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Course of major paravertebral vessels and the positional relationship to the vertebral bodies in healthy Chinese subjects: a CT-based study

Gao, Fuqiang; Zhao, Xuanji; Sun, Wei; Pradhan, Abhinav; Li, Zirong

doi: 10.3760/cma.j.issn.0366-6999.20141209
Original article
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Background Several studies, including those done in China, report that paravertebral vascular injury during posterior spinal surgery can greatly harm patients, though it is a relatively rare complication. However, few studies have examined their course and anatomic relationship to the spine. The aim of this study was to measure the course of the major paravertebral vessels and their positional relationships to the vertebral bodies in Chinese subjects using computed tomography.

Methods We studied a total of fifty subjects who underwent thoracolumbar computed tomography from T1-S1 at our institution. We measured the theoretical distance, actual distance, theoretical angle, and actual angle of the paravertebral vessels at each thoracolumbar intervertebral disc.

Results The paravertebral artery actual angle at T4-L4 ranged from -11.41 to 79.75° and the actual distance from 16.98 to 52.53 mm. The actual angle of the inferior vena cava at L1-L5 intervertebral disc ranged from -40.75 to 34.50° and the actual distance from -36.63 to 61.69 mm. There was no significant difference in the actual angle of the paravertebral vein or in the actual distance in the thoracic segments according to gender (P >0.05). However, the actual distance in the lumbar segments were significantly different according to gender (P <0.05).

Conclusions The major paravertebral vessels’ course is closer to the mid-sagittal plane as they move posterior along the vertebrae, and the actual distance of the paravertebral artery and azygos vein increase, while the actual distance of the inferior vena cava decreases. The course of the lumbar paravertebral vessels varies, especially at L4/L5, and may be more prone to intraoperative injury in female subjects.

Department of Orthopaedic Surgery, China-Japan Friendship Hospital, Beijing 100029, China (Gao FQ, Zhao XJ, Sun W, Abhinav P and Li ZR)

Correspondence to: Dr. Sun Wei, Department of Orthopaedic Surgery, China-Japan Friendship Hospital, Beijing 100029, China (Tel: 86–10–84205009. Email: 18901267995@163.com)

This study was supported by grants from the National Natural Science Foundation of China (No. 81372013) and the Research Fund of China-Japan Friendship Hospital (No. 2013-MS-27).

(Received May 24, 2014)

Acknowledgements: We thank Shu Zheng, Department of Epidemiology and Bio-statistics, School of Public Health, Peking University, Beijing, China, for help with the statistical work, Chen He and Guo Runcai (experienced radiologists) for help with data collection.

Edited by Hao Xiuyuan

Iatrogenic injury to the major vascular structures is a known complication of spinal surgery, and the incidence during posterior spinal surgery is <1 per 2 000 procedures.1,2 The most frequent vascular lesions are vessel lacerations accompanied by acute hemorrhage, pseudoaneurysm, thrombosis, and arteriovenous fistula.3 The risk of vascular injury presently ranges from 1% to 24%.1,2,4,5 Most of these injuries are venous, but arterial injuries also occur at an incidence ranging from 0.45% to 1.5%.4 Injuries to the aorta or iliac arteries carry a mortality as high as 61%,5 and if not treated promptly, vascular injury may also lead to fatality.6

Preoperative assessment of the morphology and location of paravertebral vascular structures could be helpful in reducing perioperative vascular complications in thoracic and lumbar spinal surgery.7 It is important for spinal surgeons to localize the position of major paravertebral vessels during spinal surgery. Accordingly, the purpose of this study was to observe the pathway of major paravertebral vessels and their positional relationship to the vertebral bodies in healthy Chinese subjects based on computed tomography (CT) images. Preoperative evaluation of the anatomic configuration of large thoracolumbar vessels could influence the surgical strategy in a significant percentage of subjects, which can help avoid unnecessary vascular retraction and associated vascular complications, and provide a basis for planning of thoracolumbar spinal surgery, especially the posterior approach.

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METHODS

Subjects

A total of fifty subjects (68% males and 32% females) who underwent thoracolumbar CT from T1-S1 at our institution were studied. CT was performed parallel to the intervertebral disc level. They were aged between 18 to 45 years with a mean of 33.9 years. The inclusion criteria were as follows: no vertebral deformity, no anterior vascular malformation or lesion, and no history of intrathoracic, vertebral, or retroperitoneal surgery. The study was performed in accordance with the ethical standards described by the Ethics Committee of the National Health and Family Planning Commission of the People's Republic of China and was approved by the local Ethical Committee in China.

