What Process Is Used To Repair L3

LEARNING OBJECTIVES

Afterwards reading this article and taking the test, the reader will be able to:

•.	Recognize the differences between lumbar spine fusion and stabilization and betwixt the surgical approaches used to perform them.
•.	Identify the primary types of fusion and stabilization devices on the basis of their normal imaging appearances.
•.	Depict the advantages and disadvantages of different imaging methods for evaluating lumbar spine instrumentation.

Introduction

Spinal instrumentation was first described in 1911 as a method for handling of Pott illness (^,1). Since and then, a wide range of devices have become bachelor, and lumbar spine instrumentation is now used in various clinical settings, including degenerative disk disease, spondylolisthesis, tumors, infection, and trauma. The choice of device depends on the clinical problem, the anatomic location, and the surgeon'due south preference. The instrumentation used in fusion surgery is not designed to supervene upon the bony elements of the spine, but to stabilize them during fusion, and it is more often than not accepted that instrumentation without intact osseous fusion will neglect (^,2). Deejay replacements were developed to overcome clinical problems associated with pseudarthrosis and to reduce the incidence of adjacent vertebral segment degeneration. Dynamic stabilization devices, which are designed to limit aberrant segmental motion, may be used as an culling to vertebral fusion procedures.

To recognize normal postoperative imaging appearances or detect malpositioning or complications of lumbar spine instrumentation, radiologists need an understanding of the range of approaches, techniques, and hardware devices used in lumbar fusion and stabilization and in disk replacement. The article provides an overview of these procedures and of normal postoperative imaging features that are commonly seen at radiography, magnetic resonance (MR) imaging, and computed tomography (CT).

Imaging of the Lumbar Spine after Instrumentation

Postoperative imaging is typically performed (a) to assess the progress of osseous fusion, (b) to ostend the correct positioning and the integrity of instrumentation, (c) to discover suspected complications (eg, infection or hematoma), and (d) to discover new disease or disease progression.

The modality and protocol used to image the postoperative spine depend on the site, the clinical question, and the type of instrumentation. There is currently no reference standard for noninvasive imaging evaluation of fusion (^,iii).

Radiographic Evaluation

Radiography is the noninvasive modality most commonly used for the cess of fusion, although CT is reported to exist more accurate (^,4). Radiography also is useful for the investigation of spinal instrumentation when breakage or incorrect placement is suspected (^,v). However, radiography cannot be used to reliably exclude the presence of metastases to bone or of cauda equina compression, both of which are common indications for postoperative MR imaging of the lumbar spine. In the evaluation of patients after lumbar spine instrumentation, information technology is particularly important to compare the current radiographs not merely with the well-nigh recent previous images but also with multiple previous studies then every bit to identify subtle progressive changes (eg, in spinal alignment and in the position of the hardware devices) that may signify the imminent failure of a device or other complications. Flexion and extension views have been advocated for the routine assessment of fusion (^,6,^,7), but there is no clinical consensus regarding their value for that purpose (^,8), and they are not in routine utilise at our establishment.

Evaluation with CT

CT is the modality of selection for imaging bony detail in the spine to enable accurate cess of the degree of osseous fusion; however, surgical exploration remains the reference standard for evaluating fusion. The quality of CT images may be severely degraded past starburst-type artifacts due to metallic implants, which cause marked x-ray attenuation ("hollow projections") in selected planes. Titanium has a lower x-ray attenuation coefficient than stainless steel and therefore causes a less astringent antiquity (^,9). The starburst-type antiquity seen on CT images, unlike that on MR images, is not restricted to the surface area immediately adjacent to the metallic implant (^,Fig 1). Patient movement often exacerbates such artifacts, although it is less commonly a problem since the introduction of high-speed multidetector CT technology. Imaging and reconstruction algorithms may help minimize starburst-blazon artifacts (^,10,^,11). For case, multiplanar reformation frequently results in higher-quality images that are more useful clinically than centric images solitary (^,9) (^,Fig 2).

