Imaging of Orthopedic Spinal Devices: What Every Radiologist Should Know.

Transcription

1 Imaging of Orthopedic Spinal Devices: What Every Radiologist Should Know. Poster No.: C-1656 Congress: ECR 2016 Type: Educational Exhibit Authors: E. Federici, C. Dell'atti, M. Bartocci, D. Beomonte Zobel, V. Martinelli, N. Magarelli, L. Bonomo; Rome/IT Keywords: Bones, Conventional radiography, CT, Complications, Education and training DOI: /ecr2016/C-1656 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 25

2 Learning objectives To review the most common orthopedic spinal devices and their normal imaging. To understand the role of radiologist to identify complications associated with use of these spinal devices. Page 2 of 25

3 Background Many medical devices are used in the treatment of spinal diseases and injuries, and new devices are constantly being introduced. It is necessary that radiologists have some knowledge about the most usual types of these spinal devices. SPINAL SURGERY The goals of spinal surgery can be categorised into three main groups [1]: Decompression of neural structures, for example by removal of herniated disc material, widening of a stenosed spinal canal, or removal of a displaced fracture fragment. Stabilization of the spinal column in order to reduce pain caused by motion segments, ensure stability after a fracture or resection of spinal elements, prevent progression of deformity, or reduce its degree. Excision of spinal tumours. Surgical Approaches to the spine. Spinal surgery can be performed from anterior, posterior or combined approaches [1]: An anterior approach is primarily used in the cervical spine for procedures such as anterior cervical discectomy and fusion and anterior instrumentation for corpectomy, peg fracture fixation with anterior screws, cervical foraminotomy and disc replacement. A posterior approach is used in discectomy, foraminotomy, spinal canal decompression, various types of fixation using pedicle, translaminar or transfacet screws, and insertion of interspinous spacers, as well as posterior lumbar interbody fusion and transforaminal lumbar interbody fusion. Anterior and posterior approaches can be combined in '360 fusion' procedures in which anterior interbody fusion is accompanied by posterior stabilisation with translaminar or pedicle screws, and facet joint or intertransversal fixation. Page 3 of 25

4 Findings and procedure details The most common types of orthopedic spinal devices are: osteosynthesis systems (screws, staples, nails, wires) longitudinal (plates, rods) and transverse connectors interbody devices (bone grafts, cages, artificial disks) interspinous distraction devices. OSTEOSYNTHESIS SYSTEMS Screws can be used as the primary means of repair or for the attachment of longitudinal instrumentation such as plates and rods. There are many types of screws available, characterized by their overall lengths, thread diameters pitch (distance between threads), shaft diameter and length (unthreaded segment) and design of the tip and head [2]. Staples Nails Wires can be used as single fixation element or as a complement of a stabilization system with plates and screws; there are many types of wires of different diameters and lengths. LONGITUDINAL AND TRASVERSE CONNECTORS Plates are used principally in the anterior spinal fusion. They are attached to the bone by screws and there can be certain grade of movement between them. Rods are used principally in the thoracic and lumbar column, usually are paired and connected to the vertebral body posteriorly with pedicle screws. They provide stability over a long segment. INTERBODY DEVICES Bone graft can be autograft bone, obtained from the crest iliac bone of the patient, or allograft bone, coming from a tissue bank. Cages are are usually manufactured from titanium, which has good strength and good biocompatibility. Vertebral cages have a hollow cylindrical structure with teeth on both sides for fixation to vertebral end plates superiorly and inferiorly. The hollow center is usually filled with autograft or allograft bone material to strengthen the fixation and provide later fusion [3] Artificial disks consist of two metallic plates or other hard materials that have metallic teeth to anchor them to the vertebrae above and below the Page 4 of 25

5 disk space. Between the plates is a rubber core containing polyethylene to allow for motion and cushioning [3,4]. INTERSPINOUS DISTRACTION DEVICES This kind of device is a dynamic stabilization system of the spine. The purpose of these devices is their implant between the spinous processes and their distraction (Fig.1). Thus they reduce the extension of the spine without limitation of bending, axial rotation and lateral inflections. Distraction of the interspinous space will increase the foraminal size by contiguity. Ligamentous structures distension reduces the pressure and intracanalar volume. Page 5 of 25

6 Fig. 1: Frontal (A) and lateral (B) radiographs show interspinous distraction device between L4-L5 (yellow arrows). References: Institute of Radiology, Catholic University - Rome/IT CERVICAL SPINE Cervical Plates and Rods Page 6 of 25

