88 Standard Arm traction Swimming position p value Table 2 Enhancement in the view of cervical spines after arm traction and swimming position Results Lateral cervical X-rays Mean ± SD (mm) p value 0.000a 0.001b 12.60±7.48 21.73±9.78 21.20±14.19 0.841c a Comparison of SLC X-ray and lateral cervical X-ray with traction b Comparison of SLC X-ray and lateral cervical X-ray with swimming position c Comparison of the enhancement with traction and swimming position Patients were also categorized according to whether an enhanced view of the cervical spine was obtained—with visualization of more than one third of the lowest cervical vertebral body. If the visualization was less than this height, the view was considered not enhanced. All of these X-ray evaluations and measurements were performed by a radiologist aware of the study but blinded to study subjects. Statistical analysis The study data were analyzed in SPSS 10.0 for Windows. Continuous variables were expressed as mean±standard deviation and ordinal variables expressed as median and minimum-maximum. Comparisons of two groups with normal distribution were performed by Student’ t test. The Mann-Whitney U test was used for two group comparisons without normal distribution. Related samples with normal distribution for two groups were analyzed by the related t test and dichotomized variables with the McNemar test. Normal distribution was tested by the Kolmogorov- Smirnov test for sample sizes over 30 and Shapiro-Wilk if sample sizes were under 30. All of the hypotheses were constructed as two-tailed and an alpha value of 0.05 was accepted as significant. Int J Emerg Med (2010) 3:85–90 The study population was composed of 40 volunteers. The mean age of the participants was 30 ±4.9 with a range of 20–44 years and 60% (n = 24) of them were male. The weight, height, BMI, SMD, and BAD of the participants are displayed in Table 1. There was a statistically significant difference for the increases in the view of cervical spines between SLC X-ray (12.60 ±7.48) and either lateral cervical X-ray with arm traction (21.73 ± 9.78; p = 0.000) or in the swimming position (21.20 ± 14.19; p = 0.001) (Table 2). Both arm traction and swimming position increased the field of view by approximately 9 mm. Direct comparison of increased vertical height between the arm traction and swimming position views showed no difference in increased visuali- zation (p = 0.841). Increased visualization of the cervical spine occurred for 24 of the 40 participants using the arm traction view (60.0%) and 23 participants (57.5%) using the swimming position view—results found to be statistically similar (p= 0.902) (Table 3). For the arm traction and swimming position views, there was also no difference between groups showing or not showing an enhanced view—defined earlier in this paper as visualization of more than one third of the lowest cervical vertebral body—according to age, gender, BMI, SMD, and BAD (Table 4). Fifty percent of participants had a normal BMI (BMI < 25). Using the SLC view, the number of cervical vertebrae visualized differed according to BMI—seven cervical vertebrae were visualized in participants with BMI< 25 and six vertebrae were visualized in participants with a BMI ≥25 (p= 0.007) (Table 5). The caudal endpoint for vertebral height for this study was either soft tissue opacity or the clavicle. However, vertebral bodies below the clavicle were visualized in 15 patients (37.5%) using the swimming position view, with over 70% (11/15) of these participants having a normal BMI. No images showed vertebral bodies below the Table 3 Proportions of patients classified as having an enhanced view with arm traction and swimming position Swimming position Patients with no enhancement (≥1/3 caudal vertebral height visualized) Arm traction Total Patients with enhancement Patients with enhancement 17 (42.5%) 10 (25%) 7 (17.5%) 23 (57.5%) Patients with enhancement (≥1/3 caudal vertebral height visualized) 6 (15%) 17 (42.5%) 40 (100%) Total p value 16 (40%) 24 (60%) 0.902