C-arm Cone-beam CT: Applications for Spinal Cement Augmentation Demonstrated

Transcription

1 C-arm Cone-beam CT: Applications for Spinal Cement Augmentation Demonstrated by Three Cases Jesse R. Knight, MD, Manraj Heran, MD, Peter L. Munk, MD, FRCPC, Rodney Raabe, MD, and David M. Liu, MD Spinal canal narrowing as a result of retropulsion of spinal structures before or during cement augmentation has been considered a contraindication to therapy. The authors describe three cases of compression fractures safely treated with cement augmentation with the novel application of C-arm cone-beam computed tomography (CT). All cases involved small amounts of posterior cement extrusion, after which osteotomy needles were left in place during C-arm cone-beam CT. Rapidly reformatted images were viewed with the use of bone windows, yielding three-dimensional visualization of pertinent anatomy to confirm endpoints of posterior extrusion and adequate bone filling. J Vasc Interv Radiol 2008; 19: Abbreviation: 3D three-dimensional CEMENT augmentation has been established as a method to primarilyreport is not to address nor discuss the margin has been problematic, espe- a balloon tamp. The purpose of thisdisruption of the posterior cortical relieve pain caused by vertebral com-controverspression fracture. Although applications of vertebroplasty, kyphoplasty, cement (ie, polymerized methyl- surrounding the applicacially with the injection of thin bone tions vary, osteoporosis and tumoral or other cement augmentation techniques (1,2), but rather to describe asystems. In this setting, rapid influx of methacrylate) through small needle infiltration remain the most common indications. Vertebroplasty has remained a popular choice as a result of computed tomography (CT) during the vertebral body can occur very sud- novel application of C-arm cone-beam cement into the posterior column of its proven efficacy, relatively smaller cement augmentation to further in- the safety and efficacy of ther-extrusion of bone cement may also redenly and unpredictably. End-plate cannula (vs that used for kypho-creasplasty), speed, and cost. Kyphoplasty apy. sult suddenly because of the compromised cortical bone. has been gaining popularity as a Feared complications of these ce- augmentation procedures in- A number of techniques have been method in which kyphotic wedging ofment the compression fracture can be re-cludversed, and it allows injection of ce-and end-plate breakthrough. These these two complications occurring. posterior extrusion of cement developed to minimize the chances of ment into a preformed cavity throughcomplications may occur as a result ofthe use of biplane fluoroscopic guidance during the procedure has been displacement of cancellous bone with cortical disruption by tumor infiltration. There have been suggestions of aused to allow continuous two-plane considerable increase in complication monitoring and mental construction of rate when performing vertebroplasty a three-dimensional (3D) model of the From the Angiography and Interventional Radiology Section (J.R.K., R.R., D.M.L.), Inland Imaging, or kyphoplasty in the setting of patho-vertebralogic fractures with posterior break- use of CT-guided fluoroscopy has also body. In a similar fashion, 801 South Stevens Street, Spokane, WA 99204; and Department of Radiology (M.H., P.LM.), Vancouver through (3). A published study of thebeen touted as potentially useful for General Hospital, Vancouver, British Columbia, incidence and consequences of posterior wall breakthrough 4) ( demon- distribution, as well as identification real-time observation of bone cement Canada. Received September 12, 2007; final revision received February 27, 2008; accepted April 7, Address correspondence to D.M.L.; strated that cord compression requiring surgical decompression and death (5). of tumor infiltration and bone density dliu@inlandimaging.com has occurred as a result of uncontrolled extravasation of cement outphy has revolutionized cerebral an- The advent of rotational angiogra- None of the authors have identified a conflict of interest. side the vertebral body. In earlier ex-giographperiences, the posterior extrusion of tions of cerebral vasculature, thereby in allowing 3D reconstruc- SIR, 2008 DOI: /j.jvir contrast medium as a result of tumoralallowing for better characterization of 1118

2 Volume 19 Number 7 Knight et al 1119 Figure 1. Reformatted c-arm cone-beam CT image demonstrates retropulsion of metastatic vertebral compression fracture of T9 with irregular posterior cortex in sagittal (a) and axial (b) planes. After subsequent injection of bone cement with adequate filling of cortex, there is no evidence of posterior cortical displacement (thick arrow) and end-plate breakthrough (thin arrow), resulting in cessation of the procedure, as seen in a sagittal plane (c). aneurysm location and anatomy, improved visual spatial localization in a presurgical setting (6), and overall decreases in contrast medium used, fluoroscopic time, and operator radiation exposure (7). C-arm cone-beam CT, which uses a similar technique as rotational angiography, improves anatomic visualization for needle aspirations or injections with live 3D guidance (8). Use of c-arm cone-beam CT immediately after