to make a significant impact in patient care with basic principles and techniques, certain advanced techniques can extend the application of percutaneous interventions while minimizing morbidity.

Performance of radiofrequency ablation used for metastatic spinal tumor: Numerical approach

Surgical treatment of spine metastases follows only local anatomical and biomechanical objectives. Few cases of actual solitary metastases are rather exceptional, while removal of these metastases and the primary tumor may help to eradicate the process. The aim of our subsequent numerical simulations was to find out the temperature distribution and the volume lesion in a spinal tumor. For this purpose, the parametric three-dimensional numerical model was developed. It was shown that by finite element modeling approach not only the temperature distribution but even the resulted cavity may be estimated. The numerical approach was shown as a strong tool in surgery planning.

Benign Spine Lesions: Advances in Techniques for Minimally Invasive Percutaneous Treatment

Minimally invasive percutaneous imaging-guided techniques have been shown to be safe and effective for the treatment of benign tumors of the spine. Techniques available include a variety of tumor ablation technologies, including radiofrequency ablation, cryoablation, microwave ablation, alcohol ablation, and laser photocoagulation. Vertebral augmentation may be performed after ablation as part of the same procedure for fracture stabilization or prevention. Typically, the treatment goal in benign spine lesions is definitive cure. Painful benign spine lesions commonly encountered in daily practice include osteoid osteoma, osteoblastoma, vertebral hemangioma, aneurysmal bone cyst, Paget disease, and subacute/chronic Schmorl node. This review discusses the most recent advancement and use of minimally invasive percutaneous therapeutic options for the management of benign spine lesions.

Multicenter clinical and imaging evaluation of targeted radiofrequency ablation (t-RFA) and cement augmentation of neoplastic vertebral lesions

Background

Treatment of spinal metastatic lesions by radiofrequency ablation (RFA) before cementation can potentially help in local tumor control and pain relief. This is often limited by access and tumor location. This study reports multicenter clinical and imaging outcomes following targeted RFA (t-RFA) and cement augmentation in neoplastic lesions of the spine.

Material and methods

A retrospective multicenter study of 49 patients with 72 painful vertebral lesions, evaluated for clinical and imaging outcomes following RFA and cement augmentation of spinal metastatic lesions, was undertaken. Visual Analogue Pain score (VAS) and Oswestry Disability Index (ODI) were obtained before and 2–4 weeks after treatment. Pre- and post-procedure imaging examinations including MRI and positron emission tomography (PET) were also evaluated.

Results

Mean ablation time was 3.7±2.5 min (range 0.92–15). Mean VAS scores decreased from 7.9±2.5 pre-procedure to 3.5±2.6 post-procedure (p<0.0001). Mean ODI scores improved from 34.9±18.3 to 21.6±13.8 post-procedure (p<0.0001). Post-contrast MRI resulted in a predictable pattern of decreased tumor volume and an enhancing rim. Metabolically active lesions in pre-procedure PET scans (n=10 levels) showed decreased fluorodeoxyglucose activity after ablation.

Conclusions

t-RFA followed by vertebral augmentation in malignant vertebral lesions resulted in significant pain reduction and functional status improvement, with no major complications. t-RFA permitted access to vertebral lesions and real-time accurate monitoring of the ablation zone temperature. Post-procedure MRI and PET examinations correlated with a favorable tumor response and helped to monitor tumor growth and the timing of adjuvant therapy.

Image-guided minimally invasive percutaneous treatment of spinal metastasis

In order to provide effective options for minimally invasive treatment of spinal metastases, the present study retrospectively evaluated the efficacy and safety of image-guided minimally invasive percutaneous treatment of spinal metastases. Image-guided percutaneous vertebral body enhancement, radiofrequency ablation (RFA) and tumor debulking combined with other methods to strengthen the vertebrae were applied dependent on the indications. Percutaneous vertebroplasty (PVP) was used when vertebral body destruction was simple. In addition, RFA was used in cases where pure spinal epidural soft tissue mass or accessories (spinous process, vertebral plate and vertebral pedicle) were destroyed, but vertebral integrity and stability existed. Tumor debulking (also known as limited RFA) combined with vertebral augmentation were used in cases presenting destruction of the epidural soft tissue mass and accessories, and pathological vertebral fractures. A comprehensive assessment was performed through a standardized questionnaire and indicators including biomechanical stability of the spine, quality of life, neurological status and tumor progression status were assessed during the 6 weeks-6 months follow-up following surgery. After the most suitable treatment was used, the biomechanical stability of the spine was increased, the pain caused by spinal metastases within 6 weeks was significantly reduced, while the daily activities and quality of life were improved. The mean progression-free survival of tumors was 330±54 days, and no associated complications occurred. Therefore, the use of a combination of image-guided PVP, RFA and other methods is safe and effective for the treatment of spinal metastases.

Surgical treatment of tumours and metastases of the spine by minimally invasive cavity-coblation method

Tumours and metastases of the spine are extremely stressful for patients, especially for elderly multimorbid patients. The modern cavity/coblation method offers a very good therapeutic alternative for such patients. The goal of this article was to evaluate and present the characteristics, significance, opportunities, issues of the minimum invasive cavity/coblation method as well as the results of the treatment of 302 patients with vertebral tumours and metastases.

