Metastatic Spinal Tumors

Neurosurg Focus 11 (6):Article 1, 2001, Click here to return to Table of Contents

Metastatic spinal tumors

ROBERT F. HEARY, M.D., AND CHRISTOPHER M. BONO, M.D. The Spine Center of New Jersey, New Jersey Medical School, Newark, New Jersey; and Department of Orthopaedic Surgery, Division of Spine Surgery, University of California at San Diego Medical Center, San Diego, California

Metastatic spinal tumors are the most common type of malignant lesions of the spine. Prompt diagnosis and iden- tification of the primary malignancy is crucial to overall treatment. Numerous factors affect outcome including the nature of the primary cancer, the number of lesions, the presence of distant nonskeletal metastases, and the presence and/or severity of spinal cord compression. Initial management consists of chemotherapy, external beam radiotherapy, and external orthoses. Surgical intervention must be carefully considered in each case. Patients expected to live longer than 12 weeks should be considered as candidates for surgery. Indications for surgery include intractable pain, spinal cord compression, and the need for stabilization of impending pathological fractures. Whereas various surgical approaches have been advocated, anterior-approach surgery is the most accepted procedure for spinal cord decompression. Posterior approaches have also been used with success, but they require longer-length fusion. To obtain a stable fixation, the placement of instrumentation, in conjunction with judicious use of polymethylmethacrylate augmentation, is crucial. Preoperative embolization should be considered in patients with extremely vascular tumors such as renal cell carcinoma. Vertebroplasty, a newly described procedure in which the metastatic spinal lesions are treated via a percutaneous approach, may be indicated in selected cases of intractable pain caused by non- or minimally fractured vertebrae.

KEY WORDS • metastasis • spine • tumor • tumor excision

Bone is the third most frequent metastatic site of distant tion is not always clear cut. Although various attempts spread of carcinoma.4 The vertebral column is the most have been made to devise methods for predicting life ex- common site of skeletal metastases.13 Improvements in pectancy in this population, none exists.10,31,33,37,39 Regard- oncological management have increased survival times in less, most authors agree that patients in whom expected patients with skeletal metastases. Spine surgeons are fre- survival is at least 12 weeks should be considered for pal- quently faced with decisions of how to treat patients with liative surgery. Numerous other factors must be weighed, these lesions. Although not curative, resection and stabi- however, including overall health, nutrition, the aggres- lization can have beneficial effects on neurological status, siveness of the primary tumor, and extent of preoperative function, pain, and mobility.14,17,18,24,25 These are important neurological deficit(s).31,33,37 issues, particularly in individuals in whom remaining life Once the decision for surgery has been made, the goals expectancy is no more than 1 to 2 years.38 can be more defined. If the neural elements are com- Metastatic disease of the spine can manifest in many pressed, the first fundamental step is to undertake decom- ways. Pain is present in virtually all cases and can be se- pressive surgery, excising either the anterior or posterior vere enough that basic activities such as walking become elements. Resection of tumoral material is also effective nearly impossible.9 Significant bone destruction can lead for pain relief. With various methods available, recon- to fracture, instability, and deformity. Perhaps the most struction of the spine, in which cement augmentation, dreaded complication, spinal cord compression, can result bone graft, and instrumentation can be used, is crucial for 5,17,24,25,36 from pathological fractures, direct invasion of the spinal achieving fixation. There are strong supporters of 16,20,29,35 posterior surgery over anterior surgery, whereas others canal by the tumor, or osteoblastic bone reaction. 5,9,30 Surgical treatment has a role in each of these scenarios; favor combined approaches. New minimally invasive however, the decision to proceed with operative interven- techniques, such as vertebroplasty, may also play a role for the prophylactic spinal fixation before significant vertebral collapse occurs.2,7,8 Abbreviations used in this paper: CT = computerized tomogra- The purpose of this paper is to present the current data phy; GI = gastrointestinal; MMA = methylmethacrylate; MR = concerning surgical treatment of spinal metastatic lesions. magnetic resonance; PMMA = polymethylmethacrylate; VB = ver- Relevant issues concerning evaluation, diagnostic work- tebral body. up, adjunctive preoperative procedures, and surgical tech-