MR Imaging

MR imaging is useful for evaluating sequential postoperative changes in the spine and better demonstrates intraspinal contents than do other imaging modalities. It is especially useful for detecting and monitoring infection or postoperative collections (^,Fig 3). Nevertheless, magnetic susceptibility artifact may be a problem, specially in the presence of stainless steel devices (^,Fig 4a^, ^,). Modern implants fabricated of titanium alloys are less ferromagnetic and thus produce less astringent magnetic susceptibility artifacts, but these artifacts remain a significant obstacle to visualization of areas in close proximity to metallic hardware (^,12) (^, ^,Fig 4b^,). Sequences have been developed to reduce the artifacts (^,13), but their utilize may necessitate increased prototype acquisition fourth dimension and may result in image baloney. Gradient-echo sequences are more vulnerable to magnetic susceptibility artifact than are spin-echo (SE) sequences (^,xiv) and are best avoided. Reduction of the echo time may lead to an increase in the signal-to-noise ratio while minimizing artifact. Increasing the bandwidth too helps significantly reduce the artifact magnitude with SE and turbo SE sequences, although this method also leads to a decrease in the signal-to-noise ratio. At our institution, a protocol that includes a iii-dimensional T2-weighted turbo SE sequence has been developed to reduce magnetic susceptibility antiquity in the presence of titanium implants (Bryant JA, MSc thesis, 2004) (^, ^, ^,Fig 4c). Nonmetallic devices, such as nonmetallic interbody spacers, are MR compatible and produce lilliputian artifact (^,Fig 5a^,).

Ultrasonography

The usefulness of ultrasonography for evaluation of the lumbar spine is largely restricted to the identification of postoperative fluid collections.

Nuclear Medicine

Bone scintigraphy may be performed to assess fusion (the fused segment should be "cold" later on half-dozen–12 months) (^,15). It also is useful for detecting infection.

Myelography

If MR imaging is contraindicated or MR images are nondiagnostic because of artifact, myelography may be performed (^,Fig 6). However, afterwards instrumentation of the lumbar spine, puncture of the lumbar thecal sac may be complicated by baloney of the anatomy (eg, scarring, removal of posterior elements, addition of bone graft material) or the presence of metallic implants. Occasionally in this situation a cervical puncture is necessary. Post-obit the injection of contrast cloth into the thecal sac, radiographs may be caused at an bending to avert obscuration of the relevant nervus roots by the implanted devices. Conventional myelography is normally supplemented with CT myelography.

Lumbar Spinal Fusion and Instrumentation

Rigid internal fixation (spinal instrumentation) is necessary to promote os fusion, which occurs within four–five months after spinal fusion surgery, and to prevent pseudarthrosis (^,3). Lumbar spinal fusion involves the insertion of bone graft material with or without one or more interbody spacers and other devices to provide boosted support and stability. Spinal fusion surgery is usually performed in patients who require decompression for nerve root pain and whose symptoms are largely diskogenic.

Instrumentation Used in Fusion

Interbody Spacers.—

Interbody spacers are made of titanium or a radiolucent material such every bit polyetheretherketone. They may be solid constructions (ramps) or openwork structures filled with bone graft material (cages) and may be used singly or paired (positioned side past side). On postoperative radiographs, the outlines of radiolucent cages get increasingly apparent as the side by side bone graft consolidates over fourth dimension (^,Fig five^,). Nearly spacers contain two radiopaque markers to enable radiographic assessment of the spacer position (^,Fig vii). An observation of a posterior marking located at least two mm inductive to the posterior vertebral trunk margin provides reassurance that the ramp is not protruding into the spinal canal.

Plates or Rods with Pedicle Screws.—

In these devices, pedicle screws are connected by plates or rods that bridge unmarried (^,Fig viii) or multiple (^,Fig 9) vertebral segments. Crossbars may exist added for additional force. For multilevel fusion, rods (^,Fig ten^, ^, ^,) are generally preferred over plates (^,Fig eleven^, ^, ^,) because rods can exist individually cut and molded as required to facilitate maintenance of sagittal alignment. The tips of pedicle screws should be embedded in the vertebral bone and should not breach the anterior vertebral body cortex, but there is no consensus on their optimal length. Sacral screws may be anchored in the inductive cortex of the sacrum for additional stability.

