Surgical Management of Chordomas and Chondrosarcomas of the Lumbar Spine

Abstract

Chordomas and chondrosarcomas are rare primary malignant spine tumors. In spite of recent advancements in chemotherapy, targeted therapy, and radiation therapy, surgery remains the gold standard for treatment of these lesions. Specifically, en bloc resection with wide tumor-free margins has better outcomes in terms of duration of disease-free and overall survival than does intralesional resection. Nonetheless, en bloc resections in the spine are technically demanding and highly morbid procedures, particularly in the lumbar spine because of the proximity of the lumbar plexus, great vessels, iliopsoas muscle, bowel, and others. This chapter reviews the operative management of lumbar chordomas and chondrosarcomas, emphasizing the surgical technique to achieve an en bloc resection via spondylectomy.

Keywords

Chordoma, Chondrosarcoma, Complications, En bloc, Lumbar spine, Spondylectomy

Outline
Introduction 309
- Indications and Preoperative Planning 310
- Surgical Technique and Complication Avoidance 310
- Combined Approach—Stage 1 311
- Combined Approach—Stage 2 311
Postoperative Care 312
Results 312
Conclusion 313
References 313

Introduction

Chordomas and chondrosarcomas are both primary malignant (locally aggressive) bone tumors. Chordomas are considered the most common primary malignant bone tumor of the spine and sacrum, with an incidence of 0.08 per 100,000 persons. These lesions arise from notochordal remnants and have a slow-growing, locally aggressive nature; metastases occur in 5%–40% of patients. They are more common in men, and the estimated 10-year survival rate is between 39% and 64%. The best long-term prognosis is achieved following wide en bloc resection.

On the other hand, chondrosarcomas are a heterogeneous group of malignant tumors that are characterized by their ability to form cartilage. The occurrence of chondrosarcomas in the spine is very rare, representing only 4%–10% of all chondrosarcomas ; the incidence is 0.5 cases per 100,000 persons per year, lower than the incidence of chordoma. Chondrosarcomas are more common in the thoracic spine and may arise de novo or as a secondary transformation from osteochondromas. Additionally, chondrosarcomas can arise in the context of hereditary multiple exostosis. The best long-term prognosis occurs after marginal or wide marginal en bloc resection, but the critical proximity to vital neural and vascular structures in the spine makes this difficult to achieve. Moreover, some chondrosarcomas are resistant to chemotherapy and radiotherapy, and have a high tendency of recurrence.

Given that the best long-term prognosis for both chordoma and chondrosarcoma is en bloc resection, the purpose of this chapter is to give an overview of the surgical management of these lesions in the lumbar spine.

Indications and Preoperative Planning

Given the unique anatomy surrounding the lumbar spine, performing a spondylectomy in this area is challenging. Indications for surgery include primary spinal tumors not amenable to radiation/chemotherapy, metastatic disease, and a solitary symptomatic lesion. Contraindications include tumors adherent or invading the vena cava, abdominal aorta, or adjacent visceral organs. A relative contraindication is tumors involving more than three vertebrae.

Tomita et al. described a classification system to determine which patients could undergo total en bloc spondylectomy. The system classifies the anatomic location of the tumor as follows: (1) vertebral body, (2) pedicle, (3) lamina and spinous process, (4) spinal canal (epidural space), or (5) paravertebral area. This classification is the basis of the “Surgical Classification of the Vertebral Tumors” system. A type 3 lesion, for example, involves areas 1, 2, and 3; a type 5 lesion involves the vertebral body (1), pedicle (2), lamina (3), spinal canal (4), and paravertebral area (5). A type 6 lesion involves all of the previously mentioned areas plus adjacent vertebra, and a type 7 lesion consists of multiple, skip lesions. Type 1, 2, and 3 lesions are considered intracompartmental (they do not go beyond the vertebra) and type 4, 5, and 6 are considered extracompartmental. Based on this system, spondylectomy is recommended for type 2, 3, 4, and 5 lesions, relatively indicated in type 1 and 6 lesions, and not recommended for type 7 lesions.

Preoperative planning should also include imaging, particularly magnetic resonance imaging (MRI) and computed tomography (CT) scans. These allow assessment of neural and soft-tissue involvement, and the extent of bony destruction. MRI should include T1-weighted images, T2-weighted images, and images with gadolinium contrast ( Fig. 27.1 ).

Surgical Technique and Complication Avoidance

Technically speaking, an en bloc resection is “an attempt to remove a lesion in a single piece.” En bloc resection may involve removal of an entire vertebral segment (i.e., spondylectomy), such as first described by Stener. The pathological evaluation of the specimen is used to define the surgical resection as “marginal”, “wide,” or “radical.” When the tumor is entered during its resection, this resection is called “intralesional.” Marginal resections “involve removal of the tumor with dissection along the pseudo-capsule but no entrance into the tumor.” Wide resections involve removal of “a continuous layer of surrounding healthy tissue… along with the tumor.” Lastly, radical resections “require removal of the tumor along with the entire anatomic compartment of the tumor origin.”

En bloc spondylectomy in the lumbar region is challenging for several reasons. First, the lumbar plexus is directly involved in lower extremity function, and nerve root sacrifice would most likely result in motor weakness. The ilipsoas muscle is attached to various vertebral bodies, and this requires extensive dissection or removal if the tumor is infiltrative. Lastly, the iliac vessels are also close to the lumbar vertebrae, and the ureters are also at risk for injury in this area.

Nonetheless, lumbar spondylectomy may be performed via a combined posterior/anterior approach or only via a posterior approach. Combined posterior/anterior approaches consist of two steps—en bloc resection of posterior elements and en bloc resection of the anterior column. Additionally, a combined approach may lower the risk of neurovascular injury and is the most recommended technique.

Combined Approach—Stage 1

The first stage (posterior approach) can be subdivided into exposure, Tomita saw (Medtronic, Minneapolis, Minnesota) guide introduction, and cutting of the pedicles and posterior element resection. The patient is placed under general anesthetic and positioned prone on a Jackson table. Neuromonitoring is performed via continuous electromyography, motor evoked potentials, and somatosensory-evoked potentials.

Following preparation and draping, a midline incision is made over the spinous processes, two to three levels above and below the diseased segments. Subperiosteal dissection is carried out down to the lamina, facets, and transverse processes; this is performed laterally enough to allow dissection under the transverse processes. At this point, pedicle screw instrumentation should be placed two levels above and below the diseased segments be instrumented.

Following instrumentation placement, standard laminectomies are performed, and the articulating processes, pars, pedicles, and transverse processes at the affected levels are resected to expose the neural elements underneath. The T-saw guide (C-curved and malleable) is introduced through the intervertebral foramen in a cranio-caudal direction. The tip of the guide should “be introduced along the medial cortex of the lamina and the pedicle so that the spinal cord and the nerve root are not injured.” After this is accomplished, the T-saw is passed around the pedicles at the junction of the pedicle and transverse process, and they are cut. This is performed with a “reciprocating motion of the threadwire saw.” Bone wax may be used to reduce bleeding at the cut surface of the pedicle, and the same process is repeated on the contralateral side. Following this, the posterior elements can be delivered en bloc.

The nerve roots are then identified and dissected bilaterally “to 10 cm beyond the pedicle to the level of the lumbar plexus.” The thecal sac is also mobilized anteriorly and dissected away from the vertebral bodies and any underlying tumor tissue. The ilipsoas is dissected laterally from the vertebral bodies using sharp dissection and bipolar cautery. The discs superior and inferior to the tumor margins are identified, and a Tomita saw is placed anterior to the dural sac “within the groove cut in the annulus. The ends of the saw are then coiled and tucked next to the space created by the ilipsoas/vertebral body dissection.” This same procedure is performed for both the superior and inferior discs. The Tomita saw is left in place and for use in the second stage of surgery.

Posterior instrumentation is performed with a combination of pedicle screws, sacral screws, and/or iliac screws as appropriate. Rods, transverse connectors, and cables may be utilized to add stability to the construct. The wound is copiously irrigated with normal saline and antibiotics. The transverse processes, lamina, facet joints, and spinous processes of the remaining vertebrae are decorticated using a high-speed cutting bur. Locally obtained autograft as well as demineralized bone matrix may be used as appropriate for the arthrodesis, and they may be packed laterally by using Surgicel (Ethicon, New Brunswick, NJ) casings. These are made by folding a piece of Surgicel over and suturing both ends.

Combined Approach—Stage 2

The second stage involves delivery of the tumor and anterior reconstruction. The patient is placed supine and general anesthesia is administrated. The abdomen and thighs are prepped (in case a bypass is required). Ideally, the lesion is to be delivered with a tumor-free margin between the tumor and vessels. If this is not possible, an aorta-bifemoral and inferior vena cava-bifemoral bypass may be performed, and the tumor is resected together with the bypassed segments of the great vessels.

An anterior approach may be performed via a midline retroperitoneal or transperitoneal approach for L5 lesions. For lesions above L5, the anterior approach involves a lateral retroperitoneal approach ipsilateral to the tumor. A midline laparotomy is performed, and the duodenum is reflected cephalad. Once the retroperitoneum is entered, the tissue above the aorta and inferior vena cava is mobilized with electrocautery and blunt dissection. The ureters are identified and kept under a lateral rectractor. Following ample exposure, a static retraction device is set.

The aorta, vena cava, iliac arteries, and iliac veins are exposed and mobilized; segmental vessels may be sacrificed to further mobilize the aorta. The iliolumbar veins may also be sectioned. Penrose drains are placed around the vessels to control and protect them during the osteotomies. Once the vessels are mobilized, the ilipsoas dissection planes lateral to the vertebral bodies (previously accomplished during the posterior approach) are identified and completed. The Tomita saws (left in place in the first stage) are retrieved, and the osteotomies are completed by cutting the discs at the desired levels. This permits delivery of the tumor in an en bloc fashion between the great vessels, if necessary.

Anterior reconstruction is done typically with a distractable titanium cage, which may be filled with local autograft and demineralized bone matrix. The cage may be further secured by titanium cables and/or an axial retention screw. X-rays can be taken to confirm the adequate instrumentation placement ( Fig. 27.2 ). The incision is closed “by reapproximating the retroperitoneum, allowing the abdominal contents to fall back in place, and closing the anterior abdominal incision in layers.”