Chordomas and Chondrosarcomas of the Spine: Preoperative Planning, Surgical Strategies, and Complications Avoidance

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.

Table 24.1

The Enneking Staging System

Adapted from Enneking WF. A system of staging musculoskeletal neoplasms. Clin Orthop Relat Res 1986; 204 :9–24.

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

Malignant tumours are classified as IA, IB, IIA, and IIB depending on degree of spread.

$Figure 24.1, Sagittal (A) and axial (B) magnetic resonance imaging of the cervical spine (T2 sequence) demonstrating a chondrosarcoma involving the C3, C4, and C5 vertebral bodies. The tumor extends anterolaterally encompassing the left vertebral artery [C – computed tomography (CT)–angio reconstruction] as well as infiltrating the left C3, C4, and C5 nerve roots. Sagittal (D), axial (E), and three-dimensional reconstruction (F) of CT scan of the cervical spine in the same patient demonstrating a pathological compression fracture of the C4 vertebral body with destruction of the left side facets, pedicle, and lamina by tumoral infiltration.$

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.

Figure 24.2, The Weinstein–Boriani–Biagini (WBB) classification describes the vertebral involvement as sections of a clock face (“zones”) centered on the spinal canal.

Figure 24.3, (A) The patient underwent a midline posterior approach to the cervicothoracic spine for occipito-T3 instrumentation, tumor dissection, and ligation of the left C3, C4, and C5 nerve roots (as the patient already had preoperative deltoid paresis) and left vertebral artery ligation (which was previously coiled after a balloon occlusion test that demonstrated good perfusion of the posterior circulation by the contralateral vertebral artery). (B) Subsequently, an anterior approach to the cervical spine was performed. A long longitudinal thread cut was performed in the C3, C4, and C5 vertebral bodies using a drill, followed by discectomies at the upper (C2-C3) and bottom (C5-C6) levels of the tumor. (C) Finally the tumor and the lateral two-thirds of the C3, C4, and C5 vertebral bodies on the left side were delivered in one piece. (D) The specimen was sent for immunohistochemical analysis to confirm the absence of violation of the tumor capsule. (E) Final lateral X-ray demonstrating reconstruction with expandable cage and plating and the long (occipito-T3) posterior construct.

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.

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