En bloc spondylectomy has been developed and. Late instrumentation failure after total en bloc spondylectomy. Clinical article

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1 J Neurosurg Spine 15: , 2011 Late instrumentation failure after total en bloc spondylectomy Clinical article Morio Matsumoto, M.D., 1 Kota Watanabe, M.D., 2 Takashi Tsuji, M.D., 1 Ken Ishii, M.D., 1 Masaya Nakamura, M.D., 1 Kazuhiro Chiba, M.D., 1 and Yoshiaki Toyama, M.D. 1 1 Department of Orthopaedic Surgery; and 2 Department of Advanced Therapy for Spine and Spinal Cord Disorders, Keio University, Tokyo, Japan Object. The object of this study was to investigate failures after spinal reconstruction following total en bloc spondylectomy (TES), related factors, and sequelae arising from such failures in patients with malignant spinal tumors. Methods. Fifteen patients (12 males and 3 females, with a mean age of 46.5 years) with malignant spinal tumors who underwent TES and survived for more than 1 year were included in this analysis (mean follow-up 41.5 months). Seven patients had primary tumors, including giant cell tumors in 4 patients, chordoma in 2, and Ewing sarcoma in 1. Eight patients had metastatic tumors, including thyroid cancer in 6 and renal cell cancer and malignant fibrous histiocytoma in 1 patient each. Seven patients without prominent paravertebral extension of the tumor were treated using a posterior approach alone, and 8 patients who exhibited prominent anterior or anterolateral extension of the tumors into the thoracic or abdominal cavity were treated using a combined anterior and posterior approach. Spinal reconstruction after tumor resection was performed using a combination of anterior structural support and posterior instrumentation. The relationship between instrumentation failure and clinical and radiographic factors, including age, sex, history of previous surgery, preoperative radiotherapy, tumor histology, tumor level, surgical approach, number of resected vertebrae, rod diameter, number of instrumented vertebrae, and cage subsidence, was investigated. Results. Six patients (40%) with spinal instrumentation failure were identified: rod breakage occurred in 3 patients, and breakage of both the rod and the cage, combined cage breakage and screw back-out, and endplate fracture arising from cage subsidence occurred in 1 patient each. All of these patients experienced acute or chronic back pain, but only 1 patient with a tumor recurrence experienced neurological deterioration upon instrumentation failure. Cage subsidence ( 5 mm), preoperative irradiation, and the number of instrumented vertebrae ( 4 vertebrae) were significantly related to late instrumentation failure. Conclusions. Late instrumentation failure was a frequent complication after TES. Although patients with instrumentation failure experienced back pain, the neurological sequelae were not catastrophic. For prevention, meticulous preparation of the graft site and a longer posterior fixation should be considered. (DOI: / SPINE10813) Key Words total en bloc spondylectomy instrumentation failure spinal tumor En bloc spondylectomy has been developed and used for the marginal resection of malignant spinal tumors, allowing for the local treatment of tumors with acceptable perioperative morbidity and yielding good neurological recovery in patients with preoperative neurological deficits. 1,3,6,8 12,14,16 Tomita et al. 15 described a TES technique via a posterior-only approach and using his original T-saw. This aggressive surgical procedure is Abbreviation used in this paper: TES = total en bloc spondylectomy. indicated for patients with spinal tumors, including primary malignant tumors, benign but aggressive tumors (such as giant cell tumors), and metastatic tumors with curable primary lesions. After en bloc resection of the tumors, the spinal column is totally separated, and, especially in patients with tumors extending to surrounding structures such as the paravertebral muscles and ribs, combined resection of the surrounding structures is required, making the spine extremely unstable. To restabilize the spine, robust reconstruction of the 3 spinal columns is necessary using spinal instrumentation. 320 J Neurosurg: Spine / Volume 15 / September 2011

