727 Accuracy Injection of the glenohumeral joint was successfully performed in all 100 patients enrolled in this study (Table 2). Overall access to the joint was gained on the first attempt in 83 (83%) patients, on the second attempt in 14 (14%) patients and on the third attempt in 3 (3%) patients. For fluoroscopic or US guidance the first attempt scores were 72% and 94%, respectively. With fluoroscopy a second and third attempt was needed in 22% and 6%, respectively, whereas with US guidance a second attempt in only 6%, and a third attempt was not needed in any of the cases (Table 2). The differences between the techniques in the frequency of more than one attempt needed were statistically significant (chi-square test df = 3: p = 0.026). No complications of the vital structures, such as vessels, nerves and tendons, were encountered clinically and with MR imaging. Four (4%) patients had a vasovagal reaction, two patients in the USp group and two patients in the FLa group. No further complications were reported in any of the groups as, for example, bleeding at the injection site, swelling or compromise of movements. Contrast material leakage The various injection techniques were qualitatively comparable with regard to extra-articular leakage of contrast material. In 51% of all procedures minimal (24%) and massive (27%) leakage occurred, which did not hamper in any way the evaluation of the MR images. Minimal leakage was most frequent in the FLa approach (48%) and massive leakage in both posterior approaches (FLp: 36% and USp: 32%) (Table 2). The differences in non-compromising leakage were statistically significant (chi-square test, df = 6: p = 0.045). Time assessment Fluoroscopy and US room times, overall procedure times and radiologist’s times are summarised in Table 3 as minimum - maximum times (mean). The mean room times for US guidance were signifi- cantly shorter when compared to the time needed using fluoroscopic guidance (Table 3). The shortest mean procedure time required was noted for the USa approach (1:34 min). The longest mean procedure time noted was that using the FLp approach (9:48 min). Also noteworthy is the difference in mean procedure time between the FLa (4:09 min) and FLp approach (9:48 min). The minimum procedure times were similar among all four approaches; however, the maximum procedure times were significantly shorter using US guidance (Table 3). On average the procedure under US guidance was shorter than under fluoroscopic guidance, using signifi- cantly less (>50%) room time and radiologist time (Table 3). Discomfort The VAS score obtained before and after shoulder injection is summarised in Table 4. The VAS scores before the procedure varied among the four different procedures, but not significantly so (Kruskal-Wallis p = 0.108). The varia- tion in the VAS scores post-procedure was a little bit larger and statistically significant (Kruskal-Wallis p = 0.023). In three of the four groups there was a general tendency for Table 3 Required time (minutes) for US- and fluoroscopic-guided glenohumeral injection FLa FLp USa USp FL(a + p) US(a + p) TUS:TFL Kruskal-Wallis TRoom Min – max (mean/median) 07:00 – 33:00 (17:03/17:00) 12:00 – 29:00 (20:05/20:00) 06:00 – 15:00 (09:54/10:00) 05:00 – 16:00 (09:18/09:00) 07:00 – 33:00 (18:36/18:00) 05:00 – 16:00 (09:36/09:00) 71%−48% (52%) p<0.001 TProcedure Min – Max (mean/median) 00:30 – 20:00 (04:09/11:43) 00:45 – 23:00 (09:48/09:00) 00:30 – 06:00 (01:34/01:00) 00:30 – 07:30 (03:24/03:00) 00:30 – 23:00 (06:58/07:00) 00:30 – 07:30 (02:29/02:00) 100%−33% (36%) p<0.001 TRadiologist Min – max (mean/median) 03:00 – 27:00 (09:50/08:00) 10:00 – 27:00 (17:58/19:00) 04:00 – 13:15 (06:19/06:00) 01:56 – 12:00 (05:48/05:00) 03:00 – 27:00 (13:54/15:00) 01:56 – 13:15 (06:03/06:00) 64%−49% (44%) p<0.001 TRoom = time that the room is occupied by patient. TProcedure = time required for injection (skin to skin), TRadiologist = overall time radiologist in the US or fluoroscopy room USa: US-guided anterior injection, USp: US-guided posterior injection, FLa: fluoroscopic-guided anterior injection, FLp: fluoroscopic- guided posterior injection. FL(a + p): fluoroscopic-guided anterior and posterior injection, US(a + p): US-guided anterior and posterior injection, TUS:TFL: percentage of needed room, procedure and radiologist time with US guidance in relation to the time span for fluoroscopic guidance