Single-Stage Posterolateral Transpedicle Approach for Spondylectomy, Epidural Decompression, and Circumferential Fusion of Spinal Metastases

Transcription

1 Single-Stage Posterolateral Transpedicle Approach for Spondylectomy, Epidural Decompression, and Circumferential Fusion of Spinal Metastases SPINE Volume 25, Number 17, pp , Lippincott Williams & Wilkins, Inc. Mark H. Bilsky, MD,* Patrick Boland, MD, Eric Lis, MD, Jeffrey J. Raizer, MD, and John H. Healey, MD Study Design. Retrospective review of prospectively maintained institutional spine database. Objectives. To assess the pain, neurologic, and functional outcome of patients with metastatic spinal cord compression using a posterolateral transpedicular approach with circumferential fusion. Summary of Background Data. Patients with spinal metastases often have patterns of disease requiring both an anterior and posterior surgical decompression and spinal fusion. For patients whose concurrent illness or previous surgery makes an anterior approach difficult, a posterior transpedicular approach was used to resect the involved vertebral bodies, posterior elements, and epidural tumor. This approach provides exposure sufficient to decompress and instrument the anterior and posterior columns. Methods. During the past 15 months, 25 patients were operated on using a posterolateral transpedicular approach. The primary indications for surgery were back pain (15 patients) and neurologic progression (10 patients). All patients had vertebral body disease, and 21 patients had high-grade spinal cord compression from epidural disease as assessed by magnetic resonance imaging. Seven patients underwent preoperative embolization for vascular tumors. In each patient, the anterior column was reconstructed with polymethyl methacrylate and Steinmann pins and the posterior column with long segmental fixation. Results. All patients achieved immediate stability. Pain relief was significant in all 23 patients who had had moderate or severe pain. Neurologic symptoms were stable or improved in 23 patients. One patient with an acutely evolving myelopathy was immediately worse after surgery, and one patient had a delayed neurologic worsening, progressing to paraplegia. Conclusions. The posterolateral transpedicular approach provides a wide surgical exposure to decompress and instrument the anterior and posterior spine. This technique avoids the morbidity associated with anterior approaches and provides immediate stability. Vascular tumors may be removed safely after embolization. Patients can be mobilized early after surgery. [Key words: spine metastases, posterolateral approach, embolization] Spine 2000;25: From the *Division of Neurosurgery, the Department of Orthopedic Surgery, the Department of Radiology, and the Department of Neurology, Memorial Sloan Kettering Cancer Center, New York, New York. Acknowledgement date: March 30, First revision date: September 9, Acceptance date: December 29, Device status category: 11. Conflict of interest: 12, 14. A small subset of patients with metastatic tumor to the thoracic or lumbar spine require surgery to relieve pain, maintain or improve neurologic status, and stabilize the spine. This surgery is palliative and is undertaken to improve quality of life. The operative approach is dictated primarily by the location of the tumor, with the goals of achieving maximal tumor decompression and immediate spinal stability. Vertebral body disease and anterior epidural tumor can be effectively addressed from an anterior transthoracic or retroperitoneal approach. 10,14,15,27,30,31,36 Many patients, however, have patterns of disease involving the vertebral body that are not amenable to a strictly anterior approach, requiring both an anterior and posterior decompression and fusion. This extensive surgery may be indicated in patients with three column involvement, multilevel vertebral body or epidural tumor, vertebral body tumor with bilateral or circumferential epidural spinal cord compression, or major spinal deformity. Additionally, some cancer patients who require vertebrectomy or circumferential decompression and fusion may be poor candidates for an anterior approach because of poor pulmonary function, concurrent medical illness, previous surgery, previous radiation therapy (RT), and/or unresectable, anterior paraspinal tumor or scar. To avoid an anterior approach in patients with patterns of disease that require circumferential decompression and fusion or in patients in whom an anterior approach may be difficult, spondylectomy and circumferential fusion using a single-stage posterolateral transpedicular approach (PTA) has been reported. 1,4,20,26,37 This report reviews the authors experience with this approach. Materials and Methods A retrospective review of a prospectively maintained spine tumor database between November 1997 and January 1999 revealed 104 patients who underwent decompression and instrumented fusion for metastatic disease to the spine at Memorial Sloan Kettering Cancer Center. The operative approach and reconstruction were dictated by the location of the tumor and the patient s medical and oncologic status. All patients were assessed for their suitability to undergo surgery by a multidisciplinary team. This report focuses on 25 patients who underwent a PTA for decompression of the vertebral body and epidural tumor and circumferential fusion of the thoracic or lumbar spine. This approach was chosen either because the patient required an anterior and posterior decompression and fusion (13 patients), there were medical contraindications to an 2240

