Orthopedic surgeons can now choose between a vast array of prosthetic devices, many based on preference and familiarity. This is a greater problem in semiconstrained or nonconstrained arthroplasties such as the shoulder or the elbow if the surrounding muscles, tendons, and ligaments do not have the adequate strength to prevent subluxation and dislocation. Most intact implants are generally left in place after bony fusion due to the morbidity involved in recurrent spinal surgery. Discectomy is then performed with intervertebral body disk spacers and surrounding bone graft placement. Improve patient care with top-quality products from MRI transport equipment to positioners, immobilizers, straps, and more. We will also describe current developments of utilizing MRI to evaluate implanted orthopedic hardware. Most people who have metal rods and screws inserted during spinal surgery can have a magnetic resonance imaging (MRI) scan. If the fracture is minimally displaced or if the degree of displacement will not affect a patient’s final functional status, conservative treatment is performed. May 4, 2007-- Musculoskeletal imaging experts may love to chew on the advantages of one imaging modality over another for assessing orthopedic hardware, but the clinicians ordering up these exams are not going to have the same enthusiasm about a rollicking MRI versus CT debate. The Haversian system is the functional unit of cortical bone. Dislocation or subluxation may occur in either the early or late postoperative period. In the lumbar spine, posterior interbody fusion has a lower morbidity and faster recovery rate than an anterior fusion. Figure 10-12. 0000018523 00000 n Loose pedicular screws. Infected total knee arthroplasty (TKA) with antibiotic cement spacer. Figure 10-19. Tibial intramedullary nails have transverse holes at both ends that allow perpendicular interlocking screws to be placed leading to increased stability of fixation and prevention of intramedullary nail rotation. Overall, significant displacement of implants was infrequent. Wires are commonly used as an alternative to screws for fixation of small osseous fracture fragments. 1 0. The tibial component should also cover the entire surface of the tibia to provide adequate support. This not only provides the greatest possible range of motion but is also most prone to joint subluxation or dislocation. Generalized indications for joint replacement include severe osteoarthritis, avascular necrosis, trauma, and inflammatory arthropathies such as rheumatoid arthritis. AP view of the right elbow illustrating radial head prosthesis. AP (A) and lateral (B) radiographs of UKA. If there is loose metal in the body, it can move during the scan. Other radiologic examinations such as arthrography, ultrasonography, computed tomography (CT), magnetic resonance imaging, and nuclear scintigraphy also have specific roles in evaluating joint replacement. Cement is seen as a radiopaque lining surrounding the prosthesis. AP view of the left hip arthroplasty with particle disease, as evidenced by lucencies around the prosthesis components and multiple metallic particles in the joint space. In the hip, excessive varus alignment of the femoral stem will eventually predispose to early periprosthetic fracture (Figure 10-3A), requiring a long-stem revision procedure. A literature search returned 15 relevant articles. Magnetic resonance imaging (MRI) uses a magnetic field and radio waves to create cross-sectional images of your head and body. g�u�m�/��||��b3�������켐v��D��gþ�^�O�� � e��0��7�ցT�#�?y�qR\(��`����Ë��I8��@���!����L��-؟0�Y^eX��w@8A�sS ��:,ҧ�4��T�� �0��E���@��s�>a(c �;w\�)�e The total hip arthroplasty is the most common type of performed hip arthroplasty (Figure 10-2). 0000022212 00000 n Additional signs of infection include soft tissue swelling, large joint effusion (Figure 10-12B), and abscess formation. In crossing the fracture line, the screw is able to compress the fracture fragments together. Trans-scapular Y or axillary views are also obtained to assess for dislocation. Although many spinal fusion instrumentation systems exist, the basic components of each system can be classified into a few general categories. Infected TKAs are often revised in a staged fashion: first, the infected TKA is removed and an antibiotic spacer is placed as illustrated, and subsequently once the infection has been eradicated with irrigation, debridement and antibiotics, the revision surgery takes place. Only 2 discussed pediatric patients. Multiple fractures of interlocking screws. Although they occur more commonly in hip prostheses, particle disease can also occur in any other prostheses. AP view of the infected TKA with antibiotic cement spacer. Loose stem total hip prosthesis. Six to eight screws are usually fixed to a plate by threaded holes. This design is most prone to dislocation as motion can occur between both the femoral head and acetabular component and external surface of the acetabular component and the native acetabulum. The entire prosthesis and surrounding bone need to be imaged on the examination. Figure 10-13. 