Complications of Surgery for Vertebral Body Tumors

Abstract

Vertebral column neoplasms can be categorized as primary or malignant in origin, based on whether they arise directly from spinal osseous structures or extra-spinal locations, respectively. The management of such tumors varies greatly from one patient to the next. Many primary spinal tumors are relatively resistant to chemotherapy and radiation, thus often necessitating extensive multidisciplinary operations to achieve maximal cytoreduction in such a way that negative margins are achieved. Unlike the treatment of primary tumors, the treatment of metastatic spine tumors remains palliative in nature. The management goal of primary vertebral column neoplasms is to provide long-term disease-free intervals and ultimately eradicate the neoplastic process. En-bloc tumor resection for most primary spinal tumors gives patients the best chance at achieving this goal. Unlike primary spinal tumors, surgical treatment of metastatic vertebral column tumors is palliative with the goals primarily being preservation or improvement of neurologic function, and restoration or maintenance of spinal stability. Complications during the resection of vertebral column neoplasms can be categorized into approach-related morbidities, challenges achieving stabilization and fusion, wound healing problems, length-of-surgery related problems, and intra-operative hemorrhage. Understanding these types of complications will hopefully help minimize patient morbidity by helping the surgical practitioner prevent the problem from happening and dealing effectively with it if it does occur.

Keywords

vertebral body tumor, spine tumor, complications, primary vertebral tumor, metastatic spine tumor, en bloc resection, curettage

Introduction

Vertebral column neoplasms can be categorized as primary or malignant in origin, based on whether they arise directly from spinal osseous structures or extraspinal locations, respectively. The management of such tumors varies greatly from one patient to the next. Many primary spinal tumors are relatively resistant to chemotherapy and radiation, thus often necessitating extensive multidisciplinary operations to achieve maximal cytoreduction in such a way that negative margins are achieved. Unlike the treatment of primary tumors, the treatment of metastatic spine tumors remains palliative in nature. With new adjuvant therapies for these tumors, whether primary or metastatic, there is a myriad of options available to devise a tailored treatment plan on a case-by-case basis. In this chapter, we will be discussing potential complications that can be encountered during resection of vertebral column neoplasms.

The management goal with primary vertebral column neoplasms is to provide long-term disease-free intervals and ultimately to eradicate the neoplastic process. En bloc tumor resection for most primary spinal tumors gives patients the best chance at achieving this goal. Primary tumors can be subdivided into benign, locally malignant, and malignant. Benign primary vertebral tumors include aneurysmal bone cysts, chondromas and enchondromas, hemangiomas, osteoid osteomas, and osteoblastomas. The most common locally malignant and malignant primary vertebral tumors are chordomas and sarcomas, respectively. Giant cell tumors, chordoma, and chondrosarcoma have shown better local control rates with en bloc resection versus intralesional resection: 92.3%,78%, 82% versus 72.2%, 22%, 0%. This advantage may be negated in patients who have had a prior biopsy with contamination of the biopsy tract followed by tumor resection.

Unlike primary spinal tumors, surgical treatment of metastatic vertebral column tumors is palliative with the goals primarily being preservation or improvement of neurologic function, and restoration or maintenance of spinal stability. The neurologic, oncologic, mechanical, and systemic (NOMS) criteria are a widely accepted working algorithm for decision-making in regard to metastatic spinal tumors. This framework guides the spinal surgeon through a process evaluating the patient’s neurologic condition, oncologic status, mechanical stability, and overall systemic disease burden. Radiation, whether stereotactic body radiotherapy (SBRT) or conventional external beam radiation therapy (EBRT), is the mainstay of treatment after surgery and, along with appropriate chemotherapy, may improve local disease control. One of the potential complications of SBRT is the increased rate of vertebral body fractures, which needs to be taken into account when planning surgical intervention.

Consideration of the appropriate management plan for the patient harboring a vertebral column tumor depends on several factors, such as the lesion location and goals of surgery as well as the patient’s general condition, lung capacity, prior surgery, or radiation. Spinal instrumentation and arthrodesis are generally performed for stabilization purposes and deformity correction. The longer the expected survival of the patient, the more important achieving an osseous fusion becomes. Other interventions such as vertebroplasty/kyphoplasty (VP/KP), radiofrequency ablation (RFA), and laser interstitial thermal ablation (LITT) are becoming more widely accepted adjuncts to the overall management of patients harboring spinal neoplasms. These adjuvant procedures may be incorporated into the surgical plan or performed as outpatient procedures before or after surgery by an interventionalist. Preoperative embolization may also be appropriate for hypervascular tumors before surgery.

