Abstract
Chondrosarcomas and chordomas are the most common malignant primary bone tumors involving the spine. Surgery is usually the initial treatment of these tumors. In the past two decades, surgery for spine tumors has evolved from palliative procedures to en bloc resections of tumors. In this chapter, the authors discuss the rationale for the surgical treatment of spinal chordomas and chondrosarcomas, preoperative planning, current indications for en bloc resections, surgical technique in different spinal segments, clinical and oncological results, and complications of this procedure.
Keywords
Chondrosarcoma, Chordoma, En bloc resection, Neurological surgery, Neurosurgery, Spine surgery
Outline
Introduction 281
Rationale for Surgical Treatment 282
Diagnosis and Staging 282
Indications and Surgical Planning for En Bloc Spinal Resections 282
Preoperative Embolization 285
Surgical Technique for En Bloc Resection of Spine Tumors 285
Perioperative Complications 288
Conclusions 289
References 289
© 2018 Elsevier Inc. All rights reserved. Please note that the copyright for the original figures submitted by the contributors is owned by Contributors.
Introduction
Primary bone tumors of the spine are rare with an estimated incidence of 2.5–8.5 cases per 100,000 people per year. Primary vertebral tumors account for fewer than 5% of spinal tumors. The clinical behavior of these lesions depends mainly on the pathobiology of the tumor.
Chondrosarcomas and chordomas are the most commons malignant primary bone tumors involving the spine. Between 6.5% and 10% of chondrosarcomas involve the mobile spine and approximately 5% are located within the sacrum. In the MD Anderson series of 21 spinal chondrosarcomas, 48% were located in the thoracic spine, followed by 33% in the lumbar and 19% in the cervical spine. Within the vertebra, chondrosarcoma is predominantly located in the vertebral body. Sacral chondrosarcomas are typically located eccentrically in the upper portion of the sacrum and frequently involve the sacroiliac joints. Most chordomas involve the sacrum.
Surgery is usually the initial treatment of choice for these tumors. In the past two decades, surgery for spinal tumors has evolved from palliative procedures to planned en bloc resections. Oncologic principles initially proposed by Enneking et al. in the 1980s to treat tumors affecting long bones as well as advanced surgical and instrumentation techniques have been gradually incorporated into spinal tumor surgery, and many groups have reported good clinical and oncological results with the use of more aggressive en bloc spinal resections.
In this chapter, the authors discuss the rationale for the surgical treatment of spinal chordomas and chondrosarcomas, preoperative planning, current indications for en bloc resections, surgical techniques in different spinal segments, clinical and oncological results, and complications of this type of procedure.
Rationale for Surgical Treatment
The objectives of surgery for spinal chordomas and chondrosarcomas are to preserve or even improve neurological function, relieve pain, prevent local tumor recurrence, and improve disease-free and overall survival. Surgical options range from intralesional resection to wide, “tumor-free margins” en bloc resection with spinal reconstruction.
Accumulating evidence demonstrates that en bloc resection with free margins is the best therapeutic option for achieving long-term and recurrence-free survival in patients with primary spinal tumors, including chordomas and chondrosarcomas. For example, en bloc spinal resections with disease-free margins has been shown to provide excellent local tumor control, with recurrence rates as low as 3%–8%. In contrast, intralesional resection results in recurrence rates of up to 100%. The landmark study from Kaiser et al. demonstrated that contamination of the surgical wound by cell seeding is the main factor associated with tumor recurrence. In their series, the rate of local recurrence was almost two times higher after en bloc resections that violated the tumor capsule than that achieved after en bloc resection without violation of the tumor capsule, demonstrating the key role of preserving tumor integrity during en bloc resections of spinal lesions.
Diagnosis and Staging
Correct diagnosis and staging are crucial to the management of a suspected primary bone tumor of the spine. Tissue for histological diagnosis should be obtained by percutaneous computed tomography (CT)–guided trocar biopsy, which minimizes the risk of contamination of normal tissues by tumor. The orientation of the biopsy tract should allow its incorporation in the specimen of the definitive operation. Open biopsies should be avoided.
Careful preoperative planning is essential for determining whether en bloc resection is indicated and feasible. Imaging studies including whole spine CT and magnetic resonance imaging are usually recommended. Invasion of nearby vital structures (such as the aorta or vena cava) and the presence of intradural tumor that may prevent an en bloc removal without risking spinal cord injury are factors favoring a less aggressive approach. Systemic staging with CT of the chest, abdomen, and pelvis; bone scan; and positron emission tomographic scan is also an integral part of proper preoperative staging.