2 Posterolateral Transpedicle Approach Bilsky et al 2241 Table 1. Histology of Primary Tumor Table 2. ASIA Impairment Scale Type No. of Patients Grade Description Sarcoma 5 Renal cell carcinoma 4 Breast carcinoma 4 Non small cell lung carcinoma 3 Prostate carcinoma 3 Multiple myeloma 2 Hepatocellular carcinoma 1 Carcinoma of unknown origin 2 Mixed germ cell tumor 1 Total 25 A B C D E Complete: No motor or sensory function is preserved in the sacral segments S4 S5. Incomplete: Sensory but not motor function is preserved below the neurologic level and extends through the sacral segments S4 S5. Incomplete: Motor function is preserved below the neurologic level, and the majority of key muscles below the neurologic level have a muscle grade less than 3. Incomplete: Motor function is preserved below the neurologic level, and the majority of key muscles below the neurologic level have a muscle grade greater than 3. Normal: Motor and sensory function is normal. anterior transcavitary approach (4 patients), or both (8 patients). The mean age at the time of surgery was 59 years (range, 31 to 80 years), and 13 of 25 patients were men. All tumors were high-grade, metastatic malignancies. The histologic diagnoses are shown in Table 1. Five patients had metastatic sarcoma, which reflects the large referral of this tumor histology to the authors institution. Three patients had spinal metastases at the time of the initial cancer diagnosis. Twenty-one patients had metachronous lesions at a mean interval between the initial diagnosis and symptomatic spinal metastasis of 53 months (range, 5 to 182 months). The primary site was not identified in two patients. Most patients with metachronous lesions had progression of disease after systemic chemotherapy and/or hormonal therapy. At surgery, five patients had spinal metastases only. The remaining patients had metastatic disease to other bones (6 patients), viscera (6 patients), or both (8 patients). In this series, 20 patients had previous radiation therapy (RT) to the operated spinal level. The most common fractionation schedule was 300 cgy fractions to a total dose of 3000 cgy used in 10 patients. The remainder of the patients were treated to a higher dose between 3600 to 4000 cgy in 200 to 300 cgy fractions, except a single patient treated for multiple myeloma who was treated to a total dose of 2000 cgy. The mean interval between the completion of RT and symptomatic spinal recurrence requiring surgery was 16 months (range, 6 days to 77 months). No patient required emergency surgery during RT for progression of symptoms, but six patients underwent surgery within 1 month of completing RT. The histologic diagnoses in these patients considered acute RT failures were renal cell carcinoma (2), adenocarcinoma of the prostate (2), non small cell lung cancer (1), and carcinoma of unknown origin (1). Five patients did not undergo preoperative RT directed to the operated level. Two patients had previously received RT to overlapping ports that reached spinal cord tolerance. Two patients received postoperative RT, and one patient died before receiving RT. All patients had back pain, and in 15 patients, this was the primary symptom. Four patients experienced the acute onset of back pain resulting from fracture and resultant instability. Eleven patients had a subacute worsening of pain during 1 to 6 months, the majority of whom had instability pain. Two of these patients experienced pain related to the presence of recurrent or persistent tumor after chemotherapy or RT. This tumor pain can be distinguished from instability pain by the predominance of nocturnal or early morning symptoms, and it often can be relieved in the short-term by the administration of steroids. One patient had high-grade compression of the conus medullaris and had low back pain referable to a chronically distended, neurogenic bladder despite no history of urinary retention. Foley catheter placement resolved her incapacitating back pain before decompressive surgery for progression of disease and neurologic symptoms. Pain self-assessment was based on a visual analog scale from 0 to 10. As described by Serlin, 33 0 to 4 represents mild pain; 5 to 6, moderate pain; and 7 to 10, severe pain. Of the 15 patients who had back pain as the presenting symptom, 13 had severe pain, as judged on a visual analog scale (VAS), one had moderate pain, and 1 had mild pain. Ten patients had neurologic symptoms as their primary problem. Seven of these patients had acute myelopathy, and three had radiculopathy. Three of the four patients with tumor in the lumbar spine had severe radicular pain but did not have motor weakness or cauda equina syndrome. Functional outcome was assessed using the American Spinal Injury Association (ASIA) impairment score (Table 2), 19 and performance status was assessed using the Eastern Cooperative Oncology Group (EGOG) grading system (Table 3). 8 Preoperative radiographic evaluation included magnetic resonance imaging (MRI) and plain radiographs in all patients, as well as computed tomography (CT) scan and bone scan in selected patients. No patient had a preoperative myelogram. In all patients, 50% or more of the vertebral body was infiltrated by tumor. Fourteen patients had an associated compression fracture, and 9 patients had three-column disease. Only 4 patients had single-level vertebral body involvement. Ten patients had two or more levels of adjacent vertebral body involvement, and 11 patients had discontinuous multilevel involvement. Nine patients had an associated paraspinal mass. Preoperative segmental deformities were not routinely measured because Table 3. ECOG Performance Status Grade Description 0 Fully active, able to carry on all pre-disease performance without restriction 1 Restricted in physically strenuous activity but ambulatory and able to perform light work 2 Ambulatory and capable of all self-care but unable to perform work activities (bedridden 50% of the time) 3 Capable of only limited self-care (bedridden 50% of the time) 4 Completely disabled, not capable of any self-care (bedridden 100% of the time)

3 2242 Spine Volume 25 Number many patients were unable to tolerate standing preoperative radiographs. All patients had epidural tumor as assessed by MRI scan. Epidural disease was quantified by its functional significance based on the degree of obstruction of cerebrospinal fluid (CSF) space and spinal cord deformity and its anatomic extent around the dural sac. Six patients had partial obliteration and 15 had complete obliteration of the CSF space with spinal cord compression. This degree of CSF obstruction is indicative of moderate to severe spinal cord compression. The remaining 4 patients had epidural disease with partial obliteration of the CSF space, but without significant spinal cord compression. Twelve patients had either circumferential or 270 epidural spinal cord compression. Patients with vascular tumors underwent preoperative embolization. The histology of these tumors included renal cell carcinoma (4), multiple myeloma (1), angiosarcoma (1), Ewing s sarcoma (1), and hepatocellular carcinoma (1). All patients had 100% radiographic obliteration of the tumor blood supply except that component of the vascularity provided