Modern Palliative Treatments for Metastatic Bone Disease: Awareness of Advantages, Disadvantages, and Guidance

BACKGROUND

Metastatic disease is the most common malignancy of the bone. Prostate, breast, lung, kidney, and thyroid cancer account for 80% of skeletal metastases. Bone metastases are associated with significant skeletal morbidity including severe bone pain, pathologic fractures, spinal cord or nerve roots compression, and malignant hypercalcemia. These events compromise greatly the quality of life of the patients. The treatment of cancer patients with bone metastases is mostly aimed at palliation.

OBJECTIVE

This article aims to present these palliative treatments for the patients with bone metastases, summarize the clinical applications, and review the techniques and results.

METHODS

It gives an extensive overview of the possibilities of palliation in patients with metastatic cancer to the bone.

RESULTS AND DISCUSSION

Currently, modern treatments are available for the palliative management of patients with metastatic bone disease. These include modern radiation therapy, chemotherapy, embolization, electrochemotherapy, radiofrequency ablation, and high-intensity focused ultrasound. As such it is of interest for all physicians with no experience with these developments to make palliative procedures safer and more reliable.

Palliative Interventional Oncology

Interventional oncologists are playing an ever greater role in improving the quality of life of their patients through minimally invasive procedures, many of which can be performed on an outpatient basis. Some of the most common palliative procedures currently performed will be discussed including management of intractable ascites and pleural effusions, neurolytic plexus blocks, and palliation of pain and bleeding associated with metastatic tumors.

Benign Tumors of the Spine: Has New Chemotherapy and Interventional Radiology Changed the Treatment Paradigm?

STUDY DESIGN

Clinically based systematic review.

OBJECTIVE

To determine the role of (A) medical treatment and (B) interventional radiology as either adjuvant or stand-alone treatment in primary benign bone tumors of the spine.

METHODS

A multidisciplinary panel of spine surgeons, radiation oncologists, and medical oncologists elaborated specific focused questions regarding aneurysmal bone cyst, giant cell tumor, and osteoid osteoma. Denosumab, bisphosphonate, interferon, bone marrow aspirate, doxycycline, thermal ablation, and selective arterial embolization were identified as areas of interest for the article. A systematic review was performed through MEDLINE and EMBASE. Recommendations based on the literature review and clinical expertise were issued using the GRADE system.

RESULTS

The overall quality of the literature is very low with few multicenter prospective studies. For giant cell tumor, combination with Denosumab identified 14 pertinent articles with four multicenter prospective studies. Nine studies were found on bisphosphonates and six for selective arterial embolization. The search on aneurysmal bone cyst and selective arterial embolization revealed 12 articles. Combination with Denosumab, Doxycycline, and bone marrow aspirate identified four, two, and three relevant articles respectively. Eleven focused articles were selected on the role of thermal ablation in osteoid osteoma.

CONCLUSION

Alternative and adjuvant therapy for primary benign bone tumors have emerged. Their ability to complement or replace surgery is now being scrutinized and they may impact significantly the algorithm of treatment of these tumors. Most of the data are still emerging and further research is desirable. Close collaboration between the different specialists managing these pathologies is crucial.

LEVEL OF EVIDENCE

N/A.

MRI-guided focused ultrasound ablation of lumbar medial branch nerve: Feasibility and safety study in a swine model

PURPOSE

About 10-40% of chronic low back pain cases involve facet joints, which are commonly treated with lumbar medial branch (MB) radiofrequency neurotomy. Magnetic resonance imaging-guided focused ultrasound (MRgFUS), a non-invasive, non-ionising ablation modality used to treat tumours, neuropathic pain and painful bone metastasis can also be used to disrupt nerve conduction. This work's purpose was to study the feasibility and safety of direct MRgFUS ablation of the lumbar MB nerve in acute and subacute swine models.

MATERIALS AND METHODS

In vivo MRgFUS ablation was performed in six swine (three acute and three subacute) using a clinical MRgFUS system and a 3-T MRI scanner combination. Behavioural assessment was performed, and imaging and histology were used to assess the treatment.

RESULTS AND CONCLUSIONS

Histological analysis of the in vivo studies confirmed thermal necrosis of the MB nerve could be achieved without damaging the spinal cord or adjacent nerve roots. MRgFUS did not cause changes in the animals' behaviour or ambulation.

Establishing a clinical service for the treatment of osteoid osteoma using magnetic resonance-guided focused ultrasound: overview and guidelines

Recent studies have demonstrated the effectiveness of magnetic resonance-guided focused ultrasound (MRgFUS) in the treatment of osteoid osteoma (OO), a painful, benign bone tumor. As MRgFUS is a noninvasive and radiation-free treatment, it stands to replace the current standard of care, percutaneous radiofrequency, or laser thermal ablation. Within an institution, creation of a clinical OO MRgFUS treatment program would not only provide cutting edge medical treatment at the current time but would also establish the foundation for an MRgFUS clinical service to introduce treatments currently under development into clinical practice in the future. The purpose of this document is to provide information to facilitate creation of a clinical service for MRgFUS treatment of OO by providing (1) recommendations for the multi-disciplinary management of patients and (2) guidelines regarding current best practices for MRgFUS treatment. This paper will discuss establishment of a multi-disciplinary clinic, patient accrual, inclusion/exclusion criteria, diagnosis, preoperative imaging, patient preparation, anesthesia, treatment planning, targeting and treatment execution, complication avoidance, and patient follow-up to assure safety and effectiveness.