2 Late instrumentation failure Spinal instability resulting from the failure of spinal reconstruction after TES can lead to serious sequelae, including severe pain and neurological deterioration. Because TES is indicated for patients with a long life expectancy, 15 such patients may face a greater risk of suffering from instrumentation failure during a later stage of follow-up than the patients with a shorter life expectancy, who usually undergo palliative intralesional resection surgery. Late instrumentation failure can be caused by the lack of biological osseous fusion, but patients who undergo TES suffer from many factors unfavorable to osseous fusion, including postoperative instability of the spine, a decrease in blood supply due to wide dissection of the surrounding soft tissues, radiation, chemotherapy, and so forth. Therefore, we can hypothesize that those patients may have a high rate of instrumentation failure due to a lack of solid osseous fusion during a long-term follow-up period. Although several case studies examining TES have been reported, 1,3,8 12,14,16 to our knowledge, there are few published accounts of late instrumentation failure and the resulting sequelae after TES. The purpose of the present study was to investigate instrumentation failure after TES and subsequent spinal reconstruction, related factors, and the sequelae arising from instrumentation failure in patients with a postoperative survival period longer than 1 year. Methods Patient Characteristics Between 1997 and 2009, 22 patients with primary or metastatic spinal tumors underwent a TES at our institute. Of these, 15 patients (68.2%) survived for more than 1 year after the procedure and were included in the present analysis (Table 1). These 15 patients consisted of 12 men and 3 women, with a mean age of 46.5 years (range years). The mean follow-up period was 41.5 months (range months). At the final follow-up, 13 patients were alive without evidence of disease, and 2 patients had died of disease associated with tumor recurrence at 24 and 57 months after TES. Seven patients had primary tumors, including giant cell tumors in 4 patients, chordoma in 2, and Ewing sarcoma in 1. Eight patients had metastatic tumors including thyroid cancer in 6 and renal cell cancer and malignant fibrous histiocytoma in 1 patient each. The thoracic spine was involved in 7 patients, and the thoracolumbar spine and lumbar spine were involved in 4 patients each. Total en bloc spondylectomy was indicated for patients with metastatic tumors based on the scoring system proposed by Tomita et al. 15 This system consists of 3 prognostic factors including malignancy grade of primary lesion (slow growth, 1 point; moderate growth, 2 points; and rapid growth, 4 points), visceral metastases (no metastasis, 0 points; treatable metastasis, 2 points; and untreatable metastasis, 4 points), and bone metastases (solitary or isolated, 1 point; and multiple, 2 points). The resultant score ranges between 2 and 10. Total en bloc spondylectomy was indicated for patients with a Tomita score 4. Five of the patients with metastatic tumors had a Tomita score of 2, and 3 had a Tomita score of 3. Three patients had previously undergone intralesional palliative surgery that resulted in a recurrence. Neurological status before surgery, evaluated using the Frankel classification, 5 was Grade C (motor useless) TABLE 1: Summary of demographic characteristics in 15 patients who underwent TES* Case No. Age (yrs), Sex Tumor Type Tomita Score Histology Involved Vertebrae Previous Op FU (mos) Recurrence Prognosis Frankel Grade Preop FU 1 48, F primary GCT T3 5 Y 72 N NED C E 2 28, M primary GCT L1 2 Y 75 N NED D D 3 32, M primary Ewing sarcoma L-2 N 57 Y DOD (57) C D 4 42, M primary chordoma L-4 N 24 Y DOD (24) D D 5 35, M primary GCT T-12 N 26 N NED E C 6 22, M