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Unauthenticated | Downloaded 09/28/21 09:58 PM UTC R. F. Heary and C. M. Bono nique are discussed. Effective treatment decision making astatic prostate cancer, Yamashita, et al.,39 reported longer involves the cooperation of patient and family, medical survival in patients with spinal or pelvic lesions (Group I) and radiological oncologists, and the surgical team. compared with those in whom appendicular spread had occurred (Group II). The mean survival time after initia- tion of treatment (of primary cancer) in Group I was 5.7 PATHOPHYSIOLOGY OF METASTATIC years compared with 2.4 years in Group II. The authors DISEASE hypothesized that axial metastasis was more likely in general because of the proximity of the primary tumor to the A primary carcinoma must undergo several steps before Batson venous plexus (vertebral venous system). The Bat- producing a metastasis at a distant site. Common primary son plexus is a valveless venous system that has been fre- cancers that spread to bone are lung, breast, renal, pros- quently implicated as a conduit for the metastatic spread tate, and thyroid. Lung is the most common neoplasm in of prostate tumors. Thus, they found that patients who pre- males, whereas breast is the most frequent in females. sented with vertebral lesions initially harbored the least Despite the anatomical location, the tumor must grow be- aggressive tumor, whereas in those with appendicular le- yond the bounds of the basement membrane of the cells at sions the metastasis had bypassed the Batson plexus. In- the primary (extraspinal) site of the tumor. This process is terestingly, patients with both appendicular and axial met- facilitated by enzymes known as matrix metalloproteinas- astases (Group III) an intermediate life expectancy (3.4 es causing degradation of this layer. Acting most specifi- years) was demonstrated, which was better than Group II cally to break down the Type IV collagen in the basement but worse than Group I.39 membrane, the cancerous growth is then given access to Some investigators have addressed the question of sur- surrounding blood vessels and lymph vessels. Tumor cells vival after surgery for spinal metastatic tumors. Tokuhashi can then travel to distant tissues. For the cell to success- and coworkers37 have studied the results obtained in 64 fully metastasize, it must adhere to the second site and patients who underwent surgery for spinal metastases. obligatorily stimulate the growth of new blood vessels. They included all primary diagnoses and operations per- This is known as tumor angiogenesis. Unfortunately, a formed for a variety of indications including pain and pa- well-vascularized metastasis will survive at the expense of ralysis. They formulated a score based on a number of normal healthy tissue. parameters including general systemic condition, number In the spinal column, metastatic carcinoma has a predil- of extraspinal bone metastases, number of spinal metasta- ection for the well-vascularized cancellous bone of the ses, presence of lesions in other internal organs, location VB. Less frequently, a lesion will develop only in the pos- of the primary lesion, and the severity of spinal cord in- terior elements (that is, the neural arch). In some situa- jury. Although no single parameter was predictive, scores tions, the tumor extends from the the anterior to posterior correlated with survival periods. Scores of 9 or higher columns, making it more difficult to plan a surgical de- were predictive of at least 12 months of survival; scores of bulking or resection of the tumor. 8 and lower indicated survival less than 12 months; and scores of 5 or lower predicted survival of 3 months or less. IMPORTANCE OF SURVIVAL PROGNOSIS Based on these data, it appears that the Tokuhashi system would be a valuable tool in preoperative discussions Patients with metastatic cancer have limited life expec- and decision making. Its value has been confirmed by tancies. After primary lung cancer has spread to distant other authors. Enkaoua, et al.,10 found it predictive of sur- organs, the mean survival time is 6 months. The mean survival after surgery in patients with most metastatic tumors vival after metastasis of breast, renal, or prostate carcino- to the spine. One exception was in cases of tumors of un- ma is less dismal, averaging approximately 1.5 to 2 years. known primary origin. The investigators suggested ascrib- Fewer than 10% of patients with metastatic renal cancer ing a lower score to patients in this group, because their survive more than 2 years.35 Because of recent advances in outcomes were generally poorer than predicted. It has the medical management of certain types of tumors, such been our experience that adenocarcinoma of unknown ori- as breast and prostate carcinoma, longer survival periods gin has been particularly lethal and with survival periods are being achieved, compared with those published in the frequently less than 3 months. medical literature from prior decades. Surgical treatment Some authors have found preoperative neurological sta- of skeletal disease must be considered in light of a pa- tus to be highly predictive of survival,33 whereas those tient’s projected survival. Within the surgical oncological using the Tokuhashi system have not found it to be inde- community, it is well accepted that a patient should be ex- pendently predictive. Perhaps this is related to the sim- pected to live for at least a 6-week to 3-month period. plistic grading of the Tokuhashi system in which spinal Typically it is the medical oncologist who makes this life cord deficits are divided into motor complete (Frankel expectancy estimation, basing it on natural history of the Grade A or B), motor incomplete (Frankel Grade C or D), disease itself. The surgeon, however, must consider the or intact (Frankel Grade E) groups. In subsequent studies, attendant morbidity and negative effects that the surgery however, other authors10,38 have supported the findings re- itself will have on the patient’s survival.31,37,38 It is in the ported by Tokuhashi, et al.36 surgeon’s best interest to be thoroughly familiar with all Other preoperative parameters have been analyzed. Si- factors involved. outos and coworkers33 found that patients who were am- Although a number of authors have attempted to iden- bulatory preoperatively and those in whom the disease tify clinical predictors of survival in cases of metastatic involved only one vertebra survived statistically longer disease, few have studied lesions of the spine specifical- than patients who were nonambulatory and those with ly.10,33,37–39 In a retrospective series of patients with met- multilevel disease. Overall extent of disease, age, and tu-