Indications and Surgical Planning for En Bloc Spinal Resections
Currently, two staging systems are used to classify spine tumors as a guide to treatment planning. The Enneking classification, introduced in 1980 for appendicular musculoskeletal tumors, defines surgical terminology, categorizes tumors based on grade and extent, and emphasizes both tumor-free resection margins and avoidance of tumor entry during resection. When the tumor is not entered, the resection may be considered a wide (when a margin of normal tissue around the tumor is preserved) or marginal (when the obtained margin is along the tumor pseudocapsule) resection. In spinal oncology, marginal resection is preferred to a wide margin resection achieved by dural entry. When entry into the tumor occurs, the resection is considered intralesional (curettage). Radical resection, which refers to en bloc removal of a tumor and the entire compartment of origin, is rarely achieved in the spine without unacceptable morbidity (e.g., hemicorporectomy for a distal sacral chordoma). The Enneking classification ranges from Stage 1 to Stage IIIB ( Table 24.1 ; Fig. 24.1 ). All malignant tumors should be treated with wide en bloc resection as the tumor pseudocapsule cannot be considered a safe margin. Patients with metastasis on presentation do not benefit from en bloc resections and should receive palliative surgery and adjuvant therapy.
| Stage | Grade | Site |
|---|---|---|
| IA | Low G1 | Intracompartmental T1 |
| IB | Low G1 | Extracompartmental T2 |
| IIA | High G2 | Intracompartmental T1 |
| IIB | High G2 | Extracompartmental T2 |
| IIIA | Any grade with regional or distal metastases | Intracompartmental T1 |
| IIIB | Any grade with regional or distal metastases | Extracompartmental T2 |
The Weinstein–Boriani–Biagini (WBB) classification enables staging of spinal tumors while recognizing the unique anatomic complexity of the spine, such as involvement of the spinal epidural space and adjacent vascular structures ( Fig. 24.3 ), with the goal of establishing the feasibility and preferred type of surgical resection. Ultimately, the goal of this classification is to recommend the best approach to achieve tumor-free surgical margins while sparing the spinal cord ( Fig. 24.2 ) . The Enneking and WBB classifications have been shown to display moderate interobserver reliability and near-perfect intraobserver reliability for tumor staging and treatment guidance. The Enneking classification has also been shown to successfully predict the risks of tumor recurrence and mortality in primary spinal tumors.
In summary, preoperative planning should consider the indications, goals, and feasibility of en bloc resection; more specifically, these tools should be employed to determine whether there is a surgical corridor through which the tumor can be delivered without compromising the surrounding vital structures. To remove a spinal tumor in en bloc fashion, the arch formed by the bone elements of the spinal column (vertebral body, pedicles, and lamina) must be broken widely enough to allow dissection around the spinal cord. Sites of bone cuts should be selected carefully to yield tumor-free margins. These cuts can be made either across both pedicles, completely freeing the posterior element complex, or across one pedicle and the contralateral lamina. Sometimes, in order to achieve such en bloc resection, sacrifice of nerve roots is necessary. In such cases, the expected neurological deficits should be carefully taken into account when evaluating the risks and benefits of such aggressive operations.
Contraindications to en bloc spondylectomy include the presence of distant metastases, uncontrolled systemic disease, and encasement of adjacent visceral or vascular structures that cannot be excised.
Preoperative Embolization
Preoperative embolization can dramatically reduce intraoperative blood loss and operative time, increase tumor resectability, and improve visualization of the operative field. The vascular ‘‘blush’’ of the tumor is usually well visualized on angiograms and guides selective embolization of the predominant vascular radicular arteries arising from the aorta. Even partial embolization may significantly reduce intraoperative hemorrhage. Preoperative angiography of lesions at the thoracolumbar junction also identifies the dominant radicular artery supplying the spinal cord, important information that may assist selection of the best surgical approach or even be a contraindication for surgical resection.
Surgical Technique for En Bloc Resection of Spine Tumors
Pioneers in en bloc resections of vertebral tumors include Stener, Roy-Camille et al. and Tomita et al. En bloc spondylectomies usually involve two surgical steps. First, the tumor is freed from surrounding structures to prepare the field for its en bloc resection. During this surgical stage, the required bony cuts are performed and the tumor to be removed as a single specimen is dissected as much as possible to facilitate mobilization of the specimen. In some cases, an intralesional bone cut (performed through the pedicle in most cases) is justified to preserve the spinal cord. The second stage involves removal of the tumor in an en bloc fashion while attempting to preserve the integrity of the spinal cord, the emerging nerve roots, and large blood vessels as much as possible to minimize postoperative morbidity.