primary chordoma L-2 N 15 N CDF E E 7 32, M primary GCT T8 10 N 12 N CDF E E 8 42, M metastasis 2 thyroid T8 10 N 96 N CDF C E 9 57, M metastasis 3 thyroid T12 L1 N 31 N CDF C D 10 52, M metastasis 2 thyroid T-12 N 36 N CDF E E 11 56, F metastasis 2 thyroid T-4 Y 26 N NED D E 12 64, M metastasis 2 thyroid T-4 N 25 N CDF C D 13 62, M metastasis 3 RCC T-3 N 36 N CDF C D 14 63, M metastasis 3 MFH T11 L1 N 26 N CDF E E 15 60, F metastasis 2 thyroid T-10 N 74 N CDF E E * CDF = continuously disease free; DOD = died of disease; FU = follow-up; GCT = giant cell tumor; MFH = malignant fibrous histiocytoma; NED = no evidence of disease; N = no; RCC = renal cell carcinoma; Y = yes. Tomita score applies to metastatic tumors, not primary tumors. Number in parentheses indicates the number of months between surgery and death. J Neurosurg: Spine / Volume 15 / September

3 M. Matsumoto et al. in 6 patients, Grade D (motor useful) in 3, and Grade E (recovery or normal) in 6. At the final follow-up, neurological status was Grade C in 1 patient, Grade D in 6, and Grade E in 8. Surgical Procedures Prior to surgery, 13 patients underwent preoperative embolization of the feeding arteries, 3 had received radiation therapy, and 2 had received chemotherapy (Table 2). Seven patients without prominent paravertebral tumor extension were treated using a posterior approach alone, as described by Tomita et al., 14,16 and the other 8 patients, who exhibited prominent anterior or anterolateral extension of the tumors into the thoracic or abdominal cavity, were treated using a combined anterior and posterior approach with the anterior release of tumors from the surrounding vascular and visceral structures and ligation of segmental vessels, followed by en bloc resection of the tumor and surrounding tissues via a posterior approach. The number of resected vertebrae was 1 in 9 patients, 2 in 2 patients, and 3 in 4 patients. Spinal reconstruction after tumor resection was performed using a combination of anterior structural support and posterior instrumentation. For the anterior structural support, a titanium mesh cage packed with morcelized local bone, ribs, or iliac crest without tumor contamination was used in 13 patients, and a polymethylmethacrylate block or expandable titanium cage was used in 1 patient each. For the posterior instrumentation, pedicle screw systems with or without hooks were utilized in 14 patients, and a Luque rod was used in 1 patient. Study Analyses The relationships between instrumentation failure and clinical and radiographic factors were investigated using a chi-square test. The analyzed factors were age (< 60 or 60 years), sex, history of previous surgery, preoperative chemotherapy, preoperative radiotherapy, tumor histology (primary or metastatic), tumor level (thoracic, thoracolumbar, or lumbar), surgical approach (posterior only or combined anterior and posterior), number of resected vertebrae (single or multiple), rod diameter (5.5 vs 6.35 mm), number of instrumented vertebrae, and cage subsidence (< 5 or 5 mm). The cage subsidence was measured on radiographs taken immediately after surgery and at the follow-up by using measurement software loaded on the picture archiving and communication system (Fuji Film). For statistical analyses, the statistical software PASW Statistics17 (SPSS, Inc.) was used, and a p value < 0.05 was considered statistically significant. Results Instrumentation Failure Six patients (40%) with spinal instrumentation failure were identified (Table 3). The failure was noted an average of 28.3 months (range 6 42 months) after TES. The instrumentation failures included rod breakage in 3 patients and breakage of both the rod and the cage, cage breakage and screw back-out, and endplate fracture arising from cage subsidence in 1 patient each. All 6 patients experienced back pain, which was acute and severe enough in 3 patients to require a visit to an emergency department; moderate pain was reported by 3 patients during a regular postoperative follow-up examination. Only 1 patient