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Imaging and measurement

The theoretical distance, actual distance, theoretical angle, and actual angle of the paravertebral vessels were measured at each intervertebral disc on CT images analyzed with PACS11.0 software (KODAK Carestream PACS 10.0, Japan). Scanning equipment was Toshiba Aquilion 16, the use of bone reconstruction, slice thickness 3 mm, layer from 3 mm. Bone window width 1 500, window level 550 HU, soft-tissue window width 250, window level 60 HU. CT evaluation criteria for the film: the pictures are clear, bone structure is shown clearly, does not affect the CT diagnosis. The following major vessels were assessed: the azygos vein, aorta, abdominal aorta, inferior vena cava, and the iliac vein and its major branches. The measuring plane we chose is located in the posterior superior margin of the affected vertebral body which is parallel to the plane of the intervertebral disc.

The theoretical distance of the artery and vein (Figure 1, Line OA or Line OV) was defined as the distance between the disc center (Figure 1, Point O) and the vessel center (Figure 1, Point A or Point V). The actual distance of the artery and vein (Figure 1, Line PA or Line PV) was defined as the distance between the midpoint of the vertebral posterior edge (Figure 1, Point P) and the vessel center (Figure 1, Point A or Point V). The theoretical angle of the artery and vein (Figure 2, ∠FOA or ∠FOV) was defined as the angle between the line connecting the disc center and the vascular center (Figure 2, Line OA or Line OV) and the sagittal vertebral line (Figure 2, Line OF). The actual angle of the artery and vein (Figure 2, ∠FPA or ∠FPV) was defined as the angle between the line connecting the midpoint of the vertebral posterior edge and the vascular center (Figure 2, Line PA or Line PV) and the sagittal vertebral line (Figure 2, Line PF). All data were measured by two experienced radiologists and averaged.

Figure 1.

Figure 1.

Figure 2.

Figure 2.

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Statistical analysis

All analyses were conducted using SPSS 17.0 software (SPSS Inc., IL USA). The surveyed subject characteristics were assessed by calculating the standard error, coefficient of variation, and 95% confidence interval (CI) using the bootstrap technique. The paravertebral vascular distances and angles were compared between the gender groups using pairwise comparison. Normally distributed and homogenous data were compared using the t-test or the rank sum test. Differences between the variables were considered statistically significant at P <0.05.

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RESULTS

The theoretical distance, actual distance, theoretical angle, and actual angle in the paravertebral vessels were measured and graphed, as shown in Figures 3–6. The paravertebral artery actual angle at T4-L4 ranged from -11.41° to 79.75°, and the actual distance ranged from 16.98 to 52.53 mm. The actual angle of the inferior vena cava at L1-L5 ranged from -40.75° to 34.50°, and the actual distance ranged from -36.63 to 61.69 mm. The shortest mean actual distance of thoracic aorta and abdominal aorta at T4-L4 was 25.47 mm (T5/T6); the actual angle at this location ranged from 8.36° to 45.44°. The shortest mean actual distance of the left common iliac artery and its branches at L4-S1 was 42.02 mm (L4/L5), and the actual angle ranged from -14.72° to 36.22°. The shortest mean actual distance of the right common iliac artery and its branches at L4-S1 was 44.27 mm (L5/S1), and the actual angle ranged from -18.03° to -6.62°. The shortest mean actual distance of the azygos vein at T4-T10 was 28.38 mm (T4/T5), and the actual angle ranged from -0.23° to 9.33°. The shortest mean actual distance of the inferior vena cava at L1-L5 was 38.50 mm (L4/L5), and the actual angle ranged from -21.11° to -5.50°. The shortest mean actual distance of the left and right common iliac vein and their branches at L5-S1 was 37.80 mm (L5/S1), and the actual angle ranged from -15.52° to 29.54°.

Figure 3.

Figure 3.

Figure 4.

Figure 4.

Figure 5.

Figure 5.

Figure 6.

Figure 6.

As the paravertebral vessels moved posterior along the vertebral segments, they moved closer to the mid-sagittal plane, and the actual distance of the paravertebral artery and azygos vein increased. However, the actual distance of the inferior vena cava decreased as the vertebral segments grew more posterior.

