ABSTRACT: A 55-year-old man with metastatic invasion of L4 vertebral body was treated with bipedicular percutaneous radiofrequency ablation (RFA) and vertebral augmentation using the SpineJack Implantable Fracture Reduction System (Stryker). The patient was initially treated for pathological fracture in the T11 vertebral body due to metastatic lytic lesion of unknown origin (pathologic features were suggestive of renal cell carcinoma; however, renal-specific imaging was negative for malignancy) by vertebroplasty and radiation back in 2016. After 20 months, follow-up magnetic resonance imaging of the spine demonstrated a new pathologic fracture at the left posterior L4 hemivertebra, consistent with new metastasis. The patient was then treated percutaneously, including biopsy using bipedicular approach, RFA with a navigational bipolar RFA device, vertebral augmentation using SpineJack titanium vertebral implants, and polymethylmethacrylate (PMMA) high-viscosity cementation. The patient was pain free with much improved mobility upon 2-week follow-up. Imaging at 1-month and 4-month follow-up exams showed unchanged L4 vertebral body height.
IO Learning: Epub 2020 January 10.
Key words: SpineJack; vertebral metastases; radiofrequency ablation; cancer of unknown primary (CUP)
Vertebral compression fracture can be a serious complication of vertebral metastasis and/or osteoporosis.1 It often causes severe back pain with loss of bone mass and vertebral height and progressive spine deformity such as kyphosis. Vertebroplasty/vertebral augmentation has been shown to provide significant pain relief and structural augmentation in the setting of pathologic vertebral fractures, cancer-related or not. The SpineJack Implantable Fracture Reduction System (Stryker) has been approved for treatment of pathologic fractures due to osteoporosis. The use of the SpineJack system for restoration of the vertebral height by endplate realignment is well established in osteoporotic fractures. There are, however, few reports on the use of SpineJack in cancer-related vertebral fractures to date, although its biomechanical properties would suggest that it may be beneficial in such a setting. We report a technically successful treatment of pathological fracture due to vertebral metastasis by bipedicular percutaneous radiofrequency ablation (RFA) with a navigational bipolar RFA device followed by vertebral augmentation using the SpineJack System.
A 55-year-old male with history of hypertension presented to the emergency department, complaining of severe back pain in June 2016. Upon evaluation, he was noted to have pathologic fracture in the T11 vertebra due to metastatic lytic lesion (Figure 1). Percutaneous biopsy, RFA, and cement vertebroplasty were performed at T11 (Figure 2). Postoperatively, he experienced significant pain relief. He subsequently underwent radiation therapy to T10-T12. The pathology from the initial biopsy revealed poorly differentiated clear cell adenocarcinoma, most consistent with renal cell carcinoma (RCC). Further systemic workup and imaging exams, however, did not reveal any primary tumor (particularly no RCC). The case was labeled as cancer of unknown primary (CUP).
In February 2018, the patient presented complaining of worsening back pain. Imaging showed that he had worsening angulation kyphosis at T11 due to collapse of the treated segment with cord compression (Figure 3). The decision was to proceed with spine decompression and fixation. He underwent T7-T9 and L1-L3 posterior fusions as well as complete corpectomy of T10-T12.
In October 2018, the patient returned to the clinic due to recurrent lower back pain. Roland-Morris score was 17/24. He had received 16 radiation treatment cycles and showed good imaging response, but the pain was still present and limiting his daily activities.
On physical examination, he had severe tenderness on palpation without neurological deficits at the L4 level with associated para-spinous muscle spasm. MRI and computed tomography (CT) scan of the lumbar spine revealed an enhancing lytic lesion at the left posteroinferior aspect of L4 vertebral body consistent with metastasis, but not easily accessible for biopsy (Figure 4).
Treatment options were discussed with the patient, including radiation as well as ablation and vertebral augmentation. In the multidisciplinary tumor board, the concern was raised for potential collapse after radiation at the level immediately below a fused segment, warranting preradiation stabilization. It was determined that vertebral augmentation with an implant would be preferred, and this patient was considered a good candidate for bone ablation and vertebral augmentation using the SpineJack System.
TREATMENT AND PROCEDURE
After local anesthesia at skin puncture site and periosteum applied using a 25 gauge spinal needle, bipedicular 11 gauge bone trocars were placed into the L4 vertebral body using direct intermittent biplane fluoroscopy, targeting the upper third of the vertebral body. Multiple bone marrow aspirate and core biopsy samples were obtained from bilateral bone trocars.
Bipedicular RFA was performed using the Star Tumor Ablation System (Merit Medical). Four overlapping ablations were performed until a minimum temperature of 50 °C was reached at the distal and proximal thermocouples of the probe per manufacturer’s instruction for use. During ablation probe placement, close attention was paid to not violating the posterior margin of the vertebral body in the region of the lytic lesion (Figure 5).
