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Efficacy and safety of the use of titanium mesh cages and anterior cervical plates for interbody fusion after anterior cervical corpectomy
Surgical Neurology 65 (2006) 464 – 471 www.surgicalneurology-online.com
Technology
Efficacy and safety of the use of titanium mesh cages and anterior cervical plates for interbody fusion after anterior cervical corpectomy Hao-Che Chuang, MD, Der-Yang Cho, MD4, Cheng-Siu Chang, MD, Wen-Yuen Lee, MD, Chen Jung-Chung, MD, Han-Chung Lee, MD, Chun-Chung Chen, MD Department of Neurosurgery, China Medical University Hospital, Taichung, Taiwan 404, Republic of China Received 31 May 2005; accepted 1 December 2005
Abstract
Background: To determine the safety and effectiveness of the use of titanium mesh cages (TMCs) and anterior cervical plates (ACPs) for interbody fusion after anterior cervical corpectomy. Methods: From June 2001 to June 2003, 15 patients underwent reconstruction with TMCs and ACPs for interbody fusion after anterior cervical corpectomy in our hospital. The mean follow-up is 13.6 months (range, 9-24 months). Subjects included those with cervical degenerative, traumatic, or pathological diseases. Titanium mesh cages were filled with autologous bone grafts taken from the corpectomy and iliac crest bone chips and were all filled with triosite (calcium phosphate ceramics). The patients’ observable signs, neurological reconstruction results, and complications were fully and explicitly recorded throughout the procedure. Radiological imaging studies for measurements of coronal and sagittal angles, sagittal displacements, and settling ratio changes were performed to evaluate spinal stability. We used axial cervical computed tomography (CT) and reconstructive sagittal cervical CT to demonstrate interbody fusion within titanium mesh. Results: The alleviation and frequent disappearance of the subjects’ original symptoms and the significant neurological recovery obvious in most patients indicated that postoperative spinal stability could be well maintained. No significant differences in mean cage height – related settling rates, mean sagittal displacements, and mean coronal and sagittal angle changes were observed between 1-level and multilevel corpectomy. All patients who received axial and reconstructive sagittal cervical CT scan could demonstrate true interbody fusion within TMC, and no nonunions were present. Cage malplacement was observed in one subject who had neck pain and neck stiffness, rather than from radiculopathy or myelopathy. One subject died of acute myocardial infarction. There were no ceramic-related complications. Conclusions: Based on preliminary findings from this study, reconstruction involving TMC interbody fusion with ACP fixation after anterior cervical corpectomy serves as an effective and safe method for the treatment of cervical disease. D 2006 Elsevier Inc. All rights reserved.
Keywords:
Anterior cervical plates; Cervical reconstruction; Corpectomy; Interbody fusion; Titanium mesh cage
1. Introduction
Abbreviations: ACP, anterior cervical plate; CSM, cervical spinal myelopathy; CSR, cervical spinal radiculopathy; HA, hydroxyapatite; JOA, Japanese Orthopedic Association; TMC, titanium mesh cage. 4 Corresponding author. Tel.: +886 42 2052121x4434; fax: +886 42 2052121x4435. E-mail addresses: [email protected], [email protected], [email protected] (D.-Y. Cho). 0090-3019/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2005.12.021
Anterior cervical fusion has been considered by many experts to be the treatment of choice for cervical disorders since its introduction by Smith and Robinson in 1958. Many presented papers revealed that anterior cervical fusion could provide both clinically satisfactory outcomes and radiographic stability. However, the choice of materials in interbody fusion and reconstruction of osseous defects after anterior discectomy or corpectomy is still controversial [33].
H.-C. Chuang et al. / Surgical Neurology 65 (2006) 464 – 471
Many materials have been used for interbody fusion and reconstruction in recent decades. Initially, autografts and allografts including tricortical iliac bony grafts, fibular struts, surgibone, or HA grafts were used, but a high morbidity rate was noted [25]. Donor site complications were reported in approximately 15% of patients including subcutaneous hematoma, femoral cutaneous injury, wound infection, and chronic wound pain. Nonunion, malunion, graft dislodge, and graft collapse were also reported throughout the literature. The traditional operation uses a segment of autologous bone graft to fill the corpectomy defect [26]. This method requires a large donor site graft, which increases the donor site complication rate. Autologous iliac bone grafts had been considered ideal fusion materials but are questioned because of harvesting-related morbidities [7]. Allografts such as cow bone or HA graft were also used for fusion, but have been demonstrated to yield a comparably high fusion rate [5]. Titanium mesh graft has been used recently because no donor site complication will occur. Because it has only been reported in a few preliminary reports [27,29], we evaluated the titanium mesh for post-corpectomy reconstruction for its spinal stability and clinical outcomes. 2. Materials and methods From June 2001 to June 2003, this study included 15 patients (9 males and 6 females) with an average follow-up period of 13.6 months (range, 9-24 months). Their ages ranged from 19 to 69 years old, with most patients younger than 60 years (Table 1). A total of 3 patients presented with radiculopathy, 4 patients presented with myelopathy, 5 patients presented with myeloradiculopathy, and 3 patients presented with symptoms of complete cervical spinal cord injury. The causes of cervical illness included 8 patients with degeneration diseases (spondylosis, OPLL), 6 patients with traumatic diseases (compression fracture, fracture dislocation), and 1 patient with pathological disease (cervical spinal metastases) (Table 2; Figs. 1-3) [19,20,32]. All patients underwent surgery with right anterior cervical approach. Corpectomy was done under microscope for spinal decompression and usually the posterior longitudinal ligament was removed until the spinal cord was free. All patients received TMCs (Titanium Mesh Cage, Mos Miami, United Kingdom) containing both autologous bone grafts taken from corpectomy bone chips and iliac crest, assisted with triosite in all patients. The TMCs were all locked with both upper and lower end caps to avoid and minimize subsidence of vertebral endplates. Then the TMCs were impacted into the post-corpectomy defect. Finally, constrained ACPs (Alpha plate, Dimso SA’Stryker, France) and screw fixed the upper and lower vertebral bone for supplementary fixation. The number of levels of corpectomies, height of TMCs, and diameter of TMCs are presented in Table 3. In