The 100 most-cited articles in spinal oncology

OBJECTIVE The authors' objective was to identify the 100 most-cited research articles in the field of spinal oncology. METHODS The Thomson Reuters Web of Science service was queried for the years 1864-2015 without language restrictions. Articles were sorted in descending order of the number of times they were cited by other studies, and all titles and abstracts were screened to identify the research areas of the top 100 articles. Levels of evidence were assigned on the basis of the North American Spine Society criteria. RESULTS The authors identified the 100 most-cited articles in spinal oncology, which collectively had been cited 20,771 times at the time of this writing. The oldest article on this top 100 list had been published in 1931, and the most recent in 2008; the most prolific decade was the 1990s, with 34 articles on this list having been published during that period. There were 4 studies with Level I evidence, 3 with Level II evidence, 9 with Level III evidence, 70 with Level IV evidence, and 2 with Level V evidence; levels of evidence were not assigned to 12 studies because they were not on therapeutic, prognostic, or diagnostic topics. Thirty-one unique journals contributed to the 100 articles, with the Journal of Neurosurgery contributing most of the articles (n = 25). The specialties covered included neurosurgery, orthopedic surgery, neurology, radiation oncology, and pathology. Sixty-seven articles reported clinical outcomes. The most common country of article origin was the United States (n = 62), followed by Canada (n = 8) and France (n = 7). The most common topics were spinal metastases (n = 35), intramedullary tumors (n = 18), chordoma (n = 17), intradural tumors (n = 7), vertebroplasty/kyphoplasty (n = 7), primary bone tumors (n = 6), and others (n = 10). One researcher had authored 6 studies on the top 100 list, and 7 authors had 3 studies each on this list. CONCLUSIONS This study identified the 100 most-cited research articles in the area of spinal oncology. The studies highlighted the multidisciplinary and multimodal nature of spinal tumor management. Recognition of historical articles may guide future spinal oncology research.

[Kyphoplasty combined with intraoperative radiotherapy (Kypho-IORT). Alternative therapy for patients with oligometastatic spinal metastases]

BACKGROUND

Due to a more effective systemic therapy the survival of patients suffering from malignant tumors has been significantly improved but a longer life span is often associated with a higher incidence of osseous metastases. The majority of these metastases are localized in the spine causing pain, instability and neurological impairments. The interdisciplinary management of spinal metastases previously consisted of stabilization followed by fractionated external body radiation therapy. A reduction in procedural severity and morbidity as well as consideration of self-sufficiency and hospitalization time are important target parameters for these palliative patients.

METHOD AND RESULTS

Kyphoplasty combined with intraoperative radiotherapy (Kypho-IORT) is one of several modern treatment options, which involves a minimally invasive procedure with local high-dose transpedicular irradiation of the spine with low-energy (50 kV) X-rays. Immediately following irradiation, stabilization of the spine is carried out using kyphoplasty via the same access route so that a single stage procedure with excellent pain reduction and good local tumor control can be achieved. This article presents clinical data for this procedure and the different fields of indications are critically reviewed and compared to other therapy options. Methodological improvements and options for further individualization of therapy are demonstrated.

CONCLUSION

The Kypho-IORT procedure is a safe, feasible and beneficial modern treatment option for instant stabilization and local tumor control in patients with spinal metastases. More than 100 operations have been successfully performed so that the method can be deemed suitable for inclusion in the clinical routine. A phase II dose escalation study has now been completed and submitted for publication and a 2-arm non-inferiority trial (phase III study) for comparison with conventional irradiation is in progress.

Percutaneous Image-guided Laser Photocoagulation of Spinal Osteoid Osteoma: A Single-Institution Series

PURPOSE

To retrospectively evaluate the safety and efficacy of percutaneous image-guided laser photocoagulation for the treatment of spinal osteoid osteoma (OO) in proximity to neural structures.

MATERIALS AND METHODS

This study was institutional review board-approved with waivers of informed consent. From January 1994 until October 2014, 58 patients with spinal OO (mean age, 25 years; 40 men, 17 women) were treated in one institution by using laser photocoagulation with combined computed tomographic (CT) and fluoroscopic guidance. One patient was excluded because of less than 3 months of follow-up. All patients had typical clinical and imaging findings. Clinical features, radiologic data, and procedure-related data were reviewed, and limitations, complications, and failure rate were evaluated. All data were expressed as means ± standard deviation. P values of less than .05 were indicative of statistical significance.

RESULTS

OO was in the vertebral body for 18 of 57 patients, the neural arch for 21 of 57 patients, and the articular process for 18 of 57 patients. Mean nidal diameter was 8 mm, and the mean distance from the closest neural structure was 6.6 mm (minimum distance, ≤5 mm in 35 of 57 patients). In 35 of 57 patients, no cortical coverage was present between the nidus and neural structure in danger. Mean total energy delivered was 1271 J (2-watt continuous power mode). Thermal insulation (carbon dioxide and/or hydrodissection), temperature monitoring, and electrostimulation were used in 42, 24, and one patient, respectively. Primary clinical success at 1 month was 98.2%. Total recurrence rate was 5.3%. All recurrences were addressed percutaneously. Secondary success rate was 100%. One-year follow-up is available in 54 of 57 patients. No major complications were noted.