The aortic arch traveled posterior primarily left side of the body of the 4th thoracic vertebra; it becomes continuous with the descending aorta at its caudal border. The bifurcation of the abdominal aorta was located at the posterior border of the L4 vertebral body in 24% of subjects, the L4/L5 intervertebral space in 64%, and the anterior border of the L5 vertebral body in 10% of subjects. The common iliac artery bifurcation was located at the posterior border of the L5 vertebral body in 18% of subjects and the L5/S1 intervertebral space in 48%. The confluence point of the common iliac vein was located at the L4/L5 intervertebral space in 16% of subjects and at the anterior border of L5 vertebral body in 84%. The confluence point of the internal and external iliac veins was presently primarily posterior to L5/S1.

There were significant differences in the paravertebral artery theoretical and actual angles between male and female subjects (P >0.05); however, the theoretical and actual distances were significantly different according to gender (P <0.05, Tables 1 and 2). There were no significant differences in the paravertebral vein theoretical and actual angles according to gender (P >0.05). The theoretical and actual distances showed no significant differences in the thoracic segment (P >0.05), but were significantly different in the lumbar segment (P <0.05, Tables 3 and 4).

Table 1

Table 1

Table 2

Table 2

Table 3

Table 3

Table 4

Table 4

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DISCUSSION

Vascular injury is the main complication of the posterior approach in thoracic and lumbosacral spinal surgery. While vascular injury is rare, it can result in massive potentially life-threatening intraoperative hemorrhage.1,3,5–7 Most vascular complications occur intraoperatively, immediately postoperative, or as delayed pseudoaneurysms during the long-term postoperative period.3,8 Vascular injury may lead to acute hemorrhage, pseudoaneurysm, or arteriovenous fistula.9 Most of these injuries are venous, but arterial injuries have also been reported at an incidence ranging from 0.45% to 1.5%.4 Venous injuries are primarily lacerations accompanied by hemorrhage and are caused by branch vessel avulsions during mobilization and retraction.10

Isolated arterial laceration, especially thoracic aortic injury,3,11 is the most serious type of vessel injury during spinal surgery.12 Pedicle screw penetration or misplacement can impinge on the aorta, risking perforation or pseudoaneurysm formation due to the constant pulsation of the aorta against the hardware.2 The subject may experience immediate hemorrhage with hemodynamic instability or a delayed risk of rupture associated with pseudaneurysm.13 Nakanishi et al14 reported that insertion of a guide wire or screw may increase the risk of vascular injury, and Watanabe et al15 described a case of iatrogenic descending aortic injury caused by a thoracic pedicle screw during posterior reconstructive surgery of a spinal deformity. Major vascular complications were similar to complications following anterior displacement of the intervertebral discs, as described by Daly et al16 Given the proximity of the aorta and iliac arteries to the spine, these malpositioned screws can easily perforate or impinge upon the aorta.2 These injuries can cause immediate hemorrhage intraoperatively requiring emergency intervention. Arterial injuries primarily comprise of thrombosis and are thought to be the result of vessel retraction and intimal disruption; these injuries may lead to embolization.4,10 More commonly, however, they cause pseudoaneurysm and risk delayed hemorrhage, which can occur weeks to months later.2,5,13 The clinical symptoms of delayed aortic injury are sometimes subtle and could be as simple as dorsal pain.3 These findings suggest that the vascular risk is correlated with unavoidable vessel mobilization, a maneuver that can be planned preoperatively. Therefore, preoperative evaluation of the vascular anatomy may be useful in limiting complications in vascular structures.

Using 3-dimensional CT angiography, Barrey et al7 reported that aortic bifurcation occurred most often at L4 (64% of cases). The iliocavum confluence occurred most frequently at L5 (44%). The iliolumbar ascending vein and central sacral vessels were identified in 84% and 72% of cases. Khamanarong et al17 showed that the abdominal aorta descended and bifurcated into two common iliac arteries at L4 in 131 cases (70.1%), the L4 intervertebral disc in 23 cases (12.3%), and L5 in 33 cases (17.6%). Our results are consistent with these previously reported findings. In our study, the T5-T11 segmental vessels were relatively constant in position; the azygos vein on the right side of the spine travelled slightly leftward as it coursed caudally. The thoracic aorta beginning on the left border of the spine coursed rightward as it moved posterior. Our findings showed that the major paravertebral vessels coursed ever closer to the mid-sagittal plane as they travelled posterior; and the actual distance of the paravertebral artery and azygos vein grew longer. However, the actual distance of the inferior vena cava decreased as the vessels coursed posteriorly. The abdominal aorta bifurcation was located at the posterior border of the L4 vertebral body and at the L4/L5 intervertebral space in most cases. Similarly, the common iliac artery bifurcation was located at the posterior border of the L5 vertebral body and at the L5/ S1 intervertebral space. The internal and external iliac vein confluence was generally posterior to the L5/S1 intervertebral disc. These results are consistent with those of Kang et al18 Notably, the measurement method employed in this study is different from previous protocols and can more comprehensively and intuitively display the anatomical relationship between the paravertebral vessels and spine, which is more helpful in surgical planning. The precise location of the aortic and major veins is a useful information for surgeons employing the anterior approach to the lumbosacral spine to prevent vascular injury.