Complications during the resection of vertebral column neoplasms can be categorized into approach-related morbidities, challenges achieving stabilization and fusion, wound healing problems, length-of-surgery related problems, and intraoperative hemorrhage. Understanding these types of complications will hopefully help minimize patient morbidity by helping the surgical practitioner prevent the problem from happening and dealing with it effectively if it does occur.

Approach-Related Morbidity

Spinal tumor resection can be separated into three separate parts: (1) maximum safe tumor resection, (2) neural element decompression, and (3) spinal stabilization. These different facets of surgery are influenced by tumor location and size as well as by involvement of vertebral bone, neural elements, and extraspinal tissue. Although it may be possible to accomplish all three surgical goals from one approach, in many cases multiple approaches may be needed to safely resect tumor and reconstruct the spine. It is of utmost importance that the spinal surgeon has a solid understanding not just of the involved segmental spinal anatomy, but also of the surrounding visceral and soft tissue structures that can be encountered en route.

Resection of tumors in the ventral cervical spine will almost always be through a standard anterior neck dissection. Anticipated complications of dissection include injury to the pharynx, esophagus, trachea, larynx, and nearby neurovascular structures of the neck. It is reasonable to obtain a preoperative assessment of the vocal cords by an ENT surgeon in revision surgeries for this approach. Having this knowledge may influence the side of the approach taken for the subsequent surgery. It may be difficult at times to discern typically reliable anatomic landmarks such as the uncinate process with extensive tumor infiltration. The surgeon’s sense for the midline may thus be compromised. One may consider obtaining an AP x-ray with a bent spinal needle placed inside the disc space to have a better understanding of the midline. The cervical spine is a unique anatomic segment in that the vertebral arteries course within the osseous structures (transverse foramina) from C6 to the atlas. Because of this intimate relationship between vascular and osseous structures, the vertebral arteries are at risk of injury while attempting to resect certain cervical spine tumors. This becomes relevant in the resection of tumors encasing the vertebral arteries. Resection of primary tumors encasing one vertebral artery often requires preoperative embolization in an effort to achieve an en bloc excision. Preoperative balloon occlusion testing is necessitated before permanently embolizing the vertebral artery. Unintended vertebral artery injury during resection of metastatic tumors adjacent to the vertebral artery can have disastrous consequences from hemorrhage and potentially posterior fossa infarcts. In the event of a vertebral artery injury, it is the senior author’s recommendation to pack it with hemostatic material and complete the procedure, followed by angiography, rather than aborting the procedure.

When a primary cervical spine tumor encompasses a nearby vertebral artery, sacrifice of that vessel should be considered in an effort to achieve negative margins during an en bloc resection ( Fig. 58.1 ). A preoperative diagnostic angiogram of both carotid arteries and vertebral arteries is essential to ascertain the collateral blood flow to the posterior circulation. A balloon occlusion test of the vertebral artery of interest must be performed to ensure that the patient has adequate posterior fossa perfusion from the contralateral vertebral artery or from the anterior circulation via the posterior communicating arteries. It is preferred to perform endovascular embolization before open surgical ligation of a vertebral artery. This allows occlusion of the vertebral artery in a controlled setting. The alternative would require dissecting the vertebral artery out of the tumor, which harbors significant risks. Unilateral vertebral artery ligation has been shown to be relatively safe in a small case series, although distal embolization of occlusion material may occur, leading to posterior fossa infarcts. Instrumenting the cervical spine also poses a significant risk to the vertebral arteries, particularly at C1 and C2, due to the complex course of the vertebral artery and the unique bony anatomy of the craniocervical junction. Performing tumor resection in separate stages may be a useful strategy if intraoperative ligation of the vertebral artery is performed to ascertain the patient’s neurologic function before placement of instrumentation that could injure the remaining patent vertebral artery.

In an effort to achieve an en bloc excision of a primary cervical spinal tumor, nerve roots may also need to be sacrificed. Having a candid conversation with the patient before this undertaking is extremely important in an effort to manage postoperative expectations of neurologic function. Ligation of the C2 and C3 nerve roots carries little morbidity, aside from the potential for occipital neuralgia, due to lack of motor innervation, whereas C3–5 nerve root ligation can cause unilateral diaphragm paralysis. Lower cervical nerve root sacrifice has a more clinically relevant effect on the patient’s motor and sensory function. C5 and C6 nerve root sacrifice can cause deltoid and biceps weakness, respectively. C7 nerve root ligation can cause triceps weakness, although typically without significant clinical impact, and C8 and T1 nerve root ligation can cause significant functional impairment with fine motor tasks of the hand. A neurovascular-sparing en bloc resection has been described for specific cervical primary tumors, which spares the nerve roots and vertebral arteries with utilization of multiple osteotomies, paying special attention to removal of the lateral transverse foramen.