CONCLUSION

Spinal OO can be safely and effectively treated with percutaneous laser photocoagulation. In cases that are less than 8 mm to 10 mm distance and in the absence of cortical coverage, thermal protection techniques of the neural structures should be used.

[Tumours and metastases of the spine : cavity/coblation surgery and vertebroplasty/kyphoplasty]

BACKGROUND

Radical surgery for metastases in the spine is in many cases not possible, includingthe higher risk of surgery in older patients with co-morbidities. The aims of treatment are: minimally invasive and maximally effective tumour removal, fracture position, stabilization, pain reduction, and improved quality of life. The specific features and problems of diagnosis and treatment using the cavity/coblation method, , the surgical technique, and the results of the treatment of 250 patients with spinal tumours/metastases are presented.

MATERIALS AND METHODS

Tumour resection is carried out by plasma field, via percutaneous trans-/extrapedicular access, followed by kyphoplasty. Clinical and radiological follow-up was carried out postoperatively, including data on pain reduction and improvement of quality of life.

RESULTS

Within 6 years (March 2008t February 2014) a total of 250 patients, or 812 spines were treated. In 59 cases dorsal percutaneous instrumentation and straightening were carried out. Minimal blood loss and a very low complication rate were recorded. After surgery, significant pain reduction, satisfaction, early mobilization, and improvement in quality of life were demonstrated in all patients. Immediate radio- and chemotherapy could be carried out. In 38 cases cement escaped laterally into the intervertebral space, but this had no clinical relevance. 188 patients have since died because of tumour manifestations.

CONCLUSIONS

The cavity/coblation method has been demonstrated to be a safe, minimally invasive procedure, with good short- and long-term results and lower complication rates. A comprehensive diagnostic, including tumour staging, the correct indication, and prognosis estimation, is important.

Clinical long-term outcome, technical success, and cost analysis of radiofrequency ablation for the treatment of osteoblastomas and spinal osteoid osteomas in comparison to open surgical resection

OBJECTIVE

To assess the clinical success and costs of computed tomography (CT)-guided radiofrequency ablation (RFA) of osteoblastoma (OB) and spinal osteoid osteoma (OO).

MATERIALS AND METHODS

Nineteen patients with OB and eight patients with spinal OO were treated with CT-guided RFA. The OBs were localized in the extremities (n = 10), the vertebral column (n = 2), and (juxta-)articular (n = 7). Dedicated procedural techniques included three-dimensional CT-guided access planning in all cases, overlapping RFA needle positions (median, two positions; range, 1-6 RF-electrode positions) within the OB nidus (multiple ablation technique, n = 15), and thermal protection in case of adjacent neural structure in four spinal OO. The data of eight operated OB and ten operated spinal OO patients were used for comparison. Long-term success was assessed by clinical examination and using a questionnaire sent to all operated and RFA-treated patients including visual analogue scales (VAS) regarding the effect of RFA on severity of pain and limitations of daily activities (0-10, with 0 = no pain/limitation up to 10 = maximum or most imaginable pain/limitation).

RESULTS

All patients had a clear and persistent pain reduction until the end of follow-up. The mean VAS score for all spinal OO patients and all OB patients treated either with RFA or with surgical excision significantly decreased for severity of pain at night, severity of pain during the day, and both for limitations of daily and of sports activities.

CONCLUSIONS

RFA is an efficient method for treating OB and spinal OO and should be regarded as the first-line therapy after interdisciplinary individual case discussion.

Interstitial ultrasound ablation of vertebral and paraspinal tumours: parametric and patient-specific simulations

PURPOSE

Theoretical parametric and patient-specific models are applied to assess the feasibility of interstitial ultrasound ablation of tumours in and near the spine and to identify potential treatment delivery strategies.

METHODS

3D patient-specific finite element models (n = 11) of interstitial ultrasound ablation of tumours associated with the spine were generated. Gaseous nerve insulation and various applicator configurations, frequencies (3 and 7 MHz), placement trajectories, and tumour locations were simulated. Parametric studies with multilayered models investigated the impacts of tumour attenuation, tumour dimension, and the thickness of bone insulating critical structures. Temperature and thermal dose were calculated to define ablation (>240 equivalent minutes at 43 °C (EM43 °C)) and safety margins (<45 °C and <6 EM43 °C), and to determine performance and required delivery parameters.

RESULTS

Osteolytic tumours (≤44 mm) encapsulated by bone could be successfully ablated with 7 MHz interstitial ultrasound (8.1-16.6 W/cm(2), 120-5900 J, 0.4-15 min). Ablation of tumours (94.6-100% volumetric) 0-14.5 mm from the spinal canal was achieved within 3-15 min without damaging critical nerves. 3 MHz devices provided faster ablation (390 versus 930 s) of an 18 mm diameter osteoblastic (high bone content) volume than 7 MHz devices. Critical anatomy in proximity to the tumour could be protected by selection of appropriate applicator configurations, active sectors, and applied power schemas, and through gaseous insulation. Preferential ultrasound absorption at bone surfaces facilitated faster, more effective ablations in osteolytic tumours and provided isolation of ablative energies and temperatures.