The choice between a single posterior approach and a combined approach for en bloc resections depends on the presence or absence of tumor invasion of anterior structures as well as on the affected spinal level. Although multilevel en bloc resections are inherently more challenging than single-level ones, several studies have demonstrated that such operations are feasible and can be safely performed by experienced teams.
Intraoperative monitoring with somatosensory evoked potential (SSEP) and motor evoked potential (MEP) is indicated for continuous functional assessment of the integrity of dorsal and ventral spinal cord tracts. Direct triggered electromyographic stimulation of pedicle screws can also help assure the absence of critical violation of the screws.
Next, we describe specific surgical approaches, challenges, and possible complications associated with en bloc resection of spinal tumors in different spine regions.
Cervical
Surgical treatment of cervical chordomas and chondrosarcomas is hindered by several anatomical factors such as the presence of the vertebral arteries (typically between C6 and the atlas), the difficulty of performing surgical cuts through the cervical pedicles, and the functionality of the cervical nerve roots. Associated challenges also vary depending on the specific level of the lesion in the cervical spine. Tumors arising from C1-C3 and involving the craniocervical junction are classified as high-cervical tumors, those from C4-C6 levels are classified as midcervical tumors, and tumors at C7-T1 are classified as cervicothoracic tumors ( Fig. 24.1 ).
The anatomy and physiology of the vertebral artery requires careful preoperative assessment as its injury may lead to catastrophic outcomes including ischemic or hemorrhagic brainstem and posterior fossa strokes. Even when the vertebral arteries are not directly involved by the tumor, it is frequently very challenging to achieve complete en bloc resection while preserving both vertebral arteries. A balloon test occlusion is routinely recommended to evaluate the feasibility of sacrificing one vertebral artery. Hoshino et al. analyzed the outcome of 15 patients with unilateral vertebral artery ligation in the management of cervical spinal tumors and reported no adverse events related to brainstem, cerebellar, or spinal cord ischemia in patients who underwent a successful preoperative balloon test occlusion. Because surgical access to the vertebral artery is blocked by its encasement in the vertebral foramina and surrounding venous plexus, endovascular occlusion of the vessel should be performed in anticipation of its ligation during the operation for tumor resection ( Fig. 24.3 ).
The risk of damage to the functional cervical nerve roots and potential associated neurological deficits should be thoroughly discussed with the patient and properly documented in the informed surgical consent. Although the C2 and C3 nerve roots can typically be sacrificed without any major neurological repercussion, damage to C3, C4, and C5 nerve roots may lead to ipsilateral diaphragm paralysis. Damage to C5 and C6 nerve roots is poorly tolerated, as they are essential to deltoid and biceps strength, respectively. Triceps weakness from isolated damage to C7 is also meaningful, although it may interfere to a lesser degree with routine daily activities. Injury of C8 or T1 nerve roots results in significant impairment of intrinsic hand muscles, affecting fine hand motor function.
The challenges of surgical treatment of high-cervical chordomas and chondrosarcomas result in worse outcomes with regard to tumor margins and higher rates of complications and tumor recurrence than those observed for midcervical or cervicothoracic junction tumors. Usually, C1-C2 tumors involving the skull base require a staged posteroanterior surgical strategy. The posterior approach starts with a posterior midline dissection with release osteotomies, tumor dissection, ligation of cervical nerve roots and of the vertebral artery (if indicated), and posterior instrumentation. The second stage consists of an anterior approach, in which blunt dissection removes the surrounding soft tissue from the tumor mass and completes the en bloc resection. For C1-C2 tumors not involving the skull base, a posterior-only approach (although sometimes quite challenging) may suffice for achieving an en bloc resection.
In 2014, Molina et al. reported complications in 71% of attempted wide en bloc resections of tumors involving C1-C2 compared with 22% in cases of exclusively subaxial tumors. In addition, C1-C2 chordomas and chondrosarcomas frequently involve bilateral cervical roots and vertebral arteries, precluding proper en bloc resection. Complex transmandibular or submandibular approaches including posterior pharyngeal incisions are often required for en bloc tumor resection in this region. Because of the associated surgical challenges and the inherent morbidity of such procedures, several authors have advocated intralesional resection using less aggressive approaches such as endoscopic endonasal techniques.
Conversely, tumors involving the midcervical region and the cervicothoracic junction are usually more amenable to en bloc resections. The surgery usually consists of a staged posteroanterior procedure. The posterior approach enables posterior osteotomies to break the posterior bony ring (which should be performed without violating the tumor capsule), exposure and ligation of the involved nerve roots and vertebral artery (whenever necessary), initiation of discectomies, and subsequent posterior instrumentation with lateral mass screws. The spinal cord should be detached from the posterior longitudinal ligament, and a silastic sheet is usually left in place to isolate the tumor located in the vertebral bodies from the spinal cord. The anterior approach is then pursued. It should be wide enough to provide proper visualization and enable en bloc resection of the specimen. After identification of the vertebral bodies, the bone incisions are performed with a bone chisel or a drill. Cranial and caudal discectomies are completed, followed by lateral dissections toward the silastic sheet, finally enabling en bloc delivery of the tumor.
