Table 1 Patient characteristics
|  | Training set (n = 138) | Internal validation set (n = 59) | External validation set (n = 38) | |||
|---|---|---|---|---|---|---|
Characteristic | without NVFs | NVFs | without NVFs | NVFs | without NVFs | NVFs |
Age, yr | ||||||
 Mean (± SD) | 70.9 (± 8.6) | 75.8 (± 8.3) | 72.4 (± 10.2) | 75.3 (± 7.8) | 74.8 (± 6.8) | 78.1 (± 7.4) |
Sex | ||||||
 Male | 16 (25.0) | 14 (18.9) | 7 (25.9) | 9 (28.1) | 4 (17.4) | 3 (20.0) |
 Female | 48 (75.0) | 60 (81.1) | 20 (74.1) | 23 (71.9) | 19 (82.6) | 12 (80.0) |
Surgical procedure | ||||||
 VP | 32 (50.0) | 49 (66.2) | 20 (74.1) | 23 (71.9) | 17 (73.9) | 10 (66.7) |
 BKP | 32 (50.0) | 25 (33.8) | 7 (25.9) | 9 (28.1) | 6 (26.1) | 5 (33.3) |
Number of treated vertebra(e) | ||||||
 1 | 55 (85.9) | 63 (85.1) | 21 (77.8) | 22 (68.8) | 21 (91.3) | 12 (80.0) |
  ≥ 2 | 9(14.1) | 11 (14.9) | 6 (8.1) | 10 (31.2) | 2 (8.7) | 3 (20.0) |
Location of treated vertebra(e) | ||||||
 non-TL-Junction | 19 (29.7) | 35 (47.3) | 5 (18.5) | 14 (43.8) | 7 (30.4) | 5 (33.3) |
 TL-Junction | 45 (70.3) | 39 (52.7) | 22 (81.5) | 18 (56.2) | 16 (69.6) | 10 (66.7) |
IVC | ||||||
 Negative | 60 (93.8) | 47 (63.5) | 25 (92.6) | 25 (78.1) | 19 (82.6) | 9 (60.0) |
 Positive | 4(6.2) | 27 (36.5) | 2 (7.4) | 7 (21.9) | 4 (17.4) | 6 (40.0) |
Previous VF | ||||||
 Negative | 46 (71.9) | 33 (44.6) | 22 (81.5) | 12 (37.5) | 19 (82.6) | 9 (60.0) |
 Positive | 18(28.1) | 41 (55.4) | 5 (18.5) | 20 (62.5) | 4 (17.4) | 6 (40.0) |
Previous Multi-VF | ||||||
 Negative | 57 (89.1) | 52 (70.3) | 26 (96.3) | 25 (78.1) | 22 (95.7) | 13 (86.7) |
 Positive | 7 (10.9) | 22 (29.7) | 1 (3.7) | 7 (21.9) | 1 (4.3) | 2 (13.3) |