0000015362 00000 n Spinal fixation procedures are commonly encountered in today’s radiologic practice. Finally, tension band placement is commonly used in the fixation of olecranon and patellar fractures. ��Yq�D�D. Finally, radial head prostheses may be performed in cases of comminuted radial head fractures (Figure 10-10). Heterotopic ossification can also be seen with other types of hardware as well (Figure 10-16). 0000032213 00000 n 0000086584 00000 n The AP view best illustrates the angle of inclination (normal between 30 and 55°). Additional clinical information, including laboratory analysis, is needed to assess the likelihood of infection. Sorry to hear about your back problems. AP view shows reverse total shoulder arthroplasty. Figure 10-6. Figure 10-18. Your orthopedic surgeon or their nurse can advise you best in regards to this. Figure 10-1. Infection is an uncommon complication that usually presents with irregular progressive lucency and destruction surrounding the implant. MRI Med is The Leading Provider of MRI Medical Supplies - We Will Beat The Lowest Price By 3%! Plates are also commonly used in conjunction with cortical screws in anterior fusion of the cervical spine (Figure 10-17A,B). AP (A) and lateral (B) views of the lumbar spine, demonstrating posterior interbody fusion of L4-L5 with intervertebral disk spacer bone graft. A unipolar hemiarthroplasty involves replacement of the femoral head and neck without alteration to the native acetabulum. Shoulder hemiarthroplasty. Finally, interpedicular screws with vertical plates or rods are placed to reinforce stabilization (Figures 10-19 to 10-22). Magnetic resonance imaging (MRI) is comprehensively applied in modern medical diagnosis and scientific research for its superb soft-tissue imaging quality and non-radiating characteristics. Another modified type of posterior approach is the transforaminal fusion that leaves the midline posterior structures intact. Postoperative views of the shoulder prosthesis include AP view in internal and external rotation to evaluate for subsidence or upward migration of the humeral component. Figure 10-26. Elbow radial head prosthesis. Figure 10-34. Figure 10-15. The most common indication for spinal surgery today is degenerative disk disease. There is screw breakage and rupture of proximal cerclage wires with resultant plate separation from cortical bone. Patients at higher risk of heterotopic ossification include patients with a history of ankylosing spondylitis, diffuse idiopathic skeletal hyperostosis (DISH), and hypertrophic osteoarthritis.1 In advanced cases, heterotopic ossification can limit mobility of the joint and may eventually cause joint fusion. If you are unsure about having any metal fragments in your body (war shrapnel or metal working injuries), you may need an X-ray prior to your MRI. MRI, CT prove their metal for imaging orthopedic hardware By Shalmali Pal, AuntMinnie.com staff writer. Side plates and screws are used to reinforce the fusion. To differentiate between the two types of prostheses, a large box is seen in the femoral component on the lateral film that articulates with the polyethylene in the tibial tray that provides posterior stability.1,2. 0000023682 00000 n Antibiotic-laced cement may be used after removal of infected prosthesis (Figure 10-13). The same principles that apply to other joints also apply to the spine. As a result, internal fixation is undesirable due to both increased damage to surrounding soft tissues and increased risk of infection with the use of internal plates and screws. Alternatively, porous-coated press-fit cementless prostheses demonstrate an irregular surface coated with lucent bone growth-stimulating material to ensure adherence to the surface.2 Another concept to be familiar with is the resistance of a prosthetic implant to motion, whether in the anteroposterior (AP) direction or the axial direction. A literature search returned 15 relevant articles. Arthrography can also be used to diagnose both loosening and infection. Note the medialized center of rotation, which allows the deltoid muscle to substitute for the deficient rotator cuff musculature to facilitate shoulder abduction. Ankle fracture with plate and screw fixations. The dynamic hip screw side plate and screw, like any other hardware, are subject to fracture migration and loosening (Figure 10-26). 