with a tumor recurrence experienced neurological deterioration at the time of instrumentation failure. This patient (Case 4) had a recurrence of a chordoma at L-3 that led to mild paraparesis (Frankel Grade D). Four patients underwent revision surgery, whereas 2 patients refused further surgery. The revision surgeries included TABLE 2: Details of treatment in 15 patients who underwent TES* Case No. Preop Radiation Preop Chemo Embolization Surgical Approach No. of Resected Vertebra No. of Instrumented Vertebra Upper Lower Rod Diameter (mm) Anchor Cage Type 1 N N Y posterior PS mesh 2 N N Y combined PS + hook expandable 3 Y Y Y posterior PS mesh 4 Y N N combined PS mesh 5 N N Y combined PS mesh 6 N N Y combined PS mesh 7 N N Y combined PS mesh 8 Y N Y posterior PS + hook mesh 9 N N Y combined PS mesh 10 N N Y combined PS + hook mesh 11 N N Y posterior PS mesh 12 N N Y posterior PS + hook mesh 13 N N N posterior sublaminar cement 14 N Y Y combined PS mesh 15 N N Y posterior PS mesh * Chemo = chemotherapy; PS = pedicle screw. 322 J Neurosurg: Spine / Volume 15 / September 2011

4 Late instrumentation failure TABLE 3: Instrumentation failure and revision in 15 patients who underwent TES Case No. Failure Cage Subsidence Failure Mode 1 2 Duration Btwn TES & Failure (mos) Revision Method of Revision Op 1 N N 2 N Y 3 Y Y rod breakage cage breakage 42 N 4 Y Y cage breakage L-5 screw pull-out 28 Y extension of fusion level by 1 level above & below 5 N N 6 N N 7 N N 8 Y Y cage sinking 6 Y cage removal, vascularized rib & autologous fibula graft 9 N N 10 Y Y rod breakage 38 N 11 N N 12 N N 13 N N 14 Y Y rod breakage 23 Y rod replacement 15 Y Y rod breakage 33 Y rod replacement the replacement of broken 5.5-mm rods with 6.35-mm rods in 2 patients, the rostral and caudal extension of the instrumentation in a patient with cage breakage and screw back-out, and the replacement of a dislodged cage by an autologous fibula and vascularized rib in a patient with an endplate fracture. Factors Related to Instrumentation Failure Cage subsidence ( 5 mm; p = 0.001), preoperative radiation (p = 0.018), and the number of instrumented vertebrae (p = 0.018) were significantly related to late instrumentation failure (Table 4). All 6 patients with instrumentation failure exhibited obvious cage subsidence of 5 mm. All 3 patients who had received preoperative radiation (mean dosage 50 Gy) experienced instrumentation failure, whereas only 3 of the 12 patients without preoperative radiation experienced instrumentation failure. The 3 patients with preoperative radiation also demonstrated cage subsidence. All 3 patients with 4 instrumented vertebrae experienced instrumentation failure, whereas only 3 of the 12 patients with 5 had failure. None of the other factors, including age, sex, history of previous surgery, preoperative chemotherapy, tumor histology, tumor level, surgical approach, number of resected vertebrae, or rod diameter (5.5 vs 6.35 mm) was significantly related to late instrumentation failure. Case 1 Illustrative Cases J Neurosurg: Spine / Volume 15 / September 2011 History and Examination. This 42-year-old man with a thyroid cancer metastasis at T8 10 underwent TES via a posterior-only approach (Fig. 1). He had progressive paraplegia (Frankel Grade C) at the time of surgery; he had undergone radiation treatment previously, but this therapy had failed to prevent neurological deterioration. Operation. After en bloc resection of the inferior half of T-8, the entirety of T-9, the superior three-fourths of T-10, and the right 9th rib, the spine was reconstructed using a titanium mesh cage and posterior instrumentation. Postoperative Course. Seven months after the surgery, the patient experienced severe back pain, although he had improved neurologically and was ambulatory. A radiological investigation revealed that he had a fracture of the remaining T-10 endplate. His reconstruction was revised by removal of the cage followed by grafts from an autologous fibula and vascularized rib. Although a late infection developed requiring