Int J Emerg Med (2010) 3:85–90 Table 4 Comparison of patients with and without enhanced (≥1/3 caudal vertebral height visualized) view after arm traction and swimming position Variable Lateral cervical X-ray with traction p Lateral cervical X-ray with swimming position p Age Gender male (%) BMI SMD BAD Patients with no enhancement 29.9± 5 56.3 23.9± 4.9 10.94±1.57 40.38±3.44 Patients with enhancement 30±4.9 62.5 25.5±4.2 10.75± 1.62 41.4±3 0.672 0.693 0.296 0.719 0.337 Patients with no enhancement 32±5.5 64.7 24±3.7 11.24±1.64 41.29± 2.89 SD standard deviation, BMI body mass index, SMD sternomental distance, BAD biacromial distance Patients with enhancement 28.5±3.9 56.5 25.5±5 10.52± 1.5 40.74± 3.43 89 0.055 0.601 0.343 0.162 0.592 sixth vertebra in patients with high BMI and seventh in patients with normal BMI. However, only 9 mm of additional vertical height is added with the use of arm traction or the swimming position. In this situation, all three methods, SLC X-ray, arm traction, and swimming position, are likely to be insufficient in patients with high BMI who present to the ED with trauma. CT or MRI should be alternative imaging methods in these patients as an initial choice. And also the vertebral bodies below the clavicle are more likely to be seen during the swimming position in normal patients than in patients with high BMI. Previous evidence in the literature is somewhat limited and results varied. A few studies observed the effects of arm traction on imaging of the cervical spine. Bowe et al. found that traction enhances the view of the cervical spine for more than two thirds of a vertebral body [10]. Ohiorenoya et al. reported that unless an initial cervical spine radiograph includes the upper one third of the body of the seventh cervical vertebra, the probability of attaining the C7/T1 level with arm traction is <15% [11]. Our results approximate the results of a previous study by Ireland et al., which reported that 37% of patients imaged with the swimming position view showed visualization of the posterior structures [6]. A recent retrospective study by Rethnam et al. showed inadequacy of the swimming position in visualizing the CTJ [14]. However, their study did not evaluate the possible factors affecting the view of these techniques. And the basic view of patients obtained with SLC X-ray had not been regarded in their study. Traction techniques have also been observed in the literature. Bowe et al. compared different traction techni- clavicle in participants using the arm traction view. Posterior structures could be visualized in all arm traction images and in 35% (14/40) of swimming position images. Discussion Visualizing the CTJ by SLC X-ray remains a challenge in trauma patients. Lateral cervical X-rays with arm traction and swimming position are suggested by this study as an effective alternative to visualize the CTJ in these patients. Our results demonstrate that both arm traction and swimming position views have been found to increase visualization of the cervical spine by an average of 9 mm. Both views have also been shown to increase visualization of more than one third of the caudal vertebral body in more than half of the participants. While both arm traction and swimming position views hold benefit with better visualization, each view has been shown in our study to have unique advantages. The swimming view achieves visualization below the clavicle in some participants (38%). This view also visualized posterior structures—crucial in the evaluation of trauma patients—in roughly the same proportion of participants (35%). However, the arm traction view appears to be much more effective in visualizing the posterior structures, as it did in all participants in our study. BMI does not restrict the advantages of both methods according to the results of this study. However, BMI was revealed as a limiting factor in the image field of SLC X- ray. The median cervical spine level seen in SLC is the Table 5 Number of cervical vertebrae visualized on SLC X- ray according to the BMI BMI body mass index Number of patients Number of cervical vertebrae visualized on SLC X-ray BMI <25 ≥25 C1 0 0 C2 0 1 C3 0 0 C4 0 3 C5 1 5 C6 8 6 C7 10 5 T1 1 0 Median 7 6 p 0.007