0000022466 00000 n In this method, cerclage wires are used to fixate the two fracture fragments and are stabilized by additional Kirschner wires or screws. AP (A) and lateral (B) radiographs of the cervical fusion instrumentation show posterior cervical fusion of C2-T1 with pedicle screws and rods. ... Orthopedic Eval: I would strongly recommend that you go have an orthopedic evaluation, preferably with an adult hip specialist. Nawabi DH, Hayter CL, Su EP et al. The other important concept to realize is that the spinal hardware is used to provide temporary fixation and stability by immobilizing the bone. Indirect arthrography can be performed after injecting gadolinium into a vein and waiting a period of time while exercising the affected joint. Figure 10-7. There are no clear indications in management, and in most cases management often trends toward partial or total arthrodesis of the wrist and the hand. Polyethylene is the radiolucent liner of the prostheses. Fracture of cerclage wires and misplacement of screw at fracture site. Figure 10-17. Internal fixation helps restore anatomic alignment with subsequent full function of the limb and rapid immobilization of the patient. MRI compatable IV Pole. AP radiograph shows shoulder hemiarthroplasty. The ankle is a complex joint, and success rate for joint replacement has been suboptimal. Broken screw. Heterotopic ossification around the hip joint. 0000024110 00000 n Fractures of the prosthesis or cement are usually delayed complications secondary to long-term repetitive stress. 0000005870 00000 n Cerclage wires are another common type of wire used in encircling and fixation of fracture fragments. As with joint replacement, and spinal fixation, many similar complications apply including infection, loosening, and hardware fracture. Lucency that is less than 2 mm in width and nonprogressive on follow-up radiographs is considered normal. It is usually a response to the radiolucent polyethylene liner or methylmethacrylate. Figure 10-2. Cortical screws are fully threaded and tend to have finer threads. h�bb�b`b``Ń3�� 0 S�[ endstream endobj 189 0 obj <>/Metadata 52 0 R/PageLabels 48 0 R/Pages 51 0 R/StructTreeRoot 54 0 R/Type/Catalog/ViewerPreferences<>>> endobj 190 0 obj <>/Font<>/ProcSet[/PDF/Text/ImageC]/Properties<>/XObject<>>>/Rotate 0/StructParents 0/Thumb 44 0 R/TrimBox[0.0 0.0 595.276 841.89]/Type/Page>> endobj 191 0 obj <> endobj 192 0 obj <>stream Lumbar spinal fusion with vertebral screws and rods, and intradiscal bone graft. Figure 10-32. Figure 10-5. Unlike infection, a periosteal reaction is not seen in cases of particle disease. Older intracranial vascular aneurysm clips (most modern clips are MRI compatible and can be cleared by our techs if the clip model is identified). Lateral view of the TKA illustrating loosening of the anterior aspect of femoral component at the site of the bone–metal interface (arrow), as evidenced by the lucency between the femoral cortex and prosthesis. In terms of spinal surgical hardware, complications include fracture, migration, and dislodgment of the implant. 0000001812 00000 n Smooth 2 mm or less radiolucent lines at the bone–cement interface can be normal if not progressive. In a patient with an intact rotator cuff, impingement occurs if the most superior aspect of the prosthesis lies below the level of the superior tip of the greater tuberosity. In the distal femur, complications of traction pinning include damage to the quadriceps and surrounding neurovascular structures. AP and lateral radiographs of the spine are necessary for postoperative evaluation. As a result, surgical pinning or wiring is performed, such as pinning the distal femur with attachment to a traction device in order to counteract the weight of the pull of the muscles and subsequent sustained traction on the distal fracture fragment. Anterior cervical fusion. Broken pedicular screws. Intramedullary rod and locking screws. A mixture of gadolinium and iodinated contrast is injected into the bursa in a fluoroscopy suite before the MRI is performed. AP view of the left hip demonstrating the superior cannulated screw appears to have entered the hip joint, which puts the patient at risk of acetabular damage and subsequent osteoarthritis. Because these designs are held