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this study, all patients were required to wear a neck collar for postoperative orthosis for at least 2 months. The presenting signs, neurological outcomes, and complications were recorded before and after operation. We used the JOA score to assess the clinical prognosis of neurological status. Complications of both donor site and operative site were observed. The Odom’s criteria were also used in this study to evaluate clinical outcome or recovery of occupational capacity. Radiographic assessment was performed preoperatively, immediately after the operation, and at 1, 3, 6, and 12 months postoperatively. Coronal angle, sagittal angle, and sagittal displacement ratios were used to evaluate the radiographic stability [25]. Because settling, subsidence, and telescoping were major morbidities of devices in interbody fusion, we evaluated the settling ratio to observe any hardware-related complications. Table 1 Demographic characteristics No. of patients Sex Male Female Age (y) b 50 50 - 60 N 60
9 6 7 5 3
Table 2 Patient symptoms and diagnoses No. of patients Symptoms Radiculopathy Myelopathy Myeloradiculopathy Complete cervical spinal cord injury Diagnoses Degenerative disease Spondylosis OPLL Traumatic disease Compression fracture Fracture dislocation Pathological disease Metastases
3 4 5 3 8 3 5 6 3 3 1 1
Table 3 Surgical histories No. of patients Levels of corpectomies 1 2 3 Height of TMCs (mm) b 40 N 40 Diameters of TMCs (mm) 10 12 14
8 5 2 12 3 5 9 1
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Fig. 1. This patient was diagnosed with OPLL, C5-C7. Anterior corpectomy of C6 followed by ACP fixation of C5-C7 was performed.
Because plain radiology is unable to evaluate bone growth within the TMCs because the metallic artifact has been cited for its drawbacks, we used axial cervical computed tomography (CT) and sagittal reconstructive cervical CT scans to attempt to demonstrate bone growth within the TMC 12 months after operation (Fig. 6A, B, and C).
3. Results 3.1. Clinical outcome We used the JOA score to evaluate the neurological prognosis before and after operation (Table 4). Eleven
patients experienced improvement of clinical neurological symptoms, 3 patients remained the same, and 1 patient became worse. The patient who became worse experienced an acute myocardial infarction after the operation and died. Odom’s criteria helped us to evaluate the recovery rate of patients’ occupational capacity and ability. Eleven patients had an excellent, good, or at least satisfactory rating and 4 patients had a rating of poor. Of those 4 patients with poor response, 3 patients presented with complete cervical spinal cord injury and 1 patient died (Tables 5 and 6). 3.2. Surgery-related morbidities Only 1 patient experienced dysphagia in this study.
Fig. 2. This patient was diagnosed with fracture dislocation of C4 and C5. Anterior corpectomy of C4 and C5 followed with ACP fixation of C3 - C6 was performed.
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Fig. 3. This patient was diagnosed with cervical spinal metastases with pathological fracture of C7. Anterior corpectomy of C7 followed with ACP fixation of C6-T1 was performed.
3.3. Donor site– related morbidities There were no donor site complications. 3.4. Ceramic-related morbidities
and hardware failure [25]. The settling ratio (Fig. 5) was used to evaluate the status of the radiographic stability of the TMCs. No patient experienced more than 10% of the so-called significant change of settling ratio in this study.
There were no ceramic-related complications. 3.5. Radiographic assessment On anteroposterior films, coronal angle was assessed to evaluate the radiographic stability of the TMCs (Fig. 4). The films taken immediately after the operation served as baseline films, and if the coronal angle changed more than 108 at each follow-up period, it was considered a significant instability. In this study, no patients experienced significant instability (all changes were b 108) (Table 7). On lateral films, we used the sagittal angle and the sagittal displacement ratio (Fig. 5) to evaluate the morbidities of graft collapse, extrusion, or progressive kyphosis. Kyphosis of the sagittal alignment increases the load on the anterior cervical spine with acceleration of degeneration at the adjacent segments [13]. In this study, no patients experienced a change in sagittal angle of more than 108, which indicated no significant instability. Only 1 patient experienced more than 10% of the so-called significant instability in sagittal displacement ratio. This was a 3-level corpectomy assisted with a significantly long (73 mm) TMC interbody fusion. Malplacement of the TMCs was noted intermittently in the postoperative plain film. This patient reported neck pain but no CSM or CSR irritation at the 6-month follow-up. Settling ratio. The relationship between the vertebral endplate and the TMC is important. It may indirectly decrease the height of the disc space and cause narrowing of the neuroforamen. It is also easy to induce kyphotic change
Table 4 Recovery rates (JOA scores) Recovery rate of JOA scores
No. of patients
Better No change Worse
11 3 1
Table 5 Complications No. of patients Surgery-related complications Dysphonia Dysphagia Epidural hematoma Wound infection Donor site – related complications Graft site pain Graft site infection Graft site numbness
0 1 0 0 3 0 2
Table 6 Recovery (Odom’s criteria) Recovery of Odom’s criteria
No. of patients
Excellent Good Satisfactory Poor
6 4 1 4
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Fig. 4. Sagittal angle was used to evaluate the morbidities of graft collapse, extrusion, or progressive kyphosis. Kyphosis of the sagittal alignment increases the load on the anterior cervical spine with acceleration of degeneration at the adjacent segments. In this study, no patients experienced a change in sagittal angle of more than 108, which indicated no significant instability. On anteroposterior films, coronal angle was assessed to evaluate the radiographic stability of the TMCs. The films taken immediately after the operation served as baseline films, and if the coronal angle changed more than 108 at each follow-up period, it was considered a significant instability. In this study, no patients experienced significant instability (all changes were b 10 8).