termination of vertebroplasty has been described to successfully identify cement leakage in 30 of 33 cases (9). With the development of fast-acquisition flat-panel displays and rapid volumetric reconstructions, we have used a technique in cement augmentation in which we apply standard rotational angiography acquisitions to create on-the-fly multiplanar CT like images with preexisting software, with postprocessing acquisition times as low as 10 seconds. These images can be reformatted in any orientation and viewed with bone or soft-tissue windows, allowing for identification of retropulsed fragments and direct viewing of the extent of cement extrusion. Because of the CT-like nature of the images, direct comparison can also be made with preprocedural CT images to evaluate for posterior movement of retropulsed fragments or height restoration. The potential benefits of this technique include rapid determination of cement distribution and the potential ability to redirect needle placement for optimal cement distribution. In patients with preexisting posterior wall tumoral cortical breakthrough, C-arm cone-beam CT can provide a quick way to evaluate the posterior wall and end-plate breakthrough. CASE REPORTS Our institutions do not require institutional review board approval for a retrospective case report such as this. Case 1 A 32-year-old woman presented with multilevel bony metastatic disease secondary to breast cancer. She had a 7-month history of vertebral compression fracture at T9, with no known trauma. Initially presenting with radiculopathy and severe muscle spasm, the fracture site remained painful at 7 months, with continued radicular pain, severe point tenderness, and ongoing muscle spasm. The patient reported a visual analog pain score of 8 of 10 on narcotic pain medication. Despite heavy use of narcotic pain medication, her back pain continued, and resulted in depression and a loss of ability to perform activities of daily living. On physical examination, severe paravertebral muscle spasm was elicited and radiating pain in the T9 dermatomal region was noted. Pain on percussion and palpation was noted, but lower-extremity neurovascular status remained intact. A magnetic resonance (MR) imaging study from an outside institution demonstrated high signal intensity in T9 and focal extension of the posterior wall of the vertebral body into the spinal canal. However, as a result of the quality of imaging, it was difficult to identify the extent of retropulsion or if posterior cortical margin breakthrough existed. Normal signal intensity of the spinal cord and surrounding cerebrospinal fluid was appreciated. On the day of the procedure, standard prophylactic antibiotics were provided before initiation of moderate sedation. The patient was placed in the prone position and preprocedural c- arm cone-beam CT was performed. The data set was transferred to the adjacent 3D workstation (Advantage Workstation v4.3; GE Medical Systems, Milwaukee, Wisconsin) and reviewed in axial, sagittal (Fig 1a,b), and coronal planes. These images demonstrated the extent of the posterior protrusion of the vertebral body and clearly defined the diameter of the preserved spinal canal. Subsequently, unipedicular access was achieved with a 10-gauge outer cannula (KyphX Express 10/2; Kyphon, Sunnyvale, California), with cavity formation with balloon tamps. During the course of balloon inflation, it was noted that a small herniation of the balloon was present along the inferior endplate. With standard fluoroscopic technique,

3 1120 C-arm Cone-beam CT in Spinal Cement Augmentation July 2008 JVIR Figure 2. Reformatted c-arm cone-beam CT image demonstrates extrusion of contrast medium into posterior cortex of metastatic compression fracture of T6. MR image demonstrates T6 compression fracture (arrows) on coronal short T1 inversion recovery (a) and sagittal T1-weighted images (b). Sagittal reformatted image demonstrates posterior extrusion of cement (arrow) with no progressive retropulsion or leakage of contrast medium into the spinal canal in sagittal (c) and axial (d) planes. bone cement was injected (KyphX HVR; Kyphon), with relatively controlled filling. During the injection, a linear accumulation of cement was noted along the inferior endplate, suspicious for end-plate breakthrough. With access via the cannula maintained, a rotational angiogram was obtained. Review of the reformatted images indicated good cortical filling of cement, but also inferior end-plate breakthrough (Fig 1c). Persistent protrusion of the fracture into the spinal canal was seen, with no posterior cement extrusion. No change in the amount of canal impingement was present. With satisfactory filling of the cortex confirmed, the procedure was completed. Postprocedural follow-up at 14 days revealed no clinical complications and marked improvement in pain, with a muscular soreness rating of 3 of 10 on a visual analog scale. Case 2 A 59-year-old female chronic smoker with moderate emphysema presented with diffuse bony metastatic disease secondary to non smallcell lung cancer. Initially she presented with upper thoracic spine and pelvic pain with acute onset of muscle spasm and radiculopathy, and no history of antecedent trauma. Referred pain into the anterior