M u s c u l o s k e l e t a l I m a g i n g • R ev i ew Petscavage-Thomas and Walker Advanced Imaging of the Temporomandibular Joint

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Musculoskeletal Imaging Review

Unlocking the Jaw: Advanced Imaging of the Temporomandibular Joint Jonelle M. Petscavage-Thomas1 Eric A. Walker Petscavage-Thomas JM, Walker EA

OBJECTIVE. Temporomandibular joint (TMJ) dysfunction is a common condition, affecting up to 28% of the population. The TMJ can be affected by abnormal dynamics of the disk-condyle complex, degenerative arthritis, inflammatory arthritis, and crystal arthropathy. Less commonly, neoplasms and abnormal morphologic features of the condyle are causes of TMJ symptoms. Cross-sectional imaging is frequently used for diagnosis. CONCLUSION. Knowledge of the normal imaging appearance of the TMJ, its appearance on radiological examination, and interventional techniques are useful for providing a meaningful radiologic contribution. This article will review normal TMJ anatomy; describe the normal ultrasound, CT, and MRI appearances of TMJ; provide imaging examples of abnormal TMJs; and illustrate imaging-guided therapeutic TMJ injection.

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Keywords: internal derangement, jaw, MRI, temporomandibular joint DOI:10.2214/AJR.13.12177 Received November 1, 2013; accepted without revision December 5, 2013.

emporomandibular disorder (TMD) is common, affecting 28% of the population [1]. Mechanical issues are the most frequent type of disorder, associated with ­abnormal anatomic relationships at the temporomandibular joint (TMJ) [2]. Inflammatory conditions, such as juvenile inflammatory arthritis, rheumatoid arthritis, and psoriatic arthritis, may also lead to symptomatic TMD. Developmental abnormalities, crystalline disease, and neoplasms are less common sources of TMD. Clinical symptoms of TMD, including pain, decreased mandibular movement, and mastication problems, can also occur in non-TMJ disorders [3, 4]. Thus, imaging plays a key role in delineating the anatomic changes of the TMJ, assisting in identifying the category of TMD, assessing treatment response, providing therapeutic intervention, and guiding surgical management. This article will review the use of diagnostic and therapeutic imaging of the TMJ.

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Both authors: Department of Radiology, Penn State Hershey Medical Center, 500 University Dr, Hershey, PA 17033. Address correspondence to J. M. PetscavageThomas ([email protected]). This article is available for credit. AJR 2014; 203:1047–1058 0361–803X/14/2035–1047 © American Roentgen Ray Society

Anatomy The TMJ is a synovial joint formed by the articulation of the mandibular condyle with the articular fossa of the temporal bone [5, 6]. Interposed between the bones is a biconcave fibrous articular disk. The disk contains thick anterior and posterior bands and a thin intermediate zone [7] (Fig. 1). It is devoid of blood vessels and nerve fibers [8]. The disk

divides the joint into superior and inferior compartments that do not communicate unless there is disk compromise [9]. A bilaminar zone of connective tissue attaches the posterior band of the disk to the temporal bone. Supporting ligaments include the temporomandibular, sphenomandibular, and stylomandibular [8]. The superior belly of the lateral pterygoid muscle inserts onto the disk. The inferior belly of the lateral pterygoid muscle can insert onto the mandibular condyle, or between the condyle, capsule, and disk [2, 8]. The inferior belly is active in jaw opening, protrusion, and contralateral jaw movements. Normal Biomechanics The TMJ is a ginglymoarthrodial (meaning “hinge and glide”) joint [8]. Both translational and rotational motions are supported. With a closed mouth, the condyle articulates with the temporal fossa, and the posterior band of the articular disk is at the 11–12 o’clock position [2, 8] (Fig. 1A). When the jaw is open, the mandibular condyle moves anteriorly beneath the articular eminence, and the central part of the disk is interposed between the condyle and the articular tubercle [2] (Fig. 1B). Imaging MRI MRI is the reference standard for evaluating the articular disk and soft-tissue structures of the TMJ [8]. The imaging technique

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Petscavage-Thomas and Walker includes sagittal oblique and coronal plane images of 3-mm slice thickness or less. T1and proton density–weighted or T2-weighted sequences with fat saturation are preferred in both closed- and open-mouth positions [2, 10]. Gadolinium-based contrast material can help determine the presence of an inflamed synovium or arthropathy in select patients [8]. A dual-surface coil is used to image both TMJs in plane. On sagittal images, a normal disk has a biconcave or bow-tie configuration. In the closed-mouth view, the posterior band of the disk is located near the 11–12 o’clock position [2, 8] (Fig. 2A). Normally, with mouth open, the condyle translates anteriorly to articulate with the articular eminence (Fig. 2B) and the disk remains overlying the mandibular condyle. The junction of the posterior band and the intermediate-signal-intensity bilaminar zone should fall within 10° of vertical [2, 11]. The disk is of intermediate to low signal intensity on both T1-weighted and fluid-sensitive sequences. On the coronal view, it should not overhand the mandibular condyle medially or laterally. The bilaminar zone is of intermediate signal intensity with respect to the muscle on all imaging sequences. CT CT is most useful for evaluating osseous changes, such as erosions, fracture, postsurgical deformity, and the adjacent temporal bone [12]. Westesson et al. [13] found a sensitivity of 75% and specificity of 100% for the diagnosis of condylar osseous changes. The imaging technique involves MDCT in closed- and open-mouth positions, acquired of both TMJs with thin slices (1- to 2.5-mm thickness). Multiplanar reformations are performed in coronal oblique (parallel to the long axis of the condyle) and sagittal oblique planes using both bone and soft-tissue algorithms [12]. CT with 3D reconstructions can be useful for surgical treatment planning. Normally, the mandibular condyle has a thin cortex with a smooth contour. The condyle appears broader on coronal images (Fig. 2C). The anterior and posterior articular disk bands are higher in attenuation than adjacent soft tissues but lower in attenuation than the lateral pterygoid muscle tendon [12]. The bilaminar zone and intermediate zones cannot be seen without CT arthrography. Sonography Although it is used less commonly, ultrasound does have utility for pediatric patients

