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Normal variations of bony components on plain chest radiographs: Approaching with multiplanar reconstructed computed tomography Poster No.: C-0970 Congress: ECR 2010 Type: Educational Exhibit Topic: Chest Authors: A. Yamamoto , S. Suzuki , K. Toyoda , M. Yamasaki , E. Lien , T. 1 3 1 1 1 1 2 2 3 3 O'uchi , S. Furui ; Tokyo/JP, Shiga/JP, Chiba/JP Keywords: normal variation, anomalous articulation, CT DOI: 10.1594/ecr2010/C-0970 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myESR.org Page 1 of 65 Learning objectives To illustrate the normal variants of bone and articulation on plain chest radiographs in correlation with MDCT images. To analyze, and improve understanding of bony components mimicking tumors or other pathologic conditions on chest radiographs in contrast to reconstructed MDCT images. Background The ribs, scapula, clavicle, sternum, vertebra, humerus and their joints are projected on chest radiographs. A wide variety of normal shapes, congenital or acquired deformities and unique articulation can be detected, occasionally mimicking tumors or other pathologic conditions. Knowledge and recognition of the spectrum of these manifestations can be helpful in obtaining an accurate diagnosis and avoiding unnecessary examination. We reviewed chest images of patients who received both chest radiography and MDCT within a short period of time in the past four years. The radiographs were compared with the MDCT multiplanar reconstructed or volume-rendering images. Imaging findings OR Procedure details A wide spectrum of radiographic and MDCT findings of common and uncommon conditions are demonstrated under six categories: 1. Ribs: accessory rib, short rib, grooves in the lower and upper margin, normal congenital anomalies including duplication, articulation, fusion, forked rib or hypotrophic rib. 2. Scapula: hypertrophy of the coracoid process, hook-like configuration and normal lucency including foramina-like defect . 3. Clavicle: normal asymmetry, rhomboid fossa, and grooves in the lower margin. Page 2 of 65 4. Sternum: prominent manubrium, episternal notch of the manubrium and bifid xiphoid process. 5. Vertebra: variations of congenital malformations, prominent transverse process, osteophytes and other degenerative changes. 6. Others: variations of the anomalous articulation and calcification of the cartilages of the larynx. Ribs Anatomic rib variants, including an accessory rib, short rib, duplication and fusion of ribs, grooves and calcifications of the costal cartilages, may mimic lung, rib and other thoracic wall diseases. It is important for radiologist to be familiar with the normal anatomy, the variants, and the usual radiological appearance of the ribs. 1. Accessory ribs Accessory ribs are supernumerary ribs arising from the seventh cervical vertebra (cervical rib) or lumbar vertebra (lumbar rib). The cervical rib occurs in approximately 0.5% of the population with male predominance (Figure 1)(1). Although a cervical rib is usually asymptomatic, it is clinically important when the patient presents thoracic outlet syndrome from compression of the brachial plexus or subclavian vessels. The lumbar rib is occasionally seen in the chest radiograph at L1 or rarely at L2 ipsilaterally or bilaterally th (Figure 2). It may be confused with a 12 rib fracture in trauma patients or hypotrophy th of 12 rib (Figure 3). Page 3 of 65 Fig.: 1. Cervical rib. Frontal chest radiograph (a) and VR image (b) show the bilateral cervical rib (white arrows). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Page 4 of 65 Fig.: 2-3. Figure 2. Lumbar rib. Frontal chest radiograph (a) shows osseous protrusion horizontally from L1, which simulates a hypertrophic transverse process of the lumbar vertebra (arrows). VR image (b) presents the lumbar rib from L1 bilaterally (white arrows). Figure 3. Hypotrophy of the 12th rib. Frontal chest radiograph (a) shows a short bony protrusion from Th12, which simulates transverse process of the lumbar vertebra or the lumbar rib (arrow). VR image (b) demonstrates the bony protrusion as the unfused hypotrophic right 12th rib. The contralateral 12th rib is also hypotrophic. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN 2. Short ribs Frontal chest radiography sometimes shows a shortened mid-thoracic rib arch in patients who have no history of trauma or thoracic surgery (Figure 4). Short rib is diagnosed when the lateral margin of the affected rib is more than 4mm medial to a tangent drawn between the lateral margins of adjacent ribs (2). Short rib occurs in approximately 16% of the population, with right side predominance (8% on the right side, 1% on the left side, 7% bilaterally) (2). It is reported to involve only the sixth, seventh and eighth ribs. Page 5 of 65 Fig.: 4. Short rib. Frontal chest radiograph (a) and VR image (b) show the shortening of the right 8th rib compared to the adjacent ribs. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN 2. Costal grooves Normal grooves in the lower margin of the ribs, which carry the intercostal arteries veins, and nerves, can simulate tumors of the rib or pneumothorax (Figure 5)(3). The groove is st th st observed in the lower margin of the rib in all but the 1 and 12 ribs. The 1 ribs have grooves in the upper margin formed by the subclavian vessels and the brachial plexus (Figure 6). Page 6 of 65 Fig.: 5-6. Figure 5. Groove in the lower margin of the rib. Frontal chest radiograph (a) demonstrates irregular borders of the lower margins of right 9th and 10th rib. An opacity seems to be bulging inferiorly from the inferior aspect of the 9th rib (arrow). VR image shows (b) the grooves in the lower margins of the ribs (white arrows). Figure 6. Groove at the superior surface of the 1st rib. Frontal chest radiograph (a) shows the step-like groove on the superior surface of the right 1st rib (arrow). VR image (b) shows the subclavian artery and vein along the groove (white arrow). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN 3. Other congenital anomalies and deformities of the ribs There are various types of other congenital anomalies and deformities of the ribs including developmental fusion, articulation (Figure 7) or bridge formation (Figure 8), and forked rib (bifid rib) (Figure 9). These morphologic anomalies and anatomic variants are more frequent on the right side and occur predominantly in women in 0.15-0.31% of the population (1). Fused rib is considered to be related to a segmentation defect because it sometimes accompanies vertebral segmentation abnormalities (4). Rib bridging involves a more focal joining of adjacent ribs by bone outgrowths between a pair of ribs or several adjacent ribs. Page 7 of 65 Fig.: 7-9. Figure 7. Rib articulation. Frontal chest radiograph (a) shows the notch arising from the superior surface of the left 5th rib (arrow). VR image (b) shows the rib articulation between the 4th and 5th ribs (white arrow). Figure 8. Rib bridging. Frontal chest radiograph (a) shows the rib bridging between the right 5th and 6th rib (arrow). Note that the distance between the two ribs is narrowed. VR image (b) shows the rib bridging (white arrow). Figure 9. Forked rib. Frontal chest radiograph (a) shows the poorly defined opacity, which is continuous to the 5th rib in the left middle lung (arrow). VR image (b) demonstrates the forked configuration of the left 5th rib. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN st Rib rudiments or hypoplasia of the 1 ribs are found in 0.2% in the population (Figure 8) (4). These should not be confused with cervical ribs. Page 8 of 65 Fig.: 10. Hypotrophy of the 1st rib. Frontal chest radiograph (a) shows the shortened right 1st rib. It runs straight and medially. VR image (b) demonstrates the hypotrophic right 1st rib and failure to fuse to the costal cartilage. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN 5. Calcifications of the costal cartilages. The pattern and degree of costal cartilage calcification are unique and have been used in forensics to determine sex and age (5, 6). Foraminal defects are occasionally observed in the patients with the male-type calcification of the costal cartilage (Figure 11). The asymmetrical costal calcification is easily noticed on the chest radiograph especially at st the 1 ribs (Figure 12). Page 9 of 65 Fig.: 11-12.Figure 11. Foramina-like lucency of the costal cartilage. Frontal chest radiograph (a) shows ovoid-shaped lucent areas (arrows). VR image (b) demonstrates male-type calcification of the rib cartilages with a foramina-shaped defect. Figure 12. Asymmetrical calcification of the right 1st costal cartilage. Frontal chest radiograph (a) shows asymmetrical opacity of the right sternocostal joint (white arrow). VR image (b) shows sternocostal joint calcification to be more prominent on the right compared to the left (white double arrow). Note the foraminal defect of the sternum (box arrow). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN 6. Bone island Bone island in the rib is a common opacity which simulates a intrapulmonary nodule on the chest radiograph (Figure 13). Page 10 of 65 Fig.: 13. Bone island in the rib. Frontal chest radiograph (a) shows a well-defined nodular opacity in the right upper lung (arrow). VR image (b) shows the bone island in the right 2nd rib (white arrow). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Scapula The scapulae form the posterior part of the shoulder girdle. Each scapula is a flat, triangular bone with two surfaces, three borders and three angles (Figure 14)(7). Page 11 of 65 Fig.: 14. Normal anatomy of the scapula. Costal/ventral, dorsal and lateral views of the scapula. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN The costal or ventral surface presents a broad concavity, which is called subscapular fossa. The three borders of the scapula includes the superior, axillary and vertebral border. The borders may show normal lucency on the frontal chest radiograph (Figure 15). The superior border is concaved, extending from the medial angle to the base of the coracoid process. The warpage of the superior border may simulate a clasp-like cranial margin on the frontal chest radiograph (Figure 16). Page 12 of 65 Fig.: 15-16.Figure 15. Normal radiolucency of the wing of the scapula. Frontal chest radiograph (a) shows the broad lucent area in the scapula (arrows). In the VR image (b) the thickness of the axillary border, warpage of the superior border and the thinness of the subscapular fossa are easily recognized from the same oblique view. Figure 16. Clasp-like cranial margin of the scapula. Frontal chest radiograph (a) shows the clasp-like cranial margin of the scapula, which produces a pseudo-foramen (arrows). VR image lateral view (b) shows the superior thin curved border, which forms the fossa supraspinata, appears to be absent (white arrows). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN The inferior angle formed by the union of the vertebral and axillary border occasionally forms a hook-like configuration, which may simulate intrapulmonary mass (Figure 17). Page 13 of 65 Fig.: 17. Hook-like configuration of the inferior angle of the scapula. Frontal chest radiograph (a) shows the hook-like configuration of the inferior angle of the scapula (arrow), which may mimic intraparenchymal disease. VR image (b) clearly demonstrates the configuration in the inferior angle (white arrow). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN The coracoid process is a thick curved process arising from a broad base on the upper part of the neck of the scapula. The ascending portion may simulate a cystic mass in the scapula when the X-ray beam is tangential to the cortical bone (Figure 18). The horizontal portion is flattened from above down; its upper surface is convex and irregular, and gives attachment to the Pectoralis minor and coracoacromial ligaments. The apex is embraced by the conjoined tendons of the origin of the Coracobrachialis and the insertion of the short head of Biceps brachii. Hypertrophic changes of the coracoid process or articulations between the conoid tubercle and the coracoid process are commonly observed in elderly patients (Figure 19). Page 14 of 65 Fig.: 18-19. Figure 18. Foramina-like defect of the scapular neck. Frontal chest radiograph (a) shows a focal lucent area with a sclerotic rim on the superior margin of the scapular neck (arrow). VR image (b) shows the cortical bone of the coracoid process correlates to the lucent area on the radiograph (horizontal portion of the coracoid process cut away) (arrowheads). Figure 19. Hypertrophy of the coracoid process. Frontal chest radiograph (a) shows the hypertrophic change of the coracoid process (arrow). The distal inferior aspect of the clavicle demonstrates a notch-like deformity along the coracoclavicular ligament (arrowhead). On the VR image (b) the formation of the coracoclavicular joint and its degenerative change are clearly observed. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Clavicle The clavicle is a long bone with a medullary cavity of intramembranous origin. Medially it articulates with the manubrium to form the sternoclavicular joint. Laterally it articulates with the acromion process of the scapula at the acromioclavicular joint (7). The body of the clavicle is formed by two primary ossification centers, one medial and one lateral, which appear during the 5 th and 6 th week of fetal life. The third ossification center is Page 15 of 65 secondary and represents the only epiphysis at the medial end of the bone. The normal asymmetry of the clavicle of the medial secondary ossification center is commonly seen in the healthy individuals (Figure 20)(8). An irregular concavity (rhomboid fossa) may sometimes be present on the inferior surface near the medial end of the bone at the attachment of the costoclavicular ligament (Figure 21)(8). Fig.: 20-21. Figure 20. Normal asymmetry of the clavicle. Frontal chest radiograph shows the normal asymmetry of the medial ends of the clavicle. Figure 21. Rhomboid fossa. Frontal chest radiograph (a) and VR image (b) demonstrate the rhomboid fossa, the site of attachment of the rhomboid ligament between the first rib and the clavicle. It may simulate bone destruction or a cavitary lesion in the lung. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN The lateral inferior surface of the clavicle sometimes appears irregular at the insertion of the trapezoid muscle (Figure 22). An irregularity may also be observed on the medial superior surface of the clavicle caused by the subclavian artery and vein (Figure 23). Page 16 of 65 Fig.: 22-23. Figure 22. Groove of the lower margin of the lateral inferior aspect of the clavicle. Frontal chest radiograph (a) and VR image (b) show the groove for the insertion of the coracoclavicular ligament (arrows). Figure 23. Groove of the lower margin of the medial inferior aspect of the clavicle. Frontal chest radiograph (a) shows fine irregularity of the inferior margins of the clavicle. VR image (b) demonstrates that the irregularity matches the point at which the subclavian artery and vein run through (arrow). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Sternum The sternum is a flat bone, slightly convex anteriorly and concave posteriorly. It consists of three parts: the manubrium, body, and xiphoid process (Figure 24)(7). Page 17 of 65 Fig.: 24. Normal anatomy of the sternum. VR of the frontal view shows the normal anatomy of the sternum. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN The manubrium is the broadest portion of the sternum. It has a superior central notch and two lateral fossae that articulate with the clavicles. The manubrium also articulates with the first and second ribs and the body of the sternum (9,10). The body of the sternum is flat, with an irregular anterior surface. Superiorly, it articulates with the manubrium at the manubriosternal joint and with the xiphoid process inferiorly. The xiphoid process is a thin elongated bone that is subject to many variations (Figure 25). It is cartilaginous early in life and may be ossified and fused to the sternal body in old age (11,12). Page 18 of 65 Fig.: 25. Bifid xiphoid process. Oblique lateral chest radiograph (a) shows two notches of the xiphoid process (arrow). VR images of the same oblique view as the radiograph (b) and frontal view (c) demonstrate the bifid xiphoid process (arrowheads). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Two small notches of the jugular notch are occasionally observed on the frontal chest radiograph. They may be vestiges of the episternal bones (Figure 26). Page 19 of 65 Fig.: 26. Episternal notch of the sternum. Frontal chest radiograph (a) and VR image (b) show the nodular opacity close to the superolateral aspect of the manubrium (arrows). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Episternal ossicles are retro- or supramanubrial accessory bones that result from supernumerary ossification centers. They are found in 1.5% of the population. They may be unilateral or bilateral, pyramidal in shape, and have a diameter of 2-15 mm (Figure 27). Page 20 of 65 Fig.: 27. Episternal ossicles of the sternum. Frontal chest radiograph(a), axial (b) and VR images of CT scan (c) show two small bones in back of dorsal aspect of the manubrium (arrows). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Sternal foramen, which originates from the incomplete fusion of a pair of sternebrae, has been incidentally detected on CT in nearly 5% of the population (Figure 12)(13). Degenerative change is the most common abnormality affecting the sternoclavicular, costosterna and manubriosternal joints (Figure 28,29)(14). Radiography is capable of depicting osteophytes, synovial joint fusion and calcification in these patients. Page 21 of 65 Fig.: 28-29. Figure 28. Degenerative change of the right costoclavicular joint. Frontal chest radiograph (a) shows a well-marginated opacity which continues to the right 1st rib (arrow). VR image (b) shows ossification of the right costoclavicular joint and osteophytes protruding caudally from the inferior aspect (white arrow). Figure 29. Degenerative change of the manubriosternal joint. A lateral chest radiograph (a) shows a notch-like opacity protruding into the thoracic cavity (arrow). Sagittal reconstructed CT scan (b) shows an osteophyte of the manubriosternal joint (white arrow). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Vertebra A normal vertebra has a body and posterior elements. Many intrinsic and extrinsic diseases, including congenital or acquired processes, may alter the normal vertebral body configuration. Such diseases often demonstrate specific shapes of vertebrae. 1. Variations of congenital malformations The abnormal configurations of the body of a vertebra including agenesis, hemivertebra, coronal cleft, butterfly vertebra, block vertebra, limbus vertebra or hypoplasia are lead by Page 22 of 65 failures in fusion of two ossification centers (15). The dysraphism is defined as incomplete or absent fusion of midline neural, mesenchymal, and cutaneous structures. The occult spinal dysraphism is sometimes diagnosed with radiographs (Figure 30). Fig.: 30. Congenital dysraphism of the vertebra. Frontal chest radiograph (a) and VR image (b) demonstrate congenital dysraphism of C1-Th6 vertebrae. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Pediculate anomalies include hypoplastic pedicle, retroisthmic defect and pediculate cleft. The retroisthmic defect is observed independently or in co-existence with other pediculate anomalies (Figure 31)(16). Page 23 of 65 Fig.: 31. Retroisthmic defect of the vertebra. Frontal radiograph, (a) axial CT (b) and VR images (c) (dorsal view) demonstrate the retroisthmic defect of the vertebra From Th12 to L1 with no other complications of the vertebral body or posterior element. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN 2. Normal structures that may mimic disease Normal structures sometimes mimic vertebral body fracture on chest radiographs. They include the venous sinus, in adults and synchondroses or cancellous bone in children (Figure 32). In lean patients, transverse processes sometimes simulate nodules in the lung or right hilar region (Figure 33). Page 24 of 65 Fig.: 32-33. Figure 32. Venous sinuses of the vertebrae. Lateral chest radiograph (a) shows thin, linear horizontal lucencies in the mid-portion of the vertebrae (arrows). On sagittal reconstructed CT scan (b), the venous sinus groove is shown as roughness of the traveculae (white arrows). Figure 33. Transverse process of the thoracic vertebra. Frontal chest radiograph (a) and VR image (b) demonstrate the right transverse process of the thoracic vertebra (arrows). The transverse process may be confused with hilar or intraparenchymal nodules owing to the varying angle and extension. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN 3. Degenerative change of the vertebrae (Spondylosis deformans) Degenerative changes of the vertebrae commonly simulate nodules in the lung or bone tumors in elderly patients as a result of the shearing of the outer annular (Sharpey's) fibers. They rupture with disc herniation, which separates the anterior and longitudinal spinal ligaments from the vertebral bodies. Reactive bone formation at these sites of disruption results in the formation of horizontal and vertical ostephytes (Bumpy vertebra) (Figure 34,35)(15). Bumpy vertebrae show prominent osteophytes typically prominent on the right side of vertebrae. The left aspect of the vertebrae might retain their normal shape because of the pulsation of the descending aorta. Page 25 of 65 Fig.: 34-35. Figure 34. Bumpy vertebra. Frontal chest radiograph (a) and VR image (b) demonstrate hypertrophy of the costovertebral articulations at multiple levels with right-side predominance (arrow). Figure 35. Vertebral ostephytes. Lateral chest radiograph (a) shows nodule-like opacity simulating retrocardial intraparenchymal mass (arrow). Sagittal reconstructed CT scan (b) demonstrates the osteophytes bridging the endoplates (white arrow). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN The costovertebral joint may also represent hypertrophy at one or several levels. It can be confused with paravertebral or paratracheal mass (Figure 36). Page 26 of 65 Fig.: 36. Degeneration of the costovertebral articulation. Frontal chest radiograph (a), axial (b) and coronal (c) reconstructed CT scans show the degenerative changes of the costovertebral articulation, which is an indication of pulmonary pseudolesion (arrows). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN A Schmorl's node is a contour defect in the endplate of a vertebra resulting from central herniation of a portion of the disc into the adjacent vertebra body (15). A defect or weakness in the endplate leads to such disc herniation. A Schmorl's node is seen as a radiolucent defect with a sclerotic margin subjacent to the endplate (Figure 37). Page 27 of 65 Fig.: 37. Schmorl's node. Lateral chest radiograph (a), Sagittal reconstructed CT (b) and axial CT (c) scans show the schmorl's node as a lucent defect with a sclerotic rim subjacent to the vertebral endplate (arrows). A small Schmorl's node co-exists at the left margin of the vertebra (white arrow). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Other degenerative changes include calcification of perivertebral ligaments(Figure 38), enthesopathy, and vacuum phenomenon in the disc (Figure 39). Those commonly seen in the frontal and lateral chest radiograph of elderly patients may simulate vertebral or perivertebral diseases. Page 28 of 65 Fig.: 38-39. Figure 38. Calcification of the interspinous ligament. Lateral chest radiograph (a) and VR image (b) show the calcification of the interspinous ligament, which may simulate a fracture of the processus spinosus (arrows). Figure 39. Vacuum phenomenon. Lateral chest radiograph (a) and sagittal reconstructed CT scan (b) show intervertebral gas (arrows). Note the osteophytes at multiple levels. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Others 1. Variations of anomalous articulations On chest radiographs, various anomalous articulations are observed between rib and rib, rib and scapula or rib and vertebra (Figure40-44). It is important that the radiologist be familiar with the variations in anomalous articulations. Page 29 of 65 Fig.: 40-41. Figure 40. Anomalous articulation between the 1st and 2nd ribs. Frontal chest radiograph (a) and lateral view VR image (b) demonstrate the articulation between the left 1st and 2nd ribs (arrows). Figure 41. Aneurysm formation caused by anomalous articulation between the 1st and 2nd ribs. Frontal chest radiograph (a) and lateral view VR image (b) demonstrate the articulation between the left 1st and 2nd ribs (arrows). VR image (c) with intravenous contrast medium shows the aneurysmal formation at the thoracic inlet caused by the anomalous articulation (white box arrow). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Page 30 of 65 Fig.: 42-43. Figure 42. Anomalous articulation in the 1st rib. Frontal chest radiograph (a) and coronal reconstructed CT scan (b) show the anomalous articulation in the right 1st rib simulating a fracture (arrows). Figure 43. Anomalous articulation between the ribs. Frontal chest radiograph (a) and coronal reconstructed CT scan (b) show the anomalous articulation between the 4th and 5th ribs (arrows). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Page 31 of 65 Fig.: 44. Anomalous articulation between the rib and scapula. Frontal chest radiograph (a), axial CT (b) and VR image (c) demonstrate the articulation between the scapula and adjacent rib. References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN 2. Calcification of the cartilages of the larynx The calcification of the cartilages of the larynx occurs in the healthy patients asymmetrically or heterogeneously on the frontal radiograph (Figure 45). Page 32 of 65 Fig.: 45. Calcification of the cartilages of the larynx. Frontal chest radiograph (a) shows the crown-shaped opacity laying over the cervical spine (arrows). VR image (b) shows dense calcification of the thyroid and arytenoids cartilages (white box arrows). References: A. Yamamoto; Radiology, Teikyo University, Tokyo, JAPAN Page 33 of 65 Images for this section: Fig. 1: 1. Cervical rib. Frontal chest radiograph (a) and VR image (b) show the bilateral cervical rib (white arrows). Page 34 of 65 Fig. 2: 2-3. Figure 2. Lumbar rib. Frontal chest radiograph (a) shows osseous protrusion horizontally from L1, which simulates a hypertrophic transverse process of the lumbar vertebra (arrows). VR image (b) presents the lumbar rib from L1 bilaterally (white arrows). Figure 3. Hypotrophy of the 12th rib. Frontal chest radiograph (a) shows a short bony protrusion from Th12, which simulates transverse process of the lumbar vertebra or the lumbar rib (arrow). VR image (b) demonstrates the bony protrusion as the unfused hypotrophic right 12th rib. The contralateral 12th rib is also hypotrophic. Page 35 of 65 Fig. 3: 4. Short rib. Frontal chest radiograph (a) and VR image (b) show the shortening of the right 8th rib compared to the adjacent ribs. Page 36 of 65 Fig. 4: 5-6. Figure 5. Groove in the lower margin of the rib. Frontal chest radiograph (a) demonstrates irregular borders of the lower margins of right 9th and 10th rib. An opacity seems to be bulging inferiorly from the inferior aspect of the 9th rib (arrow). VR image shows (b) the grooves in the lower margins of the ribs (white arrows). Figure 6. Groove at the superior surface of the 1st rib. Frontal chest radiograph (a) shows the step-like groove on the superior surface of the right 1st rib (arrow). VR image (b) shows the subclavian artery and vein along the groove (white arrow). Page 37 of 65 Fig. 5: 7-9. Figure 7. Rib articulation. Frontal chest radiograph (a) shows the notch arising from the superior surface of the left 5th rib (arrow). VR image (b) shows the rib articulation between the 4th and 5th ribs (white arrow). Figure 8. Rib bridging. Frontal chest radiograph (a) shows the rib bridging between the right 5th and 6th rib (arrow). Note that the distance between the two ribs is narrowed. VR image (b) shows the rib bridging (white arrow). Figure 9. Forked rib. Frontal chest radiograph (a) shows the poorly defined opacity, which is continuous to the 5th rib in the left middle lung (arrow). VR image (b) demonstrates the forked configuration of the left 5th rib. Page 38 of 65 Fig. 6: 10. Hypotrophy of the 1st rib. Frontal chest radiograph (a) shows the shortened right 1st rib. It runs straight and medially. VR image (b) demonstrates the hypotrophic right 1st rib and failure to fuse to the costal cartilage. Page 39 of 65 Fig. 7: 11-12.Figure 11. Foramina-like lucency of the costal cartilage. Frontal chest radiograph (a) shows ovoid-shaped lucent areas (arrows). VR image (b) demonstrates male-type calcification of the rib cartilages with a foramina-shaped defect. Figure 12. Asymmetrical calcification of the right 1st costal cartilage. Frontal chest radiograph (a) shows asymmetrical opacity of the right sternocostal joint (white arrow). VR image (b) shows sternocostal joint calcification to be more prominent on the right compared to the left (white double arrow). Note the foraminal defect of the sternum (box arrow). Page 40 of 65 Fig. 8: 13. Bone island in the rib. Frontal chest radiograph (a) shows a well-defined nodular opacity in the right upper lung (arrow). VR image (b) shows the bone island in the right 2nd rib (white arrow). Page 41 of 65 Fig. 9: 14. Normal anatomy of the scapula. Costal/ventral, dorsal and lateral views of the scapula. Page 42 of 65 Fig. 10: 15-16.Figure 15. Normal radiolucency of the wing of the scapula. Frontal chest radiograph (a) shows the broad lucent area in the scapula (arrows). In the VR image (b) the thickness of the axillary border, warpage of the superior border and the thinness of the subscapular fossa are easily recognized from the same oblique view. Figure 16. Clasp-like cranial margin of the scapula. Frontal chest radiograph (a) shows the clasp-like cranial margin of the scapula, which produces a pseudo-foramen (arrows). VR image lateral view (b) shows the superior thin curved border, which forms the fossa supraspinata, appears to be absent (white arrows). Page 43 of 65 Fig. 11: 17. Hook-like configuration of the inferior angle of the scapula. Frontal chest radiograph (a) shows the hook-like configuration of the inferior angle of the scapula (arrow), which may mimic intraparenchymal disease. VR image (b) clearly demonstrates the configuration in the inferior angle (white arrow). Page 44 of 65 Fig. 12: 18-19. Figure 18. Foramina-like defect of the scapular neck. Frontal chest radiograph (a) shows a focal lucent area with a sclerotic rim on the superior margin of the scapular neck (arrow). VR image (b) shows the cortical bone of the coracoid process correlates to the lucent area on the radiograph (horizontal portion of the coracoid process cut away) (arrowheads). Figure 19. Hypertrophy of the coracoid process. Frontal chest radiograph (a) shows the hypertrophic change of the coracoid process (arrow). The distal inferior aspect of the clavicle demonstrates a notch-like deformity along the coracoclavicular ligament (arrowhead). On the VR image (b) the formation of the coracoclavicular joint and its degenerative change are clearly observed. Page 45 of 65 Fig. 13: 20-21. Figure 20. Normal asymmetry of the clavicle. Frontal chest radiograph shows the normal asymmetry of the medial ends of the clavicle. Figure 21. Rhomboid fossa. Frontal chest radiograph (a) and VR image (b) demonstrate the rhomboid fossa, the site of attachment of the rhomboid ligament between the first rib and the clavicle. It may simulate bone destruction or a cavitary lesion in the lung. Page 46 of 65 Fig. 14: 22-23. Figure 22. Groove of the lower margin of the lateral inferior aspect of the clavicle. Frontal chest radiograph (a) and VR image (b) show the groove for the insertion of the coracoclavicular ligament (arrows). Figure 23. Groove of the lower margin of the medial inferior aspect of the clavicle. Frontal chest radiograph (a) shows fine irregularity of the inferior margins of the clavicle. VR image (b) demonstrates that the irregularity matches the point at which the subclavian artery and vein run through (arrow). Page 47 of 65 Fig. 15: 24. Normal anatomy of the sternum. VR of the frontal view shows the normal anatomy of the sternum. Page 48 of 65 Fig. 16: 25. Bifid xiphoid process. Oblique lateral chest radiograph (a) shows two notches of the xiphoid process (arrow). VR images of the same oblique view as the radiograph (b) and frontal view (c) demonstrate the bifid xiphoid process (arrowheads). Page 49 of 65 Fig. 17: 26. Episternal notch of the sternum. Frontal chest radiograph (a) and VR image (b) show the nodular opacity close to the superolateral aspect of the manubrium (arrows). Page 50 of 65 Fig. 18: 27. Episternal ossicles of the sternum. Frontal chest radiograph(a), axial (b) and VR images of CT scan (c) show two small bones in back of dorsal aspect of the manubrium (arrows). Page 51 of 65 Fig. 19: 28-29. Figure 28. Degenerative change of the right costoclavicular joint. Frontal chest radiograph (a) shows a well-marginated opacity which continues to the right 1st rib (arrow). VR image (b) shows ossification of the right costoclavicular joint and osteophytes protruding caudally from the inferior aspect (white arrow). Figure 29. Degenerative change of the manubriosternal joint. A lateral chest radiograph (a) shows a notch-like opacity protruding into the thoracic cavity (arrow). Sagittal reconstructed CT scan (b) shows an osteophyte of the manubriosternal joint (white arrow). Page 52 of 65 Fig. 20: 30. Congenital dysraphism of the vertebra. Frontal chest radiograph (a) and VR image (b) demonstrate congenital dysraphism of C1-Th6 vertebrae. Page 53 of 65 Fig. 21: 31. Retroisthmic defect of the vertebra. Frontal radiograph, (a) axial CT (b) and VR images (c) (dorsal view) demonstrate the retroisthmic defect of the vertebra From Th12 to L1 with no other complications of the vertebral body or posterior element. Page 54 of 65 Fig. 22: 32-33. Figure 32. Venous sinuses of the vertebrae. Lateral chest radiograph (a) shows thin, linear horizontal lucencies in the mid-portion of the vertebrae (arrows). On sagittal reconstructed CT scan (b), the venous sinus groove is shown as roughness of the traveculae (white arrows). Figure 33. Transverse process of the thoracic vertebra. Frontal chest radiograph (a) and VR image (b) demonstrate the right transverse process of the thoracic vertebra (arrows). The transverse process may be confused with hilar or intraparenchymal nodules owing to the varying angle and extension. Page 55 of 65 Fig. 23: 34-35. Figure 34. Bumpy vertebra. Frontal chest radiograph (a) and VR image (b) demonstrate hypertrophy of the costovertebral articulations at multiple levels with rightside predominance (arrow). Figure 35. Vertebral ostephytes. Lateral chest radiograph (a) shows nodule-like opacity simulating retrocardial intraparenchymal mass (arrow). Sagittal reconstructed CT scan (b) demonstrates the osteophytes bridging the endoplates (white arrow). Page 56 of 65 Fig. 24: 36. Degeneration of the costovertebral articulation. Frontal chest radiograph (a), axial (b) and coronal (c) reconstructed CT scans show the degenerative changes of the costovertebral articulation, which is an indication of pulmonary pseudolesion (arrows). Page 57 of 65 Fig. 25: 37. Schmorl's node. Lateral chest radiograph (a), Sagittal reconstructed CT (b) and axial CT (c) scans show the schmorl's node as a lucent defect with a sclerotic rim subjacent to the vertebral endplate (arrows). A small Schmorl's node co-exists at the left margin of the vertebra (white arrow). Page 58 of 65 Fig. 26: 38-39. Figure 38. Calcification of the interspinous ligament. Lateral chest radiograph (a) and VR image (b) show the calcification of the interspinous ligament, which may simulate a fracture of the processus spinosus (arrows). Figure 39. Vacuum phenomenon. Lateral chest radiograph (a) and sagittal reconstructed CT scan (b) show intervertebral gas (arrows). Note the osteophytes at multiple levels. Page 59 of 65 Fig. 27: 40-41. Figure 40. Anomalous articulation between the 1st and 2nd ribs. Frontal chest radiograph (a) and lateral view VR image (b) demonstrate the articulation between the left 1st and 2nd ribs (arrows). Figure 41. Aneurysm formation caused by anomalous articulation between the 1st and 2nd ribs. Frontal chest radiograph (a) and lateral view VR image (b) demonstrate the articulation between the left 1st and 2nd ribs (arrows). VR image (c) with intravenous contrast medium shows the aneurysmal formation at the thoracic inlet caused by the anomalous articulation (white box arrow). Page 60 of 65 Fig. 28: 42-43. Figure 42. Anomalous articulation in the 1st rib. Frontal chest radiograph (a) and coronal reconstructed CT scan (b) show the anomalous articulation in the right 1st rib simulating a fracture (arrows). Figure 43. Anomalous articulation between the ribs. Frontal chest radiograph (a) and coronal reconstructed CT scan (b) show the anomalous articulation between the 4th and 5th ribs (arrows). Page 61 of 65 Fig. 29: 44. Anomalous articulation between the rib and scapula. Frontal chest radiograph (a), axial CT (b) and VR image (c) demonstrate the articulation between the scapula and adjacent rib. Page 62 of 65 Fig. 30: 45. Calcification of the cartilages of the larynx. Frontal chest radiograph (a) shows the crown-shaped opacity laying over the cervical spine (arrows). VR image (b) shows dense calcification of the thyroid and arytenoids cartilages (white box arrows). Page 63 of 65 Conclusion Correlation of plain chest radiographs and MDCT multiplanar reconstructed or volumerendering images dramatically improve understanding of radiographic anatomy of complicated and overlapping thoracic bony components. It is important for radiologists to be familiar with the normal anatomy, the variants, and the radiological appearance of the bony components. Personal Information A. Yamamoto, S. Suzuki, K. Toyoda, M. Yamasaki, E. Lien, T. O'uchi, S. Furui. Department of Radiology, Teikyo University, 2-11-1 Kaga Itabashiku, Tokyo, Japan. mail to: [email protected] M. Yamasaki; Department of Radiology, Kohka Public Hospital, Shiga, Japan. E. Lien, T. O'uchi; Department of Radiology, Kameda Medical Center, Chiba, Japan. References 1. Kurihara Y, Yakushiji YK, Matsumoto J, et al. The ribs: anatomic and radiologic considerations. 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