by major radicular feeding arteries to the anterior spinal artery at left T11 and left T4, respectively, in one patient each. Surgical intervention was undertaken within 48 hours of embolization. Technique Approach. Patients are positioned prone on lateral chest supports. The head is placed in a Mayfield pin fixation device. A midline incision is made at least two segments above and below the level to be fused. The ligamentous attachments and muscle are taken off the spinous processes and laminae to the tips of the transverse processes. The rib heads are not exposed unless a chest wall resection is required. If the posterior elements are involved with tumor, care must be taken to dissect the ligamentous attachments and muscle off the tumor without transmitting pressure to the spinal cord. This often is done with bipolar cautery and Metzenbaum scissors. Posterior element and adjacent soft tissue tumor is then piecemeal resected to the level of the lamina. Tumor Decompression. The posterior bone work is initiated by removing the spinous processes with a rongeur. The authors have used M-8 burr on the Midas Rex drill (Fort Worth, TX) to thin the laminae to a cortical shell or to remove all of the bone exposing the ligamentum flavum, dura, or epidural tumor. Residual bone can be removed with a 2-mm Kerrison rongeur. The presence of an anterior mass compressing the spinal cord prohibits the use of large Kerrison rongeurs in the spinal canal. The laminectomy includes the bone overlying the disc spaces adjacent to the involved vertebral body segment and a normal dural plane adjacent to the epidural tumor (Figure 1). Bilateral facetectomies and complete pedicle resection to the base of the vertebral body are accomplished with the drill and curettes (Figure 1C). In the lumbar spine, a unilateral facetectomy is often sufficient to gain exposure to the vertebral body tumor. After bone removal, the ligamentum flavum and epidural tumor are resected using tenotomy scissors starting at the interface between the tumor and dura. Bipolar cautery used on a low setting at this interface may help define the proper plane for dissection. Nerve roots are ligated only if they are enveloped by tumor to maximize the epidural tumor resection. The nerve roots are dissected free of tumor before ligation with vascular clips or suture ligatures. Nerve roots have not been ligated in the lumbar spine or when a major radicular feeding artery to the spine has been identified on preoperative angiogram. Having dissected the epidural tumor from the posterior and lateral dura, the disc spaces adjacent to the diseased vertebral body are exenterated to expose normal endplates. In the thoracic spine, it may be necessary to resect a portion of the pedicle caudal to the involved vertebral body to provide exposure of the caudal disc space. A cavity is created in the vertebral body by piecemeal resection of tumor using curettes and pituitary rongeurs. The most common pattern of disease treated with PTA involves tumor extending from the vertebral body into the epidural space. With this pattern of disease, it is rare for tumor to insinuate between the posterior longitudinal ligament (PLL) and the dura. This pattern of tumor often can be predicted from the preoperative MRI scan. The anterior compressive tumor appears bilobed with a hypointense line, representing the PLL, between the vertebral body tumor and the spinal dura. Resection of the intact PLL helps provide a gross resection of tumor at the anterior dura. In the thoracic spine, the plane between the dura and PLL may be difficult to identify, but can be sharply dissected with tenotomy scissors (Figure 1D). Curettage or blunt dissection of the ligament may put excessive traction on the spinal dura and should be avoided. Once the anterolateral plane between the dura and PLL has been identified, the PLL often can be dissected along the anterior dura. No significant epidural bleeding has been encountered using this maneuver. Piecemeal resection of the vertebral body then is completed. The drill may be used to create a larger cavity or to resect infiltrated bone. Instrumented Stabilization. Spinal reconstruction is initiated anteriorly. Right angle clamps are used to create starting holes in the vertebral body at the proper depth for placement of the Steinmann pins. The pin generally is bent at a 20 angle and driven into cranial vertebral body using a needle driver with a gentle rotational movement. The pin then is driven back into the caudal vertebral body. A pin then is placed on the contralateral side. Once radiographic confirmation shows good pin placement, methylmethacrylate (PMMA) mixed with tobramycin is placed into the defect covering the Steinmann pins (Figure 1E). The PMMA conforms well to the defect and endplates if allowed to harden slightly before administration and by drying the area of blood. The PMMA expands slightly just before it hardens, so it should not directly abut the anterior dura. The PMMA should be compressed against the vertebral end plates with a Penfield 3 to prevent gaps from forming at the bone cement interface. Segmental fixation then is applied to the posterior spine. In the thoracic spine, a claw construct is applied to one side of the spine and a compression construct on the contralateral side (Figure 1F). Pedicle screw fixation is used most often in the lumbar spine and for selected thoracic fixation. In cases in which correction of kyphosis is attempted, a single rod is placed before administration of the PMMA. Kyphosis correction may be achieved by underbending the rod and translating the spine into alignment. Crosslinks are applied unless they are too prominent. The wound is pulse-irrigated with Bacitracin irrigant. Posterolateral bone graft then may be applied to decorticated bone for the patients with an expected survival time of at least 1 year.

4 Posterolateral Transpedicle Approach Bilsky et al 2243 Figure 1. Diagram showing technical aspects of PTA with circumferential fusion. A, Typical tumor pattern with vertebral body disease extending into the epidural space. B, Dotted lines indicate laminectomy extending to the levels of the adjacent disc spaces to the vertebral body. C, Pedicle resection and facetectomy. D, After rhizotomy, posterior longitudinal ligament is cut to secure anterior margin. E, Methylmethacrylate and pins placed in vertebral body defect. F, Posterior segmental fusion.