hardware removal 7 years later, he had obtained a solid bony fusion without any signs of recurrence or neurological deficits at that time. Case 5 Examination. This 63-year-old man presented with a malignant fibrous histiocytoma metastasis at T-11, T-12, and L-1. Operation. He underwent TES from T-11 to L-1 via a combined anterior and posterior approach (Fig. 2). The surgery and recovery were uneventful. Postoperative Course. At 23 months after TES, severe back pain developed and the patient visited the emergency department, where breakage of the bilateral rods was noted on radiography. The patient was neurologically intact. Radiographs and a sagittal reconstruction CT showed cage subsidence and a gap between the inhomo- 323

5 M. Matsumoto et al. Fig. 1. Case 1. Images obtained in a 42-year-old man with a thyroid cancer metastasis at T-8 to T-10. A: Enhanced sagittal T1-weighted MR image showing tumor involvement at T-8, T-9, and T-10. B: Enhanced axial T1-weighted MR image at T-9 showing tumor involvement of the T-9 vertebral body and right lamina and extending into the spinal canal. C: Postoperative radiograph showing a titanium cage placed on the inferior one-fourth of the T-10 vertebral body. D: Radiograph showing the resected specimen including the lower one-third of the T-8 vertebral body, the entire T-9 vertebral body, the right lamina, and the upper three-fourths of the T-10 vertebral body. E: Radiograph showing cage subsidence with fracture of the lower endplate. F: Coronal CT scan showing a cage replaced with autologous fibula and vascularized rib. geneous graft bone in the cage and the vertebral bodies. He underwent revision surgery during which the broken 5.5-mm rods were replaced with 6.35-mm rods, resulting in relief of the back pain. During the revision surgery, a compressive force was applied to the cage via the upper and lower vertebrae. Discussion The overall rate of late instrumentation failure after TES was 40% in this study, suggesting that such an event is not a rare complication associated with TES. However, the sequelae associated with such a failure were not catastrophic; that is, they were not associated with severe neurological deterioration, although all of the patients with failed instrumentation did experience moderate to severe back pain. One of the factors related to late instrumentation failure was the number of instrumented vertebrae. Boriani et al. 3 reported on the morbidity of en bloc resection of spinal tumors in 134 patients. These authors found posterior instrumentation failure with anterior column reconstruction in 7% of the patients. They attributed this failure to a posterior fixation that was too short. Failure of the anterior constructs was not observed. A biomechanical study by Disch et al., 4 who used a thoracolumbar en bloc spondylectomy model, demonstrated that multilevel posterior fixation resulted in better stability than did short posterior fixation with an anterolateral plate. In the present study as well, a short construct extending 2 levels above and below the point of fixation always failed. Considering these findings, fixation should be extended to 3 levels above and below the resected vertebrae. Although the rod diameter was not a significant risk factor for failure, a 6.35-mm rod may be more useful for securely holding an unstable spine than a 5.5-mm rod. Cage subsidence was also significantly associated with instrumentation failure. Because TES is, so to speak, the worst-case scenario in terms of spinal stability, a robust anterior support is essential for regaining spine stability. Cage subsidence leads to the failure of load sharing in the anterior column, resulting in an increased load im- 324 J Neurosurg: Spine / Volume 15 / September 2011