Translaminar or Facet Screws.—

Translaminar or facet screws provide an alternative class of posterior instrumentation when the posterior spinal elements are left intact. The screws may be inserted by using a minimally invasive arroyo and oriented at different angles to avoid impingement on other screws.

Hartshill Rectangles.—

Hartshill rectangles are a fixation device that consists of stainless steel rectangles held in place posteriorly by sublaminar wires (^,Fig 12^,). Because the wires (particularly those at the superior end of the rectangle) contribute to the structural integrity of the device, a wire fracture is considered a significant finding. This device was used before the advent of pedicle screws but is seldom used at present.

Posterior Surgical Approaches

A posterior approach is used when posterior decompression is required in addition to fusion.

Posterior Lumbar Interbody Fusion.—

The posterior lumbar interbody fusion procedure is performed by using a posterior surgical approach. Bilateral fractional laminectomies are performed (caudad and cephalad) and are followed by diskectomy. Bone graft fabric is packed into the anterior disk infinite before the insertion of an interbody spacer or two interbody spacers placed side by side and packed with graft cloth. Further bone graft textile is then packed into the remainder of the disk infinite. Posterior instrumentation is performed to provide a rigid support until os fusion occurs.

Transforaminal Lumbar Interbody Fusion.—

This procedure is similar to the posterior one but is performed past using a more lateral approach that leaves the midline bone structures intact, minimizes central spinal canal disruption, and reduces dural tube traction and exposure. A full facetectomy is mostly performed to gain access to the lateral disk infinite. Transforaminal interbody spacers are crescent shaped and are placed anteriorly in the disk space.

Posterolateral Fusion.—

This procedure is performed as an alternative to posterior lumbar interbody fusion when at that place is a astringent loss of disk infinite height and when the insertion of a posterior interbody spacer might crusade neurologic compromise. Bone graft material is placed laterally (betwixt transverse processes) rather than anteriorly (between vertebral bodies). Posterolateral fusion is usually supplemented by posterior instrumentation.

Inductive Surgical Approaches

Fusion is performed by using an inductive approach when pain is predominantly diskogenic and posterior decompression is not required.

Anterior Lumbar Interbody Fusion.—

Like the posterior and transforaminal lumbar interbody fusion techniques, the anterior fusion procedure is performed to remove degenerate deejay fabric, replace disk height, and give immediate stability for anterior osseous fusion. However, anterior lumbar interbody fusion is performed past using a lower intestinal incision or retroperitoneal approach through the flank. The spacers used in anterior fusion are unmarried, big cages. These are supplemented by screws and rods or plates, which may be placed either anteriorly or posteriorly, depending on access. At the level of the L5 through S1 vertebrae and sometimes that of the L4 through L5 vertebrae, anterior fusion must be supplemented by instrumentation with a posterior approach considering the iliac crests limit lateral admission. Several rod and screw devices, such as the Kaneda device (DePuy Spine, Raynham, Mass), are specifically designed for insertion with an inductive approach (^,Fig 13^, ^,).

Stand-Alone Lumbar Interbody Fusion.—

This procedure is like to the others, but the cage is stock-still with screws to the adjacent vertebral bodies to obviate further posterior instrumentation (^,Fig fourteen^, ^,).

Vertebral Body Replacement

A vertebral body replacement may exist necessary afterward a resection (corpectomy) because of a tumor, infection, or major trauma. The vertebral trunk replacement device may exist an expandable hollow cylinder packed with bone graft material or cement, like the Synex cage (Synthes Spine, Paoli, Pa) (^,Fig xv), or made of mesh, like the Moss muzzle (DePuy-AcroMed) (^,Fig xvi). Vertebral trunk replacement may involve 1 or more segments. Stackable carbon-cobweb-reinforced polymer cages are radiolucent, but the metallic rods that hold them together marker their position, as do radiopaque metallic dots (^,Fig 17). Lateral, anterior, or posterior screws with plates or rods are inserted for boosted stability.