5 2244 Spine Volume 25 Number Table 4. Level of Vertebral Body Resection Level Results No. of Patients T1 T4 5 T5 T8 9 T9 T11 1 T12 L1 5 L2 L4 4 T5 and T10 1 Surgery The levels of vertebral body decompression are seen in Table 4. Two patients required major resection of two adjacent vertebral bodies, and four had partial resection of an adjacent vertebral body. Discontinuous disease created the need for resection of two vertebral bodies at T5 and T10 in one patient. Bilateral single-level or multilevel thoracic rhizotomies were performed in 13 patients, and unilateral rhizotomies were performed in 5. Gross total resection of epidural disease was achieved in all cases. Segmental fixation spanned a mean of nine levels and a median of seven levels. This posterior fixation was extended to incorporate other anterior levels of disease that did not require vertebral body resection and to prepare for disease progression. The mean intraoperative blood loss was 1700 ml (range, ml) as assessed by the anesthesiologist. The blood loss in patients with vascular tumors that had been embolized before surgery did not differ significantly from patients whose tumors did not require embolization (1900 vs ml). Blood loss in patients with embolized tumors did not appear to be from increased tumoral bleeding, but from venous hypertension, which was not encountered in the patients without embolized tumors. The mean intraoperative transfusion requirement was 3.5 U (range, 0 10 U). The mean operating time was 7 hours. Hospital Stay and Complications The mean hospital stay was 11 days, with a range of 4 to 22 days. Eight patients were hospitalized for less than 1 week. No patient required placement of a chest tube or the use of an external orthosis after surgery. Complications are listed in Table 5. The probability of survival as estimated by Kaplan and Meier 21 was 40 weeks from the time of surgery. Thirteen patients remained alive at a Table 5. Postoperative Complications Complication No. of Patients Neurologic progression 3 Clostridium difficile colitis 1 Orthostatic headache 1 Wound dehiscence 1 Ulcer perforation/gi bleed 2 Pulmonary embolism 1 30-day mortality 3 GI gastrointestinal. median survival time of 39 weeks from the first spinal surgery (range, weeks). Twelve patients have died after surgery, at a median of 16 weeks from surgery (range, 2 50 weeks). Three deaths occurred within 30 days of surgery. One death was a result of complications from toxic megacolon in a patient treated with preoperative antibiotics for a urinary tract infection. The second patient was walking independently after surgery and was discharged on postoperative day 10. On day 28, she was admitted to an outside hospital with a massive upper gastrointestinal hemorrhage from which she died. These two deaths were related, in part, to antibiotics and highdose steroids used during the preoperative period. The remaining patient had a hepatocellular carcinoma with ascites. He developed fulminant hepatic failure, and on postoperative day 14, he perforated a gastric ulcer and could not be resuscitated. Outcome Pain relief was immediate and durable. The relation between preoperative and postoperative pain based on patient s self-assessment before surgery and at 2 to 4 weeks after surgery is seen in Table 6. The two patients who died in the hospital after surgery were excluded. Fifteen patients with severe back or radicular pain before surgery rated their pain as mild after surgery, and two others improved to moderate pain status. Five patients with moderate or mild preoperative pain experienced only mild postoperative pain. Mechanical back pain, cancer pain, and radicular pain all improved after surgery. No patient developed significant, recurrent mechanical back pain or loss of fixation. Neurologic outcomes are seen in Table 7. Patients who were neurologically intact before surgery remained neurologically normal, except one patient with T12 L1 disease who had unilateral iliopsoas weakness after surgery. Five patients improved a grade to become neurologically intact (ASIA D to E). Patients with significant neurologic deficit before surgery (ASIA C) did not fair as well as patients who were neurologically intact. The two patients in this group who worsened neurologically had the acute onset of myelopathy and radiographic highgrade spinal cord compression. Both patients were early RT failures. The first patient progressed in the immediate postoperative period from an ASIA C to B. Postoperative Table 6. Pain Assessment: Preoperative versus Postoperative Postoperative Pain Assessment Preoperative Pain Assessment Mild Moderate Severe Mild Moderate 3 Severe Pain levels assessments were obtained from a self-administered visual analog scale, with mild, 0 4; moderate, 5 6; severe, Figures within boxes indicate number of patients within each functional category.