CONCLUSIONS

Parametric and patient-specific studies demonstrated the feasibility and potential advantages of interstitial ultrasound ablation treatment of paraspinal and osteolytic vertebral tumours.

Management of skeletal metastases: An orthopaedic surgeon's guide

Skeletal metastasis is a common cause of severe morbidity, reduction in quality of life (QOL) and often early mortality. Its prevalence is rising due to a higher rate of diagnosis, better systemic treatment, longer lives with the disease and higher disease burden rate. As people with cancer live longer and with rising sensitivity of body imaging and surveillance, the incidence of pathological fracture, metastatic epidural cord compression is rising and constitutes a challenge for the orthopedic surgeon to maintain their QOL. Metastatic disease is no longer a death sentence condemning patients to "terminal care." In the era of multidisciplinary care and effective systemic targeted and nontargeted therapy, patient expectations of QOL, even during palliative end of care period is high. We lay emphasis on proving the diagnosis of metastasis by biopsy and histopathology and discuss imaging modalities to help estimate fracture risk and map disease extent. This article discusses at length the evidence and decision-making process of various modalities to treat skeletal metastasis. The modalities range from radiation including image-guided, stereotactic and whole body radiation, systemic targeted or hormonal therapy, spinal decompression with or without stabilization, extended curettage with stabilization, resection in select cases with megaprosthetic or biological reconstruction, percutaneous procedures using radio frequency ablation, cementoplasties and discusses the role of emerging modalities like high frequency ultrasound-guided ablation, cryotherapy and whole body radionuclide therapy. The focus lies on the role of multidisciplinary care, which considers complex decisions on patient centric prognosis, comorbidities, cost, feasibility and expectations in order to maximize outcomes on QOL issues.

Irreversible electroporation of the lumbar vertebrae in a porcine model: is there clinical-pathologic evidence of neural toxicity?

PURPOSE

To evaluate the effects of irreversible electroporation (IRE) in the porcine spine.

MATERIALS AND METHODS

This study was approved by the institutional animal care and use committee. Twenty computed tomographically guided IRE ablations in either a transpedicular location or directly over the posterior cortex were performed in the lumbar vertebrae of 10 pigs by a single operator. T1- and T2-weighted magnetic resonance (MR) imaging was performed with and without contrast material 2 or 7 days after ablation. Mathematical modeling was performed to estimate the extent of ablation. Clinical, radiologic, pathologic, and simulation findings were analyzed. The Miller low-bias back transformation was used to construct 95% confidence intervals for the mean absolute percentage difference between the maximum length and width of the ablation zone on MR images and pathologic measurements by using square-root-transformed data.

RESULTS

Bipolar IRE electrode placement and ablation were successful in all cases. The mean distances from the IRE electrode to the posterior wall of the vertebral body or the exiting nerve root were 2.93 mm ± 0.77 (standard deviation) and 7.87 mm ± 1.99, respectively. None of the animals had neurologic deficits. Well-delineated areas of necrosis of bone, bone marrow, and skeletal muscle adjacent to the vertebral body were present. Histopathologic changes showed outcomes that matched with simulation-estimated ablation zones. The percentage absolute differences in the ablation measurements between MR imaging and histopathologic examination showed the following average errors: 24.2% for length and 28.8% for width measurements on T2-weighted images, and 26.1% for length and 33.3% for width measurements on T1-weighted contrast material-enhanced images.

CONCLUSION

IRE ablation in the porcine spine is feasible and safe and produces localized necrosis with minimal neural toxicity. Signal intensity changes on images acquired with standard MR imaging sequences demonstrate the ablation zone to be larger than that at histopathologic examination.

Bone and soft tissue ablation

Bone and soft tissue tumor ablation has reached widespread acceptance in the locoregional treatment of various benign and malignant musculoskeletal (MSK) lesions. Many principles of ablation learned elsewhere in the body are easily adapted to the MSK system, particularly the various technical aspects of probe/antenna design, tumoricidal effects, selection of image guidance, and methods to reduce complications. Despite the common use of thermal and chemical ablation procedures in bone and soft tissues, there are few large clinical series that show longitudinal benefit and cost-effectiveness compared with conventional methods, namely, surgery, external beam radiation, and chemotherapy. Percutaneous radiofrequency ablation of osteoid osteomas has been evaluated the most and is considered a first-line treatment choice for many lesions. Palliation of painful metastatic bone disease with thermal ablation is considered safe and has been shown to reduce pain and analgesic use while improving quality of life for cancer patients. Procedure-related complications are rare and are typically easily managed. Similar to all interventional procedures, bone and soft tissue lesions require an integrated approach to disease management to determine the optimum type of and timing for ablation techniques within the context of the patient care plan.