Disk Replacement

Total disk replacement is performed in patients whose pain is believed to originate primarily from disk degeneration without nervus root involvement, rather than from spinal stenosis or spondylolisthesis. The presence of facet joint degeneration is a contraindication to total disk replacement. There must be at least four mm of residual disk height and a lack of significant endplate degeneration to provide satisfactory anchorage for the replacement device. The goal of deejay replacement is to avoid arthrodesis-related complications of pseudarthrosis, iliac crest donor site hurting, and degeneration of the next segment. The technique is still evolving. The first human deejay prosthesis, which consisted of a single ball bearing, was inserted in the late 1950s (^,16). Mod artificial disks consist of two parallel plates (commonly fabricated of a metal blend) with outside toothlike projections that are designed to anchor the device securely to the adjacent vertebrae (^,17). A polyethylene core between the plates allows motion and provides cushioning (^,Figs xviii^, ^,, ^,19^, ^,).

Dynamic Stabilization

Dynamic stabilization may exist an alternative to fusion in some patients with low back pain originating from chronic degeneration of the lumbar spine. By altering load bearing and controlling aberrant motion, stabilization helps limit the stress placed on the segment next to the level of fusion and thus helps forestall progressive degeneration.

A wide variety of dynamic stabilization devices are in diverse stages of clinical development (^,Table). These devices may be used lonely for stabilization or used in combination with fusion devices. Dynamic stabilization devices may be broadly grouped, according to their design, in the following categories: (a) pedicle screws and bogus ligaments (eg, Dynesys device [^,Fig twenty^, ^, ^,], Graf ligament [^,Fig 21^, ^, ^,]), (b) inter–barbed process decompression devices (eg, Wallis system [^,Figs 3, ^,22^, ^,], X STOP), and (c) posterior chemical element replacement systems. Inter–barbed process devices cannot be used at the level of L5 through S1 because of the lack of a distal anchorage indicate.

Conclusions

Various fixation devices may be implanted during lumbar spine fusion procedures to prevent segmental motion while os fusion occurs; total deejay replacement may be performed equally an alternative to fusion in certain situations; and dynamic stabilization devices may be implanted to provide stability while allowing limited movement. An understanding of the types of devices used in these different procedures is necessary, as is a familiarity with normal postoperative appearances, if complications are to be recognized at imaging. In addition, noesis well-nigh the type of device and the elective materials facilitates the choice of an appropriate modality for imaging of the postoperative spine.

**Dynamic Stabilization Devices**

**Figure 1.** Centric CT myelogram shows an extensive streak artifact caused past a metallic device implanted in the lumbar spine.

**Figure 2.** Volume-rendered three-dimensional reformatted CT image shows the position of pedicle screws and plates at the level of the L5 through S1 vertebrae. The tip of one screw has breached the inductive sacral cortex (arrow). Bone graft material too tin can be seen anteriorly in the L5-S1 deejay infinite. Reformatted CT images often allow a better and more complete three-dimensional evaluation of spinal instrumentation.

**Figure 3.** Axial T2-weighted MR epitome clearly demonstrates a simple postoperative fluid collection *(C)* located inductive to a Wallis ligament *(W)* dynamic stabilization device.

**Figure 4a.** Centric MR images testify susceptibility artifacts of varying severity. **(a)** Stainless steel pedicle screws cause a meaning susceptibility artifact that completely degrades the diagnostic quality of the image. **(b)** Titanium alloy pedicle screws cause a much less severe antiquity than that in **a. (c)** The severity of the susceptibility antiquity from the titanium screws in b is further reduced on an prototype obtained with a T2 weighted turbo SE sequence.

**Effigy 4b.** Axial MR images bear witness susceptibility artifacts of varying severity. **(a)** Stainless steel pedicle screws cause a significant susceptibility artifact that completely degrades the diagnostic quality of the prototype. **(b)** Titanium alloy pedicle screws cause a much less severe artifact than that in **a. (c)** The severity of the susceptibility artifact from the titanium screws in b is farther reduced on an image obtained with a T2-weighted turbo SE sequence.

**Effigy 4c.** Axial MR images show susceptibility artifacts of varying severity. **(a)** Stainless steel pedicle screws crusade a significant susceptibility antiquity that completely degrades the diagnostic quality of the image. **(b)** Titanium blend pedicle screws cause a much less astringent artifact than that in **a. (c)** The severity of the susceptibility artifact from the titanium screws in b is further reduced on an image obtained with a T2-weighted turbo SE sequence.