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Unauthenticated | Downloaded 09/28/21 09:58 PM UTC Metastatic spinal tumors mor location (that is, anterior or posterior elements of the Spinal cord or cauda equina injury is most effectively spine) were not predictive. Not surprisingly, patients with treated by means of decompressive surgery.5,9,30,38 Radio- metastatic renal carcinoma survived the longest, whereas therapy, although a useful adjuvant, does not produce those with breast experienced longer life spans than indi- long-lasting results by itself.35 In a series of 43 patients, viduals with lung metastases. Weigel, et al.,38 corroborat- Sundaresan, et al.,35 reported neurological improvement in ed these findings, reporting that patients 60 years of age or 45% of patients in whom radiotherapy alone was per- younger survived statistically longer than those older than formed, whereas surgery before or after radiotherapy re- 60 years of age, whereas tumor location was not statisti- sulted in 100 and 60% improvement, respectively. In the cally significant. In contrast to the findings of Sioutos, et short term, radiotherapy may be more effective in patients al., Weigel, et al., did not find preoperative neurological in whom no evidence of bone compression is present.27 In function to be an important factor in survival. Similar to contrast, the use of high-dose corticosteroid therapy has the Tokuhashi system, Weigel, et al., simplistically graded demonstrated beneficial effects on outcome in patients neurological status as ambulatory or nonambulatory. In with metastatic spinal cord compression. In a prospective actuality, ambulatory status is probably influenced by fac- randomized study of 57 patients, high-dose dexametha- tors other than neural compression such as pain and gen- sone therapy resulted in 18% more patients becoming eral systemic condition. ambulatory than those who had undergone radiotherapy.34 Side effects, such as GI or infectious complications, must NEURAL COMPRESSION be considered, because they occur in approximately 11% of cases. Although some may advocate moderate- or low- Spinal cord compression, or more accurately, neurolog- dose steroid treatment to minimize these side effects, there ical deficit is an unfortunately common sequela of spi- is little evidence that they have an impact on metastatic nal metastatic tumors. Because of its perceived influence spinal cord compression.15 To our knowledge, the use of on prognosis and its high incidence, this topic deserves steroids for cauda equina injury is not beneficial, because particular discussion. The basic pathological feature caus- this is a lower motor neuron lesion. ing spinal cord compression is encroachment of tumor or bone into the spinal canal. In the cervical and thoracic regions, this causes spinal cord compression, whereas le- Nonoperative Management sions in the lumbar spine can cause stenosis and cauda This group of treatment modalities can be termed pal- equina syndrome. The exact mechanism of disruption of liative care. Tokuhashi, et al.,37 reported that palliative nerve function remains unclear. Commonly accepted the- treatment should be reserved for patients who are poor ories include pressure-induced impedance of neural firing candidates for surgery. There are limited conservative op- and cord ischemia secondary to compromise of the blood tions for the treatment of metastatic spinal tumors. Prac- supply.29 The actual mechanism is likely a combination of titioners must keep in mind the goals of nonsurgical treat- these two factors. ment. Pain relief is probably the most common indication. Spinal metastases–induced canal compromise can be Radiation therapy localized to the area of the lesion can caused by a number of factors. Most commonly, lytic le- successfully relieve pain and is probably a useful first-line sions weaken the supporting bone of the VB, creating an modality in cases of most tumors. Some tumors are inher- impending fracture. With little undue force, a pathological ently radioresistant, such as renal cell and GI tumors, with fracture can ensue. The posterior VB can be retropulsed in fewer than half of cases responding. The benefit of radio- a burstlike pattern, compressing the neural structures. therapy must be balanced against the potential harmful Another mechanism occurs via direct extension of the le- side effects to the local tissue and skin. This can be an sion beyond the confines of the posterior VB, which can, issue if surgery is planned in the near future. A minimum by itself, compromise the spinal canal without a frank of 3 weeks should be allowed between the completion of pathological fracture. The third mechanism is the rarest external-beam radiotherapy and surgery in the zone of but an important one of which to be aware. Blastic tumors treatment. can cause pathological bone overgrowth in the region of Spinal instability is not cured by radiotherapy, and in the spinal canal. Hirschfeld, et al.,16 have reported two some cases, it can cause further bone weakening. Al- such cases: one in a woman with metastatic breast cancer though there is little evidence in the literature to support and another in a man with prostate carcinoma. In contrast their benefit in the long term, braces are commonly pre- to renal cell or lung carcinomas, both breast and prostate scribed for patients with pathological spinal fractures. cancers are well-known causes of blastic lesions. Usually, extension-type braces are most useful in the tho- Neurological injury occurs in 5 to 10% of patients with racolumbar spine, because impending kyphotic deformi- cancer.1,3,28 The mean survival after spinal cord compres- ties secondary to anterior column destruction are the fre- sion–induced paraplegia is 3.4 months.38 Compression can quent presentation. Patients harboring cervical lesions may occur at one or more sites. More than one site of com- receive some degree of comfort from wearing a hard or pression is present in 23% of patients with spinal cord soft cervical collar. The collar’s effectiveness in prevent- compression secondary to prostate metastasis. Although ing an impending pathological fracture is unknown. Le- one site might be obvious, systemic clinical and radiolog- sions at the cervicothoracic junction may require a cus- ical examination of the entire spine is essential to detect tom-made orthosis that includes both a cervical and upper additional lesions. The most sensitive neurodiagnostic im- thoracic/chest component. In cases of lesions in the upper aging studies for detecting additional lesions are MR im- cervical spine, a halo fixator can be a better option. In aging, with and without intravenous contrast, or bone all situations, the patient’s comfort should be the pri- scanning. mary goal.