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who cannot undergo an MRI. A 40-year review of the literature showed ultrasound to have a sensitivity of 13–100% for disk displacement, 70–94% for condylar erosion, and 70.6–83.9% for evaluation of joint effusion [14]. The article also showed variability in ultrasound technique, with linear transducer frequency ranging from 5 to 20 MHz [14]. The transducer can be aligned along the axis of the mandibular ramus at the level of the zygomatic arch or parallel to the axis of the zygomatic arch. Normally, on ultrasound images, the articular eminence and mandibular condyle are hypoechoic with a hyperechoic cortex due to high reflection of sound waves. The disk may be hyperechoic, hypoechoic, and isoechoic, whereas the surrounding capsule, pterygoid muscle tissue, and retrodiscal tissues are isoechoic (Fig. 2D). One caveat is that changes in the incident angle of sound energy can lead to changes in disk echogenicity that may not be pathologic. Bone Scans Bone scans are useful tools for the diagnosis of TMJ osteoarthritis or joint inflammation. Kircos et al. [15] have reported that, in patients with TMD, the sensitivity of bone scan procedures was 93% and the specificity was 86%. In another study, the sensitivity of bone scans for diagnosis of osteoarthritis was 72.2% and the specificity was 57.7% [16]. Findings in TMD include increased uptake ratios in the TMJ. Bone scans, however, do not reveal the level of anatomic detail of MRI and CT. Imaging of Specific Disorders Internal Derangement Internal derangement is defined as an abnormal anatomic relationship of the disk to the mandibular condyle [2]. Disk displacement has been reported in 16–31% of asymptomatic patients but is statistically more common in patients with symptoms [3, 17]. A displaced disk may be reduced (“recaptured”) with mouth opening, and this is often accompanied by an audible and palpable click. As disease progresses, the disk may be nonreducible, resulting in limited motion with the absence of an audible click. The condition is three to five times more common among women and typically is seen at ages 20–40 years [8, 9]. Causes of internal derangement include trauma, malocclusion, bruxism, stress, and primary osseous abnormalities [18].

Disk Displacement With Reduction Early in disease, MRI findings include anterior disk displacement in the closed-mouth view, with reduction in the open-mouth view (Figs. 3A and 3B). The most sensitive signs of internal derangement are a rounded or biconvex disk shape and abnormal disk position [8]. The earliest finding may be increased T2 signal in the bilaminar zone. Disk degeneration is seen as loss of T1 and T2 signal [18]. Additionally, the angle between the posterior band and the vertical orientation of the condyle exceeds 10° [19, 20]. Disk Displacement Without Reduction With disease progression, increased laxity of retrodiscal soft tissues results in disk displacement without reduction [2] (Figs. 3C and 3D). There is further thickening of the posterior band and reduced mass of the anterior band. A folded or flattened shape is found in more severe cases of internal disk derangement [21]. A stuck disk is one that remains in a fixed position in both the open- and closedmouth views. This is presumably due to the formation of adhesions [2]. Although most disk displacement occurs anteriorly, 30% of cases are medial or lateral [15]. Posterior direction of disk displacement is rare. Other MRI findings of internal derangement include high T2 signal of the retrodiscal tissues, indicating inflammation and pain [22]. Alternatively, low T2 signal in this region can be seen, indicating fibrosis of a chronically displaced disk [23]. A nonenhancing joint effusion is seen more often in patients with disk displacement and pain [24]. Associated cortical erosions, condylar head flattening, osteophytes, subchondral marrow edema, and low-signal sclerosis are also reported in more severe cases with secondary osteoarthritis [8]. The inferior lateral pterygoid muscle is hyperactive in internal derangement [25], resulting in a thickened attachment that, when parallel to the anteriorly displaced disk, shows a “double-disk sign” [2, 26] (Fig. 3E). The muscle may also be hypertrophied, atrophied, or fibrosed. Inflammatory Arthritis Rheumatoid arthritis—Rheumatoid arthritis is a chronic inflammatory polyarticular disease most common among women in their 40s [27]. Rheumatoid arthritis is the most common inflammatory arthritis in adults to affect the TMJ, with incidence ranging from 5% to 86% of patients [28]. Patients experi-