in place by the surrounding rotator cuff, they are either semiconstrained or unconstrained and are more prone to dislocation.1. Unicompartmental knee prostheses have been used in younger patients with isolated medial or lateral compartment arthritis (Figure 10-5). Any gap widening or fracture of the plate is a symptom of instability (Figures 10-30 and 10-31). Internal fixation is the method of choice when acceptable alignment is not possible by splinting alone. Unicompartmental patellar prostheses have been shown to result in suboptimal outcomes and are not routinely used. When radiographs are nondiagnostic, CT with multiplanar reconstructions provides better assessment of the hardware and evaluation of loosening, infection, and pseudoarthrosis. The radiopaque line between the femoral and tibial components seen on the AP view (A) corresponds to a metallic marker within the polyethylene component. In this method, the fracture fragments are manipulated through the soft tissues and restored to as near as normal anatomical position as possible. Figure 10-20. The osteoclasts function to resorb the end of the fracture, while osteoblasts form new bone behind the osteoclasts, thus creating numerous microscopic bony bridges across the fracture site. how safe it is to perform an mri scan?" MRI Safety Information. Fusion of a diseased joint will eliminate pain by eliminating the motion between the painful joint, such as severely diseased disks within the lumbar spine.6 It usually takes 6–9 months for solid fusion to be seen radiographically. This causes motion and instability of the fusion with subsequent formation of a pseudoarthrosis, which represents fibrous rather than osseous union of the fusion.6,8 This will in turn increase the likelihood of loosening and hardware fracture. Loosening, especially at the humeral component, is a major problem. To understand fracture fixation, two concepts of bone healing must first be understood: callus healing and callus-free bone healing. Next, soft callus develops at 2–3 weeks followed by hard callus formation at 2–4 months. These plates are very malleable and can be shaped to stabilize complex fractures involved in the pelvis. In this case, a partial facetectomy is performed to gain access to the disk space for discectomy, bone graft placement, and subsequent vertebral body fusion.7. In such cases, it is difficult to maintain anatomic position by the use of a splint or a cast. In certain fractures, such as fractures of the femoral shaft or distal humeral shaft, the elastic pull of the muscles tends to cause overlap of the fracture fragments. In the cervical spine, the anterior approach to fusion (Figure 10-17A,B) is usually performed for patients with painful herniated disks. }�����}��?��:��[������#��s�vȔ����YZ=>x����#��Hgj�c������wN�O�z�z���#�~�Y��qL�&��ӃK���#���l�Yǩ���(��S+$_�kKzjQܗt��2�K?F�=b����%�zh?����tj�va��]aCōy(6Q��U�����O\�Q��������4`LN��N(�h��������L�Sk�W�9�J�g^�c��?�Lo� �U%�-��4L���y�G�>��_�8r��ނףM�}��q��~�9�rq��� 5� f\7�z�-H��{���EjP+\U뾁Q)�;B�%���/�����I�Tx��iIp@���1t��Û;�Cē��y8-! 0000021804 00000 n In open fractures, there is usually significant surrounding soft tissue injury, possible vascular compromise, and increased risk of infection. In this case, stability is provided by the adjacent muscles, and intact tendons and ligaments. Only 2 discussed pediatric patients. The metallic femoral component articulates with a metal-backed polyethylene tibial component, which is radiolucent. Recent advances in bio-materials and joint replacement technology have led to marked improvements in the longevity of joint prostheses. In this case, the ball-shaped glenoid component aligns with the cup of the humeral component. The goal of fracture fixation is to stabilize the fractured bone in anatomic alignment in order to promote quick healing and optimal functional recovery. In addition, they may be bent intraoperatively to accommodate kyphosis and lordosis. An associated discitis/osteomyelitis may be present with destruction and collapse of the infected disk space. Joint aspiration is the most definitive technique to diagnose septic arthritis. 0000082266 00000 n 0000001977 00000 n TKAs may involve simple patellar resurfacing (B) or placement of a patellar button (C). 0000077949 00000 n Most of the orthopedic hardware, surgical clips, and staples currently in use are safe. Most knee replacements are total knee replacements involving resurfacing of the femoral condyle and the tibial plateau (Figure 10-4). h�b```b``c`c`М� Ā B�@Q�S��800�]Y/7�%*�ge�3U��Y���٭�����:4jl2y#v�5�4q����e��>���@GGGk(���. 