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SURGERY-RELATED GOALS AND INDICATIONS Prior to the 1970s, surgery was considered an overly aggressive treatment for malignant spinal tumors.12 With improvements in technique and the routine use of prophylactic antibiotics, indications broadened. In 1970, Martin and Williamson21 summarized their indications for surgery: a documented progressive neurological deficit, an impending pathological fracture, or obtaining a biopsy sample of a lesion of unknown primary origin. More recently, the concept of surgical stabilization to provide pain relief and to treat progressive deformity has been intro- duced, and the clinical results have been good.17,25

TREATMENT-RELATED OUTCOMES Pain relief is accomplished by partial or total excision of the lesion from the vertebra. This lesion may be in the anterior or posterior elements. The rate of pain relief after surgery for metastatic tumors is generally high. Weigel, et al.,38 have reported at least moderate pain relief in 89% of patients after performing anterior decompressive surgery and stabilization. Similarly, Rompe, et al.,30 and Hussein, et al.,17 have documented pain relief in approximately 90% of their cases. Both Shimizu, et al.,32 and Cahill and Kumar5 have reported 100% pain relief after undertaking surgery via posterior approaches. The mechanism of pain relief is not clearly understood but is most likely effected after removal of the offending lesion in addition to the Fig. 1. A 54-year-old woman with known metastatic renal cell increase in mechanical stability. carcinoma who was neurologically intact with back pain. Upper

Neurological deficits are common sequelae of metasta- Left: Sagittal T2-weighted MR image demonstrating involvement tic spinal tumors. They can occur at the level of the spinal of the posterior elements of L-3 (arrow). Lower Left: Axial T1- cord or cauda equina. Progressive deficits are an indica- weighted MR image revealing the L-3 spinous process and lami- tion for surgical decompression, which can be effected by na infiltrated by tumor, with anterior structures intact (arrow). anterior or posterior methods.5,17,18,38 Corpectomy at the Right: Bone scan demonstrating numerous additional sites of metastatic disease (ribs, skull, and scapula) in addition to L-3 (arrow). site of the lesion is performed to decompress the anterior The patient underwent simple posterior decompression. canal, whereas a posterior decompression is achieved via laminectomy. The details of these procedures including reconstruction will be discussed in greater detail below. Although both methods have been used with success, the site at which laminectomy was performed in patients most authors currently believe that in patients with better with significant loss of the anterior weight-bearing portion prognoses restoration of the anterior weight-bearing por- of the spine. In more recent reports the authors have tion of the spine may help prevent collapse of the involved placed elongated rigid posterior constructs after decom- vertebral segment. This can be achieved using an anterior pressive laminectomy (Fig. 2). Despite these differences corpectomy or posteriorly using a lateral extracavitary and trends, the rates of neurological improvement after approach. surgery are comparable. Laminectomy for decompression of spinal metastatic Rompe, et al.,30 undertook surgery via the posterior tumors has fallen out of favor. Because the anterior col- approach in 50 patients with metastatic tumors of multi- umn destruction was not treated, progressive kyphotic ple origins, they used long segmental hook stabilization deformity was frequent. Removal of the posterior ele- alone. Twenty-six patients suffered a neurological deficit, ments can further destabilize an already compromised of whom 14 (53%) improved at least one Frankel grade spine. In some relatively rare cases in which a metastatic postoperatively. One patient (4%) became worse and 11 carcinoma predominantly invades the posterior elements (42%) remained unchanged. The authors recommended of the spine, a laminectomy may be appropriate (Fig. 1). the posterior approach in cases of multi-level metastatic Although the anterior resection and reconstruction more disease that would be difficult to manage via an anterior directly address the typical site of spinal cord compression approach. Interestingly, the only two cases of hardware- and vertebral column destruction, some surgeons believe related failure occurred in patients with single-level dis- these procedures are associated with a high rate of mor- ease. Similar rates of neurological improvement were bidity, which may not be justified in this patient popula- documented by Shimizu, et al.32 Of 11 patients with mul- tion.23,30 The failures of earlier series involving simple tilevel metastatic disease, nine patients (82%) experienced posterior decompression, without stabilization, were prob- neural improvement after undergoing posterior decom- ably secondary to inadequate fixation above and below pression and stabilization.