6 Late instrumentation failure Fig. 2. Case 5. Images obtained in a 63-year-old man with a malignant fibrous histiocytoma metastasis at T-11, T-12, and L-1. A: Sagittal T2-weighted MR image showing prominent ventral extension of the tumor. B: Enhanced MR image showing the tumor extending from T-11 to L-1. C: Radiograph showing the marked upper subsidence of the cage and rod breakage. D: Radiograph obtained after the revision surgery, showing broken rods replaced with 6.35-mm rods. E: Sagittal reformatted CT scan showing the cage subsidence and the nonhomogeneous graft bone inside the cage. posed on the posterior instrumentation. Cage subsidence may develop because of the fragility of the vertebral bodies, the condition of the interface between the cage and the graft site, or the failure of osseous fusion between the grafted autologous bone in the cage and the vertebral bodies. 7,13 Lim et al. 7 examined the relationship between the biomechanical strength and the condition of the graft-endplate in an anterior cervical fusion model. They conducted a destructive compression test on specimens with different endplate conditions and found that the load that produced failure in specimens with an intact endplate was significantly greater than that producing failure in specimens with no endplate. Togawa et al. 13 conducted a histological study of the contents of clinically failed interbody cages retrieved from human patients. These authors found a relatively high prevalence of hyaline and fibrocartilage in the cages and stressed the importance of graft and graft-site preparation for bone-graft incorporation. J Neurosurg: Spine / Volume 15 / September 2011 As reported in these studies, graft-site preparation is a critical factor for preventing cage subsidence. As shown in the patient in Case 1, cutting more than half of the vertebral bodies may lead to a weak and insufficient graft site for the cage. In such cases, the excisional line should be extended to the disc space above or below the involved vertebral body so that the cage can be placed on the bony endplates with better mechanical strength. Because irradiation is known to have a negative impact on bone quality and strength, 2 preoperative radiation can be a risk factor for cage subsidence and successive instrumentation failure. Therefore, the oncological need for preoperative irradiation should be weighed against successful TES without instrumentation failure. For patients expected to have a long survival period, measures for achieving solid osseous fusion should be considered, including the placement of an autologous vascularized or nonvascularized strut graft as an adjunct to the placement of a titanium cage. 325

7 M. Matsumoto et al. TABLE 4: Factors associated with instrumentation failure Parameter (no. of patients) No. of Patients (%) p Value age in yrs 0.63 <60 (11) 4 (36.4) 60 (4) 2 (50.0) sex 0.79 M (12) 5 (41.7) F (3) 1 (33.3) history of previous op 0.79 Y (3) 1 (33.3) N (12) 5 (41.7) preop chemo Y (2) 2 (100.0) N (13) 4 (30.8) radiotherapy 0.018* Y (3) 3 (100.0) N (12) 12 (25.0) histology of tumor 0.40 primary (7) 2 (28.6) metastatic (8) 4 (50.0) level of tumors 0.70 thoracic (7) 2 (28.6) thoracolumbar (4) 2 (50.0) lumbar (4) 2 (50.0) surgical approach 0.83 posterior only (7) 3 (42.9) combined (8) 3 (37.5) no. of resected vertebrae (9) 4 (44.4) 2 (2) 0 (0) 3 (4) 2 (50.0) rod diameter in mm (6) 3 (50.0) 6.35 (9) 3 (33.3) no. of instrumented vertebrae 0.018* 2 (3) 3 (100.0) 3 (12) 3 (25.0) cage subsidence 0.001* Y (7) 6 (85.7) N (8) 0 (0.0) * Statistically significant. The present study has several limitations, including its retrospective design, small sample size, and diversity of tumor histologies and surgical methods. And because of these limitations, we were not able to fully identify factors related to the achievement of biological osseous fusion, which is essential to successful long-term results after TES. We must improve the statistical power with a multicenter study to elucidate those factors. Nonetheless, this is the first case study to describe in detail late instrumentation failure, the resulting sequelae, and the related factors after TES. The information obtained from this study may contribute to the improvement of reconstruction methods after TES. Conclusions Late instrumentation failure was a frequent complication