Table 3.
CFRP screw accuracy and assessability depending on imaging modality.
| iCT | rCBCT | CBCT | p-value | |
|---|---|---|---|---|
| Total no. of navigated screws | 93 | 99 | 51 | n/a |
| Not assessable, n (%) | 1 (1%, T8) | 9 (9%, T 7–12) | 3 (6%, T11–12) |
*0.0472 (iCT vs. rCBCT) |
| Screws intraoperatively corrected, n (%) | 6 (7%) | 0 | 0 | 0.0853 |
| Screw accuracy (A + B), n (%) | 69 (74%) | 68 (69%) | 25 (49%) |
**0.0064 (rCBCT vs. CBCT and iCT vs. CBCT) |
| Pedicle breach 2–4 mm (C), n (%) | 14 (15%) | 19 (19%) | 13 (25%) | 0.3395 |
| Pedicle breach > 4 mm (D), n (%) | 9 (10%) | 3 (3%) | 10 (20%) |
**0.0042 (rCBCT vs. CBCT) |
| Median pedicle isthmus diameter of instrumented pedicles without breach (A, mm) | 6.5 (5.5–13) | 6.5 (5.5–15) | 9 (6–12) |
*0.0407 (rCBCT vs. CBCT) |
| Median pedicle isthmus diameter of instrumented pedicles with breached screws (B–D, mm) | 5.7 (3.9–8.8) | 5.8 (3.4–10) | 6.1 (4.5–11) | 0.4982 |
| Median isthmus/screw diameter–ratio in screws without breach (A) | 1.2 | 1.2 | 1.4 | 0.1180 |
| Median isthmus/screw diameter–ratio in breached screws (B–D) | 1.04 | 1.1 | 1.1 | 0.9360 |
| Number of pedicle screws larger than pedicle isthmus, n (%) | 5 (5%) | 13 (13%) | 10 (19%) |
*0.0353 (iCT vs. CBCT) |
| Screw accuracy (A + B) without screws larger than the pedicle isthmus, n (%) |
67/91 (74%) Th: 39/57 (68%) TLJ: 24/26 (92%) L: 4/4 (100%) (n.s.) |
56/77 (73%) Th: 41/60 (68%) TLJ: 8/10 (80%) L: 6/6 (100%) (n.s.) |
17/37 (46%) Th: 5/20 (25%) TLJ: 5/8 (63%) L: 7/8 (88%) (*p = 0.0202) |
**0.0056 (iCT vs. CBCT, rCBCT vs. CBCT) |
| Median time for accuracy assessment (seconds) | 120 (27–540) | 120 (17–720) | 180 (24–1080) | 0.5551 |
Values are given in total number with percentage or as median with total range, as appropriate.
iCT Intraoperative CT, rCBCT robotic cone beam CT, CBCT cone beam CT, n.s. not statistically significant. Based on SIN score: L = lumbar (L2-5), Th = thoracic (Th1-10), TLJ = thoraco-lumbar junction (Th11-L1).