Int J Emerg Med (2010) 3:85–90 Fig. 3 Position for the lateral cervical X-ray taken in the swimming position 87 Cervical X-rays were taken by a radiology technician with 20 years of experience. An assistant professor of radiology and the research assistant from our ED accom- panied him. Study participants were placed on the X-ray table in a supine position with complete contact of the head with the X-ray table. The X-ray film cartridge was placed to the right side of the participant’s head and at 4 cm superior to the ear pinnacle. The central X-ray source was located perpendicularly to the film cartridge at the approximate level of the fourth cervical vertebra. The SLC X-rays used a standard dose of radiation within a time interval of 0.08– 0.12 ms, using 65–70 kW of voltage and a current of 100 mA. The position of the study participants and placement of X-ray source and film cartridge during the SLC X-ray are shown in Fig. 1. Lateral cervical X-ray with arm traction Four kilograms of weight were fixed onto both arms over the elbows. The weights were hung down the end point of the X-ray table through the feet of the patient (Fig. 2). The X-ray machine and film cartridge were placed similarly to the SLC X-ray and the same doses were used. We believed that the weight placed over the elbows would be effective in overcoming the opposing resistance from voluntary muscle contraction. Lateral cervical X-ray in the swimming position Patients were placed in the supine position with the right arm placed overhead with full extension of the shoulder and the left arm undergoing traction caudally. The film cartridge was placed under the axilla on the right side with the superior edge of the cartridge located 4 cm superior to the ear pinnacle. The X-ray source focused on the CTJ (level between the seventh cervical vertebra and first thoracic vertebra). A standard dose of radiation was used, within a time interval of 0.12–0.16 ms, using 65–75 kW of voltage and a current of 150 mA. Figure 3 shows the position for the lateral cervical X-ray taken in the swimming position. All X-rays were taken with the Toshiba TF-6-TL-6 machine from 100 cm distance using cartridges with a size of 24 ×30 cm. Outcome measures Lateral cervical spine X-rays were performed in all subjects with the SLC view, arm traction view, and swimming position view, with the heights of the lowest vertebra measured in each case. The vertical height of the SLC view was then compared with that of the arm traction and swimming position views. The lowest point seen in the X-rays constituted by the superior edges of the clavicle or soft tissue was accepted as the reference point for all three views. Table 1 Demographics of study participants Variable Age Gender, male/female (%) Weight Height BMI SMD BAD Mean ± SD Median (min.-max.) 30±4.9 24 (60)/16 (40) 71.25±16.82 168.55±8.93 24.87±4.52 10.83±1.58 40.98±3.18 30 (20–44) 70 (45–110) 170 (148–187) 24.5 (18–36.3) 11 (8–14) 41.5 (34–46) SD standard deviation, BMI body mass index, SMD sternomental distance, BAD biacromial distance, min. minimum, max. maximum