Table 4.
Distribution of screws and pedicle violation rates in the lumbar spine.
| Level | No. of screws | Grade 0 | Grade I | Grade II | Grade III | Anterior violation | Antero-lateral violation | Overall violation rate | 95% CI |
|---|---|---|---|---|---|---|---|---|---|
| L1 | 30 | 30 (100%) | 0 (0%) | 0 (0%) | 0 (0%) | 0 (0%) | 0 (0%) | 0 (0%) | 0.00–0.00 |
| L2 | 26 | 25 (96.15%) | 1 (3.85%) | 0 (0%) | 0 (0%) | 0 (0%) | 0 (0%) | 1 (3.85%) | 2.40–5.30 |
| L3 | 55 | 54 (98.18) | 1 (1.82%) | 0 (0%) | 0 (0%) | 0 (0%) | 0 (0%) | 1 (1.82%) | 1.34–2.29 |
| L4 | 186 | 173 (93.01%) | 11 (5.91%) | 2 (1.08%) | 0 (0%) | 0 (0%) | 0 (0%) | 13 (6.99%) | 6.72–7.26 |
| L5 | 228 | 223 (97.81%) | 1 (0.44%) | 3 (1.32%) | 0 (0%) | 0 (0%) | 1 (0.44%) | 5 (2.19%) | 2.07–2.32 |
| S1 |
86 |
84 (97.67%) |
0 (0%) |
0 (0%) |
0 (0%) |
2 (2.33%) |
0 (0%) |
2 (2.33%) |
1.98–2.67 |
| Total | 611 | 589 (96.4%) | 14 (2.29%) | 5 (0.82%) | 0 (0%) | 2 (0.33%) | 1 | 22 (3.6%) | 3.54–3.66 |
Pedicle violation was evaluated according to the Gertzbein classification: grade 0, screws fully contained in the pedicle; breaches of ≤2 mm, grade I; breach of 2–4 mm, grade II; and breach >4 mm, grade III. CI, confidence interval.