In those en bloc resections of cervical tumors in which endovascular occlusion of the vertebral arteries is planned, the instrumentation and posterior dissection of the tumor can be separated into two stages, such that the lateral mass screws are placed while both vertebral arteries are still patent. This first posterior approach (focused exclusively on instrumentation) is then followed by the endovascular procedure for vertebral artery occlusion, after which the second posterior approach for tumor dissection is performed. Finally, the anterior approach is conducted with the goal of en bloc tumor delivery. During the second posterior approach, the posterior longitudinal ligament should be incised as completely and as laterally as possible on the contralateral side to facilitate delivering the tumor in one piece during the anterior approach. Because of the multiplicity of approaches and the possibility of upper airway and esophageal edema caused by the extensive surgical manipulation, preoperative tracheostomy and percutaneous gastrostomy should also be considered.
Thoracic
Usually an isolated posterior approach is preferred for thoracic tumors whose anterior margin is contained within the vertebral body. If the anterior margin of the tumor extends beyond the vertebral body (involving visceral structures or blood vessels), a combined approach is usually required. This involves an initial posterior approach to dissect the lesion from the involved posterior spinal elements and to achieve stability through spinal instrumentation, followed by an anterior approach to dissect the tumor from the anterior structures and to deliver it with clear margins. The main advantage of performing the posterior approach as the first step is that the spinal cord can be carefully observed throughout the procedure, especially during anterior spinal column osteotomies, corpectomies, and spinal reconstruction. Nerve roots are frequently sacrificed during posterior approaches to thoracic spondylectomies. The loss of thoracic roots from T2-T12 is usually well tolerated, resulting in an associated band of numbness but no clinically important motor loss. Special care should be taken during T2 spondylectomy to avoid manipulation of the T1 nerve roots, which can result in hand weakness and significant functional impairment.
Special care should be taken when considering ligation of the nerve roots in the lower thoracic spine because of the possible presence of the artery of Adamkiewicz (also known as arteria radicularis magna ). In 75% of people, the artery of Adamkiewicz originates on the left side of the aorta between the T8 and L1 vertebral segments. In tumors involving the lower thoracic spine, preoperative angiography to determine the presence and location of such an artery is indicated, as ligation of the artery at these levels (especially on the left side) may lead to spinal cord ischemia and significant myelopathy. Before ligating segmental arteries in this region, most surgeons clamp them in a reversible fashion and observe neurophysiologic potentials. If no changes in SSEPs and MEPs occur, then they will proceed with the surgical ligation.
It is also important to emphasize that following posterior needle biopsies the needle track should be included in the tumor resection.
Lumbar
Tumors involving L1 and even L2, similar to thoracic tumors, can usually be resected by an isolated posterior approach. Sacrifice of L1 or L2 nerve roots in isolation will produce weakness of iliopsoas, but this initial motor loss is usually compensated and well tolerated over time in most patients. For tumors at or below L3, a combined posteroanterior strategy is preferred, as adding an anterior stage may significantly lower the risks of damaging the lumbosacral plexus, ureters, and great vessels. ( Fig. 24.4 ). In tumors below L3, a resected vertebral body may be large enough to injure the L3, L4, and L5 nerve roots or the lumbar plexus as it is rolled out around the dural tube between the nerve roots, possibly causing serious neurologic deficits. After the initial posterior stage in which the initial tumor dissection and instrumentation are performed, the tumor is approached anteriorly through an anterolateral (retroperitoneal) approach, for L3 and most L4 tumors, or an anterior midline transperitoneal or retroperitoneal approach, for L5 tumors. Usually, the anterolateral approach is performed on the side of tumor presentation. A midline approach with mobilization of the aorta and inferior vena cava can be considered for tumors involving the L3 or L4 vertebral body if the tumor extends ventrally on both sides.
Related posts:
Pathology of Chordoma and Chondrosarcoma of the Axial Skeleton
Midline Subfrontal Approaches: The Transbasal Approach and Extended Modifications to Access the Clivus
Chordomas and Chondrosarcomas of the Skull Base: Transpetrosal Approaches
Staged Approaches for Large Skull Base Chordomas and Chondrosarcomas
Stereotactic Radiosurgery for Skull Base Chordomas and Chondrosarcomas
Recurrent Skull Base Chordomas: Role of Surgery
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