Fusion rate. We used the axial CT and sagittal reconstructive CT scans to attempt to demonstrate bone growth within the TMC (Fig. 6A, B, and C). From the CT scan, we noticed that mature bony trabeculae bridging the interbody space (sentinel sign) were present, and it means true interbody fusion occurs. In our study, all patients were arranged to receive cervical CT scan 1 year after operation. In all patients who underwent CT scan survey, exactly mature bony trabeculae bridging within TMC are all demonstrated.
4. Discussion The goals of interbody fusion devices are to provide spinal stability or arthrodesis environment and to reduce associated morbidity. 4.1. Spinal stability and outcomes Because low settling rate was noted in this study, the TMCs could keep the height of interbody space and neuroforamen rigidly. The anterior correction of the cervical kyphotic deformity can improve myelopathy, neck pain, and sagittal alignment [6,13]. In these cases, there were no significant changes in sagittal angle or sagittal displacement ratio. In this study, we improved the prognosis of radiographic stability. There were no significant changes in coronal angle, sagittal angle, and settling ratio. Early radiographic stability is predicted in almost all patients and it could possibly lead to successful fusion [8,22]. Usually, the postoperative spinal stability is closely related to clinical
outcome. Therefore, improvement of JOA score and Odom’s score would be expected. In this study, more than 70% of patients had a better JOA score and Odom’s criteria. More than 90% of patients have both clinical and radiographic stability, especially
Table 7 Changes No. of patients Change in sagittal angle None 1- 48 5 - 98 N 108 Not readable Change in coronal angle None 1- 48 5 - 98 N 108 Not readable Change in sagittal displacement None 1-5% 6 - 9% N 10% Not readable Change in settling ratio None 1-5% 6 - 9% N 10% Not readable
2 10 2 0 1 2 11 1 0 1 3 5 4 1 2 7 3 3 0 2
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Fig. 5. Sagittal displacement ratio was used to evaluate the morbidities of graft collapse, extrusion, or progressive kyphosis. In this study, no patients experienced a change in sagittal angle of more than 108, which indicated no significant instability. The settling ratio was used to evaluate the status of the radiographic stability of the TMCs. No patient experienced more than 10% of the so-called significant change of settling ratio in this study.
early stability. No donor site infection was reported. During follow-up, there were no collapses of the TMC and no displacement of ACPs. There were nearly no surgery-related complications, with only 1 patient experiencing dysphagia. Malplacement of the TMCs was noted in 1 patient, but the patient only experienced neck pain without CSM or CSR. Only 1 patient died during the study due to acute myocardial infarction. Epstein [11,12,18] reported that ACPs can provide stabilization to supplement the interbody fusion devices. This can decrease the occurrence of settling ratio, subsidence, and early hardware failure. In our opinion, internal fixation with ACPs may help the TMCs to avoid migration. Although there were no significant relationships between construct length and graft subsidence in the literature [4,7,25], we experienced a problem maintaining stability possibly related to the length of the TMCs. In this study, a patient with 3 levels of cervical corpectomy with TMC interbody fusion experienced cage displacement. No screw fixation between the TMC and ACP was prone to cause cage instability if the TMC length is longer. Unlike the tricortical iliac bony graft, we could insert 1 or more screws into the graft and perform more supplementation of fixation. Especially in an osteoporotic patient, spinal instability is not well maintained. 4.2. Fusion We used TMCs with autologous bony graft from the corpectomy bone chips. If there were not enough bone chips, we added triosite to fill the cages. All patients have an intermittently stable radiographic status of cages and instruments, and it may lead to successful fusion. In many presented papers, cages filled with autologous bony
graft can cause clinical, radiographic, and histological fusion [1-3,10,16,17,20,30,31]. Triosite is composed of 40% beta-calcium phosphate and 60% HA. Hydroxyapatite was noted to have new bone growth in a goat study by Mooney et al [24]. Triosite can be used to prevent donor site complications because we need no more wound for autograft donation. Because pure HA graft for interbody frequently leads to graft collapse, dislodge, and nonunion [28], TMCs filled with triosite and assisted with ACPs interbody fusion may create a better environment for successful fusion. According to Cho et al [4], triosite ceramic in a polyetheretherketone cage for cervical spondylosis may provide radiographic fusion after 6 months of follow-up. Time to fusion is later in a polyetheretherketone cage with autograft filled. Because there are no donor site– related complications, the use of triosite can shorten hospital stay, reduce blood loss, and reduce operation time. Because titanium mesh is not radiolucent, we cannot directly determine if trabeculation has occurred. Because intracage fusion is very difficult to assess, plain radiographic evaluation of extracage fusion may be facilitated by placement of the graft outside and around cages against the decorticated endplate [9]. We also can use indirect evidence to judge the successful fusion, such as lack of movement on dynamic views [23] or absence of periimplant lucencies [14]. In this study, almost all patients have intermittently radiographic stability at follow-up. According to Hanley et al [15], we should be able to predict fusion rate by the presence of mature bony trabeculae bridging the interbody space, the so-called sentinel sign. We can use the axial CT and sagittal reconstructive CT scans to attempt to demonstrate bone growth within
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Fig. 6. Axial CT (A) and sagittal reconstructive CT scans (B, C) are used to demonstrate bone growth within the TMC. From the CT scan, mature bony trabeculae bridging the interbody space (sentinel sign) were present, and it means true interbody fusion occurs.