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Unauthenticated | Downloaded 09/28/21 09:58 PM UTC Metastatic spinal tumors

Fig. 2. A 61-year-old man who underwent nephrectomy 16 years previously for renal cell carcinoma. He developed severe back pain and paraparesis. He had a history of heavy smoking and recent 20-pound weight loss. The patient underwent subtotal T-11 corpectomy and T8–L1 stabilization with pedicle screw/rod construct. The patient fractured his right

hip 5 days after spinal surgery and underwent an open reduction internal fixation procedure. A: Sagittal T1-weighted MR image demonstrating significant collapse of T-11 with tumor extending anteriorly and posteriorly; the posterior aspect of the tumor displaces the spinal cord (large arrow). Multiple lower lumbar vertebrae have small metastatic

deposits but no structural deficiencies (small arrow). B: Axial T1-weighted gadolinium-enhanced MR image demonstrating near-total replacement of T-11 VB with tumor, minimal preservation of the right side of T-11 (arrow), and spinal cord displacement on the left side. C: Angiogram demonstrating significant blush from tumor, which was successfully embolized preoperatively. D: Intraoperative photograph obtained after subtotal T-11 corpectomy via a posterior approach. Stabilization was performed using pedicle screws (three levels above, two levels below) and rods. E: Postop- erative plain anteroposterior radiograph revealing good coronal-plane alignment and screw placement. F: Postoperative plain lateral radiograph demonstrating good sagittal-plane alignment and screw placement. G: Postoperative axial CT scan revealing good pedicle screw positioning in T-9. H: Plain radiograph of right hip demonstrating good alignment after open reduction internal fixation of the pathological hip fracture.

Weigel, et al.,38 used a variety of approaches in 45 cases rate of neurological improvement. There are no random- of metastatic disease with a neural deficit. Sixty-two per- ized prospective studies currently available, however, in cent of patients improved after anterior surgery whereas which the authors compare anterior and posterior ap- 50% improved after laminectomy. The investigation was proaches, and thus, nonuniform selection criteria likely retrospective and there was no attempt to randomize pa- create a bias. tients. King, et al.,18 reported a 50% rate of neurological improvement of at least one Frankel grade in 20 patients after anterior decompression combined with posterior sta- PREOPERATIVE EVALUATION bilization without laminectomy. Based on these data, it is Obtaining a complete history and performing a physical difficult to conclude that anterior surgery leads to a better examination are the initial steps in preoperative evalua-

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Unauthenticated | Downloaded 09/28/21 09:58 PM UTC R. F. Heary and C. M. Bono tion. A review of systems must include pulmonary, car- SURGICAL PROCEDURES diac, and urinary issues. It is essential to document bowel and bladder status before surgery because these results Posterior Approach may indicate neurological involvement. Obstipation can Standard techniques of laminectomy are well known to occur in patients with GI tumors and should be evaluated spine surgeons. The principles of spinal canal decompres- before spinal surgery. The general overall health of the pa- sion in cases of metastatic tumors are identical. The dura tient must be assessed, as should nutritional status. The mater should be protected throughout the procedure. Fo- likelihood of malnutrition in terminally ill cancer patients raminal encroachment should be assesed following central is high, which can influence wound healing and the rate of canal decompression and treated accordingly. infection. Optimization by tube feedings, hyperalimenta- After decompression, reconstruction of the spine can be tion, or parenteral supplementation should be considered. performed using a number of different constructs. Hook or Standard laboratory workup includes complete blood pedicle screw systems can be used for segmental fixation count with differential, serum electrolytes, amylase levels, along the segments to be fused. When posterior fixation and liver function tests, as well as albumin levels. Serum alone is required after laminectomy, the construct must transferrin levels are useful to assess the patient’s nutri- span a number of levels above and below (Fig. 2). This is tional status. Furthermore, hypercalcemia can be present influenced by the strength of the bone, the quality of fixa- in patients with metastatic spinal lesions, and this can be a tion, and the presence of additional metastases within the risk factor for cardiac irregularities in the perioperative fusion segment.30 A sound biomechanical plan is manda- period. Whenever possible, electrolyte imbalances should tory to provide sufficient fixation for the remainder of the be corrected prior to surgery. Collaboration with the med- patient’s life. ical oncology team is paramount. Noting the limitations of laminectomy and posterior Patients often have multiple areas of metastatic disease. surgery, some surgeons have devised methods to treat the Lesions around large weight-bearing joints such as the hip anterior and posterior columns via a single posterior ap- and knee can affect postoperative ambulatory status and proach. Cahill and Kumar5 have reported the use of such recovery. In most situations, an impending hip fracture a procedure in nine patients with metastatic spinal disease. should be treated first, provided the neurological status is After performing a wide laminectomy, the neural elements static (Fig. 2). Whole-body bone scanning is a useful mo- were protected using a rigid retractor resting on the poste- dality for a global survey to detect these lesions, as well as rior aspect of the VB. This allowed aggressive removal of additional spinal metastases. the anterior and middle columns through the interval Plain radiography is the first-line imaging modality. between the retractor and the lateral elements (remaining Lesions can be missed, however, because approximately pars or facet joints). With the body excavated bilaterally, 30 to 40% of the bone must be eroded before it is de- the anterior column was reconstructed by pouring MMA tectable on plain x-ray films. At obvious sites of fracture, cement around two metal pins longitudinally interposed angulation should be measured, and the pattern of the between the cranial and caudal VBs. The authors warned pathological fracture, if present, is characterized. Middle- that extreme caution is necessary to avoid contact between column disruption is difficult to appreciate on plain radio- the MMA and the dura mater. In addition, a shell of ante- graphs. Computerized tomography scanning is a more ef- rior bone should be maintained to avoid extravasation of fective method of evaluating spinal canal compromise cement into the retroperitoneum where it could cause vas- secondary to bone or lesional retropulsion. cular injury. Once the MMA hardened, it provided an The level of decompression should be evaluated preop- effective anterior column reconstruction. Supplemental eratively using CT myelography or, preferably, MR imag- posterior stabilization was provided by a segmental hook ing. The latter provides true sagittal and coronal images of construct. The authors reported no technique-related long sements of the spine. The entire spine should be eval- deaths or neurological injury. One case of hardware-relat- uated to detect any missed lesions. In planning recon- ed failure occurred because of construct ended at an apex struction of the spine, instrumentation should not end at of kyphotic deformity. the level of an involved segment; rather, it should be spanned so as not to create a stress riser that may potenti- Anterior Surgery ate pathological fracture. Additionally, constructs should be placed to avoid terminating the stabilization at the apex Various options are available for exposure of the anteri- of a kyphosis or at a junctional region (either the cervi- or column of the spine. Standard retroperitoneal approach- cothoracic or thoracolumbar junctions). es in the lumbar spine or thoracotomy in the thoracic spine Specifically in cases of renal cell metastasis, a preoper- are useful. The upper thoracic vertebral region is more ative arteriogram is recommended (Fig. 2). Because these challenging to access anteriorly. It lies outside the zone of tumors are highly vascular, intraoperative bleeding can be the standard anterior cervical exposure and is usually too life threatening. The benefit of preoperative embolization rostral to expose using a thoracotomy. Kurz, et al.,19 of renal cell spinal tumors has documented numerous Comey, et al.,6 and Sundaresan, et al.,36 have described a studies.11,18,26 In cooperation with the interventional radiol- similar approach to pathological lesions in the upper tho- ogist, exhaustive attempts should be made to avoid em- racic spine. An L- or T-shaped incision is centered over bolizing major spinal feeding arteries, which are present the sternum and clavicle. After developing the plane be- in the lower thoracic spine (that is, the artery of Adam- tween the sternocleidomastoid muscles and the midline kiewicz). With special attention to this detail, Olerud, et strap muscles, they are reflected superiorly from the bor- al.,26 documented no neurological complications related to ders of the sternum and the medial clavicle. The superior embolization in 21 patients. part of the manubrium and the medial third of the clavicle