The theoretical and actual distances in the thoracic segments were similar in male and female subjects. However, in the lumbar segments, the theoretical and actual distances were significantly greater in males than in females. The paravertebral vessels may be at higher risk of injury in female subjects during posterior lumbar spinal procedure and warrant particular caution. However, without a large case-control study, the specific relationship between gender and paravertebral vascular injury remains unknown. Among the known case reports, Olcay et al19 described the case of a woman who experienced a left common iliac artery laceration during spinal surgery. Chao et al20 described a male subject with rupture of a pseudoaneurysm in the right common iliac artery after spinal surgery to treat intervertebral disc herniation. In a case study by Lopera et al,21 the arterial injuries caused by misplacement of fixation screws were reportedly similar between the six male and female subjects. Other studies have found that the surgical window in lower lumbar procedures is larger in males than in females; a more exposed approach can be used in male subjects, which decreases the risk of damage and postoperative complications.22 As we observed, course of the lumbar paravertebral vessels is variable, especially at L4/L5. Therefore, careful planning is required in surgery of the lumbar spine. The right and left common iliac arteries are frequently injured intraoperatively according to a previous report (43% and 29% of subjects, respectively).23 The iliac artery is also reportedly prone to injury during surgery.24 A literature review showed that these lesions are more frequent after surgeries performed at L4-L5 than at L5-S1.25 These iatrogenic vascular injuries require immediate and aggressive treatment.26 Understanding the course and anatomy of the paravertebral vessels can reduce vascular complications. Early diagnosis and surgical repair of these injuries may decrease morbidity and mortality.

Radiologic methods provide a more intuitive and accurate reflection of the paravertebral vessel course and its relationship to the thoracic and lumbar vertebrae, and provides a useful basis for surgical planning. However, our analysis was mainly descriptive, and the vascular windows of the thoracolumbar spine were not measured on fresh cadaveric specimens, which is a limitation of our study. Measurement of these parameters in cadavers is impossible as an adequate sample size cannot be procured, and the cost would be prohibitive. Additionally, distortion errors may be caused by tissue shrinkage after formalin fixation. Thus the present study, does offer certain limitations. However, this study is only a preliminary study. We are also planning to perform a multi-center clinical study in the future in various regions of China to expand the sample size and validate our findings.

As the clinician moves posterior along the vertebral segments, the major paravertebral vessels move closer to the mid-sagittal plane, and the actual distance of the paravertebral artery and azygos vein increase, while the actual distance of the inferior vena cava decreases. The course of the lumbar paravertebral vessels varies, especially at L4/L5. The paravertebral vessels may also be more prone to intraoperative injury in female subjects.