the TMC (Fig. 6A and B). From the CT scan, we noticed that mature bony trabeculae bridging the interbody space (sentinel sign) were present, and it means true interbody fusion occurs.
favorable materials for cervical interbody fusion and reconstruction [5,6,8,10,16-19,21,22,26,27,29-33].
References 5. Conclusion Titanium mesh cage interbody fusion assisted with ACP fixation can correct kyphotic deformation of C-spine and lead to neurological improvement. Clinical and radiographic stability can create a wonderful environment for successful fusion. Titanium is not a radiolucent material so we must evaluate fusion status indirectly. Sagittal reconstruction of axial and sagittal CT scan is attempting to demonstrate bone growth within the TMC. Titanium mesh cages/ACPs have been used to reconstruct the anatomic structure of vertebral space after corpectomy. Titanium mesh cages/ACPs may also be
[1] Akamaru T, Kawahara N, Tsuchiya H, et al. Healing of autologous bone in a titanium mesh cage used in anterior column reconstruction after total spondylectomy. Spine 2002;27:E329 - 33. [2] Brantigan JW, Steffee AD, Geiger JM. A carbon fiber cage implant to aid interbody lumbar fusion. Mechanical testing. Spine 1991;16: 277 - 82. [3] Brodke DS, Willie BM, Maaranen EA, et al. Spinal cage retrieval and assessment of biologic response. J Spinal Disord Tech 2002;15: 206 - 12. [4] Cho DY, Liau WR, Lee WY, et al. Preliminary experience using a polyetheretherketone (PEEK) cage in the treatment of cervical disc disease. Neurosurgery 2002;51:1343 - 9. [5] Cook SD, Reynolds MC, Whitecloud TS, et al. Evaluation of hydroxylapatite graft materials in canine cervical spine fusions. Spine 1986;11:305 - 9.
H.-C. Chuang et al. / Surgical Neurology 65 (2006) 464 – 471 [6] Cunningham BW, Polly Jr DW. The use of interbody cage devices for spinal deformity: a biomechanical perspective. Clin Orthop Relat Res 2002;394:73 - 83. [7] Dorai Z, Morgan H, Coimbra C. Titanium cage reconstruction after cervical corpectomy. J Neurosurg 2003;(1 Suppl):3 - 7. [8] Dvorak MF, Kwon BK, Fisher CG, et al. Effectiveness of titanium mesh cylindrical cages in anterior column reconstruction after thoracic and lumbar vertebral body resection. Spine 2003;28:902 - 8. [9] Eck KR, Bridwell KH, Ungacta FF, et al. Analysis of titanium mesh cages in adults with minimum two-year follow-up. Spine 2000;25: 2407 - 15. [10] Eck KR, Lenke LG, Bridwell KH, et al. Radiographic assessment of anterior titanium mesh cages. J Spinal Disord 2000;13:501 - 9. [11] Epstein NE. Anterior cervical diskectomy and fusion without plate instrumentation in 178 patients. J Spinal Disord 2000;13:1 - 8. [12] Epstein NE. Reoperation rates for acute graft extrusion and pseudoarthrosis after one level anterior corpectomy and fusion with and without plate instrumentation: etiology and corrective management. Surg Neurol 2001;56:73 - 81. [13] Ferch RD, Shad A, Cadoux-Hudson TA, et al. Anterior correction of cervical kyphotic deformity: effects on myelopathy, neck pain, and sagittal alignment. J Neurosurg 2004;(1 Suppl Spine):13 - 9. [14] Hacker RJ, Cauthen JC, Gilbert TJ, et al. A prospective randomized multicenter clinical evaluation of an anterior cervical fusion cage. Spine 2000;25:2646 - 54. [15] Hanley SD, Gun MT, Osti O, et al. Radiology of intervertebral cages in spinal surgery. Clin Radiol 1999;54:201 - 6. [16] Hasegawa K, Abe M, Washio T, et al. An experimental study on the interface strength between titanium mesh cage and vertebra in reference to vertebral bone mineral density. Spine 2001;26:957 - 63. [17] Hee HT, Majd ME, Holt RT, et al. Complications of multilevel cervical corpectomies and reconstruction with titanium cages and anterior plating. J Spinal Disord Tech 2003;16:1 - 9. [18] Hoshijima K, Nightingale RW, Yu JR, et al. Strength and stability of posterior lumbar interbody fusion: comparison of titanium fiber mesh cage implant and tricortical bone graft. Spine 1997;22:1181 - 8. [19] Kanayama M, Cunningham BW, Haggerty CJ, et al. In vitro biochemical investigation of the stability and stress-shielding effect of lumbar interbody fusion devices. J Neurosurg 2000; 93(2 Suppl):259 - 65. [20] Klemme WR, Cunningham BW, Polly Jr LDDW. Microradiographic and histopathologic findings in a human cage explant after two-level corpectomy: a case report. Spine 2002;27:E15 - 7. [21] Majd ME, Vadhva M, Holt RT. Anterior cervical reconstruction using titanium mesh cages with anterior plating. Spine 1999;24:1604 - 10. [22] Masciopinto JE, Johnson JP, et al. Interbody fusion in infections. Tech Neurosurg 2001;7:162 - 8. [23] McAfee PC. Interbody fusion cages in reconstructive operations of the spine. J Bone Joint Surg Am 1999;81:859 - 80.