6 Posterolateral Transpedicle Approach Bilsky et al 2245 Table 7. Functional Status: Preoperative versus Postoperative ASIA Score Postoperative Score Preoperative Score A B C D E A 1 B 1 C 1 D 1 1 E 5 15 Figures within boxes indicate number of patients within each functional category. myelogram showed a normal flow of dye without evidence of compression. The second patient improved after surgery from an ASIA C to D. On day 7, he had a pulmonary embolism and hypoxic event. After this episode, the patient acutely became paraplegic. Neither patient has improved. Functional status was assessed (ECOG grading system) before surgery and at 1 month after surgery (Table 8). The three deaths are excluded from analysis. All nine patients who were fully ambulatory before surgery (ECOG 0 2) remained so (ECOG 0 1). Ten patients who were bedridden more than 50% of the time or who were completely disabled (ECOG 3 to 4) improved to ambulatory status (ECOG 0 2), and 4 patients in this preoperative category did not improve (ECOG 3 to 4). In one of these patients, the neurologic status and mechanical back pain improved after surgery, but a progressively symptomatic femur metastasis prevented ambulation. Two patients developed symptomatic tumor recurrence at the previous level of decompression. The first patient had stage IV prostate cancer refractory to hormones and chemotherapy. In May 1998, he received 3000 cgy RT to the spine for metastasis at T3 with resolution of his pain. In September 1998, he was seen for a compression fracture and a high-grade, circumferential epidural tumor resulting in back pain and myelopathy (ASIA D). He underwent PTA with a return of function (ASIA E), but was seen again 6 months later with recurrent back and bilateral lower extremity weakness (ASIA D). Myelogram showed a recurrent compression, and he underwent a second posterior decompression of epidural tumor with return of neurologic function (ASIA E). Table 8. Performance Status: ECOG Scores Postoperative Grade Preoperative Grade Figures indicate number of patients within each functional category. The second patient is a 30-year-old mother of two who had a high-grade spindle cell sarcoma resected from the thoracolumbar paraspinal area in 1993, followed by external beam RT and brachytherapy. She was diseasefree until April 1994 when she underwent a left upper lobectomy for a pulmonary metastasis, followed by right upper and middle lobectomies a year later for recurrent metastasis. She subsequently underwent bilateral chest wall resections for symptomatically recurrent metastasis. In February 1998, she was seen for 3 days of acute back pain which had improved from severe to moderate. She had no neurologic symptoms. An MRI scan showed high-grade spinal cord compression at T4 with a pathologic compression fracture and kyphosis (Figures 2A and B). Because of the multiple previous surgeries, the thoracic surgeons did not believe she would tolerate a thoracotomy. A PTA at T4 was performed (Figures 2C and D), and she was discharged 5 days after surgery, neurologically normal (ASIA E). She declined postoperative RT and chemotherapy. She developed recurrent back pain and was categorized as ASIA D and ECOG 2 in September Myelogram showed recurrent tumor with epidural compression at T4 (Figure 2E). She underwent decompression through a posterior approach with resection of the epidural and paraspinal tumor to the level of the anterior PMMA. Because of the previous thoracic procedures and the prospects for future RT, a trapezius flap was rotated over the hardware before skin closure. She returned to ASIA E and ECOG 4 status and received postoperative RT without experiencing wound complications. Her tumor subsequently recurred a third time in March 1999, and she underwent a third decompression procedure. She is currently 14 months from her original presentation and remains fully ambulatory. Discussion Surgical Treatment The role of surgery in the treatment of spinal metastases is still being defined. Initial attempts at spinal decompression using a laminectomy alone or with adjuvant RT proved to be no better than RT alone. 5,7,10,22,24,27,28,36 The reason for poor outcomes using this approach resulted from the inability to address anterior vertebral body or epidural tumor. Also, resection of the posterior elements without instrumentation often leads to progressive kyphosis and increased neurologic deficits. Based on this data, the majority of patients who are seen at this institution with bone and/or epidural spinal tumor undergo RT as initial therapy. Before making a decision about the best treatment alternative, all patients are evaluated by specialists from the radiation therapy, neurosurgery, orthopedic surgery, and neurology departments. Patients with radioresistant tumors (e.g., sarcoma, renal cell carcinoma), spinal instability, and/or a pathologic fracture with bone in the spinal canal are considered for surgery before RT. Additionally, in the authors experience, patients with a circumferential epidural tumor that is moderately to highly radioresistant

7 2246 Spine Volume 25 Number Figure 2. A, Sagittal magnetic resonance imaging (MRI) showing compression fracture with 47 kyphosis at T4. B, Axial MRI showing high-grade, 270 epidural spinal cord compression and paraspinal mass. The posterior longitudinal ligament is intact posterior to the vertebral body tumor as indicated by the hypointense line between dura and vertebral body. Surgical resection of the posterior longitudinal ligament provided a clean anterior dural margin. C and D, Anteroposterior and lateral radiographs after PTA and circumferential fusion. E, Myelogram/CT (7/7/98) revealed the paraspinal mass had grown into the canal with resultant cord compression requiring reoperation through a posterolateral approach.