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Advanced Imaging of the Temporomandibular Joint ence symptoms of pain, tenderness, swelling, and limited jaw movement [29]. In rheumatoid arthritis, the inflammatory synovial pannus destroys the articular disk and bilaminar zone, resulting in abnormal disk position (superior in > 50% of cases) and biplanar morphologic features on crosssectional imaging [30] (Fig. 4A). There can also be complete disk destruction. Joint effusion is nonspecific for rheumatoid arthritis, but an enhancing synovial proliferation suggests active rheumatoid arthritis [31] (Fig. 4B). Synovial enhancement is often a precursor to osseous changes. The osseous changes include bony apposition, with destroyed intervening soft tissues and secondary osteoarthritis [9], and 65% of cases show limited condylar motion on both open- and closedmouth images [31]. MRI has the highest accuracy (95%) for the diagnosis of rheumatoid arthritis. MRI and CT have been shown to similarly depict the osseous changes of condylar and articular eminence erosions, subchondral sclerosis, and bony apposition [32]. Lin et al. [33] developed grading categories of rheumatoid arthritis on MRI. Grade 0 is a normal condyle and joint. Grade 1 is mild rheumatoid arthritis involvement, with irregularity in the mandibular condyle, osseous destruction, bone marrow changes, and minimal joint space narrowing. Medium severity, or grade 2, includes significant erosion in the condyle, destruction, and joint space narrowing. Grade 3 (severe) involves complete destruction of the condyle and joint space narrowing [33]. Psoriatic arthritis—Psoriatic arthritis is a chronic inflammatory seronegative spondyloarthropathy that occurs in 5–8% of patients with psoriatic skin disease [34]. It is rarely associated with TMJ symptoms. Findings are similar to those for rheumatoid arthritis, including osseous erosions, condylar head flattening, decreased jaw motion between open- and closed-mouth views, joint effusion, and abnormal disk morphologic features and position [35] (Fig. 4C). CT scans may also show resorption of the mandibular condyle with new bone formation along and within the joint space [36]. Juvenile inflammatory arthritis—Juvenile inflammatory arthritis is the most commonly diagnosed rheumatologic condition in children, with about 300,000 affected children in the United States and a female predilection [37]. Several factors are associated with an increased risk of TMJ arthritis in juvenile inflammatory arthritis, including longer dis-

ease duration, young age at disease onset, and polyarticular or systemic course [38]. The rate of TMJ involvement differs significantly among the seven juvenile inflammatory arthritis subtypes, with 61% of cases associated with the extended oligoarticular subtype, 52% associated with the polyarticular rheumatoid factor–negative subtype, 50% associated with the psoriatic subtype, 36% associated with the systemic subtype, 33% associated with the polyarticular rheumatoid factor–positive subtype, 33% associated with the persistent oligoarticular subtype, 30% associated with the unclassified juvenile inflammatory arthritis subtype, and 11% associated with enthesitis-related arthritis [39]. The TMJ is more susceptible than other synovial joints to damage from arthritis because of the close proximity of the growth plate of the condylar head to the location of inflammation or synovitis [38]. Early diagnosis and treatment of TMJ synovitis are particularly important in the pediatric population, because acute and chronic inflammation in the TMJ joint can lead to joint deformity and functional limitations. Physical examination of children with TMJ arthritis is challenging, because there is often a paucity of TMJ signs or symptoms, and pain is not a reliable indicator of inflammation or damage in this population [38, 40]. Despite the high prevalence of radiographic evidence of TMJ disease in patients with juvenile inflammatory arthritis, most of the children have no TMJ signs or symptoms at examination [41–43]. Ultrasound examination of the TMJ allows dynamic evaluation of TMJ joint motion and fast detection of joint effusion, condylar erosions, and increased power Doppler flow due to synovitis (Fig. 4D). Sonography is suboptimal at detecting medial or lateral disk displacements [44]. CT findings include condylar concavities, condylar flattening, erosions, chronic hypoplasia or dysplasia of the condyle, and joint effusion. The condylar concavities can result in a bifid appearance (Fig. 4E). MRI with gadolinium-based contrast material is the most sensitive tool for detecting TMJ arthritis in juvenile inflammatory arthritis [38]. The most common abnormal findings in the TMJ on MRI are (in order of decreasing frequency) erosion of the condylar head, synovial enhancement, articular surface flattening (Fig. 4F), abnormality in jaw motion, subchondral sclerosis of the articular eminence, joint effusion, deformed or displaced disk in the open- or closedmouth position, bone marrow edema, scle-

