16 The Role of Navigation in the Resection of Primary Spinal Tumor
Abstract
The primary spinal tumor can be effectively treated with total en bloc spondylectomy (TES) to achieve margin-free resection of the tumor. However, en bloc resection of spine tumors is a technically demanding surgery. Although more and more surgeons have started to perform en bloc resections in the recent two decades, the complication rate is reportedly as high as 35%. These complications include but are not limited to the injury of the vena cava, late aortic dissections, intraoperative hemorrhage, and other less severe complications. The emerging navigation and robotic assistance focus on the precision of the spine surgery, decreasing of the surgical errors, and improving the patient outcomes. With showing a difficult surgical case of an advanced-staged spinal tumor, step by step, from preoperative and intraoperative surgical planning to accurate osteotomy and reconstruction, this chapter illustrates how spine navigation technology provides a high level of accurate visualization to facilitate the en bloc resection of the primary spinal tumor with a full circumferential tumor-free margin. Although en bloc resection still carries a high complication profile, the application of navigation and robotics has made it safer and more efficient.
16.1 Introduction
The treatment of primary spinal tumors has evolved over the past four decades. The development of an oncological staging system for spinal tumors 1 , 2 has afforded a better understanding of the biological behavior of single histotypes and, in turn, more advanced surgical planning.
Stener 3 was the first to coin and develop the concept of en bloc tumor resection in the spine and Roy-Camille et al 4 and Tomita et al 5 then systemized the procedure by single posterior approach. But these techniques, known as TES (total en bloc spondylectomy) can achieve an appropriate margin-free tumor resection only if the tumor is located inside the vertebral body. If the tumor grows extracompartmentally, a combination of approaches is generally required for a full margin control. Subsequent modifications of the technique for the treatment of vertebral neoplasm according to the tumor extension has provided a chance for oncological appropriate resection margins, thereby improving tumor control and overall survival. 4 , 5 In a series reported by Boriani et al, 70.4% of the patients were free from recurrence at mid/long term after en bloc resections. 6 Up to 83.4% of patients were in remission when treated for de novo disease.
Today, en bloc resections are more commonly performed and a large series of studies have been published in the spine literature. However, there is still a high complication rate associated with the procedure, with reported rates of approximately 35%, including intraoperative death due to injury of the vena cava, late aortic dissections, massive intraoperative hemorrhage, and other less severe complications. The complication rate has been reported at 10.6% for the single posterior approach and much higher for a double-approach resection. 6
Surgical decision-making in cases of primary spinal tumors can be complicated and nuanced. The extent of tumor resection needs to be tailored based on a shared decision-making model between patient and physician. Sometimes, for a true wide margin en bloc tumor resection, vital structures including nerve roots, dura, or vascular structures must be sacrificed. Other times, oncological principles of wide dissection may be violated, the so-called intentional transgression, 7 potentially placing the patient at higher risk for recurrence, but likely sparing some other dysfunction (e.g., neurologic). In this setting, a multidisciplinary approach (medical and radiation oncology) for adjuvant therapy can sometimes compensate for margin violation according to the specific tumor histotypes. Sometimes, tumor extension can exceed the anatomical criteria to perform a tumor-free margin en bloc resection. 8 This so-called incidental transgression 7 requires adjuvant therapy as well.
This is the case reported here: the extension of the tumor (desmoplastic fibroma of bone, ICD-O code 8823/0: a low-grade locally aggressive tumor) was so huge that it was considered impossible to perform an en bloc resection with a full circumferential tumor-free margin. The major constraint was considered the intrathoracic extension under the scapula. Therefore, an intentional transgression to separate the huge tumor in two major pieces was planned as the best possible oncologically appropriate surgery. On the operative field, however, the spine navigation technology allowed such a high level of accurate visualization to make possible the en bloc resection with a full circumferential tumor-free margin.