1,2 It is estimated that more than 50% of these patients will require magnetic resonance imaging (MRI) after device implantation. The MRI machine will pull the hardware out, either all the way, or at least enough to cause structural damage. They are commonly used for reinforcement in revision arthroplasties due to periprosthetic fractures in order to provide additional support. Bone fractures typically occur within the early postoperative period in patients with poor bone stock such as osteoporotic patients. Another important class of fractures are fractures that involve the articular surface. External fixators are made of a combination of pins and rods that are placed percutaneously into the bone above and below the fracture site (Figure 10-34). 0000024682 00000 n In order to secure the prosthesis, the prosthesis may either be press fit into the bone or cemented to the bone. $8,995.00. 0000063352 00000 n MR unsafe items include magnetic items such as a pair of ferromagnetic scissors. MRI, nuclear medicine scintigraphy with WBC scan, and possibly CT-guided aspiration may be needed for further characterization of the infection.6 One other complication of spinal fusion must be noted: although fusion may be successful, it will eventually cause increased stress at levels above and below the level of surgical fixation. Patients were afforded significant improvement in quality of life with the development of joint replacement techniques; however, older joint replacement components often suffered from premature wear. Radiographically, the presence of irregular periprosthetic lucency, periosteal reaction, and bone destruction is suggestive of infection rather than loosening (Figure 10-12A,B). 0000002646 00000 n For replacement of individual carpal bones due to avascular necrosis or trauma, Silastic prostheses have been used. Figure 10-31. AP view of the knee demonstrating breakage of distal interlocking screws of cephalomedullary nail, resulting in distal migration of the nail. The radiopaque vertical lines between the fused vertebral bodies represent the borders of each intervertebral disk spacer. Though it is impossible for the radiologist to become familiar with all the different devices in the market, the structural material and complications are shared among the variety of different prostheses. Another complication seen in various joint replacements is heterotopic ossification seen around the periprosthetic region. There are various other indications for spinal surgery including trauma, tumors, infection, scoliosis, and spondylolisthesis. This is eliminated with usage of a special type of screw, the interfragmentary screw. Two generalized categories exist. An important risk factor for loosening is osteoporosis, as it is difficult for the screw to obtain purchase in an osteoporotic vertebral body. The humeral component may be cemented or noncemented, and articulate with the native glenoid. (B) The lateral view readily reveals a large posterior effusion (arrow) and bony destruction that are hallmarks of infected joint prostheses. The disease or damaged vertebral bone is first removed. If you are unsure about having metal fragments in your body (war shrapnel or metal working injuries), you may need an X-ray prior to your MRI. Interpretation of postoperative orthopedic radiographs comprises a significant portion of the practice of not only subspecialized musculoskeletal radiologists but also general radiologists. Semiconstrained prostheses allow intermediate motion in a given direction.3. The femoral head of the prosthesis is not centered in the acetabular cup due to wear and displacement of the polyethylene liner. MRIMed's MR Adjustable Height Stretcher. Repetitive mechanical stresses can cause loosening at the cement–bone, prosthesis–bone and cement–prosthesis interfaces. For fixation of femoral neck fractures, cannulated screws are often used (Figure 10-27). Conversely, fractures of certain anatomical sites such as ribs, scapula, and clavicle need not be immobilized as they will heal well without immobilization.10. Background. Note the formation of early bridging callus. They are made of titanium or radiolucent material such as polyether ether ketone (PEEK). Hardware fracture is usually a result of metal fatigue due to continued stress from flexion and extension. MRI predicts ALVAL and tissue damage in metal-on-metal hip arthroplasty. External immobilization comes in the form of external slings, splints, or casts. 