Once the RFA probes were removed, the SpineJack System (size kit of 5.8 mm) was used for the vertebral augmentation. The bilateral SpineJack vertebral augmentation devices were introduced into the vertebral body and simultaneously deployed under fluoroscopic guidance, ensuring satisfactory alignment (Figure 6). Deployment of the SpineJack targeted the superior endplate for maximal support of the adjacent fusion construct. Once optimal deployment of the devices was achieved, the deployment cannula was removed.
Polymethylmethacrylate (PMMA) bone cement was then mixed and injected into the vertebral body via the bilateral SpineJack cannula (Figure 7), under direct biplane fluoroscopy. There was minimal left lateral extension of cement along the vertebral body margin. Adequate filling of the vertebral body surrounding the SpineJack devices was achieved. No cement herniation or spinal canal violation were noted on final images. PMMA was noted to fill the posterior tumor just anterior to the posterior vertebral body cortical line.
The patient had an uneventful postprocedural recovery. He stayed overnight for observation and was discharged home early the next morning with his lower back much improved.
OUTCOME AND FOLLOW-UP
At the 2-week clinic follow-up, the patient reported much improved pain and greater mobility. His daily activity has similarly been much improved. Follow-up x-ray images demonstrated stable appearance of the treated L4 lesion. Fluorodeoxyglucose positron emission tomography CT exams were performed 1 and 4 months after bilateral SpineJack placement, demonstrating maintenance of the L4 vertebral body height, with the devices in excellent position (Figure 8).
The diagnosis of CUP is made in patients who have metastatic cancer but no identifiable primary tumor by a comprehensive work-up.2 CUP is a well-recognized clinical syndrome, accounting for 3%-5% of all malignancies.3 The bone is the third most common site of metastatic CUP, following the lymph nodes and lungs.4,5 Adenocarcinomas of unknown primary site comprise approximately 70% of CUPs. Although these cancers may arise from a wide variety of primary sites, the most frequently identified sites in autopsy series are lung, pancreas, hepatobiliary tree, and kidney, together accounting for approximately two-thirds of all autopsied CUP cases.6 In our case, the suspected primary is the kidney.
Radiation therapy is a common and well-established modality in treating spine metastases and is often the initial treatment. Radiation therapy can be delivered as a single-fraction tumor dose (usually 8 Gy) while sparing adjacent spinal cord and nerve roots.7 Greenwood et al reported a local tumor control rate of 100% when radiation therapy was combined with RFA.8
The combination of RFA with a navigational bipolar device and vertebroplasty has been commonly used in cases of spinal oligometastases with significant pain reduction and no local tumor recurrence after 3 months.9,10 Wallace et al recently published local control rates of 70% at 1-year follow-up using the same technique in a study of 55 patients with spinal oligometastases. However, the local control rate decreased slightly to 67% in cases with simultaneous extra-spinal metastases.11
Due to the increased mechanical loads on L4 in our patient under the fusion construct, our approach needed to preserve height and prevent future failure of adjacent levels. The SpineJack System is made of titanium and is currently only approved for osteoporotic fractures in the United States.13,14 Vanni et al found that the postoperative increase in vertebral body height using the SpineJack System was greater than that achieved by kyphoplasty for fractures secondary to trauma and primary or secondary bone tumors.12,15
Using a bilateral transpedicular approach, the SpineJack titanium implant can deliver as much as 1000 Newtons of lifting force to reduce and stabilize the adjacent endplates. The distraction created by the device reduces the fracture by ligamentotaxis, especially when acting on the anterior longitudinal ligament. This system allows a progressive and controlled reduction of the vertebral fractures and facilitates recovery of collapsed vertebra and stabilization of the vertebrae in axial compression.16 After the reduction, PMMA is injected into the vertebral body to further solidify the vertebra.
We reported one of the first cases of successful treatment of vertebral fractures due to metastasis by using the SpineJack System, in the hope of expanding the knowledge of this technique and increasing the demand for further research about its effectiveness and long-term outcomes.
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From the 1Faculty of Medicine, Jordan University of Science and Technology, Irbid 11220, Jordan; and 2Vascular and Interventional Radiology, Department of Radiology, Medical College of Wisconsin, Milwaukee, Wisconsin.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Tutton reports consultant income from Stryker, outside the submitted work. The remaining authors report no conflicts of interest regarding the content herein.
Address for Correspondence: Hasan A. Obeidat, MBBS, Faculty of Medicine, Jordan University of Science and Technology, P.O. Box 3030, Irbid 11220, Jordan. Email: email@example.com