8 Posterolateral Transpedicle Approach Bilsky et al 2247 may have a greater propensity for neurologic progression during RT when compared with patients with other patterns of epidural tumor, and surgery is recommended as the initial treatment. After previous RT that has reached spinal cord tolerance, patients are considered for surgery based on progression of neurologic symptoms, radiographic progression of tumor, and spinal instability. Patients undergoing surgical resection are medically assessed for their ability to tolerate the proposed surgical procedure by an internist and have an expected survival time of 6 months as assessed by the treating oncologist. With improvement in surgical techniques, the role of surgery in the treatment of spinal metastasis as initial therapy or after failed radiation therapy continues to evolve. Improved surgical outcomes have been seen using techniques that provide exposure for more radical tumor resection than laminectomy. Reconstruction after these aggressive approaches is now possible using rigid posterior segmental fixation and anterior instrumentation. 37 These approaches include 1) anterior transcavitary 6,11 15,18,29 32,35,38,39,40,43 2) posterolateral transpedicular, 1,3,4,9,17,20,23,25,26,37 and 3) en bloc spondylectomy. 2,16,41,42 The decision to use a particular surgical approach is dependent on the location of the bone, epidural, and paraspinal tumor, type of reconstruction required, patient comorbidities, extent of disease, and surgeon s familiarity. All of the patients in the current series were considered for an anterior approach because of the extent of vertebral body involvement. The PTA was chosen primarily because the medical or oncologic status of the patient prohibited an anterior approach and/or because the pattern of tumor involvement required a circumferential decompression and fusion. In this series, PTA was deemed appropriate in 24% of cases, which is similar to the rate reported in other series in which this approach was used. 1,4 In most series reported, PTA was chosen to reduce the morbidity in patients who cannot tolerate an anterior approach because of concomitant chest disease, poor pulmonary function, or previous chest or retroperitoneal surgery. 1,26 Additionally, two of our patients had paravertebral tumors that the surgical oncologists thought were unresectable. Both patients received postoperative, external beam RT and have not demonstrated a symptomatic recurrence. In patients who previously received RT to spinal cord tolerance, postoperative stereotactic radiosurgery may be useful in decreasing the chance of recurrent spinal cord compression from unresected paraspinal masses. This technology may decrease the need to resect paraspinal tumors with its inherent risk in this patient population. The PTA provides exposure to resect three-column bone disease, but little attention has been focused on the improved exposure for resection of certain patterns of epidural tumor. Gross resection of the epidural tumor is important to decompress the spinal cord and to prevent recurrent symptoms of spinal cord compression. The completeness of epidural tumor resection is especially important in patients previously undergoing RT to spinal cord tolerance in whom no further effective adjuvant therapy is available. Patterns of epidural tumor for which PTA is the preferred approach typically extend from the vertebral body around the posterior longitudinal ligament (PLL) to compress the spinal cord bilaterally or circumferentially. Anterior compression results from pathologic fractures of the vertebral body or from tumor elevating the PLL, but rarely does tumor directly abut the ventral dura. Additionally, the epidural tumor may extend over vertebral body levels adjacent to the infiltrated vertebral body. Anterior transcavitary approaches provide exposure to decompress the anterior spinal dura by resection of the PLL and the lateral dura on the side of the thoracotomy by unilateral pedicle resection. However, 270 or circumferential epidural tumor is difficult to resect, and multilevel epidural tumor may require additional levels of vertebral body resection and an extended anterior fusion. Conversely, the PTA has the advantage of developing the plane between the tumor and the dura starting from uninvolved dura. Posterior and lateral tumor are readily resected. Although the anterior dura is not well exposed using the PTA, the PLL can be dissected from the ventral dura to obtain an anterior margin. Thus, 270 or circumferential epidural tumor can be resected as well as a multilevel epidural tumor without additional levels of vertebral body resection. The goal of reconstruction after three-column tumor decompression is immediate fixation that is durable. In all series using this approach, posterior fixation was used. 1,3,4,17,20,26,34,37 Anterior column reconstruction was variably performed using PMMA and pins or screws. 1,4,20,25,26 Bone graft also has been placed from a posterolateral approach. 4,23 Several authors have reported a posterolateral approach without vertebral body reconstruction, relying on rigid, posterior, segmental fixation for support. Vertebral body reconstruction may not be necessary if less than 50% of the vertebral body has been resected. Bridwell et al 3 treated 25 patients without anterior reconstruction of the spine and had only one fixation failure. The vertebral body decompression was performed through a transpedicular approach, however, without extensive resection of the spinous processes and laminae. This may create less spinal instability, obviating the need for anterior reconstruction, but there seems to be less exposure for tumor resection. Aykeson and McCutcheon 1 used an anterior reconstruction strategy similar to that presented here, but they had a 16% rate of PMMA dislodgment that required revision surgery. Two technical points differed in the present series that may have prevented anterior failures: 1) The posterior instrumentation used in that study was a Luque rectangle with sublaminar wires. In the current series, the use of rigid posterior segmental fixation under compression resulted in no anterior failures; and 2) Complete vertebrectomy was performed in their patients regardless of the degree of tumor involvement. In the

9 2248 Spine Volume 25 Number authors patients, vertebral body resection was restricted predominantly to the infiltrated bone, generally maintaining the intact cortical bone. This lesser degree of resection may provide additional anterior support. Sagittal and coronal segmental deformity correction can be achieved with the PTA approach. Simultaneous release of the anterior and posterior elements by resection of the facet joints and vertebral body enables the surgeon to translate the spine into alignment. In many series using an anterior approach, major deformities were addressed through a two-stage anterior and posterior procedure. From a PTA, Magerl and Coscia 26 and Cahill and Kumar 4 used an interbody distractor to realign the spine and the placement of Shanz screws and variable-angle connectors to hold the corrected alignment before the placement of posterior instrumentation. The majority of patients in the present study were fused in situ with the positioning on the operating table providing spinal realignment. In some patients, the sagittal plane deformity was corrected by underbending the rods to reduce the kyphosis. On follow-up plain radiographs, there has been no progression of spinal deformity or loss of correction in these patients, even in patients who have documented extension of their tumor to other vertebral body levels. The recently described en bloc spondylectomy is founded on sound oncologic principles. 