**Figure 5a.(a)** Sagittal T1-weighted MR epitome shows a nonmetallic muzzle that is situated posteriorly within the disk space and slightly wedged to enhance lumbar lordosis. **(b)** Radiograph shows the linear outline of the radiolucent cage, which has become more visible as the adjacent bone graft has consolidated around it.

**Figure 5b.(a)** Sagittal T1-weighted MR epitome shows a nonmetallic muzzle that is situated posteriorly inside the disk space and slightly wedged to enhance lumbar lordosis. **(b)** Radiograph shows the linear outline of the radiolucent cage, which has get more visible as the next bone graft has consolidated around it.

**Figure 6.** Fluoroscopic myelogram obtained in a patient with a lumbar spinal fusion device consisting of stainless steel rods and screws (Isola; DePuy-AcroMed, Cleveland, Ohio).

**Effigy seven.** Anteroposterior (left) and lateral (right) radiographs bear witness the metallic markers (arrows) used to enable a radiographic assessment of the position of intervertebral ramps. 1 marker is positioned at the lower right inductive attribute of the ramp, and the other is positioned at the upper left posterior aspect of the ramp. Note the spondylolysis depicted in the lateral view. Posterior instrumentation was afterwards performed in this case.

**Figure viii.** Anteroposterior radiograph shows unmarried-level instrumentation (L5 through S1 vertebrae) with a device made of rods and screws.

**Figure 9.** Anteroposterior radiograph shows a rod and screw device that spans multiple levels.

**Figure 10a.** Rod and screw device. **(a)** Diagram shows spinal fusion with a typical rod and screw device spanning the L4 through S1 vertebrae. **(b)** Photograph shows a metallic rod and screw device (Isola). **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs testify the aforementioned device as in b after positioning at the L4 through S1 vertebral levels. Radiopaque markers that delineate the anterior and posterior aspects of spacers in the L4–L5 and L5-S1 disk spaces also are visible.

**Figure 10b.** Rod and screw device. **(a)** Diagram shows spinal fusion with a typical rod and screw device spanning the L4 through S1 vertebrae. **(b)** Photo shows a metallic rod and spiral device (Isola). **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs show the aforementioned device as in b after positioning at the L4 through S1 vertebral levels. Radiopaque markers that delineate the anterior and posterior aspects of spacers in the L4–L5 and L5-S1 deejay spaces also are visible.

**Figure 10c.** Rod and screw device. **(a)** Diagram shows spinal fusion with a typical rod and screw device spanning the L4 through S1 vertebrae. **(b)** Photograph shows a metallic rod and screw device (Isola). **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs show the same device as in b later positioning at the L4 through S1 vertebral levels. Radiopaque markers that delineate the anterior and posterior aspects of spacers in the L4–L5 and L5-S1 disk spaces also are visible.

**Effigy 10d.** Rod and screw device. **(a)** Diagram shows spinal fusion with a typical rod and screw device spanning the L4 through S1 vertebrae. **(b)** Photograph shows a metallic rod and screw device (Isola). **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs show the same device as in b after positioning at the L4 through S1 vertebral levels. Radiopaque markers that delineate the inductive and posterior aspects of spacers in the L4–L5 and L5-S1 disk spaces besides are visible.

**Effigy 11a.** Plate and screw device. **(a)** Diagram shows spinal fusion with a typical plate and screw device spanning the L4 through S1 vertebrae. **(b)** Photograph shows a Steffee interbody fusion device, which consists of a metal plate and pedicle screws. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs depict spinal fusion with the plate and screw construct shown in b at the L3 through L5 vertebral levels. In d, a burst fracture is visible in the L4 vertebra with retropulsion of a vertebral fragment.

**Figure 11b.** Plate and spiral device. **(a)** Diagram shows spinal fusion with a typical plate and spiral device spanning the L4 through S1 vertebrae. **(b)** Photograph shows a Steffee interbody fusion device, which consists of a metallic plate and pedicle screws. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs draw spinal fusion with the plate and screw construct shown in b at the L3 through L5 vertebral levels. In d, a outburst fracture is visible in the L4 vertebra with retropulsion of a vertebral fragment.