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[24] Mooney V, Massie JB, Lind BI, et al. Comparison of hydroxyapatite granules to autogeneous bone graft in fusion cages in a goat model. Surg Neurol 1998;49:628 - 33. [25] Narotam PK, Pauley SM, McGinn GJ. Titanium mesh cages for cervical spine stabilization after corpectomy: a clinical and radiological study. J Neurosurg 2003;(2 Suppl):172 - 80. [26] Rieger A, Holz C, Marx T, et al. Vertebral autograft used as bone transplant for anterior cervical corpectomy: technical note. Neurosurgery 2003;52:449 - 54. [27] Riew KD, Rhee JM. The use of titanium mesh cages in the cervical spine. Clin Orthop Relat Res 2002;394:47 - 54. [28] Thalgott JS, Fritts K, Giuffre JM, et al. Anterior interbody fusion of the cervical spine with coralline hydroxyapatite. Spine 1999;24: 1295 - 9. [29] Theodore N, Vishteh AG, et al. Titanium mesh cage interbody fusion in the thoracolumbar spine. Tech Neurosurg 2001;7:119 - 26. [30] Togawa D, Bauer TW, Brantigan JW, et al. Bone graft incorporation in radiographically successful human intervertebral body fusion cages. Spine 2001;26:2744 - 50. [31] Togawa D, Bauer TW, Lieberman IH, et al. Histology of tissues within reserved human titanium mesh cages. Spine 2003;28:246 - 53. [32] Weigel B, Maghsudi M, Neumann C, et al. Surgical management of symptomatic spinal metastases. Spine 1999;24:2240 - 6. [33] Winn RH. Youmans neurological surgery. 5th ed. Philadelphia7 Saunders; 2004.
Commentary Chuang et al discuss their experience reconstructing cervical vertebral body defects after corpectomy using titanium mesh cages filled with autograft and calcium phosphate ceramic material. The cages were supplemented with screw plate fixation. The clinical results in this small series are acceptable. Titanium mesh cages appear to provide an acceptable way to reconstruct the anterior column after corpectomy. These cages provide a strut graft, but are not meant to serve as stand-alone devices. They require supplemental internal fixation with screws and plates. Curtis A. Dickman, MD Barrow Neurological Institute Phoenix, AZ 85013, USA
Technology
Efficacy and safety of the use of titanium mesh cages and anterior cervical plates for interbody fusion after anterior cervical corpectomy Hao-Che Chuang, MD, Der-Yang Cho, MD4, Cheng-Siu Chang, MD, Wen-Yuen Lee, MD, Chen Jung-Chung, MD, Han-Chung Lee, MD, Chun-Chung Chen, MD Department of Neurosurgery, China Medical University Hospital, Taichung, Taiwan 404, Republic of China Received 31 May 2005; accepted 1 December 2005
Abstract
Background: To determine the safety and effectiveness of the use of titanium mesh cages (TMCs) and anterior cervical plates (ACPs) for interbody fusion after anterior cervical corpectomy. Methods: From June 2001 to June 2003, 15 patients underwent reconstruction with TMCs and ACPs for interbody fusion after anterior cervical corpectomy in our hospital. The mean follow-up is 13.6 months (range, 9-24 months). Subjects included those with cervical degenerative, traumatic, or pathological diseases. Titanium mesh cages were filled with autologous bone grafts taken from the corpectomy and iliac crest bone chips and were all filled with triosite (calcium phosphate ceramics). The patients’ observable signs, neurological reconstruction results, and complications were fully and explicitly recorded throughout the procedure. Radiological imaging studies for measurements of coronal and sagittal angles, sagittal displacements, and settling ratio changes were performed to evaluate spinal stability. We used axial cervical computed tomography (CT) and reconstructive sagittal cervical CT to demonstrate interbody fusion within titanium mesh. Results: The alleviation and frequent disappearance of the subjects’ original symptoms and the significant neurological recovery obvious in most patients indicated that postoperative spinal stability could be well maintained. No significant differences in mean cage height – related settling rates, mean sagittal displacements, and mean coronal and sagittal angle changes were observed between 1-level and multilevel corpectomy. All patients who received axial and reconstructive sagittal cervical CT scan could demonstrate true interbody fusion within TMC, and no nonunions were present. Cage malplacement was observed in one subject who had neck pain and neck stiffness, rather than from radiculopathy or myelopathy. One subject died of acute myocardial infarction. There were no ceramic-related complications. Conclusions: Based on preliminary findings from this study, reconstruction involving TMC interbody fusion with ACP fixation after anterior cervical corpectomy serves as an effective and safe method for the treatment of cervical disease. D 2006 Elsevier Inc. All rights reserved.