The image-based technology creates a virtual, three-dimensional (3D) model of the patient’s spine, essentially a digital roadmap or blueprint to help guide the surgeon. It is especially useful to the complex spine surgery like en bloc resection of spine tumors. Over the past decade, 3D navigation system is reported to have assisted surgeons to perform complex spine surgeries in a much safer manner. 9 Computed tomography (CT)-based image-guidance technology represents one of the most recent advancements in 3D navigation in spine surgery. Intraoperative cone-beam CT (O-arm, Medtronic, Minneapolis, MN), frequently coupled with stereotactic navigation (StealthStation, Medtronic), is increasingly used in the surgical management of spine surgery. It is gaining popularity due to the ability to provide automated registration with an intraoperative, post-positioning CT scan with the theoretical benefit of enhanced safety and accuracy. 10 , 11 It is one of the options advocated to limit instrumentation misplacement. The use of 3D CT-based navigation in TES treating primary neoplasm, however, has not been well studied or reported. 12 In this chapter, we will introduce our experience based on the previously introduced tumor resection, performed under O-arm navigation.
16.2 Relative Indication and Contraindication
Tomita classified spinal tumors into seven types according to the extent of tumor invasion. 5 , 13 , 14 TES was mainly indicated in Tomita lesion types 2 to 5, and lesion types 1 and 6 were only relatively indicated. With the improvement of the surgical techniques, more and more Tomita type 1 and 6 lesions have been reported to be successfully resected en bloc. Multisegmental resection of more than three levels in a single procedure has been reported in recent years, and although reportedly successful, increasing numbers of resected segments has been shown to be an independent predictor of major complications, 6 with 100% complications in four-level resection compared with 50% in three-level resection, 45.5% in two-level resection, and 34.9% in single-level resection. 15
16.3 Case Example
A 46-year-old female presented with a history of back pain and numbness on lower part of the torso for 9 years and was admitted after progressive girdle band sensation around the waist for 1 month. She started to have back pain and mild numbness around the waist and bilateral leg pain, numbness, and tingling. MRI revealed multiple osteolytic lesions from the second and the third thoracic vertebrae expanding through the transverse processes to the ribs on the right side, with the spinal canal involvement and spinal cord compression. Physical examination demonstrated back pain in the area of the second and third thoracic vertebrae and decreased mobility of the thoracic spine with moderate-to-severe neurological deficit, including perineal hypoesthesia, bilateral hyperreflexia, bilateral patellar and ankle clonus, and reduced sensorium. Computed tomography showed a tumor at the described thoracic level Th2–Th3, involving the third rib on the right side, with the second and the third thoracic spondylolisthesis (Fig. 16‑1).
16.3.1 Navigation Techniques
Preparation before the Surgery
Surgical preparation for navigation started several days prior to the surgery. Cytology from a preoperative CT-guided needle aspiration of the paraspinal mass showed a myofibroblast type tumor. No evidence of distant metastasis was found on PET-CT and bone scintigraphy. Using patient’s MRI and CT scans and the help of the 3D printing technology, a 3D model of the tumor and its surrounding area was created. This model allowed better understanding of the exact positioning of the tumor and how it interfered with the blood vessels and nerves. An en bloc resection of the second to fourth thoracic vertebral level followed by a second-stage intrathoracic tumor resection through thoracotomy was planned (Fig. 16‑2).
Preparation in the Operating Room
The patient was positioned prone on a Jackson table. The design of the O-arm allows it to work ideally with the Jackson table, which does not have a base obstructing movement along the long axis of the patient and table. The Jackson table enables the O-arm to be positioned along any level of the spinal axis. 16 The table is well designed for imaging purposes, with its core structure containing minimal radio-dense metal, resulting in minimal radiographic artifact.
A three-pronged Mayfield head clamp was used to position the head in the usual fashion at the accepted anatomic landmarks and all pressure points were well padded. The O-arm is then used to take fluoroscopy image in anteroposterior and lateral views to assure that the Th2, Th3 vertebrae are in the center of the O-arm gantry. The reference frame is attached. A “spin” is acquired and the 3D reconstructed images are obtained and transmitted to the StealthStation. The O-arm is then removed and the surgical site is prepped and draped in the usual fashion, avoiding any disturbance to the sterile reference pin.
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