**Figure 11c.** Plate and screw device. **(a)** Diagram shows spinal fusion with a typical plate and screw device spanning the L4 through S1 vertebrae. **(b)** Photograph shows a Steffee interbody fusion device, which consists of a metallic plate and pedicle screws. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs draw spinal fusion with the plate and screw construct shown in b at the L3 through L5 vertebral levels. In d, a burst fracture is visible in the L4 vertebra with retropulsion of a vertebral fragment.

**Figure 11d.** Plate and screw device. **(a)** Diagram shows spinal fusion with a typical plate and spiral device spanning the L4 through S1 vertebrae. **(b)** Photograph shows a Steffee interbody fusion device, which consists of a metallic plate and pedicle screws. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs describe spinal fusion with the plate and spiral construct shown in b at the L3 through L5 vertebral levels. In d, a burst fracture is visible in the L4 vertebra with retropulsion of a vertebral fragment.

**Figure 12a.(a)** Diagram shows lumbar spinal fusion with a Hartshill rectangle. **(b)** Anteroposterior radiograph shows a Hartshill rectangle secured in position posteriorly past sublaminar wires.

**Figure 12b.(a)** Diagram shows lumbar spinal fusion with a Hartshill rectangle. **(b)** Anteroposterior radiograph shows a Hartshill rectangle secured in position posteriorly by sublaminar wires.

**Figure 13a.(a)** Diagram shows the Kaneda device, which consists of two threaded rods secured by orthopedic staples and vertebral body screws. The device is inserted by using an anterior approach. **(b)** Anteroposterior radiograph shows the staples (arrowheads), which reinforce the buy of the screws in the vertebrae, resulting in very house fixation. Surgical clips (arrows) on segmental vessels should not be dislocated with the metallic markers inside spacers. **(c)** Lateral radiograph shows the same device as in b.

**Effigy 13b.(a)** Diagram shows the Kaneda device, which consists of 2 threaded rods secured past orthopedic staples and vertebral body screws. The device is inserted by using an anterior approach. **(b)** Anteroposterior radiograph shows the staples (arrowheads), which reinforce the purchase of the screws in the vertebrae, resulting in very firm fixation. Surgical clips (arrows) on segmental vessels should not be confused with the metal markers inside spacers. **(c)** Lateral radiograph shows the aforementioned device every bit in b.

**Figure 13c.(a)** Diagram shows the Kaneda device, which consists of ii threaded rods secured by orthopedic staples and vertebral body screws. The device is inserted by using an inductive arroyo. **(b)** Anteroposterior radiograph shows the staples (arrowheads), which reinforce the purchase of the screws in the vertebrae, resulting in very firm fixation. Surgical clips (arrows) on segmental vessels should non be dislocated with the metallic markers within spacers. **(c)** Lateral radiograph shows the same device as in b.

**Figure 14a.(a)** Diagram shows a stand-solitary lumbar interbody fusion muzzle. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs bear witness the screws that fix the cage to the next vertebrae.

**Figure 14b.(a)** Diagram shows a stand-alone lumbar interbody fusion cage. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs testify the screws that fix the cage to the adjacent vertebrae.

**Figure 14c.(a)** Diagram shows a stand up-alone lumbar interbody fusion cage. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs testify the screws that fix the muzzle to the side by side vertebrae.

**Effigy xv.** Anteroposterior radiograph shows an expandable metallic cage (Synex) placed in the L1 vertebral body after a burst fracture. Such cages may be tilted or positioned noncentrally inside the vertebral body, depending on the private instance. Lateral instrumentation was performed with rods and screws for stability.

**Figure 16.** Anteroposterior radiograph shows a Moss cage placed in the L1 vertebra for direction of a burst fracture, and a Kaneda device positioned for boosted stability.

**Figure 17.** Anteroposterior radiograph shows stackable carbon fiber–reinforced cages held together by metal rods (arrows). Radiopaque dots marker the positions of individual cages.