Keywords:
Anterior cervical plates; Cervical reconstruction; Corpectomy; Interbody fusion; Titanium mesh cage
1. Introduction
Abbreviations: ACP, anterior cervical plate; CSM, cervical spinal myelopathy; CSR, cervical spinal radiculopathy; HA, hydroxyapatite; JOA, Japanese Orthopedic Association; TMC, titanium mesh cage. 4 Corresponding author. Tel.: +886 42 2052121x4434; fax: +886 42 2052121x4435. E-mail addresses: [email protected], [email protected], [email protected] (D.-Y. Cho). 0090-3019/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2005.12.021
Anterior cervical fusion has been considered by many experts to be the treatment of choice for cervical disorders since its introduction by Smith and Robinson in 1958. Many presented papers revealed that anterior cervical fusion could provide both clinically satisfactory outcomes and radiographic stability. However, the choice of materials in interbody fusion and reconstruction of osseous defects after anterior discectomy or corpectomy is still controversial [33].
H.-C. Chuang et al. / Surgical Neurology 65 (2006) 464 – 471
Many materials have been used for interbody fusion and reconstruction in recent decades. Initially, autografts and allografts including tricortical iliac bony grafts, fibular struts, surgibone, or HA grafts were used, but a high morbidity rate was noted [25]. Donor site complications were reported in approximately 15% of patients including subcutaneous hematoma, femoral cutaneous injury, wound infection, and chronic wound pain. Nonunion, malunion, graft dislodge, and graft collapse were also reported throughout the literature. The traditional operation uses a segment of autologous bone graft to fill the corpectomy defect [26]. This method requires a large donor site graft, which increases the donor site complication rate. Autologous iliac bone grafts had been considered ideal fusion materials but are questioned because of harvesting-related morbidities [7]. Allografts such as cow bone or HA graft were also used for fusion, but have been demonstrated to yield a comparably high fusion rate [5]. Titanium mesh graft has been used recently because no donor site complication will occur. Because it has only been reported in a few preliminary reports [27,29], we evaluated the titanium mesh for post-corpectomy reconstruction for its spinal stability and clinical outcomes. 2. Materials and methods From June 2001 to June 2003, this study included 15 patients (9 males and 6 females) with an average follow-up period of 13.6 months (range, 9-24 months). Their ages ranged from 19 to 69 years old, with most patients younger than 60 years (Table 1). A total of 3 patients presented with radiculopathy, 4 patients presented with myelopathy, 5 patients presented with myeloradiculopathy, and 3 patients presented with symptoms of complete cervical spinal cord injury. The causes of cervical illness included 8 patients with degeneration diseases (spondylosis, OPLL), 6 patients with traumatic diseases (compression fracture, fracture dislocation), and 1 patient with pathological disease (cervical spinal metastases) (Table 2; Figs. 1-3) [19,20,32]. All patients underwent surgery with right anterior cervical approach. Corpectomy was done under microscope for spinal decompression and usually the posterior longitudinal ligament was removed until the spinal cord was free. All patients received TMCs (Titanium Mesh Cage, Mos Miami, United Kingdom) containing both autologous bone grafts taken from corpectomy bone chips and iliac crest, assisted with triosite in all patients. The TMCs were all locked with both upper and lower end caps to avoid and minimize subsidence of vertebral endplates. Then the TMCs were impacted into the post-corpectomy defect. Finally, constrained ACPs (Alpha plate, Dimso SA’Stryker, France) and screw fixed the upper and lower vertebral bone for supplementary fixation. The number of levels of corpectomies, height of TMCs, and diameter of TMCs are presented in Table 3. In
465
this study, all patients were required to wear a neck collar for postoperative orthosis for at least 2 months. The presenting signs, neurological outcomes, and complications were recorded before and after operation. We used the JOA score to assess the clinical prognosis of neurological status. Complications of both donor site and operative site were observed. The Odom’s criteria were also used in this study to evaluate clinical outcome or recovery of occupational capacity. Radiographic assessment was performed preoperatively, immediately after the operation, and at 1, 3, 6, and 12 months postoperatively. Coronal angle, sagittal angle, and sagittal displacement ratios were used to evaluate the radiographic stability [25]. Because settling, subsidence, and telescoping were major morbidities of devices in interbody fusion, we evaluated the settling ratio to observe any hardware-related complications. Table 1 Demographic characteristics No. of patients Sex Male Female Age (y) b 50 50 - 60 N 60
9 6 7 5 3
Table 2 Patient symptoms and diagnoses No. of patients Symptoms Radiculopathy Myelopathy Myeloradiculopathy Complete cervical spinal cord injury Diagnoses Degenerative disease Spondylosis OPLL Traumatic disease Compression fracture Fracture dislocation Pathological disease Metastases
3 4 5 3 8 3 5 6 3 3 1 1
Table 3 Surgical histories No. of patients Levels of corpectomies 1 2 3 Height of TMCs (mm) b 40 N 40 Diameters of TMCs (mm) 10 12 14
8 5 2 12 3 5 9 1
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Fig. 1. This patient was diagnosed with OPLL, C5-C7. Anterior corpectomy of C6 followed by ACP fixation of C5-C7 was performed.