rosis of the fossa, sclerosis of head, and the presence of osteophytes [45]. Other Types of Arthritis and Related Conditions Osteoarthritis—Osteoarthritis is the most common arthropathy of the skeleton and includes both primary and secondary causes. Primary osteoarthritis of the TMJ is more common in older patients and is associated with poor dentition. Secondary osteoarthritis may be seen in patients with internal derangement and other arthropathy. Imaging findings on both CT and MRI are similar to those for other joints in the body and include one or more of the following: condyle flattening, osteophytes, erosions, joint space loss, and subchondral sclerosis [46] (Fig. 5A). In more advanced cases, joint fusion may occur [8]. Avascular necrosis—Avascular necrosis is a common but underrecognized condition that involves the TMJ. It is more common in patients with disk displacement without destruction. It is postulated that the anteriorly displaced disk mechanically compromises the extraosseous and venous blood flow to the condyle by compression of the lateral pterygoid muscle insertion onto the mandibular condyle [47]. Avascular necrosis can lead to osteoarthritis and condylar collapse [47]. CT images show sclerosis of the subchondral bone and, as disease advances, subchondral collapse (Fig. 5A). MRI may show decreased T1 signal; decreased, increased, or variable T2 signal; and abnormalities of condylar morphologic features [48]. Calcium pyrophosphate dehydrate deposition disease—Calcium pyrophosphate dehydrate deposition disease is caused by deposition of calcium pyrophosphate dehydrate crystals in articular cartilage [49]. Typically, this involves fibrocartilage and hyaline cartilage, but crystals may also deposit in synovium, joint capsule, tendon, and intraarticular ligaments [49]. In the TMJ, calcium pyrophosphate dehydrate deposition disease is a rare condition of unknown cause. On radiographs and CT, one can see chondrocalcinosis of the fibrous disk and adjacent osseous changes of joint space narrowing, osteophytosis, and subchondral cyst formation [50] (Fig. 5B). Crystal accumulation can also mimic tumor or mass lesions because of erosion of adjacent condyle and temporal bone. MRI findings include low-signal-intensity periarticular masses on T2-weighted images with inhomogeneous enhancement [50]. The differential diagnosis for periarticular low-signal-intensity formation includes amyloid, gout, and synovial chondromatosis.

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Petscavage-Thomas and Walker Septic arthritis—Septic arthritis is uncommon in the TMJ. It is most often the result of hematogenous spread of distant infection, including sexually transmitted diseases and reactive arthritis [51]. Locally, septic arthritis may result from local trauma, burns, or spread of local infection. Typically, infection is due to a bacterial pathogen, most commonly Staphylococcus aureus [51]. Septic arthritis is most often seen in men presenting with pain and trismus at a mean age of 36 years [52]. On contrast-enhanced CT, findings include a large joint effusion (Fig. 5C), synovial enhancement, cortical breakdown, and, in some cases, osteomyelitis [52]. MRI reveals joint effusion with enhancing synovium and adjacent bone marrow changes, ranging from edema to erosions and findings of osteomyelitis. Tumors and Tumorlike Conditions Synovial chondromatosis—Synovial chondromatosis is an uncommon benign condition of synovial neoplasia with intraarticular proliferation of cartilaginous nodules originating from the synovial membrane [53]. It is a rare entity in the TMJ and is present more often in women aged 40–60 years. Clinically, patients present with pain, swelling, crepitation, and limited jaw movements, which can be associated with cranial nerve dysfunction. It is now thought that synovial chondromatosis is a neoplasia, not a metaplasia. Imaging findings include joint space widening, joint effusion, soft-tissue swelling, irregular surfaces of the joint, and multiple calcified loose bodies, which are seen as ossified bodies on CT and as amorphous isointense signal on MRI in up to 86.4% of cases [54] (Fig. 6A). Low-signal-intensity nodules might appear as both small round and punctate forms, correlating with calcified and ossified nodules on pathologic examination [55]. MRI is helpful in assessing for skull base changes that indicate a more aggressive course. Thus, preoperative CT and MRI are very useful because synovial chondromatosis requires surgery for treatment. In some cases, there is extracapsular and intracranial extension and malignant transformation [56]. Pigmented villonodular synovitis—Pigmented villonodular synovitis is another uncommon but reported tumorous synovial disease of the TMJ. It is typically a monoarticular hyperplastic inflammatory process of large joints of the extremities [57]. CT findings in the TMJ include bone erosion and cyst formation of the mandibular condyle

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and soft-tissue masses with attenuation lower than that of adjacent skeletal muscle [57, 58]. MRI features include areas of low signal on all imaging sequences due to hemosiderin deposition. Areas of high T2 signal may represent loculated cysts of joint fluid [57, 58]. Tumors—Neoplasms are rare in the TMJ. However, symptoms can be similar to those of TMD. A meta-analysis of the literature of 285 different reported tumorlike conditions found that 81.8% of lesions were benign [59]. However, when benign tumorlike conditions, such as pseudotumors, synovial chondromatosis, pigmented villonodular synovitis, and eosinophilic granuloma, were excluded, 64.2% of cases were malignant. The most common malignant tumors are sarcoma (53.8%) and metastatic disease (32.7%) (Figs. 6C and 6D). Malignant entities are more often a mixed lytic and softtissue pattern involving the mandibular condyle on CT, compared with radiolucency without a soft-tissue component for benign entities. Benign neoplastic entities reported in the TMJ include aneurysmal bone cysts and fibrous dysplasia, with imaging appearances similar to those of other osseous sites of involvement [59, 60]. Condylar Aplasia and Hypoplasia Aplasia and hypoplasia—Condylar deficiency can range from minimal to complete absence of the mandibular condyle and can be due to abnormal development and growth of the TMJ [6]. Common causes of aplasia include rheumatoid arthritis, radiation therapy, and parathyroid hormone–related processes affecting chondro­ cyte differentiation [61, 62]. Aplasia is also associated with hemifacial micro­ somia, Goldenhar syndrome, Treacher Collins syndrome, Proteus syndrome, Morquio syndrome, and auriculo-condylar syndrome [8]. Agenesis is associated with external ear, auditory canal, and middle and inner ear abnormalities [8], whereas external ear deficiencies are not a feature of condylar hypoplasia. On CT and MRI, altered condylar shape is associated with a shallow sigmoid notch, a short ramus and mandibular body, and underdeveloped glenoid fossa (Fig. 7A). Hyperplasia—Hyperplasia is typically idiopathic, although it has been associated with endocrine disturbances [63]. Patients may have an elongated ramus and body (Fig. 7B), resulting in deviation of the chin to the unaffected side [63]. The condyle may also

be morphologically normal or elongated and may impinge on the zygomatic process [64]. Traumatic Conditions Trauma to the TMJ includes condylar process fracture, mandibular fossa fracture, and TMJ dislocation. Fractures—Mandibular fractures are typically the result of motor vehicle crashes and assaults [65]. Condylar fractures account for 25–50% of mandibular fractures and are classified as condylar neck (low, medium, or high) and condylar head (extra- or intracapsular) [65]. Fracture displacement is usually medial because of the action of the lateral pterygoid muscle. CT is useful in multiplanar reconstruction and assessment of adjacent zygomatic process and external auditory canal injury (Fig. 8A). Dislocation—Dislocation of the TMJ can be traumatic or nontraumatic, such as that precipitated by yawning, eating, dental treatment, or oral intubation [66]. Dislocation at the TMJ is defined as excessive forward movement of the condyle beyond the articular eminence, with complete separation of the articular surfaces and fixation of the condyle in that position [67]. Dislocation can be seen on imaging when there is persistent location of the condyle under the articular eminence in both open- and closed-mouth positions (Fig. 8B). Associated condylar fractures may be seen. Clinically, the patient cannot fully close the mouth and has pain and difficulty speaking and swallowing. There is increased risk of dislocation in patients with shallow articular fossa or connective tissue disease. Therapeutic Joint Injection Although arthroscopy is the primary treatment for patients with internal derangement, nonsurgical management can be attempted. Fluoroscopically guided intraarticular steroid injection has been shown to increase active mouth opening by 10 mm [68]. Therapeutic injection is often used for patients with juvenile inflammatory arthritis to maintain optimal joint function, reduce orofacial symptoms, and avoid permanent damage and unfavorable growth alterations [68]. However, a systematic review of corticosteroid injection of TMJ in juvenile inflammatory arthritis found only limited conclusions on efficacy and no long-term effect data on outcomes or effect on mandibular growth alterations and or damage [69]. The imaging-guided technique involves palpation of the lower edge of the zygoma

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Advanced Imaging of the Temporomandibular Joint and posterior edge of the condyle of the mandible. The injection is done with the mouth wide open. A 23- to 25-gauge needle is inserted almost vertically (directed slightly forward) at the base of the tragus. The tip of the needle lies intraarticularly at about 1.5 cm. Contrast material outlining the joint space confirms the intraarticular location (Fig. 9). Recent studies have shown that injection of the inferior joint space or double joint space results in greater maximal mouth opening and alleviation of pain compared with superior space injection [70]. Temporomandibular Joint Arthroplasty Another treatment option, particularly for patients for whom therapeutic joint injections and arthroscopy have failed, is TMJ replacement. Both partial joint prostheses that replace the fossa eminence and total joint prostheses are available. Partial replacements may be composed of silastic or metal material (Fig. 10). In total joint replacement, the neurovascular structures and disk are removed, and one of several U.S. Food and Drug Administration–approved devices is implanted [71]. These devices typically contain a metal condylar component, mesh or metal fossa component, and radiolucent ultra-high-molecular-weight polyethylene material for the articular surface. In a study of 442 total TMJ replacements in 288 patients, 69.5% had decreased interference with eating, 67.5% had less pain, and 44.6% had increased incisal opening at 3 years [72]. Another study of 103 joints showed improved pain, an increase in maximal incisal opening of 22–33 mm, and improved dietary score at 1-year follow-up [73]. Potential complications of TMJ arthroplasty include infection; foreign body reaction to metal or polyethylene; fossa wear-through; facial nerve dysfunction; neuroma formation; dislocation, loosening, or displacement of the implant; heterotopic bone formation; screw fracture; and corrosion of joint surface or degenerative changes resulting from implants. Conclusion Knowledge of normal TMJ anatomy, expected cross-sectional imaging appearance, pathologic appearance, and therapeutic technique is important for a radiologist to assist in the management of patients with TMJ dysfunction.

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Petscavage-Thomas and Walker 33. Lin YC, Hsu ML, Yang JS, Liang TH, Chou SL, Lin HY. Temporomandibular joint disorders in patients with rheumatoid arthritis. J Chin Med Assoc 2007; 70:527–534 34. Brower A, Flemming DJ. Arthritis in black and white: expert consult, 3rd ed. Philadelphia, PA: Elsevier Saunders, 2012 35. Melchoirre D, Calderazzi A, Maddali Bonqi S, et al. A comparison of ultrasonography and magnetic resonance imaging in the evaluation of temporomandibular joint involvement in rheumatoid arthritis and psoriatic arthritis. Rheumatology (Oxford) 2003; 42:673–676 36. Kulkarni AU, Gadre PK, Kulkarni PA, Gadre KS. Diagnosing psoriatic arthritis of the temporomandibular joint: a study in radiographic images. BMJ Case Rep 2013; 2013:bcr2013010301 37. Sacks JJ, Helmick CG, Luo YH, Ilowite NT, Bowyer S. Prevalence of and annual ambulatory health care visits for pediatric arthritis and other rheumatologic conditions in the United States in 20012004. Arthritis Rheum 2007; 57:1439–1445 38. Ringold S, Cron RQ. The temporomandibular joint in juvenile idiopathic arthritis: frequently used and frequently arthritic. Pediatr Rheumatol Online J 2009; 7:11 39. Cannizzaro E, Schroeder S, Müller LM, Kellenberger CJ, Saurenmann RK. Temporomandibular joint involvement in children with juvenile idiopathic arthritis. J Rheumatol. 2011; 38:510–515 40. Pedersen TK, Küseler A, Gelineck J, Herlin T. A prospective study of magnetic resonance and radiographic imaging in relation to symptoms and clinical findings of the temporomandibular joint in children with juvenile idiopathic arthritis. J Rheumatol 2008; 35:1668–1675 41. Twilt M, Mobers SM, Arends LR, ten Cate R, van Suijlekom-Smit L. Temporomandibular involvement in juvenile idiopathic arthritis. J Rheumatol 2004; 31:1418–1422 42. Weiss PF, Arabshahi B, Johnson A, et al. High prevalence of temporomandibular joint arthritis at disease onset in children with juvenile idiopathic arthritis, as detected by magnetic resonance imaging but not by ultrasound. Arthritis Rheum 2008; 58:1189–1196 43. Müller L, Kellenberger CJ, Cannizzaro E, et al. Early diagnosis of temporomandibular joint involvement in juvenile idiopathic arthritis: a pilot study comparing clinical examination and ultrasound to magnetic resonance imaging. Rheumatology (Oxford) 2009; 48:680–685 44. Bas B, Yılmaz N, Gökce E, Akan H. Diagnostic value of ultrasonography in temporomandibular disorders. J Oral Maxillofac Surg 2011; 69:1304–1310 45. Abramowicz S, Cheon JE, Kim S, Bacic J, Lee EY. Magnetic resonance imaging of temporomandibular joints in children with arthritis. J Oral Maxillofac Surg 2011; 69:2321–2328

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46. Westesson PL. Structural hard-tissue changes in temporomandibular joints with internal derangement. Oral Surg Oral Med Oral Pathol 1985; 59:220–224 47. Fu KY, Li Y, Zhang Z, Ma X. Osteonecrosis of the mandibular condyle as a precursor to osteoarthrosis: a case report. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 107:e34–e38 48. Schellhas KP, Wilkes CH, Fritts HM, Omlie MR, Lagrotteria LB. MR of osteochondritis dissecans and avascular necrosis of the mandibular condyle. AJR 1989; 152:551–560 49. Lv H, Fan Z, Han Y, Xu L, Wang H. A case of pseudogout of the temporomandibular joint with giant cell reparative granuloma of the temporal bone. Am J Otolaryngol 2013; 34:762–765 50. Marsot-Dupuch K, Smoker WRK, Gentry L, Cooper KA. Massive calcium pyrophosphate dehydrate crystal deposition disease: a cause of pain of the temporomandibular joint. AJNR 2004; 25:876–879 51. Gayle EA, Young SM, McKenna SJ, McNaughton CD. Septic arthritis of the temporomandibular joint: case reports and review of the literature. J Emerg Med 2013; 45:674–678 52. Trimble LD, Schoenaers JA, Stoelinga PJ. Acute suppurative arthritis of the temporomandibular joint in a patient with rheumatoid arthritis. J Maxillofac Surg 1983; 11:92–95 53. Koyama J, Ito J, Hayashi T, Kobayashi F. Synovial chondromatosis in the temporomandibular joint complicated by displacement and calcification of the articular disk: report of two cases. AJNR 2001; 22:1203–1206 54. Wang P, Tian Z, Yang J, Yu Q. Synovial chondromatosis of the temporomandibular joint. MRI findings with pathological comparison. Dentomaxillofac Radiol 2012; 41:110–116 55. Heffez LB. Imaging of internal derangements and synovial chondromatosis of the temporomandibular joint. Radiol Clin North Am 1993; 31:149–162 56. Lim SW, Leon SJ, Choi SS, Choid KH. Synovial chondromatosis in the temporomandibular joint: a case with typical imaging features and pathological findings. Br J Radiol 2011; 84:e213–e216 57. Bemporad JA, Chaloupka JC, Putman CM, et al. Pigmented villonodular synovitis of the temporomandibular joint: a diagnostic imaging and endovascular therapeutic embolization for a rare head and neck tumor. AJNR 1999; 20:159–162 58. Bravo SM, Winalski CS, Weissman BN. Pigmented villonodular synovitis. Radiol Clin North Am 1996; 34:311–326 59. Poveda-Roda R, Bagán JV, Sanchis JM, Margaix M. Pseudotumors and tumors of the temporomandibular joint: a review. Med Oral Patol Oral Cir Bucal 2013; 18:e392–e402 60. Rai KK, Dharmendrashinh R, Shiva Kumar HR. Aneurysmal bone cyst, a lesion of the mandibular condyle. J Maxillofac Oral Surg 2012; 11:238–242

61. Neville BW, Damm DD, Allen CM, Bouquot JE. Developmental defects of the oral and maxillofacial region. In: Neville BW, Damm DD, Allen CM, Bouquot JE, eds. Oral and maxillofacial pathology, 2nd ed. Philadelphia, PA: Saunders, 2002:17–18 62. Shibata S, Suda N, Fukada K, et al. Mandibular coronoid process in parathyroid hormone-related protein-deficient mice shows ectopic cartilage formation accompanied by abnormal bone modeling. Anat Embryol (Berl) 2003; 207:35–44 63. McLoughlin PM, Hopper C, Bowley NB. Hyperplasia of the mandibular coronoid process: an analysis of 31 cases and a review of the literature. J Oral Maxillofac Surg 1995; 53:250–255 64. Costa YM, Porporatti AL, Stuginski-Barbosa J, et al. Coronoid process hyperplasia: an unusual cause of mandibular hypomobility. Braz Dent J 2012; 23:252–255 65. Sommer OJ, Aigner F, Rudisch A, et al. Cross-sectional and functional imaging of the temporomandibular joint: radiology, pathology, and basic biomechanics of the jaw. RadioGraphics 2003; 23:e14 66. Thangarajah T, McCulloch N, Thangarajah S, Stocker J. Bilateral temporomandibular joint dislocation in a 29-year-old man: a case report. J Med Case Rep 2010; 4:263 67. Vasconcelos BC, Porto GG, Lima FT. Treatment of chronic mandibular dislocations using miniplates: follow-up of 8 cases and literature review. Int J Oral Maxillofac Surg 2009; 38:933–936 68. Samiee A, Sabzerou D, Edalatpajouh F, Clark GT, Ram S. Temporomandibular joint injection with corticosteroid and local anesthetic for limited mouth opening. J Oral Sci 2011; 53:321–325 69. Stoustrup P, Kristensen KD, Verna C, et al. Intraarticular steroid injection for temporomandibular joint arthritis in juvenile idiopathic arthritis: a systematic review on efficacy and safety. Semin Arthritis Rheum 2013; 43:63–70 70. Li C, Zhang Y, Lv J, Shi Z. Inferior or double joint spaces injection versus superior joint space injection for temporomandibular disorders: a systematic review and meta-analysis. J Oral Maxillofac Surg 2012; 70:37–44 71. Baur DA. Temporomandibular joint replacement. Medscape website. emedicine.medscape.com/ article/1986499-overview. Published June 27, 2013. Accessed October 25, 2013 72. Giannakopoulos HE, Sinn DP, Quinn PD. Biomet microfixation temporomandibular joint replacement system: a 3-year follow-up study of patients treated during 1995 to 2005. J Oral Maxillofac Surg 2012; 70:787–794 73. Sidebottom AJ, Gruber E. One-year prospective outcome analysis and complications following total replacement of the temporomandibular joint with the TMJ Concepts system. Br J Oral Maxillofac Surg 2013; 51:620–624 (Figures start on next page)

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Advanced Imaging of the Temporomandibular Joint Fig. 1—Normal temporomandibular joint (TMJ) anatomy. (Illustrations by Walker EA) A, Illustration of normal TMJ anatomy in closedmouth view shows mandibular condyle (C) articulating with articular fossa (AF). Disk is biconcave with thin intermediate zone. Posterior band (P) is at 11–12 o’clock position of condyle. Superior belly of lateral pterygoid muscle (SHLP) inserts onto anterior band of disk (A), whereas inferior belly (IHLP) can attach to disk or mandibular condyle. Posterior band is connected to temporal bone by connective tissue called bilaminar zone. AE = articular eminence. B, Illustration of normal TMJ anatomy in open-mouth view shows condyle now articulates with articular eminence of temporal bone. Disk remains between eminence and condyle.

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Fig. 2—Three patients with normal temporomandibular joint imaging appearance. A and B, 35-year-old woman. Closed-mouth proton density–weighted fat-saturated image (A) and open-mouth T1-weighted sagittal image (B) show hypoechoic biconcave shaped disk with anterior (white arrow) and posterior (black arrow) bands. Posterior band of disk is at 11–12 o’clock position in closed-mouth view. Lateral pterygoid muscle (LP) is anterior to condyle (C). AE = articular eminence, EAC = external auditory canal. C, 45-year-old man. Coronal CT image in bone window shows rounded contour of mandibular condyle with thin cortex and normal disk space. D, 15-year-old girl. Ultrasound image with 12-MHz linear transducer aligned along long axis of mandibular ramus at level of zygomatic arch shows articular eminence (AE), hypoechoic disk (arrow), and erosion-free mandibular condyle.

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Fig. 3—Three patients with internal derangement. A and B, 57-year-old woman with pain and clicking. Sagittal closed-mouth proton density–weighted fat-saturated image (A) shows disk is anteriorly displaced (white arrow). There is also increased T2 signal (black arrow) in bilaminar zone and flattening of normal shape of disk. Sagittal open-mouth T1-weighted image (B) shows that disk (arrow) reduces to normal position. C and D, 45-year-old woman with internal derangement/temporomandibular dysfunction. Sagittal T1-weighted image (C) shows that disk (arrow) in closed-mouth position is anteriorly displaced and slightly irregular in shape. Sagittal T1-weighted open-mouth view (D) shows no reduction of disk displacement (arrow) and globular disk shape. E, 39-year-old woman with internal derangement/temporomandibular dysfunction. Proton density–weighted fat-saturated image shows two hypoechoic horizontal bands attaching to condyle. This represents double-disk sign of thickened inferior lateral pterygoid muscle (arrow) and anteriorly displaced disk.

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Fig. 4—Four patients with inflammatory arthritides. A and B, 33-year-old woman with rheumatoid arthritis. Sagittal proton density–weighted fat-saturated image (A) shows disk is anteriorly displaced and globular in configuration (arrow). Condyle is also eroded and diminished in size. Coronal T1-weighted contrast-enhanced fat-saturated image of right temporomandibular joint (TMJ) (B) shows joint effusion with enhancing synovitis, absence of normal appearing disk, and posterior pannus (arrow). C, 45-year-old man with psoriatic arthritis. Sagittal T1-weighted fat-saturated gadolinium-enhanced image shows enhancing synovium, destroyed disk, and flat irregular condyle with new bone formation. (Fig. 4 continues on next page)

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Advanced Imaging of the Temporomandibular Joint

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E Fig. 4 (continued)—Four patients with inflammatory arthritides. D, 17-year-old girl with juvenile inflammatory arthritis. Ultrasound image of mandibular condyle in long axis shows erosion of mandibular condyle (arrow) and hypoechoic synovitis along TMJ. E and F, 14-year-old boy with juvenile inflammatory arthritis. CT coronal image in bone algorithm (E) shows bifid appearance of condyle due to central erosion. T1-weighted contrast-enhanced fatsaturated image of patient’s other TMJ (F) shows erosion and flattening of condyle, bone marrow enhancement, and enhancing synovium with large joint effusion. Normal disk is not apparent.

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Fig. 5—Three patients with other types of arthritis and related conditions. A, 55-year-old man with avascular necrosis. Coronal CT image in bone window of both temporomandibular joints (TMJs) shows joint space narrowing of both, with subchondral sclerosis and subchondral cystic change. Increased serpiginous sclerosis in right mandibular condyle is due to avascular necrosis. (Fig. 5 continues on next page)

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Fig. 5 (continued)—Three patients with other types of arthritis and related conditions. B, 58-year-old woman with calcium pyrophosphate dehydrate deposition disease. Sagittal CT image in soft-tissue window shows linear chondrocalcinosis of TMJ, flattening of condyle, and subchondral cysts. C, 35-year-old man with septic arthritis who presented with fever and elevated erythrocyte sedimentation rate. Axial contrast-enhanced CT image in soft-tissue window shows joint effusion in right TMJ (arrow) with enhancement. Joint aspiration confirmed septic arthritis.

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Fig. 6—Three patients with tumors and tumorlike conditions. A, 55-year-old woman with synovial chondromatosis. Sagittal CT image in bone algorithm shows multiple intraarticular ossified bodies, narrowing of left temporomandibular joint (TMJ), and osseous erosion and subchondral cyst. B, 44-year-old woman with left TMJ dysfunction. T2-weighted fat-saturated coronal image shows multiple round and punctate low-signal-intensity nodules with joint effusion (arrowhead) in left TMJ overlying condyle (arrow), consistent with synovial chondromatosis. C and D, 64-year-old man with primary adenocarcinoma of lung. Axial CT image in bone algorithm (C) shows soft-tissue mass in TMJ with lytic destruction of anterior aspect of mandibular condyle. Axial fused PET/CT image (D) shows uptake in left TMJ consistent with metastatic disease.

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Advanced Imaging of the Temporomandibular Joint Fig. 7—Two patients with dysplasia. A, 20-year-old man with dysplasia. Coronal CT image in bone window shows underdeveloped left mandibular condyle and shallow articular fossa compared with normal right side. B, 22-year-old man with dysplasia. Coronal CT image in bone window shows hyperplasia of mandibular condyle (arrow), with impingement on adjacent temporal bone and lateral subluxation in respect to articular fossa.

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Fig. 8—Two patients with trauma. A, 25-year-old man with impaction fracture. Coronal CT image in bone window shows impaction fracture of mandibular condyle, with bone fragment within joint space (arrow). Condyle is also medially subluxated in respect to fossa. B, 33-year-old man with dislocation due to yawning. Sagittal CT image in bone window shows condyle is anteriorly dislocated in respect to articular eminence.

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Fig. 9—25-year-old woman who received therapeutic injection. Lateral fluoroscopic image shows needle in disk space and contrast agent outlining temporomandibular joint, consistent with intraarticular location.

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Fig. 10—65-year-old woman who underwent temporomandibular joint (TMJ) arthroplasty. A, Radiograph shows bilateral partial TMJ replacement as metal articular fossa implants. B, Sagittal CT image in bone window shows partial articular fossa TMJ arthroplasty of metal. This acts as spacer to maintain joint space, alleviate pain, and allow jaw opening and eating functionality.

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