**Figure 18a.** Total deejay replacement with the ProDisc device (Spine Solutions, New York, NY). **(a)** Diagrams show right anteroposterior (left) and lateral (right) positioning of the disk replacement device. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs show two deejay replacement devices in the correct position: The endplates announced to be parallel in b, and the devices are well contained within the intervertebral disk spaces in c.

**Effigy 18b.** Total deejay replacement with the ProDisc device (Spine Solutions, New York, NY). **(a)** Diagrams testify correct anteroposterior (left) and lateral (right) positioning of the deejay replacement device. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs show two disk replacement devices in the correct position: The endplates appear to be parallel in b, and the devices are well contained within the intervertebral disk spaces in c.

**Figure 18c.** Total deejay replacement with the ProDisc device (Spine Solutions, New York, NY). **(a)** Diagrams show right anteroposterior (left) and lateral (correct) positioning of the disk replacement device. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs testify two disk replacement devices in the correct position: The endplates appear to exist parallel in b, and the devices are well contained within the intervertebral disk spaces in c.

**Figure 19a.** Total disk replacement with the SB Charité device (Waldemar Link, Hamburg, Germany). **(a)** Diagrams evidence right anteroposterior (left) and lateral (right) positioning of the replacement disk device. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs show the device in the lumbar spine. Note the iii anterior and three posterior teeth that anchor each (superior and junior) one-half of the device to the adjacent vertebrae. A metallic ring within the device helps identify its location and evaluate positioning.

**Figure 19b.** Total deejay replacement with the SB Charité device (Waldemar Link, Hamburg, Germany). **(a)** Diagrams show correct anteroposterior (left) and lateral (right) positioning of the replacement disk device. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs show the device in the lumbar spine. Note the iii anterior and three posterior teeth that anchor each (superior and junior) half of the device to the side by side vertebrae. A metallic band within the device helps identify its location and evaluate positioning.

**Figure 19c.** Total disk replacement with the SB Charité device (Waldemar Link, Hamburg, Germany). **(a)** Diagrams prove correct anteroposterior (left) and lateral (right) positioning of the replacement disk device. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs show the device in the lumbar spine. Note the three anterior and iii posterior teeth that anchor each (superior and inferior) half of the device to the next vertebrae. A metallic ring inside the device helps identify its location and evaluate positioning.

**Figure 20a.** Dynesys semirigid artificial ligament organization. **(a)** Diagram shows correct positioning of the device in the lumbar spine. **(b)** Photo shows the device, which consists of two titanium alloy pedicle screws continued by a cylindrical polycarbonaturethane spacer through which a polyester cord (the artificial ligament) is strung. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs show the device positioned correctly in the lumbar spine. To avoid interfering with facet joint function, the screws are positioned more than laterally than are normal pedicle screws. In this case, fusion of the segment at L5 through S1 was performed (note the presence of a spacer at this level) and the Dynesys system was used for dynamic stabilization of the L4 through L5 segment.

**Effigy 20b.** Dynesys semirigid artificial ligament system. **(a)** Diagram shows correct positioning of the device in the lumbar spine. **(b)** Photograph shows the device, which consists of two titanium blend pedicle screws connected by a cylindrical polycarbonaturethane spacer through which a polyester cord (the artificial ligament) is strung. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs evidence the device positioned correctly in the lumbar spine. To avoid interfering with facet joint function, the screws are positioned more laterally than are normal pedicle screws. In this case, fusion of the segment at L5 through S1 was performed (annotation the presence of a spacer at this level) and the Dynesys system was used for dynamic stabilization of the L4 through L5 segment.

**Figure 20c.** Dynesys semirigid bogus ligament arrangement. **(a)** Diagram shows correct positioning of the device in the lumbar spine. **(b)** Photo shows the device, which consists of two titanium alloy pedicle screws connected by a cylindrical polycarbonaturethane spacer through which a polyester cord (the bogus ligament) is strung. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs evidence the device positioned correctly in the lumbar spine. To avoid interfering with facet joint role, the screws are positioned more laterally than are normal pedicle screws. In this case, fusion of the segment at L5 through S1 was performed (note the presence of a spacer at this level) and the Dynesys arrangement was used for dynamic stabilization of the L4 through L5 segment.