Because plain radiology is unable to evaluate bone growth within the TMCs because the metallic artifact has been cited for its drawbacks, we used axial cervical computed tomography (CT) and sagittal reconstructive cervical CT scans to attempt to demonstrate bone growth within the TMC 12 months after operation (Fig. 6A, B, and C).
3. Results 3.1. Clinical outcome We used the JOA score to evaluate the neurological prognosis before and after operation (Table 4). Eleven
patients experienced improvement of clinical neurological symptoms, 3 patients remained the same, and 1 patient became worse. The patient who became worse experienced an acute myocardial infarction after the operation and died. Odom’s criteria helped us to evaluate the recovery rate of patients’ occupational capacity and ability. Eleven patients had an excellent, good, or at least satisfactory rating and 4 patients had a rating of poor. Of those 4 patients with poor response, 3 patients presented with complete cervical spinal cord injury and 1 patient died (Tables 5 and 6). 3.2. Surgery-related morbidities Only 1 patient experienced dysphagia in this study.
Fig. 2. This patient was diagnosed with fracture dislocation of C4 and C5. Anterior corpectomy of C4 and C5 followed with ACP fixation of C3 - C6 was performed.
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Fig. 3. This patient was diagnosed with cervical spinal metastases with pathological fracture of C7. Anterior corpectomy of C7 followed with ACP fixation of C6-T1 was performed.
3.3. Donor site– related morbidities There were no donor site complications. 3.4. Ceramic-related morbidities
and hardware failure [25]. The settling ratio (Fig. 5) was used to evaluate the status of the radiographic stability of the TMCs. No patient experienced more than 10% of the so-called significant change of settling ratio in this study.
There were no ceramic-related complications. 3.5. Radiographic assessment On anteroposterior films, coronal angle was assessed to evaluate the radiographic stability of the TMCs (Fig. 4). The films taken immediately after the operation served as baseline films, and if the coronal angle changed more than 108 at each follow-up period, it was considered a significant instability. In this study, no patients experienced significant instability (all changes were b 108) (Table 7). On lateral films, we used the sagittal angle and the sagittal displacement ratio (Fig. 5) to evaluate the morbidities of graft collapse, extrusion, or progressive kyphosis. Kyphosis of the sagittal alignment increases the load on the anterior cervical spine with acceleration of degeneration at the adjacent segments [13]. In this study, no patients experienced a change in sagittal angle of more than 108, which indicated no significant instability. Only 1 patient experienced more than 10% of the so-called significant instability in sagittal displacement ratio. This was a 3-level corpectomy assisted with a significantly long (73 mm) TMC interbody fusion. Malplacement of the TMCs was noted intermittently in the postoperative plain film. This patient reported neck pain but no CSM or CSR irritation at the 6-month follow-up. Settling ratio. The relationship between the vertebral endplate and the TMC is important. It may indirectly decrease the height of the disc space and cause narrowing of the neuroforamen. It is also easy to induce kyphotic change
Table 4 Recovery rates (JOA scores) Recovery rate of JOA scores
No. of patients
Better No change Worse
11 3 1
Table 5 Complications No. of patients Surgery-related complications Dysphonia Dysphagia Epidural hematoma Wound infection Donor site – related complications Graft site pain Graft site infection Graft site numbness
0 1 0 0 3 0 2
Table 6 Recovery (Odom’s criteria) Recovery of Odom’s criteria
No. of patients
Excellent Good Satisfactory Poor
6 4 1 4
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Fig. 4. Sagittal angle was used to evaluate the morbidities of graft collapse, extrusion, or progressive kyphosis. Kyphosis of the sagittal alignment increases the load on the anterior cervical spine with acceleration of degeneration at the adjacent segments. In this study, no patients experienced a change in sagittal angle of more than 108, which indicated no significant instability. On anteroposterior films, coronal angle was assessed to evaluate the radiographic stability of the TMCs. The films taken immediately after the operation served as baseline films, and if the coronal angle changed more than 108 at each follow-up period, it was considered a significant instability. In this study, no patients experienced significant instability (all changes were b 10 8).
Fusion rate. We used the axial CT and sagittal reconstructive CT scans to attempt to demonstrate bone growth within the TMC (Fig. 6A, B, and C). From the CT scan, we noticed that mature bony trabeculae bridging the interbody space (sentinel sign) were present, and it means true interbody fusion occurs. In our study, all patients were arranged to receive cervical CT scan 1 year after operation. In all patients who underwent CT scan survey, exactly mature bony trabeculae bridging within TMC are all demonstrated.
4. Discussion The goals of interbody fusion devices are to provide spinal stability or arthrodesis environment and to reduce associated morbidity. 4.1. Spinal stability and outcomes Because low settling rate was noted in this study, the TMCs could keep the height of interbody space and neuroforamen rigidly. The anterior correction of the cervical kyphotic deformity can improve myelopathy, neck pain, and sagittal alignment [6,13]. In these cases, there were no significant changes in sagittal angle or sagittal displacement ratio. In this study, we improved the prognosis of radiographic stability. There were no significant changes in coronal angle, sagittal angle, and settling ratio. Early radiographic stability is predicted in almost all patients and it could possibly lead to successful fusion [8,22]. Usually, the postoperative spinal stability is closely related to clinical
outcome. Therefore, improvement of JOA score and Odom’s score would be expected. In this study, more than 70% of patients had a better JOA score and Odom’s criteria. More than 90% of patients have both clinical and radiographic stability, especially
Table 7 Changes No. of patients Change in sagittal angle None 1- 48 5 - 98 N 108 Not readable Change in coronal angle None 1- 48 5 - 98 N 108 Not readable Change in sagittal displacement None 1-5% 6 - 9% N 10% Not readable Change in settling ratio None 1-5% 6 - 9% N 10% Not readable
2 10 2 0 1 2 11 1 0 1 3 5 4 1 2 7 3 3 0 2
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Fig. 5. Sagittal displacement ratio was used to evaluate the morbidities of graft collapse, extrusion, or progressive kyphosis. In this study, no patients experienced a change in sagittal angle of more than 108, which indicated no significant instability. The settling ratio was used to evaluate the status of the radiographic stability of the TMCs. No patient experienced more than 10% of the so-called significant change of settling ratio in this study.
