Minimally Invasive Treatment of Spinal Tumors Evan Frangou, MD, and Daryl R. Fourney, MD, FRCSC, FACS In an effort to reduce the burden of harm that our treatments cause to our patients, there has been a trend toward the minimalization of spine surgery. We review the minimally invasive procedures used in the treatment of spinal tumors, including minimally invasive diagnostic techniques, vertebral augmentation, radiofrequency ablation, endoscopic/ thoracoscopic spine surgery, and minimal access open spine surgery. Semin Spine Surg 21:112-120 © 2009 Elsevier Inc. All rights reserved. KEYWORDS minimally invasive spine surgery, minimal access spine surgery, spine tumors, spinal metastases, spine neoplasm A lthough primary tumors of the spinal cord and vertebral column are relatively rare, spinal metastases remain a pervasive and costly problem. In fact, spinal metastases rep- resent more than 90% of all spinal tumors. 1 They occur in approximately 5% of cancer patients (61,000 Americans) per year 2 and affect approximately one-third to two-thirds of cancer patients at autopsy. 3,4 The treatment of spinal tumors has historically relied on open surgical excision and radiation therapy. However, as new innovations permit improved access to lesions while minimizing approach-related morbidity, we are able to pro- vide our patients with better care and improved quality of life. Radiosurgery and radiation therapy are important nonin- vasive techniques that have considerably advanced the treat- ment of spinal tumors. These topics are beyond the scope of this review, and are covered elsewhere in this journal. Minimally Invasive Diagnostic Techniques Spinal tumors are being detected at earlier stages and smaller sizes than before, as a result of the widespread application of advanced imaging techniques, particularly MRI. 1,5 These le- sions are often deep and lie in close proximity to critical neural and vascular structures. A tissue diagnosis is often the key in determining the most appropriate treatment plan. Open biopsy can impart significant morbidity to the patient. For cer- tain rare primary tumors (eg, chordoma, chondrosarcoma), open biopsy can result in dissemination of tumor cells, signifi- cantly reducing the likelihood of achieving local disease control with surgery. The concept of minimally invasive spinal biopsy is not new. In fact, the first report of percutaneous biopsy of the spine was in 1935 by Robertson and Ball. 6 In 1956, Craig modernized this technique by developing a core biopsy nee- dle to improve diagnostic yield. 7 Image guidance with fluo- roscopy or computed tomography (CT) has significantly in- creased the precision of percutaneous spinal biopsies. 8-14 Likewise, the transpedicular approach 5,15-18 and the transfo- raminal approach 19 allow the avoidance of complications en- countered by conventional approaches, which invade the paraspinal space (ie, pneumothorax, visceral, and vascular injury). The rates of tissue diagnosis with these techniques are 71%-100%. 5,11,15,18,20 A positive tissue diagnosis is more likely with a larger sample volume. 10,11,13,18 A recent meta-analysis by Nourba- khsh et al 21 suggested a trend toward increased biopsy accu- racy, adequacy, and complication rate with the use of increas- ing inner diameter of the biopsy needle. Fine-needle aspiration biopsy allows an assessment of the cytology but not the tissue architecture. As a result, we generally recom- mend that percutaneous biopsies be performed with a trocar, especially if imaging studies suggest the possibility of a pri- mary osteogenic tumor. Some studies have suggested that CT has a slightly lower rate of complication than fluoroscopy for image-guided biopsy, but this was not statistically significant in a meta-analysis. 21 Vertebral Augmentation Vertebroplasty Until recent years, treatment of painful spinal metastases was limited to conservative medical management, with rare indi- Division of Neurosurgery, University of Saskatchewan, Saskatoon, Saskatche- wan, Canada. Address reprint requests to Daryl R. Fourney, MD, FRCSC, FACS, Divi- sion of Neurosurgery, Royal University Hospital, 103 Hospital Drive, Saskatoon, Saskatchewan, Canada S7N 0W8. E-mail: daryl.fourney@ saskatoonhealthregion.ca 112 1040-7383/09/$-see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1053/j.semss.2009.03.001