after TES. Although patients with instrumentation failure experienced back pain, the neurological sequelae were not catastrophic. For prevention, meticulous preparation of the graft site and a longer posterior fixation should be considered. Disclosure Drs. Matsumoto and Watanabe are paid consultants for Medtronic Sofamor Danek Japan. Author contributions to the study and manuscript preparation include the following. Conception and design: Matsumoto, Chiba. Acquisition of data: Matsumoto, Watanabe, Tsuji, Ishii, Nakamura. Analysis and interpretation of data: Matsumoto. Drafting the article: Matsumoto. Critically revising the article: Matsumoto. Statistical analysis: Matsumoto. Study supervision: Chiba, Toyama. References 1. Abe E, Kobayashi T, Murai H, Suzuki T, Chiba M, Okuyama K: Total spondylectomy for primary malignant, aggressive benign, and solitary metastatic bone tumors of the thoracolumbar spine. J Spinal Disord 14: , Alsaadi G, Quirynen M, Komárek A, van Steenberghe D: Impact of local and systemic factors on the incidence of late oral implant loss. Clin Oral Implants Res 19: , Boriani S, Bandiera S, Donthineni R, Amendola L, Cappuccio M, De Iure F, et al: Morbidity of en bloc resections in the spine. Eur Spine J 19: , Disch AC, Schaser KD, Melcher I, Luzzati A, Feraboli F, Schmoelz W: En bloc spondylectomy reconstructions in a biomechanical in-vitro study. Eur Spine J 17: , Frankel HL, Hancock DO, Hyslop G, Melzak J, Michaelis LS, Ungar GH, et al: The value of postural reduction in the initial management of closed injuries of the spine with paraplegia and tetraplegia. I. Paraplegia 7: , Liljenqvist U, Lerner T, Halm H, Buerger H, Gosheger G, Winkelmann W: En bloc spondylectomy in malignant tumors of the spine. Eur Spine J 17: , Lim TH, Kwon H, Jeon CH, Kim JG, Sokolowski M, Natarajan R, et al: Effect of endplate conditions and bone mineral density on the compressive strength of the graft-endplate interface in anterior cervical spine fusion. Spine (Phila Pa 1976) 26: , Matsumoto M, Ishii K, Takaishi H, Nakamura M, Morioka H, Chiba K, et al: Extensive total spondylectomy for recurrent giant cell tumor in the thoracic spine. Case report. J Neurosurg Spine 6: , Melcher I, Disch AC, Khodadadyan-Klostermann C, Tohtz S, Smolny M, Stöckle U, et al: Primary malignant bone tumors and solitary metastases of the thoracolumbar spine: results by management with total en bloc spondylectomy. Eur Spine J 16: , Murakami H, Kawahara N, Demura S, Kato S, Yoshioka K, Tomita K: Neurological function after total en bloc spondylectomy for thoracic spinal tumors. Clinical article. J Neurosurg Spine 12: , Roy-Camille R, Saillant G, Mazel CH, Monpierre H: Total vertebrectomy as treatment of malignant tumors of the spine. Chir Organi Mov 75 (1 Suppl):94 96, J Neurosurg: Spine / Volume 15 / September 2011

8 Late instrumentation failure 12. Sakaura H, Hosono N, Mukai Y, Ishii T, Yonenobu K, Yoshikawa H: Outcome of total en bloc spondylectomy for solitary metastasis of the thoracolumbar spine. J Spinal Disord Tech 17: , Togawa D, Bauer TW, Lieberman IH, Sakai H: Lumbar intervertebral body fusion cages: histological evaluation of clinically failed cages retrieved from humans. J Bone Joint Surg Am 86-A:70 79, Tomita K, Kawahara N, Baba H, Tsuchiya H, Nagata S, Toribatake Y: Total en bloc spondylectomy for solitary spinal metastases. Int Orthop 18: , Tomita K, Kawahara N, Kobayashi T, Yoshida A, Murakami H, Akamaru T: Surgical strategy for spinal metastases. Spine (Phila Pa 1976) 26: , Tomita K, Toribatake Y, Kawahara N, Ohnari H, Kose H: Total en bloc spondylectomy and circumspinal decompression for solitary spinal metastasis. Paraplegia 32:36 46, 1994 Manuscript submitted November 17, Accepted May 5, Please include this information when citing this paper: published online June 3, 2011; DOI: / SPINE Address correspondence to: Morio Matsumoto, M.D., Department of Orthopaedic Surgery, Keio University, Shinanomachi 35, Shinjuku-ku, Tokyo # , Japan. morio@sc.itc.keio. ac.jp. J Neurosurg: Spine / Volume 15 / September