Percutaneous bone lesion ablation

Benign tumors and metastatic bone lesions can be treated by ablation techniques performed either alone or in combination with other percutaneous techniques. Ablation techniques include ethanol or acetic acid injection and thermal ablation by means of energy deposition [including laser, radiofrequency, microwave, cryoablation, radiofrequency ionization and magnetic resonance (MR)-guided high-intensity focused ultrasound (HIFU)]. Goal definition of the therapy is crucial: ablation techniques can be proposed as curative treatments in benign bone tumors or oligometastatic disease (<3 lesions). Alternatively, these techniques can be proposed as palliative treatments aiming at reduction of pain, local control of the disease and tumor decompression. Depending on the lesion's location ablation can be combined with cementation with or without further metallic augmentation; local tumor control can be enhanced by combining ablation with transarterial bland embolization or chemoembolization. Thermal ablation of bone and soft tissues is characterized by high success and relatively low rates of potential complications, mainly iatrogenic thermal damage of surrounding sensitive structures. Successful thermal ablation requires a sufficient ablation volume and thermal protection of the surrounding vulnerable structures. This article will describe the general principles governing ablation and the mechanism of action for each technique and in addition will review the literature about safety and effectiveness of percutaneous imaging-guided ablation for benign and malignant (primary and metastatic) lesions.

Percutaneous image-guided ablation of bone and soft tissue tumours: a review of available techniques and protective measures

Background

Primary or metastatic osseous and soft tissue lesions can be treated by ablation techniques.

Methods

These techniques are classified into chemical ablation (including ethanol or acetic acid injection) and thermal ablation (including laser, radiofrequency, microwave, cryoablation, radiofrequency ionisation and MR-guided HIFU). Ablation can be performed either alone or in combination with surgical or other percutaneous techniques.

Results

In most cases, ablation provides curative treatment for benign lesions and malignant lesions up to 3 cm. Furthermore, it can be a palliative treatment providing pain reduction and local control of the disease, diminishing the tumour burden and mass effect on organs. Ablation may result in bone weakening; therefore, whenever stabilisation is undermined, bone augmentation should follow ablation depending on the lesion size and location.

Conclusion

Thermal ablation of bone and soft tissues demonstrates high success and relatively low complication rates. However, the most common complication is the iatrogenic thermal damage of surrounding sensitive structures. Nervous structures are very sensitive to extremely high and low temperatures with resultant transient or permanent neurological damage. Thermal damage can cause normal bone osteonecrosis in the lesion’s periphery, surrounding muscular atrophy and scarring, and skin burns. Successful thermal ablation requires a sufficient ablation volume and thermal protection of the surrounding vulnerable structures.

Teaching points

• Percutaneous ablations constitute a safe and efficacious therapy for treatment of osteoid osteoma.

• Ablation techniques can treat painful malignant MSK lesions and provide local tumour control.

• Thermal ablation of bone and soft tissues demonstrates high success and low complication rates.

• Nerves, cartilage and skin are sensitive to extremely high and low temperatures.

• Successful thermal ablation occasionally requires thermal protection of the surrounding structures.

The distribution of heat in bone during radiofrequency ablation of an ex vivo bovine model of osteoid osteoma

Osteoid osteoma is treated primarily by radiofrequency (RF) ablation. However, there is little information about the distribution of heat in bone during the procedure and its safety. We constructed a model of osteoid osteoma to assess the distribution of heat in bone and to define the margins of safety for ablation. Cavities were drilled in cadaver bovine bones and filled with a liver homogenate to simulate the tumour matrix. Temperature-sensing probes were placed in the bone in a radial fashion away from the cavities. RF ablation was performed 107 times in tumours < 10 mm in diameter (72 of which were in cortical bone, 35 in cancellous bone), and 41 times in cortical bone with models > 10 mm in diameter. Significantly higher temperatures were found in cancellous bone than in cortical bone (p < 0.05). For lesions up to 10 mm in diameter, in both bone types, the temperature varied directly with the size of the tumour (p < 0.05), and inversely with the distance from it. Tumours of > 10 mm in diameter showed a trend similar to those of smaller lesions. No temperature rise was seen beyond 12 mm from the edge of a cortical tumour of any size. Formulae were developed to predict the expected temperature in the bone during ablation.

Percutaneous radiofrequency ablation of spinal osteoid osteoma under CT guidance

OBJECTIVE

Osteoid osteoma (OO) accounts for approximately 10-12% of all benign bone tumours and 3% of all bone tumours. Spinal involvement appears in 10-25% of all cases. The purpose of this study was to evaluate the safety and efficacy of CT-guided radiofrequency (RF) ablation in the treatment of spinal OOs and report our experience.

METHODS

13 patients suffering from spinal OO and treated at the authors' institution using CT-guided RF ablation were retrospectively evaluated. The RF probe was introduced through a 11-G Jamshidi(®) needle, and the lesion was heated at 90°C for 6 min.

RESULTS

All procedures were considered technically successful as the correct positioning of the probe was proven by CT. 11 of the 13 patients reported pain relief after RF ablation. In two cases, RF ablation was repeated 1 month after the first procedure. Pain relief was achieved in both cases after the second procedure. No recurrence was reported throughout the follow-up. No complications like skin burn, soft-tissue haematoma, infection, vessel damage or neurological deficit were reported.

CONCLUSION

This study demonstrates that CT-guided percutaneous RF ablation is a safe and effective method for the treatment of spinal OOs.

ADVANCES IN KNOWLEDGE

The data of this study support the efficacy and safety of the recently applied CT-guided percutaneous RF ablation technique for the treatment of spinal OOs.