7 Anterior and posterior cervical fusion plates are used in cervical spine surgery for trauma, tumor, or degenerative or inflammatory conditions. They are used in conjunction with supporting bone grafts and dowels as interbody disk spacers [3]. Anterior cervical plates are designed to span two or three vertebral bodies, and they are anchored to the underlying vertebral bodies with screws, which should enter the anterior cortex of each vertebral body and be seated in the posterior cortex without impinging on the cord (Fig.2,3). Posterior cervical plates and rods are less common than anterior cervical fusion plates but are used commonly in trauma patients. Posterior plates limit both extension and flexion, and they are usually attached to the underlying vertebrae by screw fixation to the articular masses. Currently, two major types of plates or rod systems are used posteriorly in the cervical spine: those that are attached through screws placed in the pedicles of the cervical vertebrae and those that are attached through screws placed in the lateral mass of each cervical vertebra (Fig.4). Fig. 2: Frontal (A) and lateral (B) radiographs view cervical spine. Plate, screws and intersomatic cage (yellow arrow). Page 7 of 25

8 References: Institute of Radiology, Catholic University - Rome/IT Fig. 3: Frontal radiograph (A) and coronal (B) and sagittal (C) CT images view cervical spine. Plate, screws and intersomatic cage. References: Institute of Radiology, Catholic University - Rome/IT Page 8 of 25

9 Fig. 4: Coronal (A) and sagittal (B) CT images of cervical spine show occipitalspinal strut with U-shaped rod, screws and wires, used to stabilize the cervical spine. References: Institute of Radiology, Catholic University - Rome/IT Posterior Cervical Spine Wiring Use of posterior cervical spine wiring is now less common than fixation with anterior cervical fusion plates [5]. Posterior cervical spine wiring is very good for limiting flexion of the spine, and it is less complicated than anterior cervical fusion and plating. These include wires under the lamina, over the lamina, and through holes drilled in the facets or spinous processes [3]. Odontoid Fracture Fixation Devices Type I odontoid fractures occur at the tip of the odontoid and are stable and heal with conservative treatment. Page 9 of 25

10 Type II odontoid fractures run transversely at the base of the odontoid. They are considered to be unstable and sometimes do not heal adequately with simple external fixation. For these types of fractures, internal fixation may be performed, especially when reduction of the odontoid is needed. Posterior cervical fixation wires are commonly used for treating type 2 odontoid fractures. They usually achieve satisfactory odontoid fusion, but they may limit neck rotation. Because of this, odontoid fracture fixation may use an odontoid compression screw [6], running caudad to cephalad through the body of C-2, the odontoid fracture line, and into the body of the odontoid. Type III odontoid fractures involve the vertebral body of C-2 below the level of the odontoid. They are usually stable and heal adequately. Cervical Collars and Halo Vests There are many kinds of cervical spine immobilization devices, including cervical collars, braces, and halo vests. Cervical collars are commonly placed on trauma patients in the emergency department. No neck collar provides adequate long-term neck stabilization for unstable cervical spine fractures. Unlike cervical collars, cervical braces are designed for the long-term treatment of cervical spine fractures. They consist of chin and occipital supports that are connected to a thoracic vest by metal rods. Cervical braces do provide good prevention against harmful flexion, but they are not as effective in preventing harmful extension. The halo vest contains a metallic ring (the halo) that is attached to the outer table of the skull by screws (Fig.5)[7]. The halo is connected to a padded fiberglass or plastic thoracic cast by metal rods (the struts), which hold up the patient's head. Although halo vests involve placement of screws into the skull and are a major undertaking for both the patient and the physician, they provide the best long-term fixation of the cervical spine. They are especially indicated for unstable fractures and dislocations and work best in the upper cervical spine. Page 10 of 25

11 Fig. 5: Axial (A) and surface-rendered 3D (B,C,D) CT images show the halo vest that contain a metallic ring (the halo) attached to the outer table of the skull by screws. References: Institute of Radiology, Catholic University - Rome/IT THORACIC AND LUMBAR SPINE Posterior Spinal Instrumentation. Page 11 of 25

12 Posterior spinal instrumentation is preferred over anterior spinal instrumentation in the thoracic and lumbar regions. Currently, it is quite common to combine bone grafting with the use of spinal fixation apparatus to improve fusion rates. The devices used for posterior spinal instrumentation are rods, plates, screws, connectors, cage and osseus graft (Fig.6,7). Fig. 6: Frontal (A) and lateral (B) radiographs view lumbar spine. Rods, screws and trasverse connectors. Page 12 of 25