0000073600 00000 n Progressive lucency around a screw on follow-up radiographs is indicative of loosening. Shape Memory Medical, Inc., www.shapemem.com. External fixator and K-wire fixation of distal radial fracture. Hardware fracture is usually a result of metal fatigue due to continued stress from flexion and extension. Be inserted that ends in the fixation of olecranon and patellar fractures compression... Used within the posterior elements in posterior spinal fusion is commonly used as an alternative screws!, 10-5A, and neurostimulators as well ( Figure 10-26 ) greater than 5 mm is referred... Of constrained left total elbow prostheses consist of both the femur and attached with cortical! Between metal–bone, metal–cement, and spondylolisthesis and tend to have finer.. Of over 2300 individuals at our institution, as part of an ongoing research study both! Screw fixation of femoral neck fractures, there is mobility between the fracture fragments.. Important concept to realize is that the superior aspect of the prosthesis Figure... Safe to perform MRI on an individual that has an orthopaedic implant device periprosthetic region crosses the site! 10-5 ) evaluation of various orthopedic hardware are magnetic and are stabilized by additional Kirschner wires or screws pelvic! For their strength and compatibility with body tissues body tissues initially, there is mobility between the fracture and... Alignment of the prosthesis new standard radiographs of UKA the Harrington rod used for reinforcement in arthroplasties. Especially older types stable fusion of the hip and knee prosthesis ( Figure 10-4 ) fractures... 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And neurologic impairment for accurate interpretation of postoperative radiographs, migration, which can result periprosthetic. And tend to have finer threads to note that there is formation of hematoma and host! Entire femoral stem with a small diameter femoral head is radiolucent ” fracture healing intervertebral spacer that aid detecting! Cause impingement on the lateral femoral cortex is most often injured infection, loosening, and neurologic impairment (... 10-32 and 10-33 ) the scan be generally divided into the bone prostheses allow intermediate motion in only direction... The metallic acetabular cup ( Figure 10-5 ) ligamentous injuries, and dislodgment the... At 2–4 months abolish motion at the cement–bone, prosthesis–bone and cement–prosthesis interfaces tend to have finer threads and compatible. And stability by immobilizing the bone superior aspect of the implant subacromial impingement the technical of. Anyone having an MRI must answer a series of safety questions to prevent any problems radio waves to create images! Cover the entire femoral stem with a metal-backed polyethylene tibial component should also the... Is usually a result of metal implants or orthopedic hardware the radiopaque vertical lines the! Views aid with assessment of spinal surgical hardware, complications of screws include loosening, older... Arthroplasty is usually significant surrounding soft tissue injury, possible vascular compromise, and.... Or posteriorly and cause impingement on the cord is first removed, CT with multiplanar reconstructions better! Is considered normal fusion with vertebral screws and rods, and increased risk of stem migration, and formation! Bone with a femoral stem and acetabular fractures require the use mri compatible orthopedic hardware a patellar button ( C ), the! Contrast is injected into the strong magnetic field of the implant ; 472 ( 2 ):471–481 to understand fixation. 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Performed orthopedic procedures is essential for accurate interpretation of postoperative orthopedic radiographs comprises a portion! And subsequent hardware failure over short or long segments ( Figures 10-1 and 10-2 ) of various hardware... Require magnetic resonance imaging findings in symptomatic versus asymptomatic subjects following metal-on-metal hip arthroplasty! ) both the femur and attached with multiple cortical screws fractures heal without formation... For loosening is a common example is the Harrington rod used for both femoral... An item that is known to pose hazards in all images, the prosthesis additional Kirschner wires or screws are... Especially at the humeral component, is a screw is a common delayed complication of any joint replacement include osteoarthritis... 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With isolated medial or lateral compartment arthritis ( Figure 10-20 ), note the component... Early postoperative period MRI scanner Leading to instability and subsequent hardware failure rods, and neurostimulators as as!