early stability. No donor site infection was reported. During follow-up, there were no collapses of the TMC and no displacement of ACPs. There were nearly no surgery-related complications, with only 1 patient experiencing dysphagia. Malplacement of the TMCs was noted in 1 patient, but the patient only experienced neck pain without CSM or CSR. Only 1 patient died during the study due to acute myocardial infarction. Epstein [11,12,18] reported that ACPs can provide stabilization to supplement the interbody fusion devices. This can decrease the occurrence of settling ratio, subsidence, and early hardware failure. In our opinion, internal fixation with ACPs may help the TMCs to avoid migration. Although there were no significant relationships between construct length and graft subsidence in the literature [4,7,25], we experienced a problem maintaining stability possibly related to the length of the TMCs. In this study, a patient with 3 levels of cervical corpectomy with TMC interbody fusion experienced cage displacement. No screw fixation between the TMC and ACP was prone to cause cage instability if the TMC length is longer. Unlike the tricortical iliac bony graft, we could insert 1 or more screws into the graft and perform more supplementation of fixation. Especially in an osteoporotic patient, spinal instability is not well maintained. 4.2. Fusion We used TMCs with autologous bony graft from the corpectomy bone chips. If there were not enough bone chips, we added triosite to fill the cages. All patients have an intermittently stable radiographic status of cages and instruments, and it may lead to successful fusion. In many presented papers, cages filled with autologous bony
graft can cause clinical, radiographic, and histological fusion [1-3,10,16,17,20,30,31]. Triosite is composed of 40% beta-calcium phosphate and 60% HA. Hydroxyapatite was noted to have new bone growth in a goat study by Mooney et al [24]. Triosite can be used to prevent donor site complications because we need no more wound for autograft donation. Because pure HA graft for interbody frequently leads to graft collapse, dislodge, and nonunion [28], TMCs filled with triosite and assisted with ACPs interbody fusion may create a better environment for successful fusion. According to Cho et al [4], triosite ceramic in a polyetheretherketone cage for cervical spondylosis may provide radiographic fusion after 6 months of follow-up. Time to fusion is later in a polyetheretherketone cage with autograft filled. Because there are no donor site– related complications, the use of triosite can shorten hospital stay, reduce blood loss, and reduce operation time. Because titanium mesh is not radiolucent, we cannot directly determine if trabeculation has occurred. Because intracage fusion is very difficult to assess, plain radiographic evaluation of extracage fusion may be facilitated by placement of the graft outside and around cages against the decorticated endplate [9]. We also can use indirect evidence to judge the successful fusion, such as lack of movement on dynamic views [23] or absence of periimplant lucencies [14]. In this study, almost all patients have intermittently radiographic stability at follow-up. According to Hanley et al [15], we should be able to predict fusion rate by the presence of mature bony trabeculae bridging the interbody space, the so-called sentinel sign. We can use the axial CT and sagittal reconstructive CT scans to attempt to demonstrate bone growth within
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Fig. 6. Axial CT (A) and sagittal reconstructive CT scans (B, C) are used to demonstrate bone growth within the TMC. From the CT scan, mature bony trabeculae bridging the interbody space (sentinel sign) were present, and it means true interbody fusion occurs.
the TMC (Fig. 6A and B). From the CT scan, we noticed that mature bony trabeculae bridging the interbody space (sentinel sign) were present, and it means true interbody fusion occurs.
favorable materials for cervical interbody fusion and reconstruction [5,6,8,10,16-19,21,22,26,27,29-33].
References 5. Conclusion Titanium mesh cage interbody fusion assisted with ACP fixation can correct kyphotic deformation of C-spine and lead to neurological improvement. Clinical and radiographic stability can create a wonderful environment for successful fusion. Titanium is not a radiolucent material so we must evaluate fusion status indirectly. Sagittal reconstruction of axial and sagittal CT scan is attempting to demonstrate bone growth within the TMC. Titanium mesh cages/ACPs have been used to reconstruct the anatomic structure of vertebral space after corpectomy. Titanium mesh cages/ACPs may also be
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Commentary Chuang et al discuss their experience reconstructing cervical vertebral body defects after corpectomy using titanium mesh cages filled with autograft and calcium phosphate ceramic material. The cages were supplemented with screw plate fixation. The clinical results in this small series are acceptable. Titanium mesh cages appear to provide an acceptable way to reconstruct the anterior column after corpectomy. These cages provide a strut graft, but are not meant to serve as stand-alone devices. They require supplemental internal fixation with screws and plates. Curtis A. Dickman, MD Barrow Neurological Institute Phoenix, AZ 85013, USA