13 References: Institute of Radiology, Catholic University - Rome/IT Fig. 7: Frontal (A) and lateral (B) radiographs view lumbar spine. Rods, screws and intersomatic cage (yellow arrow). References: Institute of Radiology, Catholic University - Rome/IT Anterior Spinal Instrumentation. The devices used for anterior spinal instrumentation are similar to those used for posterior spinal fixation and usually include plates and screws. Anterior spinal fixation is common in the cervical spine, but it is uncommon in the thoracic or lumbar spine. When it is used in the thoracic or lumbar regions, it is often designed to stabilize or correct a marked kyphosis or scoliosis The anterior spinal apparatus is placed to impart a distracting force on the concave side of the scoliosis or a compressing force on the convex side of the scoliosis [3]. Page 13 of 25

14 Vertebroplasty. Vertebroplasty is designed to provide pain relief from benign osteoporotic compression fractures or less common, destructive vertebral lesions [8]. Methyl methacrylate is injected directly into a vertebral body to strengthen the bone structure of the vertebrae and immobilize fractures, which provides immediate pain relief. Because the methyl methacrylate is mixed with barium sulfate, it is visible on radiographs and on cross-sectional images (Fig.8)[2]. Fig. 8: Frontal and lateral radiographs show multiple vertebroplasty (yellow arrows). Page 14 of 25

15 References: Institute of Radiology, Catholic University - Rome/IT THE ROLE OF IMAGING The role of the radiologist is to evaluate the correct positioning and integrity of the osteosynthesis material and to identify complications associated with use of these devices (infection, malposition, instrumentation migration or broken). The most common imaging modalities are: Radiography: advantages (low cost, absence of metal artifacts), disadvantages (difficult to assess the positioning of fixation devices to overlay images) CT: advantages (greater anatomical resolution, multiplanar), disadvantages (higher dose of radiation, the presence of metal artifacts) MRI: advantages (no radiation exposure, ideal for evaluating soft tissues), disadvantages (high cost, presence of motion artifacts and metal artifacts). Page 15 of 25

16 Images for this section: Fig. 2: Frontal (A) and lateral (B) radiographs view cervical spine. Plate, screws and intersomatic cage (yellow arrow). Institute of Radiology, Catholic University - Rome/IT Page 16 of 25

17 Fig. 3: Frontal radiograph (A) and coronal (B) and sagittal (C) CT images view cervical spine. Plate, screws and intersomatic cage. Institute of Radiology, Catholic University - Rome/IT Page 17 of 25

18 Fig. 4: Coronal (A) and sagittal (B) CT images of cervical spine show occipital-spinal strut with U-shaped rod, screws and wires, used to stabilize the cervical spine. Institute of Radiology, Catholic University - Rome/IT Page 18 of 25

19 Fig. 5: Axial (A) and surface-rendered 3D (B,C,D) CT images show the halo vest that contain a metallic ring (the halo) attached to the outer table of the skull by screws. Institute of Radiology, Catholic University - Rome/IT Page 19 of 25

20 Fig. 6: Frontal (A) and lateral (B) radiographs view lumbar spine. Rods, screws and trasverse connectors. Institute of Radiology, Catholic University - Rome/IT Page 20 of 25

21 Fig. 7: Frontal (A) and lateral (B) radiographs view lumbar spine. Rods, screws and intersomatic cage (yellow arrow). Institute of Radiology, Catholic University - Rome/IT Page 21 of 25

22 Fig. 1: Frontal (A) and lateral (B) radiographs show interspinous distraction device between L4-L5 (yellow arrows). Institute of Radiology, Catholic University - Rome/IT Page 22 of 25

23 Fig. 8: Frontal and lateral radiographs show multiple vertebroplasty (yellow arrows). Institute of Radiology, Catholic University - Rome/IT Page 23 of 25

24 Conclusion It is important for the radiologist to recognize the presence of a spinal device and to have an understanding of its function as well as to be able to recognize the complications associated with its use. Page 24 of 25

25 References Grainger & Allison's Diagnostic Radiology, 6th edition, Churchill Livingstone, R. M. Sloan et al., "Orthopedic Fixation Devices," Radiographics 1991; 11: Hunter Tb, Yoshino MT, Dzioba RB, et al. Medical devices of the head, neck, and spine. Radiographics. 2004; 24: Murtagh RD, Quencer RM, Cohen DS, et al. Normal and abnormal imaging findings in lumbar total disk replacement: Devices and complications. Radiographics. 2009;29: JohnsonRM,OwenJR,HartDL,CallahanRA. Cervical orthoses. Clin Orthop 1981; 154: Esses SI, Bednar DA. Screw fixation of odontoid fractures and nonunions. Spine 1991; 16:S483-S485. Bucholz RD, Cheung KC. Halo vest versus spinal fusion for cervical injury: evidence from an outcome study. J Neurosurg 1989; 70: Cotten A, Boutry N, Cortet B, et al. Percutaneous vertebroplasty: state of the art. RadioGraphics 1998; 18: Page 25 of 25