41,42 The intent of this surgery is en bloc resection of the tumor with negative histologic margins. This surgery is feasible as a one-stage or two-stage procedure, but is technically quite demanding. 2,16,41,42 Results with this approach are encouraging, both in terms of functional outcome and local control; however, this approach is reserved for patients in whom the spine surgery is being performed as a curative rather than as a palliative procedure. Based on anatomic considerations, the majority of patients in the present series would not have been candidates for this type of surgery because of the extensive epidural disease, multilevel vertebral body involvement, and large paraspinal masses. Outcome Analysis The most impressive outcome measured in this series was pain resolution. All patients with severe or moderate pain before surgery improved, and no patients experienced worse pain after surgery. Other series have confirmed this result, showing a % improvement in pain resolution. 1,3,4,17,20,26,34,37 Mechanical, radicular, and tumor-related pains were all improved. Late pain recurrence may be reflective of recurrent disease. 1 The majority of patients in this series were neurologically normal before surgery despite high-grade epidural compression and extensive vertebral body involvement with compression fractures. Eighty percent of patients in the series remained or improved to become neurologically normal, and 86% of those who survived 1 month were ambulatory and capable of self care (ECOG 0 2). This result is similar to that reported for other surgical series using this approach. 1,3,4,17,20,26,34,37 The complication rates reported in the literature using PTA range from 11 to 48%. 1,3,4,17,20,26,34,37 In the present series, the major complications using this approach, including the three deaths (12%), were primarily medical complications related to antibiotic and steroid usage. Wound dehiscence occurred in 4% of patients in this series, but wound dehiscence and infection have been reported in up to 28% of patients undergoing laminectomy for spinal metastases. Trapezius or latissimus dorsi rotation flaps have been used prophylactically for wounds at high risk or at the time of wound dehiscence for successful closure. Use of these flaps has significantly reduced the morbidity associated with this complication. Cerebral spinal fluid leaks have been reported in up to 16% of patients undergoing PTA 1 ; however, no CSF cutaneous fistulas were experienced in the present series, although a single patient resolved orthostatic headaches related to a repaired dural tear at the time of surgery. This is most often the result of failure to adequately ligate a root or repair a dural tear in patients who have poor wound healing. To prevent postoperative complications with CSF leaks, the intrathoracic pressure is increased to 40 cm H 2 0 before closure to ensure that there are no occult CSF leaks. If a CSF leak has been repaired intraoperatively, thrombin glue may be placed over the repair, and drains are routinely placed above the fasciae and not in the epidural space. Concern has been expressed in the literature that uncontrolled bleeding may result from the vertebral body resection using a posterior approach. 11 Major, uncontrolled hemorrhage did not occur in patients in the current study. Resection of vascular tumors (e.g., renal cell carcinoma) may be performed safely after embolization, although venous hypertension may cause increased bleeding during the dissection. Summary The posterolateral transpedicular approach works well in a selected patient population with thoracic or lumbar metastatic tumor. Indications for this approach include three-column disease, multilevel vertebral body or epidural involvement, and vertebral body involvement with high-grade spinal cord compression from epidural disease. It also can be applied to patients in whom morbidity from an anterior approach is prohibited by the patient s medical condition or unresectable anterior disease. The technical benefits of this approach for decompression include the completeness of epidural tumor resection and three-column disease from a single approach. Reconstruction of the anterior and posterior spine provides immediate stability that allows a patient to walk after surgery without a brace. Deformity correction is possible. Pain relief is immediate and durable in the majority of patients. Neurologic and performance

10 Posterolateral Transpedicle Approach Bilsky et al 2249 status are improved in most patients, and complications rates were relatively low. Key Points The posterolateral transpedicular approach successfully addresses tumor that traditionally requires an alterior and posterior approach through a posterolateral approach only. Spine reconstruction provides immediate stability. Embolized tumors in the vertebral body may be resected from this approach. References 1. Akeyson E, McCutcheon IE. Single-stage posterior vertebrectomy and replacement combined with posterior instrumentation for spinal metastasis. J Neurosurg 1996;85: Boriani S, Biagini R, DeFure F, et al. Resection surgery in the treatment of vertebral tumors. Chir Organi Mov 1998;1-2: Bridwell K, Jenny A, Saul T, et al. Posterior segmental spinal instrumentation (PSSI) with posterolateral decompression and debulking for metastatic thoracic and lumbar spine disease: Limitations and technique. Spine 1998;13: Cahill DW, Kumar R. Palliative subtotal vertebrectomy with anterior and posterior reconstruction via single posterior approach. J Neurosurg (Spine 1) 1999;90: Constans JP, DeDivitiis E, Donzelli R, et al. Spinal metastases with neurological manifestations: Review of 600 cases. J Neurosurg 1983;59: Cooper P, Errico T, Martin R, et al. A systematic approach to spinal reconstruction after anterior decompression for neoplastic disease of the thoracic and lumbar spine. Neurosurgery 1993;32: Dunn, RC Jr., Kelly WA, Wohns RNW, et al. Spinal epidural neoplasia. A 15-year review of the results of surgical therapy. J Neurosurg 1980;52: Eastern Cooperative Oncology Group Performance Status Scale. Eastern Cooperative Oncology Group. Revised March 25, Faccioli F, Lima J, Bricolo A, et al. One-stage decompression and stabilization in the treatment of spinal tumors. J Neurosurg Sci 1985;29: Gilbert RW, Kim JH, Posner JB. Epidural spinal cord compression from metastatic tumor: Diagnosis and treatment. Ann Neurol 1978;3: Gokaslan ZL, York JE, Walsh