chest and exacerbation of pain with movement was noted on examination, with only mild improvement over the course of 2 weeks. The patient reported a score of 7 of 10 on a visual analog scale. On presentation to the clinic, there was point tenderness at the T6 region, with intact neuromuscular status. The patient described sharp electrical pains on movement and rotation of the upper thoracic spine. Diffuse pelvic pain was described without exacerbation of pain on provocative maneuvers. A screening MR imaging study demonstrated a metastatic lesion within the T6 body with severe height loss (Fig 2a,b). There was retropulsion of the posterior wall of the vertebral body, contacting but not effacing the spinal cord. In addition, the pedicles were noted to be relatively small, measuring less than 4 mm in diameter. The patient was deemed a candidate for vertebroplasty in consideration of the size of the pedicles and concerns regarding retropulsion of a fragment during the cement augmentation procedure. On the day of the procedure, standard prophylactic antibiotics and moderate sedation were initiated. Standard fluoroscopy demonstrated very osteopenic bone, likely as a result of chronic steroid use for her underlying severe chronic obstructive pulmonary disease, and diffuse metastatic disease. The T6 vertebra was localized and the usual sterile field was prepared. Unipedicular access with a standard 13-gauge osteotomy needle (Osteosite; Cook, Bloomington, Indiana) was achieved with no evidence of cortical breakthrough. Difficulty was encountered during access as a result of the sharp angulation of the pedicle, osteopenia, and relatively light sedation (as a result of her chronic obstructive pulmonary disease). Standard methylmethacrylate (Vertefix; Cook) was injected under direct fluoroscopic guidance. During pressurized injection, sudden extrusion of a finger of cement into the posterior third of the vertebral body was noted. This finding immediately raised concern for disruption of the retropulsed portion of the pathologic fracture. C-arm conebeam CT was performed, which demonstrated cement extending posteriorly into but not beyond the retropulsed fragment (Fig 2c,d). There was no change in diameter of the spinal canal, and no significant movement of the retropulsed fragment was seen. In view of adequate distribution of cement, the procedure was deemed complete, and the needle was removed. Follow-up phone call at 48 hours elicited marked improvement of upper back pain with no neurologic deficit. The patient was subsequently lost to follow-up.

4 Volume 19 Number 7 Knight et al 1121 Figure 3. C-arm cone-beam CT study performed with the needle in place and bone cement in a malleable state demonstrates filling of the vertebrobasilar artery. Single reconstructed image with volumetric acquisition demonstrates excellent filling of bone cement, with posterior extension of cement that was demonstrated to be filling of the vertebrobasilar artery (white arrow) Case 3 A 67-year-old woman presented with spinal metastases from multiple myeloma and an acute compression fracture resulting in sudden onset of pain. No neurologic deficits were reported on physical examination; however, the patient s pain was debilitating and required intervention. Imaging with CT and bone scan revealed a focal vertebral compression fracture at T9 amenable to cement augmentation. The T9 vertebra was localized, and unipedicular access with a standard 13-gauge osteotomy needle (Osteosite; Cook) and standardized technique was obtained. Methylmethacrylate (Vertefix; Cook) was injected under direct fluoroscopic guidance. During pressurized injection, sudden extrusion of a finger of cement posteriorly was suspected; therefore, c-arm cone-beam CT was performed (Fig 3). There was no change in diameter of the spinal canal, and the finger of cement extruding to the posterior direction was confirmed to be filling of the vertebrobasilar artery without compromise of the posterior wall or spinal canal. Immediate pain relief was reported, with clinical follow-up confirming the patient to be pain-free 2 months after the intervention. DISCUSSION Multiple case series describe the efficacy of vertebroplasty for pain control in patients with metastatic spinal disease (10 13). Significant pain relief is noted immediately in 80% 97% of patients treated. This pain relief appears durable, lasting for months during follow-up. Quality of life and patient mobility significantly improve in a majority of patients with pathologic fractures treated with vertebroplasty (14,15). Spinal canal narrowing secondary to a retropulsed fragment has historically been considered a relative contraindication for vertebroplasty because of the risk of spinal canal compromise. Complications of vertebroplasty are mainly related to cement leakage. Safe performance of vertebroplasty in patients with canal compromise has been described (16,17), as it has for patients with disruption of the posterior wall of the vertebral body secondary to metastases (5). Various techniques have been employed to assist visualization of the spinal canal and evaluate for cement extrusion into the canal, including performing vertebroplasty in the CT scanner or administering contrast medium intrathecally (5,12). The application of c-arm cone-beam CT for spinal cement augmentation procedures is a novel technique that may provide additional information regarding treatment outcome, cement distribution, and instant identification of complications. We have provided a summary of two flat-panel systems (Table). Potential uses of c-arm conebeam CT include immediate preprocedural evaluation of posterior fracture protrusion and disruption of the posterior cortical margin. Intraprocedural uses include monitoring the posterior wall after cement injection, evaluating for cement extrusion, and evaluating for aggravation of spinal canal compromise. Potential disadvantages include increased time to produce images and technician time to create reformatted images on the workstation, although, in the authors experience, the time to create images has been within the timeframe of standard injection. In situations involving single-plane fluoroscopy, additional acquisition time is minimal, as in most cases the c-arm has been optimized to transition between anteroposterior and lateral planes in a single smooth arc. With the latest 3D workstations, transfer and image display can be achieved in seconds. Unlike fluoroscopy, this technique does not allow for real-time imaging. The question of radiation exposure with c-arm cone-beam CT has not been fully defined, and further studies are needed to evaluate the extent of radiation exposure to the patient relative to the additional fluoroscopic time that would be required to obtain the same clinical information. It is intuitive that the operator would experience less radiation, as image acquisition can be performed with the operator outside the fluoroscopic suite. The authors have found c-arm cone-beam CT valuable in performing technically and anatomically challenging vertebroplasty and kyphoplasty procedures. We report these three

5 1122 C-arm Cone-beam CT in Spinal Cement Augmentation July 2008 JVIR Summary of the Parameters of Two Flat-panel Systems Specification GE Innova 4100IQ Siemens Syngo XWP 3D workstation Advantage workstation 3.4 Leonardo workstation VA60B Rotation arc Frame rate (frames/sec) Voxel size (mm 3 ) Window/level 4,096/2,048 6,092/2,100 cases in the hope of presenting an alternative to CT fluoroscopy guided cement augmentation or the performance of single/biplane fluoroscopy, which potentially compromises adequate or safe injection. References 1. Tomita S, Molloy S, Abe M, Belkoff SM. Ex vivo measurement of intravertebral pressure during vertebroplasty. Spine 2004; 29: Mathis JM. Percutaneous vertebroplasty or kyphoplasty: which one do I choose? Skeletal Radiol 2006; 35: Cotten A, Dewatre F, Cortet B, et al. Percutaneous vertebroplasty for osteolytic metastases and myeloma: effects of the percentage of lesion filling and the leakage of methyl methacrylate at clinical follow-up. Radiology 1996; 200: Nussbaum DA, Gailloud P, Murphy K. A review of complications associated with vertebroplasty and kyphoplasty as reported to the Food and Drug Administration medical device related web site. J Vasc Interv Radiol 2004; 15: Van der Linden E, Kroft LJ, Dijkstra PD. Treatment of vertebral tumor with posterior wall defect using imageguided radiofrequency ablation combined with vertebroplasty: preliminary results in 12 patients. J Vasc Interv Radiol 2007; 18: Missler U, Hundt C, Wiesmann M, Mayer T, Bruckmann H. Threedimensional reconstructed rotational digital subtraction angiography in planning treatment of intracranial aneurysms. Eur Radiol 2000; 10: Bridcut RR, Murphy E, Workman A, Flynn P, Winder RJ. Patient dose from 3D rotational neurovascular studies. Br J Radiol 2007; 80: Racadio JM, Babic D, Homan, R, et al. Live 3-D guidance in the interventional radiology suite. AJR Am J Roentgenol 2007; 189: Hodek-Wuerz R, Martin J, Wilhelm K, et al. Percutaneous vertebroplasty: Preliminary experiences with rotational acquisitions and 3D reconstructions for therapy control. Cardiovasc Intervent Radiol 2006; 29: Deramond H, Darrasson R, Galibert P. La vertébroplastie percutanée acrylique dans le traitement des hémangiomes vertébrauz agressifs. Rachis 1989; 1: Cortet B, Cotten A, Boutry N, et al. Percutaneous vertebroplasty in patients with osteolytic metastases or multiple myeloma. Rev Rhum Engl Ed 1997; 64: Kaemmerlen P, Thiesse P, Jonas P, et al. Percutaneous injection of orthopedic cement in metastatic vertebral lesions. N Engl J Med 1989; 321: Weill A, Chiras J, Simon JM, Rose M, Sola-Martinez MT, Enkaoua E. Spinal metastases: indications for and results of percutaneous injection of acrylic surgical cement. Radiology 1996; 199: Cheung G, Chow E, Holden L, et al. Percutaneous vertebroplasty in patients with intractable pain from osteoporotic or metastatic fractures: a prospective study using quality-of-life assessment. Can Assoc Radiol J 2006; 57: Alvarez L, Perez-Higueras A, Quinones D, Calvo E, Rossi RE. Vertebroplasty in the treatment of vertebral tumors: postprocedural outcome and quality of life. Eur Spine J 2003; 12: Appel NB, Gilula LA. Percutaneous vertebroplasty in patients with spinal canal compromise. AJR Am J Roentgenol 2004; 182: Hiwatashi A, Westesson P. Vertebroplasty for osteoporotic fractures with spinal canal compromise. AJNR Am J Neuroradiol 2007; 28: