Ponticulus posticus - not such a rare finding on lateral cervical spine radiographs

Transcription

1 Ponticulus posticus - not such a rare finding on lateral cervical spine radiographs Poster No.: C-0545 Congress: ECR 2014 Type: Scientific Exhibit Authors: A. M. Calin, M. Calin ; Cluj-Napoca/RO, Cluj Napoca/RO Keywords: Epidemiology, Education and training, Normal variants, Education, Plain radiographic studies, Conventional radiography, Musculoskeletal bone, Head and neck, Anatomy DOI: /ecr2014/C Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 25

2 Aims and objectives The atlas stands as the first cervical vertebra, being articulated with the occipital bone above and the axis vertebra below. It has the shape of a ring and 2 arches. The anterior arch is short and articulates with the dens of the axis vertebra, while the posterior arch bears a groove on its surface for the vertebral artery and the dorsal ramus of the first cervical spine nerve. The vertebra has 2 transverse processes, which form a foramen transversarium, crossed by the vertebral artery and also 2 lateral masses, which articulate with the occipital condyles and form an ellipsoid type of synovial joint. Fig. 1: Atlas, first cervical vertebra - anatomy References: After its exit from the transverse foramina, the vertebral artery passes over the posterior arch of the atlas, forming a groove called the vertebral artery sulcus, which varies in size and can sometimes be very deep, located on the posterolateral margin of the posterior arch of the atlas. Page 2 of 25

3 Fig. 3: Vertebral artery - lateral view References: Inferiorly and posteriorly to the posterior arch of the atlas, the posterior occipital ligament is attached. It is connected above with the posterior margin of the foramen magnum and appears as a broad, but thin ligament. Its lateral divisions, the oblique atlanto-occipital ligaments, create with the vertebral artery sulcus an opening for the vertebral artery and the suboccipital nerve. Page 3 of 25

4 Fig. 2: Median sagittal section through the occipital bone and first three cervical vertebrae. References: Variants and asymptomatic deviations from the normal vertebral anatomy are often confusing. This is the reason they have to be studied carefully to insure an adequate differentiation from a pathological process. If anomalous ossification occurs, a bony arch - named ponticulus posticus - bridges the sulcus, encloses the foramen arcuate and through this, the vertebral artery and the subocccipital nerve pass. Page 4 of 25

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6 Fig. 5: CT 3D reconstruction of cervical spine, lateral view - complete unilateral ponticulus posticus (blue arrow) References: - Cluj-Napoca/RO Ponticulus posticus is a possible cause of posterior circulation ischemia, cervicogenic headache, vertigo, neck pain, discopathy. This condition had not been a matter of concern for physicians until its surgical significance in the insertion of screws in the lateral mass of the atlas was reported. Our interest for this anatomic variant was stimulated by its incidental appearance in various lateral cervical spine examinations. This study`s purpose was to determine occurrence, varieties, distribution by age and sex of ponticulus posticus in a Radiology Ambulatory Care Service from Cluj-Napoca. Images for this section: Fig. 1: Atlas, first cervical vertebra - anatomy Page 6 of 25

7 Fig. 2: Median sagittal section through the occipital bone and first three cervical vertebrae. Page 7 of 25

8 Fig. 3: Vertebral artery - lateral view Page 8 of 25

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10 Fig. 5: CT 3D reconstruction of cervical spine, lateral view - complete unilateral ponticulus posticus (blue arrow) Page 10 of 25

11 Methods and materials Our present longitudinal, retrospective study was carried out over a period of a year in the Radiology Department of the Integrated Ambulatory Service Care of the Infectious Disease Clinic in Cluj - Napoca. The protocol was approved by the institutional review board of our institution. We included 462 patients, 276 women, 186 men, with ages between 4 and 90 years, who underwent cervical spine radiographs for other symptoms than due to this variant. The main symptoms in the adult population who referred to our service were chronic neck pain and headache. Children mostly underwent lateral cervical spine radiographs after traumatic events. Only the radiographs of patients with clearly visible skull base and no history of craniocervical operation were included in the study. The radiographs were obtained by conventional X-ray equipment. The X-ray exposure parameters were73 kv and 12 ma. Films were processed automatically with a computed radiograph system and interpreted on a flat screen. Each radiograph was carefully inspected to look for the presence of a ponticulus posticus and arcuate foramen. The complete type was defined as a clear bony bridge between the superior articular process and the posterior arch of the atlas, whereas the partial type included partial posterior ponticuli, noted as distinct bony spicule extending from the superior articular facet overhanging the dorsal arch. Because we inspected only a neutral lateral radiograph, we were not able to determine in all cases on which side ponticulus posticus occurs more often. Besides the incidence and type of ponticulus posticus, its distribution by age and gender was also analyzed. Page 11 of 25

12 We could not specify that the prevalence of ponticuli in the patients we analyzed would represent that of the normal Romanian population, because the studied patients addressed our service for certain complaints, leaving the asymptomatic patients out of the study. Results Ponticulus posticus was observed in 12.55% of the patients, with a slight female (53.44%) predominance. Incomplete bony outgrow was present in 51.72% of the cases. The prevalence of incomplete ponticulus posticus was higher in female patients (63.33%). When ossification was incomplete, the defect was mostly found at the anterior margin (70%), although incomplete ossification may be found at any point in the arch. The rest of 48.27% of the patients had a complete arch, with a male domination (57.14%). Bilateral complete foramen was seen in 10.34% of the cases, 4 of them being female and 2 being male patients. The highest incidence was in the group between 40 and 49 years (30.76%). The youngest patient who presented ponticulus posticus was 9 years old and the oldest patients in our study was 78 years old. There was a variation in size, configuration and position of the bony arch. Some of the patients presented an incomplete and sometimes difficult to recognize arch, while other patients had a thick and amorphous bony outgrow. The sulcus of the vertebral artery also varied widely. Page 12 of 25

13 Images for this section: Page 13 of 25

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15 Fig. 6: Lateral cervical radiograph - unilateral incomplete ponticulus posticus (blue arrow); the bony projection grows from anterior to posterior Fig. 10: Incidence of ponticulus posticus in our study Page 15 of 25

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17 Fig. 7: Lateral cervical radiograph - unilateral incomplete bony outgrow (blue arrow) from the posterior margin Fig. 11: Prevalence of Ponticulus Posticus as reported in literature Page 17 of 25

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19 Fig. 8: Lateral cervical radiograph - complete ponticulus posticus (blue arrow) Page 19 of 25

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21 Fig. 9: Lateral cervical radiograph - bilateral ponticuli (blue arrows) Page 21 of 25

22 Conclusion Some studies analyzed the presence of ponticulus posticus on anatomical specimens, such as dry vertebrae (4), (12), (18), (19). Other authors discovered this variant on cephalograms (13), (20), or lateral cervical spine radiographs (6), (10), (16), like we did in our study. In our study, the incidence of ponticulus posticus was 12.55%, whereas in other carried studies it varied between 4.3% and 33.3%. (13,15) The closest results regarding incidence were obtained by Pyo and Lowman, who found an incidence of 12.67%. (20) Our results revealed a higher incidence of an incomplete bony arch (51.72%), similar to all carried studies. (1-20) Pyo and Lowman (20) showed that in incomplete ponticuli, the defect was usually found at the posterior margin. This goes contrary to our study which states the fact that the defect was mostly found at the anterior margin (70%). Regarding gender, the data indicate that the general distribution of the presence of the bony bridge in the first cervical vertebra (53.44%) and the presence of an incomplete bony arch (63.3%) is higher in female patients than in men. In comparison, the highest incidence of complete ossification occurred in male patients (57.14%). The data can be corroborated with the study carried out by Schilling J, Schilling A & Suazo G.I. (18) Michael J Huang and John A Glaser (9) observed that the groove for the vertebral artery on atlas varies in size and depth from a slight impression to a clear sulcus, which was also observed in our study. In our study, no clear relationship with age was found, since we found this variant in 5 cases of children, 2 of them having complete ossification. In their study, Lamberty and Zivanovic observed ponticulus posticus in fetuses and children, making it even clearer that this condition is not age-dependent. (4) Therefore, it should not be considered as a calcification or ossification of the lateral segment of the posterior atlanto-occipital ligament, but rather an ossification with functional significance, developed in order to protect the passage of the vertebral artery Page 22 of 25

23 in a region in which, by its sinuosity, is susceptible of being damaged or compressed as a result of the craniocervical dynamics. (18) Young et al have demonstrated that when examining a specimen with an arcuate foramen through a standard dorsal approach, the broad ponticulus posticus can be easily mistaken for a widened posterolateral aspect of the posterior arch of the atlas, when in reality it is a foramen containing the vertebral artery. The placement of a lateral mass screw into the atlas in this situation can predispose the vertebral artery to injury. (16) It must especially alert the surgeon to avoid using the ponticulus posticus as a starting point for a lateral mass screw, in order not to injure the vertebral artery, since the placement of lateral mass screws into the atlas has become a popular means of treating atlantoaxial instability. (16) Ponticulus posticus is a relatively common finding in our patients and should be mentioned by radiologists in their reports; the awareness of the presence of this variant can improve later management of head and neck symptoms. Limitations In many cases, it was difficult to determine which side is affected more frequently, since only a single lateral film was available. Some studies certified that the plain cervical radiograph is not suitable for screening the ponticuli, because in some cases it is not visible and bilateralness and completeness are difficult to assess. (13) Personal information References 1) Soni P, Sharma V, Sengupta J. Cervical vertebral anomalies: incidental findings on lateral cephalograms. Angle Orthod 2008;78: ) Farman AG, Escobar V. Radiographic appearance of the cervical vertebrae in normal and abnormal development. Br J Oral Surg 1982;20: Page 23 of 25

24 3) Wight S, Osborne N, Breen AC. Incidence of ponticulus posterior of the atlas in migraine and cervicogenic headache. J Manipulative Physiol Ther 1999;22: ) Lamberty BGH, Zivanovic S. The retroarticular vertebral artery ring of the atlas and its significance.acta Anatomica 1973;85: )White AA, Panjabi MM. Clinical biomechanics of the spine (2nd edn). Lippincott Williams & Wilkins, ) Stubbs DM. The arcuate foramen: variability in distribution related to race and sex. Spine1992;17: ) Takaaki M, Masanori O, Hidenori U, Eikazu H, Seisuke T, Sotaro I. Ponticulus ponticus: Its clinical significance. Acta Medica Kinki Univ 1979;4: ) Simsek S, Yigitkanli K. Posterior osseous bridging of C1. J Clin Neurosci 2008;15: ) Huang MJ, Glaser JA. Complete arcuate formane precluding C1 lateral mass screw fixation in a patient with rheumatoid arthritis: case report. Iowa Orthop J. 2003; 23: ) Unur E, Erdogan N, Ülger H, Ekinci N, Öztürk O. Radiographic incidence of complete arcuate foramen in Turkish population. Erciyes Med J 2004;26: ) Cederberg RA, Benson BW, Nunn M, English JD. Arcuate foramen: prevalence by age, gender and degree of calcification. Clin Orthod Res 2000;3: ) Cakmak O, Gurdal E, Ekinci G, Yildiz E, Cavdar S. Arcuate foramen and its clinical significance.saudi Med J 2005;26: ) Sharma V, Chandhary D, Mitra D. Prevalence of ponticulus posticus in Indian orthodontic patients. Dentomaxillofac Radiol 2010; 39(5): ) Krishnamurthy A, Nayak SR, Khan S, Prahbu LV, Ramanathan LA, Ganesh Kumar C, Abhishek PS. Arcuate foramen of atlas: incidence, phylogenetic and clinical significance. Romanian Journal of Morphology and Embryology 2007; 48(3): Page 24 of 25

25 15) Shashi M, Puja C, Sadakat A, Mahima M, Punam V, Armeen A. Prevalence of Ponticulus Posticus of Atlas: A Radiological And Cadaveric Study in Hilly Regions of Uttarakhand. National Journal of Medical and Dental Research 2013;1(3): ) Young JP, Young PH, Ackermann MJ, Anderson PA, Riew KD. The ponticulus posticus: implications for screw insertion into the first cervical lateral mass. J. Bone Joint Surg. Am., 87:2495-8, ) Malukar O, Prajapati VP, Nagar SK. Ponticulus posticus of the atlas vertebra. National Journal of Medical Research. 1(2):51-53, ) Schilling J, Schilling A, Suazo GI. Ponticulus posticus on the posterior arch of atlas, prevalence analysis in asymptomatic patients. Int. J. Morphol., 28(1): , ) Paraskevas G, Papaziogas B, Tsonidis C, Kapetanos G. Gross morphology of the bridges over the vertebral artery groove on the atlas. Surg. Radiol. Anat., 27(2):129-36, ) Pyo J. & Lowman R. M. The ponticulus posticus of the first cervical vertebra. Radiology 1959; 72(6): Page 25 of 25