Spondylectomy for Spinal Tumors

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Chapter 107 Spondylectomy for Spinal Tumors

Spondylectomy is defined as removal of an entire segment of the spine, including the vertebral body, pedicles, superior and inferior articulating processes, pars, transverse processes, lamina, and spinous process. Removal of the entire spinal segment en bloc is possible only with sacrifice of the spinal cord or the cauda equina, as the spinal cord and cauda equina lie within the spinal canal, incarcerated by the spine. Tumors within the spine can be removed either in a piecemeal fashion (intralesional) or en bloc (in one piece, without violation of the tumor margin). To achieve an en bloc resection of a tumor, the technique of a total spondylectomy can be employed (Fig. 107-1). As a point of semantics, the tumor is removed en bloc, but the spondylectomy is usually not an en bloc spondylectomy.1

Techniques for en bloc resection of a tumor are complex and entail significant risk to the patient; they are reserved for certain tumor pathologies that oncologically may benefit from such resection. In general, when such an operation is contemplated, the tumor should be a solitary tumor without evidence of metastasis. The usual indication for an en bloc resection is malignant primary bone tumors when resection may result in cure or long-term tumor-free survival for the patient. Such tumor pathologies include chordoma, chondrosarcoma, and osteosarcoma. Other, less aggressive primary bone tumors for which en bloc resection is contemplated include giant cell tumor, aneurysmal bone cyst, osteoid osteoma, and osteoblastoma. Exceptions to this rule occur, and in certain circumstances of solitary metastasis to the spine (such as renal cell carcinoma or breast cancer), some oncologists advocate the use of this technique for local tumor control. This is a highly contentious area of debate, and the use of en bloc resection is evolving, especially with the advent of other adjunctive therapies such as stereotactic radiosurgery for the spine.

General Concepts and Surgical Planning

The anatomic location of the tumor to be removed within a particular vertebral segment or segments will dictate the steps in achieving an en bloc resection via a spondylectomy.1 For simplicity, the planning can be divided into two stages: a preparatory stage and a stage in which the tumor is delivered. Accomplishment of the first stage, the preparatory stage, may require multiple procedures.

The goal of the preparatory stage is to free the tumor specimen from the surrounding structures so that the tumor can be delivered while the spinal cord and critical nerves are protected with minimal functional sacrifice. The goal of the delivery stage is to deliver the specimen in an en bloc fashion. As a general rule, the preparatory stage occurs on the side of the spinal cord, or thecal sac, opposite the tumor. The portion of the vertebral segment and the tumor to be removed as a single specimen are dissected as much as possible to mobilize the specimen during the preparatory stage.

In certain instances, vascular and neurologic structures may need to be sacrificed to free the en bloc specimen. The anticipated vascular complication and the deficit produced from doing so must be thoroughly understood and discussed with the patient before embarking on the treatment. Certain tumor architectures require more aggressive sacrifice that results in significant morbidity, the consequence of which must be balanced against the potential oncologic benefit and the patient’s acceptance of a life with the expected permanent handicap that may result.

The vascular structures involved in the resection vary at different levels of the spine. In the cervical spine, a vertebral artery might need to be sacrificed to achieve a resection, and doing so might result in posterior fossa ischemia and stroke. In the thoracic spine, multiple segmental vessels might need to be ligated, increasing the risk of ischemia to the spinal cord. In the lumbar spine, the iliac arteries and veins might need to be manipulated or even bypassed, potentially causing ischemia to the bowel, kidneys, or lower extremities. Manipulation or sacrifice of the inferior vena cava and iliac vessels increases the chance for thrombus formation and consequent pulmonary embolus.

Neurologic sacrifice can be entertained only if the deficit that will be produced is tolerable to the patient’s expectations and lifestyle acceptance. Sacrifice of a certain root alone might not produce a significant deficit, but combinations of roots sacrificed can be crippling (Table 107-1). C1-4 can usually be sacrificed without significant morbidity. Sacrifice of C3 and C4 together could result in diaphragm weakness. Cutting C5, C6, C8, or T1 usually results in profound weakness. Sacrifice in the thoracic spine (T2-12) will result in a bandlike distribution of numbness but usually has inconsequential motor loss. Sacrifice of L1 or L2 in isolation will produce weakness, but over time, patients usually are able to compensate for the loss quite well. L3 loss will result in quadriceps weakness and may require bracing of the knee to walk. L4 sacrifice can also result in quadriceps weakness, but the problem that is usually noted is proprioceptive difficulty of the knee joint. Without proper proprioception of the knee, a patient may find the knee week and can complain of the knee buckling at times during ambulation. L5 loss results in footdrop. S1 sacrifice is usually well tolerated but does results in gastocnemius weakness, which can make it difficult for a patient to stand on the toes. S4, S5, and the coccygeal nerves can usually be sacrificed without significant consequences. Loss of bilateral S2 and S3 nerve roots will result in loss of bowel, bladder, and sexual function. Unilateral S2 and S3 sacrifice usually allows a patient to have fairly normal bowel, bladder, and sexual function. Bilateral S3 sacrifice and S2 preservation will provide some function, but most patients will have difficulty with bowel, bladder, and sexual function.

Table 107-1 Deficits from Specific Nerve Root Sacrifice

Nerve Sacrifice Deficit
C3 and C4 Possible diaphragm weakness
C5 Deltoid weakness
C6 Bicep weakness
C8 or T1 Hand intrinsics weakness
T2–T12 Dermatomal sensory loss
L1 or L2 Iliopsoas weakness, usually compensated over time
L3 Quadriceps weakness
L4 Quadriceps weakness, knee proprioceptive difficulty, and footdrop
L5 Footdrop
S1 Minimal deficit
Unilateral S2 and S3 Bowel/bladder/sexual function abnormal but functional
Bilateral S2 and S3 Loss of bowel/bladder/sexual function
Bilateral S3 with S2 sparing Some bowel/bladder/sexual function
S4, S5, and coccygeal nerves Dermatomal sensory loss

Planning for postoperative adjunct therapies is necessary in contemplating a surgical approach. If postoperative high-dose radiation therapy such as proton beam irradiation is a possibility, then this should be taken into account preoperatively. Structures that may be at risk of injury from the radiation may benefit from reposition or from protection with complex plastic surgery flaps. It may be desirable to avoid certain approaches, such as the transoral and transmandibular approaches, which have considerable risk of postoperative pharyngeal dehiscence and mandibular pseudarthrosis with adjuvant proton beam radiation therapy.

The first stage of the operation, the preparatory stage, is designed to mobilize the tumor specimen so that it can be eventually delivered and at the same time minimize the neurologic and vascular impact on the patient. This stage, as a general rule, starts on the side of the spinal cord or thecal sac opposite the tumor. The spinal segment can be thought of as a ring of bone that encases the spinal cord. In order for a portion of that ring to be delivered away from the spinal cord, a portion of it will have to be resected, creating a window that is at least as large as the diameter of the spinal canal. This will allow the spinal cord and dura to pass through this window as the remaining portion of the ring, with the specimen, is delivered away from the cord. For simplicity, this chapter describes the technique for en bloc resection starting in the thoracic spine and then the technique for the lumbar spine, and finally the technique for the cervical spine will be delineated. Nuances for each section of the spine will be discussed in more detail. This chapter does not describe the techniques of en bloc sacral resections.