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Unauthenticated | Downloaded 09/28/21 09:58 PM UTC Metastatic spinal tumors are carefully resected. This allows deeper exposure of the interval between the carotid artery sheath and esophagus. The arch of the aorta can be palpated at the inferior extent of the field and is protected with a renal vein retractor. Retraction of the carotid artery sheath and the esophagus exposes the anterior longitudinal ligament along the VBs. Resection, corpectomy, and reconstruction with MMA cement can then be performed.19 Exposure down to the T-3 or T-4 level can be achieved.6,19,36 Because of difficul- ties associated with healing of these complex upper anterior thoracic exposures, we have favored use of a median sternotomy approach to the upper thoracic spine. In our experience, this has provided quicker access with exposure to T-4 and possibly T-5, as well as a lower rate of postoperative morbidity (Fig. 3). Corpectomy is an effective means of decompressing the anterior spinal canal. In cases of metastatic lesions, Fig. 4. A 50-year-old woman who had undergone mastectomy care must be taken when burring down to the posterior 5 years earlier for breast carcinoma. Follow-up x-ray films re- longitudinal ligament. The diseased tissue often adheres vealed collapse of T-12 and kyphotic deformity. She suffered to the dura or has already broken through the ligament, moderate back pain and was neurologically intact. Left: Intraop- making decompression a daunting task. Although com- erative photograph obtained after T-12 corpectomy, titanium cage plete excision of the tumor is not necessary, sufficent bone placement, screw/rod stabilization; arrow indicates the space be- and lesion must be removed to relieve the pressure on the tween titanium cage and dura (left is posterior and right is anteri- neural elements. One should observe the standard princi- or). Right: Postoperative plain anteroposterior radiograph reveal- ple of a pedicle-to-pedicle decompression of the involved ing good alignment of spine, cage, and construct, which was vertebra (Fig. 4). placed via a left-sided approach. The diagnosis was metastatic Resection of the VBs leaves an anterior column defi- breast carcinoma. ciency. This must be reconstructed using a stable strut. Most authors have agreed that PMMA bone cement is 1 year. Some authors warn that PMMA is durable for only preferable to allograft struts because it has less of a chance 6 months.22 to subside. King et al.,18 have reported construct-related Reconstruction using PMMA can be achieved in con- failure when using an iliac crest strut graft. Because of the junction with the use of various metallic devices. Metal limited life expectancy of these patients incorporation of pins can be placed longitudinally to span the defect and a bone graft seems unlikely. The prime objective is imme- PMMA molded around them in a doughy state. Alterna- diate stability that is durable enough to last approximately tively, various types of cages have recently become available. These cages may be made of titanium mesh or car- bon fiber, which can be filled with cement or bone and interposed between the vertebrae. Supplemental rod or plate fixation can also be added (Fig. 4). Screw purchase can be augmented using additional PMMA injected into the drilled holes in the intact VBs. Vertebroplasty for Pathological Lesions Vertebroplasty is a relatively new technique of stabilization in the treatment of pathological lesions of the spine, requiring minimally invasive surgery.2,7,8 The procedure involves cannulation of the pedicle by using a hol- low bore needle and injection of PMMA into the cancellous bone of the VB. Initially developed for the treatment of osteoporotic compression fractures, numerous authors have documented successful pain relief in patients with metastatic spinal tumors.2 The technique requires the Fig. 3. A 62-year-old man with presence of an intact posterior VB wall to prevent cement progressive paraparesis and upper extravasation into the spinal canal. The main goal of a thoracic pain. No preoperative diag- vertebroplasty in patients with tumors is to enhance the nosis was established. Left: Post- operative plain anteroposterior ra- anterior column of the spine (Fig. 5). Pain relief has been dramatic, with reports of success between 50 and 80% in diograph obtained after T-2 corpectomy and T1–3 stabilization 2,7,8 performed via a median sternotomy approach (note the sternal carefully selected patients. wires [arrow]). Right: Postoperative axial CT scan demonstrating good spinal decompression, structural iliac crest autograft strut, CONCLUSIONS and an anterior plate. A diagnosis of metastatic large cell carcinoma of the lung was reached. Indications for surgery in patients with metastatic spi-