A preliminary study of the safety and efficacy of radiofrequency ablation with percutaneous kyphoplasty for thoracolumbar vertebral metastatic tumor treatment

Background

Thoracolumbar vertebral metastasis (TVM) affects a large number of cancer patients. However, safe and effective palliative care remains controversial. The aim of the present study was to investigate the safety and efficacy of minimally invasive image-guided radiofrequency ablation (RFA) with percutaneous kyphoplasty (PKP) for TVM treatment.

Material/Methods

A retrospective study of 26 patients (mean age: 59.31±11.62 years) was conducted, including 38 vertebral metastases at T₁₁, T₁₂, L₁, L₂, L₃, L₄, L₅, and S₁ with abundant blood vessels. Patients underwent RFA with PKP (4–6 min, 95±5°C, 150 W, effective electrode area of 1.5–2.0 cm) under general anesthesia from February 2005 to January 2009. Electrodes were inserted into the lesions and pre- and post-operative visual analog scale (VAS) scores and X-rays were collected on day 3, week 1, and months 1, 3, and 6. Tumor recurrence and pain level were also evaluated. Safety assessment was conducted based on complications and adverse events. The mean follow-up time was 8.4±2.1 months.

Results

A mean of 2.69±0.93 ablation was performed per patient. The ablation procedure required a mean of 15.08±4.64 min, while the injection of bone cement required a mean of 6.73±0.83 min, for a mean total operating time of 47.77±7.13 min. Postoperative VAS scores were significantly lower on day 3, week 1, and months 1, 3, and 6 (P<0.01), without any complications or tumor recurrence.

Conclusions

Image-guided RFA with PKP was safe and effective for TVM treatment when used with careful consideration of bone cement volume/viscosity, injection location, and temperature.

Bipolar radiofrequency ablation of spinal tumors: predictability, safety and outcome

BACKGROUND

Bone metastases are often the cause of tumor-associated pain and reduction of quality of life. For patients that cannot be treated by surgery, a local minimally invasive therapy such as radiofrequency ablation can be a useful option. In cases in which tumorous masses are adjacent to vulnerable structures, the monopolar radiofrequency can cause severe neuronal damage because of the unpredictability of current flow.

PURPOSE

The aim of this study is to show that the bipolar radiofrequency ablation provides an opportunity to safely treat such spinal lesions because of precise predictability of the emerging ablation zone.

STUDY DESIGN

Prospective cohort study of 36 patients undergoing treatment at a single institution.

PATIENT SAMPLE

Thirty-six patients in advanced tumor stage with primary or secondary tumor involvement of spine undergoing radiofrequency ablation.

OUTCOME MEASURES

Prediction of emerging ablation zone. Clinical outcome of treated patients.

METHODS

X-ray-controlled treatment of 39 lesions by bipolar radiofrequency ablation. Magnetic resonance imaging was performed pre- and postinterventionally. Patients were observed clinically during their postinterventional stay.

RESULTS

The extent of the ablation zones was predictable to the millimeter because it did not cross the peri-interventional planned dorsal and ventral boundaries in any case. No complications were observed.

CONCLUSIONS

Ablation of tumorous masses adjacent to vulnerable structures is feasible and predictable by using the bipolar radiofrequency ablation. Damage of neuronal structures can be avoided through precise prediction of the ablation area.

Osteoid osteoma

Osteoid osteomas consist of a nidus with surrounding sclerotic bone. The differential diagnosis covers a wide range of conditions due to the variable presentation of osteoid osteoma. The natural history is for regression to occur within 6 to 15 years with no treatment; however, this can be reduced to 2 to 3 years with the use of aspirin and non-steroidal anti-inflammatory drugs. Computed tomography-guided percutaneous techniques, including trephine excision, cryoablation, radiofrequency ablation, and laser thermocoagulation, are described.

Painful boney metastases

Boney metastasis may lead to terrible suffering from debilitating pain. The most likely malignancies that spread to bone are prostate, breast, and lung. Painful osseous metastases are typically associated with multiple episodes of breakthrough pain which may occur with activities of daily living, weight bearing, lifting, coughing, and sneezing. Almost half of these breakthrough pain episodes are rapid in onset and short in duration and 44% of episodes are unpredictable. Treatment strategies include: analgesic approaches with "triple opioid therapy", bisphosphonates, chemotherapeutic agents, hormonal therapy, interventional and surgical approaches, steroids, radiation (external beam radiation, radiopharmaceuticals), ablative techniques (radiofrequency ablation, cryoablation), and intrathecal analgesics.

Interest of electrostimulation of peripheral motor nerves during percutaneous thermal ablation

PURPOSE

We present our experience of utilizing peripheral nerve electrostimulation as a complementary monitoring technique during percutaneous thermal ablation procedures; and we highlight its utility and feasibility in the prevention of iatrogenic neurologic thermal injury.

METHODS

Peripheral motor nerve electrostimulation was performed in 12 patients undergoing percutaneous image-guided thermal ablations of spinal/pelvic lesions in close proximity to the spinal cord and nerve roots. Electrostimulation was used in addition to existing insulation (active warming/cooling with hydrodissection, passive insulation with CO2 insufflation) and temperature monitoring (thermocouples) techniques. Impending neurologic deficit was defined as a visual reduction of muscle response or need for a stronger electric current to evoke muscle contraction, compared with baseline.