Complex retropharyngeal approaches may be utilized on rare occasions to fully access a primary tumor of the upper cervical spine ( Fig. 58.2 ). This oftentimes necessitates preoperative tracheostomy and gastrostomy tube placement. Cerebrospinal fluid (CSF) leaks during such approaches may also be very challenging to manage. High cervical neoplasms are associated with significant surgical morbidities.

Thoracic vertebral column tumors may involve adjacent vasculature and mediastinal structures. Extensive vascular reconstruction may be required after an en bloc spondylectomy if the aorta is intimately involved, with a primary thoracic spine tumor necessitating excision of part of the aorta in an effort to obtain negative margins. Such lesions often require a combined anterior-posterior approach, necessitating the utilization of operative corridors through the thoracic cavity. Nerve root ligation is often necessary to gain access to the ventral compartment of the spine from a posterior approach. This may be the case if there is significant ventral epidural disease and a transpedicular, costotransversectomy, or extracavitary approach is being undertaken to achieve access. Aside from T1 innervation of hand intrinsics, thoracic nerve root ligation is well tolerated. When performing complex thoracolumbar approaches, the artery of Adamkiewicz must be avoided. This artery usually arises between T9 and T12. It is a major blood source to the spinal cord. Identification of the artery of Adamkiewicz on preoperative angiography is helpful when contemplating ligation of multiple segmental vessels. Injury can lead to spinal cord hypoperfusion and ischemia, causing significant neurologic dysfunction. In an anterior vertebrectomy through a transthoracic or lateral extracavitary approach, there is a risk of injury to the thoracic duct, which can lead to chylothorax in addition to the anticipated pneumothorax/hemothorax. Chylothorax is a challenging condition to treat because it often requires significant dietary modification and potentially decompression of the pleural space with tube thoracostomy or repeated thoracentesis. The posterior thoracic spine approach was found to have a higher incidence of wound infection compared with anterior approaches (26.7% vs 4.5%), in addition to a higher rate of deep vein thrombosis (DVT; 15.6% vs 0%). In patients where the pleura is violated for tumor access, the duration of chest tube use was greater in the combined anterior/posterior approach group compared with the anterior-only group. The overall rate of complications was higher in patients who underwent a combined simultaneous anterior and posterior approach than in patients who were treated using a single posterior approach (53.24% vs 32.1%).

Lumbar spine tumors with significant ventral disease can be particularly challenging to surgically resect from a posterior-only approach due to the significant neurologic morbidity that can occur with lumbar nerve root injury. In some patients with primarily upper lumbar spine tumors, L1 and L2 nerve root ligation can be well tolerated, so a posterior-only approach can be considered. A combined anterior-posterior approach must be undertaken for primary tumors involving L3 and below. Ligating nerve roots anywhere from L3 to L5 can cause significant motor and sensory impairment. An anterior approach to the lumbar spine would potentially necessitate mobilization of the inferior vena cava (IVC), aorta, or their branches, thus placing these vessels at risk of injury during surgery.

The iliac vessels and rectum are in close proximity when operating on sacral tumors ( Fig. 58.3 ). During a sacrectomy for a primary bone tumor, sacrifice of the sacral nerve roots may be warranted to obtain an en bloc resection. Vascular reconstruction may also be needed if the iliac vessels are intimately involved with the tumor. Inevitably, bowel, bladder, and sexual function are significantly altered with sacrectomies, depending on how rostral the sacral amputation is. The higher the sacral amputation, the more likely it is that bowel/bladder will be adversely affected. It has also been shown that preoperative functional status in the context of bowel/bladder function is predictive of long-term function. Historically, surgery for high sacral primary neoplasms was performed via an anterior/posterior approach. The anterior approach gives the surgeon direct access and visualization of the rectum and vasculature ventral to the sacrum. This technique does carry the inherent risks of an open laparotomy, including bowel injury. In addition, there is less control of the thecal sac and its neural elements distal to S1 utilizing an anterior-only approach, and hence it is often combined with a posterior approach. Posterior-only approaches to sacral neoplasms have been described, which can avoid some of the described approach-related morbidities. The posterior approach gives the surgeon direct access to the sacral nerve roots should it be necessary to ligate them distal to S1. A posterior-only approach may be feasible when there is no rectal invasion by the tumor, the tumor is above L5/S1, and there is no iliac vessel involvement.