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8. Deramond H, Depriester C, Galibert P, et al: Percutaneous vertebroplasty with polymethylmethacrylate. Technique, indications, and results. Radiol Clin North Am 36:533–546, 1998 9. Durr HR, Maier M, Pfahler M, et al: Surgical treatment of os- seous metastases in patients with renal cell carcinoma. Clin Orthop 367:283–290, 1999 10. Enkaoua EA, Doursounian L, Chatellier G, et al: Vertebral metastases: a critical appreciation of the preoperative prognostic tokuhashi score in a series of 71 cases. Spine 22:2293–2298, 1997 11. Giehl JP, Kluba T: Metastatic spine disease in renal cell carcinoma—indication and results of surgery. Anticancer Res 19: 1619–1623, 1999 12. Halnan KE, Roberts PH: Paraplegia caused by spinal metastasis from thyroid cancer. Br Med J 3:534–536, 1967 13. Harrington KD: Metastatic disease of the spine. J Bone Joint Surg Am 68:1110–1115, 1986 14. Harrington KD: Orthopedic surgical management of skeletal complications of malignancy. Cancer 80 (Suppl 8): 1614–1627, 1997 15. Heimdal K, Hirschberg H, Slettebo H, et al: High incidence of serious side effects of high–dose dexamethasone treatment in patients with epidural spinal cord compression. J Neurooncol 12:141–144, 1992 Fig. 5. A 59-year-old man with known multiple myeloma and 16. Hirschfeld A, Beutler W, Seigle J, et al: Spinal epidural com- severe back pain who was neurologically intact. This lateral post- pression secondary to osteoblastic metastatic vertebral expan- operative plain radiograph was obtained after vertebroplasty was sion. Neurosurgery 23:662–665, 1988 performed to treat fractures of T-11, T-12, and L-1, which pro- 17. Hussein AA, El-Karef E, Hafez M: Reconstructive surgery in duced dramatic symptomatic relief (minimal cement leak into disc spinal tumors. Eur J Surg Oncol 27:196–199, 2001 space at L-1, which was asymptomatic). 18. King GJ, Kostuik JP, McBroom RJ, et al: Surgical management of metastatic renal carcinoma of the spine. Spine 16:265–271, 1991 19. Kurz LT, Pursel SE, Herkowitz HN: Modified anterior ap- nal tumors are intractable pain, progressive neurological proach to the cervicothoracic junction. Spine 16 (Suppl 10): deficit, or an unknown histological diagnosis. Treatment S542–S547, 1991 can effectively relieve pain and improve neurological 20. Loblaw DA, Laperriere NJ: Emergency treatment of malignant function in patients with canal compromise. Candidates extradural spinal cord compression: an evidence–based guide- for surgery should have a life expectancy of at least 3 line. J Clin Oncol 16:1613–1624, 1998 months. Operative choices include anterior, posterior, and 21. Martin NS, Williamson J: The role of surgery in the treatment of malignant tumors of the spine. J Bone Joint Surg Br combined approaches, each with its advantages and disad- 52:227–237, 1970 vantages. Newer percutaneous procedures such as verte- 22. McAfee PC, Bohlman HH, Ducker T, et al: Failure of stabiliza- broplasty can be efficacious in a selected group of patients tion of the spine with methylmethacrylate. A retrospective in whom pain presents without neurologic deficit. analysis of twenty-four cases. J Bone Joint Surg Am 68: 1145–1157, 1986 23. Moore AJ, Uttley D: Anterior decompression and stabilization of the spine in malignant disease. Neurosurgery 24:713–717, References 1989 24. Nagashima C, Iwasaki T, Okada K, et al: Reconstruction of the 1. Bansal S, Brady LW, Olsen A, et al: The treatment of metasta- atlas and axis with wire and acrylic after metastatic destruction. tic spinal cord tumors. JAMA 202:686–688, 1967 Case report. J Neurosurg 50:668–673, 1979 2. Barr JD, Barr MS, Lemley TJ, et al: Percutaneous vertebroplas- 25. Olerud C, Jonsson B: Surgical palliation of symptomatic spinal ty for pain relief and spinal stabilization. Spine 25:923–928, metastases. Acta Orthop Scand 67:513–522, 1996 2000 26. Olerud C, Jonsson H Jr, Lofberg AM, et al: Embolization of 3. Barron KD, Hirano A, Araki S, et al: Experiences with meta- spinal metastases reduces perioperative blood loss. 21 patients static neoplasms involving the spinal cord. Neurology 9: operated on for renal cell carcinoma. Acta Orthop Scand 64: 91–106, 1959 9–12, 1993 4. Bridwell KH: Treatment fo metastatic prostate cancer of the 27. Pigott KH, Baddeley H, Maher EJ: Pattern of disease in spinal spine. Urol Clin North Am 18:153–159, 1991 cord compression on MRI scan and implications for treatment. 5. Cahill DW, Kumar R: Palliative subtotal vertebrectomy with Clin Oncol 6:7–10, 1994 anterior and posterior reconstruction via a single posterior 28. Posner JB: Neurological complications of systemic cancer. approach. J Neurosurg 90 (Suppl 1):42–47, 1999 Med Clin North Am 55:625–646, 1971 6. Comey CH, McLaughlin MR, Moossy J: Anterior thoracic cor- 29. Rodriguez M, Dinapoli RP: Spinal cord compression: with spe- pectomy without sternotomy: a strategy for malignant disease cial reference to metastatic epidural tumors. Mayo Clin Proc of the upper thoracic spine. Acta Neurochir 139:712–718, 55:442–448, 1980 1997 30. Rompe JD, Eysel P, Hopf C, et al: Decompression/stabilization 7. Cortet B, Cotten A, Boutry N, et al: Percutaneous vertebroplas- of the metastatic spine. Cotrel-Dubousset-Instrumentation in 50 ty in patients with osteolytic metastases or multiple myeloma. patients. Acta Orthop Scand 64:3–8, 1993 Rev Rhum Engl Ed 64:177–183, 1997 31. Saengnipanthkul S, Jirarattanaphochai K, Rojviroj S, et al:

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Unauthenticated | Downloaded 09/28/21 09:58 PM UTC Metastatic spinal tumors

Metastatic adenocarcinoma of the spine. Spine 17:427–430, for the preoperative evaluation of metastatic spine tumor prog- 1992 nosis. Spine 15:1110–1113, 1990 32. Shimizu K, Shikata J, Iida H, et al: Posterior decompression and 38. Weigel B, Maghsudi M, Neumann C, et al: Surgical manage- stabilization for multiple metastatic tumors of the spine. Spine ment of symptomatic spinal metastases. Postoperative outcome 17:1400–1404, 1992 and quality of life. Spine 24:2240–2246, 1999 33. Sioutos PJ, Arbit E, Meshulam CF, et al: Spinal metastases 39. Yamashita K, Denno K, Ueda T, et al: Prognostic significance from solid tumors. Analysis of factors affecting survival. Can- of bone metastases in patients with metastatic prostate cancer. cer 76:1453–1459, 1995 Cancer 71:1297–1302, 1993 34. Sørensen S, Helweg-Larsen S, Mouridsen H, et al: Effect of high-dose dexamethasone in carcinomatous metastatic spinal cord compression treated with radiotherapy: a randomized trial. Eur J Cancer 30A:22–27, 1994 35. Sundaresan N, Scher H, DiGiacinto GV, et al: Surgical treatment of spinal cord compressionin kidney cancer. J Clin Oncol Manuscript received October 24, 2001. 4:1851–1856, 1986 Accepted in final form November 2, 2001. 36. Sundaresan N, Shah J, Foley KM, et al: An anterior surgical ap- Address reprint requests to: Robert F. Heary, M.D., The Spine proach to the upper thoracic vertebrae. J Neurosurg 61: Center of New Jersey, New Jersey Medical School, 90 Bergen 686–690, 1984 Street, DOC Suite 7300, Newark, New Jersey 07103. email: heary 37. Tokuhashi Y, Matsuzaki H, Toriyama S, et al: Scoring system @umdnj.edu.

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