RESULTS

Significant reduction of the muscle response to electrostimulation was observed in three patients during the ablation, necessitating temporary interruption, followed by injection of warm/cool saline. This resulted in complete recovery of the muscle response in two cases, while for the third patient the response did not improve and the procedure was terminated. No patient experienced postoperative motor deficit.

CONCLUSION

Peripheral motor nerve electrostimulation is a simple, easily accessible technique allowing early detection of impending neurologic injury during percutaneous image-guided thermal ablation. It complements existing monitoring techniques and provides a functional assessment along the whole length of the nerve.

Interstitial laser photocoagulation for the treatment of osteoid osteoma: retrospective study on 35 cases

PURPOSE

The aim of our retrospective study was to evaluate the efficacy of interstitial laser photocoagulation for the treatment of osteoid osteomas and to identify the factors leading to failure of the procedure.

MATERIAL AND METHODS

Thirty-five patients received interstitial laser photocoagulation treatment. A minimum of 3 months follow-up was required. The laser fibre was positioned within the nidus under CT guidance, and energy between 500 and 1800 J was delivered at a power of 2 Watts/s. Follow-up was by outpatient appointment and through a questionnaire sent to the patients.

RESULTS

Thirty patients replied to the questionnaire. Mean follow-up was 40 months. The technical success rate was 100%. The primary success rate (no pain at 1 month) was 94.3%. The rate of recurrence was 6%. The rate of complications was 11.4% (a skin burn, patellar enthesopathy, a broken item of material, sacro-iliac fibrous alterations). Factors likely to favour failure of the procedure are the size of the nidus (P=0.04) and poor positioning of the laser fibre (P=0.03).

CONCLUSION

Interstitial laser photocoagulation is an effective and safe treatment for osteoid osteomas.

[Radiofrequency ablation in spinal osteoid osteoma. Options and limits]

Osteoid osteoma was first described by Jaffe in 1935 as a benign bone neoplasm mainly located in the diaphyseal areas of long bones: 10% are located in the spine, mainly in the lumbar and thoracic posterior elements. Therapy is required due to nocturnal pain independent of the physical load and responds especially well to anti-inflammatory drugs due to the excessive production of prostaglandins in the nidus. Diagnosis is confirmed by multi-slice computed tomography (CT), magnetic resonance imaging (MRI) and skeletal scintigraphy scans. In cases with typical symptoms and imaging, open biopsies are rarely needed. Although CT-guided radiofrequency ablation is accepted as the gold standard treatment option for osteoid osteoma in the extremities, this technique is limited in spinal applications due to the risk of thermal damage to adjacent neurovascular structures. Technical advances in the administration of radiofrequency ablation have, however, resulted in new and expanded indications in the spine so that the necessity for open surgical excision of spinal osteoid osteoma is becoming less.

Thermometry during coblation and radiofrequency ablation of vertebral metastases: a cadaver study

PURPOSE

To evaluate safety of coblation of simulated lytic metastases in human cadaveric vertebral bodies by measuring heat distribution during thermal tissue ablation and comparing it to radiofrequency ablation (RFA).

MATERIALS AND METHODS

Three devices were compared: a 10 mm single-needle RFA electrode, a 20 mm array RFA electrode and the coblation device. To simulate bone metastases, a spinal tumor model was used stuffing a created lytic cavity with muscle tissue. Measuring of heat distribution was performed during thermal therapy within the vertebral body, in the epidural space and at the ipsilateral neural foramen. Eight vertebral bodies were used for each device.

RESULTS

Temperatures at heat-sensitive neural structures during coblation were significantly lower than using RFA. Maximum temperatures measured at the end of the procedure at the neural foramen: 46.4 °C (± 2.51; RFA 10 mm), 52.2 °C (± 5.62; RFA 20 mm) and 42.5 °C (± 2.88; coblation). Maximum temperatures in the epidural space: 46.8 °C (± 4.7; RFA 10 mm), 49.5 °C (± 6.48; RFA 20 mm) and 42.1 °C (± 2.5; coblation). Maximum temperatures measured within the vertebral body: 50.6 °C (± 10.48; RFA 10 mm), 61.9 °C (± 15.39; RFA 20 mm) and 54.4 °C (± 15.77; coblation).

CONCLUSION

In addition to RFA, the application of coblation is a safe method to ablate vertebral lesions with regards to heat distribution at heat-sensitive neural spots. The measured temperatures did not harbor danger of thermal damage to the spinal cord or the spinal nerves.

Intraoperative radiofrequency ablation for metastatic spine disease: report of 4 cases and review

Metastatic spine disease (MSD) is a complex disease entity requiring multi-discipline and multi-modality approach to obtain the most reasonable clinical outcomes. As one of these trials, radiofrequency ablation (RFA) has been tried. Here, we describe four cases of metastatic spine lesions (2 hepatomas, 1 lung cancer, 1 breast cancer) that were treated with intraoperative RFA to control the lesion and to limit tumor contamination. During 3-month follow-up, most patients experienced effective pain relief and improvement of their functional status. However, their final results were diverse. There were no complications related to this procedure. In two cases, the treated lesions were re-evaluated radiologically using PET-CT and diffusion-weighted MRI. Up to the time of this report, the patients are well without progressive deterioration of the treated lesion. With review of the related literatures, we discuss the efficacy and safety of this therapeutic approach as one of options for the treatment of MSD with neurologic manifestations.