G, et al. Transthoracic vertebrectomy for metastatic spinal tumors. J Neurosurg 1998;89: Hall D, Webb J. Anterior plate fixation in spine tumor surgery. Indications, techniques, and results. Spine 1991;3:S80 S Harrington K. The use of methylmethacryate for vertebral body replacement and anterior stabilization of pathological fracture dislocations of the spine due to metastatic malignant disease. J Bone Joint Surg 1981;63A: Harrington K. Anterior cord decompression and spinal stabilization for patients with metastatic lesions of the spine. J Neurosurg 1984;61: Harrington K. Anterior decompression and stabilization of the spine as a treatment for vertebral body collapse and spinal cord compression for metastatic malignancy. Clin Orthop 1988;233: Heary R, Vaccaro A, Benevenia J, et al. En bloc vertebrectomy in the mobile lumbar spine. Surg Neurol 1998;50: Heller M, McBroom R, MacNab T, et al. Treatment for metastatic disease of the spine with posterolateral decompression and Luque instrumentation. Neuroorthopedics 1986;2: Hosono N, Yonenobu K, Fuji T, et al. Vertebral body replacement with ceramic prosthesis for metastatic spinal tumors. Spine 1995;20: International Standards for Neurological, Functional Classifications of Spinal Cord Injury. Chicago, IL: American Spinal Injury Association, 1982;(Revised 1996):9: Johnston F, Uttley D, Marsh HT, et al. Synchronous vertebral decompression and posterior stabilization in the treatment of spinal malignancy. Neurosurgery 1989;25: Kaplan E, Meier P. Nonparametric estimation from incomplete observations. J Am Statistical Association 1958;53: Kollman H, Diemath HE, Strohecker J, et al. Spinal metastases as the first manifestations. Adv Neurosurg 1984;12: Lesoin F, Rousseaux M, Lozes G, et al. Posterolateral approach to tumors of the dorsolumbar spine. Acta Neurochir 1986;81: Livingston KE, Perrin RG. The neurosurgical management of spinal metastases causing cord and cauda equina compression. J Neurosurg 1978;49: Lozes G, Fawaz A, Devos P, et al. Operative treatment of thoraco-lumbar metastases, using methylmethacrylate and Kempf s rods for vertebral replacement and stabilization. Report of 15 cases. Acta Neurochir 1987;84: Magerl F, Coscia M, Total posterior vertebrectomy of the thoracic and lumbar spine. Clin Orthop 1988;232: Maranzano E, Latini P. Effectiveness of radiation therapy without surgery in metastatic spinal cord compression: Final results from a prospective trial. Int J Radiat Oncol Biol Phys 1995;32: Miles J, Banks AJ, Dervin E, et al. Stabilization of the spine affected by malignancy. J Neurol Neurosurg Psychiatry. 1984;47: Moore A, Uttley D. Anterior decompression and stabilization of the spine in malignant disease. Neurosurgery 1989;24: Onimus M, Schraub S, Berfin D, et al. Surgical treatment of vertebral metastasis. Spine 1986;11: Perrin RG, McBroom RJ. Anterior versus posterior decompression for symptomatic spinal metastasis. Can J Neurolog Sci 1987;14: Perrin RG, McBroom RJ. Spinal fixation after anterior decompression for symptomatic spinal metastasis. Neurosurgery 1998;22: Serlin RC, Mendoza TR, Nakamura Y, et al. When is cancer pain mild, moderate, or severe? Grading pain severity by its interference with function. Pain 1995;61: Shaw B, Mansfield F, Borges L, et al. One-stage posterolateral decompression and stabilization for primary and metastatic vertebral tumors in the thoracic and lumbar spine. J Neurosurg 1989;70: Siegal T, Siegal T. Surgical decompression of anterior and posterior malignant epidural tumors compressing the spinal cord: A prospective study. Neurosurgery 1985;17: Stark RJ, Henson RA, Evans SJW. Spinal metastases: A retrospective survey from a general hospital. Brain 1982;105: Steffee A, Stikowski D, Topham LS, et al. Total vertebral body and pedicle arthroplasty. Clin Orthop 1986;203: Sundaresan N, Galicich J, Lane JM, et al. Treatment of neoplastic epidural cord compression by vertebral body resection and stablization. J Neurosurg 1985;63: Sundaresan N, DiGiacinto G, Hughes JE, et al. Spondylectomy for malignant tumors of the spine. J Clin Oncol 1989;7: Sundaresan N, Steinberger AA, Moore F, et al. Indications and results of combined anterior posterior approaches for spine tumor surgery. J Neurosurg 1996;85: Tomita K, Kawahara N, Toribatake Y, et al. Total en bloc spondylectomy for solitary spinal metastasis. Int Orthop 1994;18: Tomita K, Kawahara N, Baba H, et al. Total en bloc spondylectomy: A new surgical technique for primary malignant vertebral tumors. Spine 1997;22: Walsh GL, Gokaslan ZL, McCutcheon IE, et al. Anterior approaches to the thoracic spine in patients with cancer: Indications and results. Ann Thorac Surg 1997;64: Address reprint requests to Mark H. Bilsky, MD Department of Neurosurgery Box York Ave New York, NY 10021

11 2250 Spine Volume 25 Number Point of View Katsuro Tomita, MD Department of Orthopaedic Surgery Kanazawa University Kanazawa, Japan The authors introduce the posterolateral transpedicular approach, which provides a wide surgical exposure to decompress and instrument the anterior and posterior spine. I have three main comments to make on this article. The advantage of this method is to be able to perform circum-spinal decompression (360 ) in one operative field that reaches both posterior and anterior spinal tumors. This technique allows the surgeon to keep close watch on the spinal cord throughout the decompression surgery. It is an atraumatic procedure and protects the spinal cord from damage. This approach also provides exposure sufficient to instrument the anterior and posterior column. In these senses, this type of surgery resembles our total en bloc spondylectomy (TES) technique. However, the first aim of this surgery is spinal cord decompression and does not seem to address the longterm prognosis. It can be understood as a method to improve symptoms, not to resolve the tumor condition. Since tumors are removed in piecemeal fashion (segments) throughout the operation, tumor contamination, dissemination, or residue are inevitable, probably leading to high local reoccurrence rate, if these patients survive longer. This limited degree of reconstruction using bone cement enables temporary weight support only in the short term. If the patient survives beyond the short-term stage, there would be the fear of secondary instrumentation failure or cement block displacement. Patients and their families as well as physicians should be well informed regarding this point. In summary, this approach is one of the palliative options for the surgical treatment of spinal metastasis, especially for those patients whose expected survival is around 6 months, as authors mentioned.