**Effigy 20d.** Dynesys semirigid artificial ligament system. **(a)** Diagram shows correct positioning of the device in the lumbar spine. **(b)** Photograph shows the device, which consists of two titanium blend pedicle screws continued by a cylindrical polycarbonaturethane spacer through which a polyester cord (the artificial ligament) is strung. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs show the device positioned correctly in the lumbar spine. To avert interfering with facet joint role, the screws are positioned more laterally than are normal pedicle screws. In this instance, fusion of the segment at L5 through S1 was performed (note the presence of a spacer at this level) and the Dynesys organization was used for dynamic stabilization of the L4 through L5 segment.

**Effigy 21a.** Graf artificial ligament system. **(a)** Diagram provides a lateral view of correct positioning of the device in the lumbar spine. **(b)** Photograph shows the device, which consists of two metallic pedicle screws effectually which a polyester band is looped. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs show the use of Graf artificial ligaments for dynamic stabilization at two levels (L3 through L4 vertebrae and L4 through L5 vertebrae). The fracture of wire markers within the polyester bands (arrowheads in c) is often mistaken for band failure but is actually of no consequence.

**Figure 21b.** Graf artificial ligament system. **(a)** Diagram provides a lateral view of correct positioning of the device in the lumbar spine. **(b)** Photograph shows the device, which consists of ii metal pedicle screws around which a polyester ring is looped. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs evidence the apply of Graf artificial ligaments for dynamic stabilization at two levels (L3 through L4 vertebrae and L4 through L5 vertebrae). The fracture of wire markers within the polyester bands (arrowheads in c) is often mistaken for band failure merely is really of no outcome.

**Figure 21c.** Graf artificial ligament system. **(a)** Diagram provides a lateral view of correct positioning of the device in the lumbar spine. **(b)** Photograph shows the device, which consists of ii metallic pedicle screws around which a polyester band is looped. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs show the apply of Graf artificial ligaments for dynamic stabilization at two levels (L3 through L4 vertebrae and L4 through L5 vertebrae). The fracture of wire markers within the polyester bands (arrowheads in c) is ofttimes mistaken for band failure but is actually of no consequence.

**Effigy 21d.** Graf artificial ligament system. **(a)** Diagram provides a lateral view of correct positioning of the device in the lumbar spine. **(b)** Photograph shows the device, which consists of two metallic pedicle screws around which a polyester band is looped. **(c, d)** Anteroposterior **(c)** and lateral **(d)** radiographs evidence the utilize of Graf artificial ligaments for dynamic stabilization at 2 levels (L3 through L4 vertebrae and L4 through L5 vertebrae). The fracture of wire markers within the polyester bands (arrowheads in c) is frequently mistaken for band failure simply is actually of no consequence.

**Figure 22a.** Wallis stabilization system. **(a)** Diagram provides a lateral view of the correct positioning of the device in the lumbar spine. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs show the device positioned at the level of the L4 through L5 vertebral processes. Radiopaque markers within an interbody spacer in the L4–5 disk space likewise are visible in b. The spacer is anchored in position by tape, which is wrapped effectually the adjacent spinous processes and is under tension. Metal bands (arrowheads in c) aid secure the tape.

**Figure 22b.** Wallis stabilization system. **(a)** Diagram provides a lateral view of the correct positioning of the device in the lumbar spine. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs evidence the device positioned at the level of the L4 through L5 vertebral processes. Radiopaque markers within an interbody spacer in the L4–five disk space besides are visible in b. The spacer is anchored in position past tape, which is wrapped around the adjacent spinous processes and is under tension. Metal bands (arrowheads in c) help secure the tape.

**Figure 22c.** Wallis stabilization system. **(a)** Diagram provides a lateral view of the correct positioning of the device in the lumbar spine. **(b, c)** Anteroposterior **(b)** and lateral **(c)** radiographs testify the device positioned at the level of the L4 through L5 vertebral processes. Radiopaque markers inside an interbody spacer in the L4–5 deejay space also are visible in b. The spacer is anchored in position past tape, which is wrapped around the adjacent spinous processes and is under tension. Metallic bands (arrowheads in c) assistance secure the tape.

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Source: https://pubs.rsna.org/doi/full/10.1148/rg.276065205

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