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REFERENCES

1. Szolar DH, Preidler KW, Steiner H, Riepl T, Flaschka G, Stiskal M, et al.Vascular complications in lumbar disk surgery: report of four cases. Neuroradiology 1996; 38: 521-525.
2. Loh SA, Maldonaldo TS, Rockman CB, Lamparello PJ, Adelman MA, Kalhorn SP, et al. Endovascular solutions to arterial injury due to posterior spine surgery. J Vasc Surg 2012; 55: 1477-1481.
3. Tong X, Gu P, Yu D, Guo F, Lin X. An endovascular treatment of a thoracic aortic injury caused by a misplaced pedicle screw: Case report and review of the literature. J Formos Med Assoc 2013. doi: 10.1016/j.jfma. 2013. 09.014. [Epub ahead of print]
4. Garg J, Woo K, Hirsch J, Bruffey JD, Dilley RB. Vascular complications of exposure for anterior lumbar interbody fusion. J Vasc Surg 2010; 51: 946-950.
5. Bingol H, Cingoz F, Yilmaz AT, Yasar M, Tatar H. Vascular complications related to lumbar disc surgery. J Neurosurg 2004; 100: 249-253.
6. Kwon TW, Sung KB, Cho YP, Kim DK, Ko GY, Yoon HK, et al. Large vessel injury following operation for a herniated lumbar disc. Ann Vasc Surg 2003; 17: 438-444.
7. Barrey C, Ene B, Louis-Tisserand G, Montagna P, Perrin G, Simon E. Vascular anatomy in the lumbar spine investigated by three-dimensional computed tomography angiography: the concept of vascular window. World Neurosurg 2013; 79: 784-791.
8. Rossi G, Mavrogenis A, Angelini A, Rimondi E, Battaglia M, Ruggieri P. Vascular complications in orthopaedic surgery. J Long Term Eff Med Implants 2011; 21: 127-137.
9. Brewster DC, May AR, Darling RC, Abbott WM, Moncure AC. Variable manifestations of vascular injury during lumbar disk surgery. Arch Surg 1979; 114: 1026-1030.
10. Brau SA, Delamarter RB, Schiffman ML, Williams LA, Watkins RG. Vascular injury during anterior lumbar surgery. Spine J 2004; 4: 409-412.
11. Stulík J, Vyskocil T, Bodlák P, Sebesta P, Kryl J, Vojácek J, et al. Injury to major blood vessels in anterior thoracic and lumbar spinal surgery. Acta Chir Orthop Traumatol Cech 2006; 73: 92-98.
12. Yu HP, Hseu SS, Sung CS, Cheng HC, Yien HW. Abdominal vascular injury during lumbar disc surgery. Chin Med J (Taipei) 2001; 64: 649-654.
13. Carmignani A, Lentini S, Acri E, Vazzana G, Campello M, Volpe P, et al. Combined thoracic endovascular aortic repair and neurosurgical intervention for injury due to posterior spine operation. J Card Surg 2013; 28: 163-167.
14. Nakanishi K, Tanaka M, Sugimoto Y, Ozaki T. Posterior cervical spine arthrodesis with laminar screws: a report of two cases. Acta Medica Okayama 2007; 61: 115-119.
15. Watanabe K, Yamazaki A, Hirano T, Izumi T, Sano A, Morita O, et al. Descending aortic injury by a thoracic pedicle screw during posterior reconstructive surgery: a case report. Spine 2010; 35: E1064-E1068.
16. Daly KJ, Ross ER, Norris H, McCollum CN. Vascular complications of prosthetic inter-vertebral discs. Eur Spine J 2006; 15: 644-649.
17. Khamanarong K, Sae-Jung S, Supa-Adirek C, Teerakul S, Prachaney P. Aortic bifurcation: a cadaveric study of its relationship to the spine. J Med Assoc Thai 2009; 92: 47-49.
18. Kang ZS, Wang WJ, Cao QQ, Zhu YP, Yan YG. 3D-CT angiography of anterior vessels and their circumferential structure at lower lumbar vertebraes (in Chinese). Chin J Spine Spinal Cord 2009; 19: 540-544.
19. Olcay A, Keskin K, Eren F. Iliac artery perforation and treatment during lumbar disc surgery by simple balloon tamponade. Eur Spine J 2013; 22: S350-S352.
20. Chao CM, Wu CD, Sung KC, Lin WT, Lee KK, Lai CC. Right iliac aortic aneurysmal hemorrhage as a complication of lumbar discectomy. World Neurosurg 2013; 80: 901. e7-e8.
21. Lopera JE, Restrepo CS, Gonzales A, Trimmer CK, Arko F. Aortoiliac vascular injuries after misplacement of fixation screws. J Trauma 2010; 69: 870-875.
22. Duan GC. Study on applied anatomy of lumbar anterior lateral vessels and nerves. Nantong University. 2006. DOI:10.7666/ d.y957772.
23. Sadhasivam S, Kaynar AM. Iatrogenic arteriovenous fistula during lumbar microdiscectomy. Anesth Analg 2004; 99: 1815-1817.
24. Bierdrager E, van Rooij W J, Sluzewski M. Emergency stenting to control massive bleeding of injured iliac artery following lumbar disk sugery. Neuroradiology 2004; 46: 404-406.
25. Jue-Denis P, Kieffer E, Benhamou M, Le-Thoai H, Richard T, Natali J. Injuries to abdominal vessels after surgery of disk herniation. Rev Chir Orthop Reparatrice Appar Mot 1984; 70: 141-145.
26. Kim HS, Chong HS, Nanda A, Park JO, Moon SH, Lee HM, et al. Vascular injury in thoracolumbar spinal surgeries and role of angiography in early diagnosis and management. J Spinal Disord Tech 2010; 23: 418-424.
Keywords:

spine; major paravertebral vessels; posterior approach surgery; applied anatomy; computed tomography

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