Table 1 Patient characteristics
|  | Landmark-guided group n = 40 | Ultrasound-assisted group n = 40 | P-value |
|---|---|---|---|
Age (y) | 82.3 ± 7.1 | 83.3 ± 6.7 | 0.549 |
Height (cm) | 156.7 ± 7.0 | 156.9 ± 7.2 | 0.925 |
Weight (kg) | 50.6 ± 8.4 | 53.2 ± 10.1 | 0.203 |
BMI (kg/m2) | 20.6 ± 3.0 | 21.6 ± 3.6 | 0.176 |
Sex (male/female) | 7/33 | 10/30 | 0.412 |
ASA Classification | 0.502 | ||
 I | 0 (0%) | 0 (0%) |  |
 II | 22 (55%) | 19 (47.5%) |  |
 III | 18 (45%) | 21 (52.5%) |  |
Degree of back curvature | 0.635a | ||
 Backward | 4 (10%) | 2 (5%) |  |
 None | 33 (82.5%) | 36 (90%) |  |
 Forward | 3 (7.5%) | 2 (5%) |  |
Scoliosis | 1.000 | ||
 Positive | 6 (15%) | 6 (15%) |  |
 Negative | 34 (85%) | 34 (85%) |  |
Ease of landmark palpation | 0.654a | ||
 Easy | 34 (85%) | 31 (77.5%) |  |
 Moderate | 5 (12.5%) | 7 (17.5%) |  |
 Difficult | 1 (2.5%) | 2 (5%) |  |