Table 1 Gertzbein-Robbin assessment of pedicle screw placement
| Number of Screws Instrumented (N) | Screw Violation | Gertzbein Robbins Grade |
|---|---|---|
| Case 1 | ||
| N = 4 | 4/4 screws without violation | 4/4 screws Grade A |
| Case 2 | ||
| N = 4 | 3/4 screws without violation | 3/4 screws Grade A |
| 1/4 screw with lateral cortical violation | 1/4 screw Grade B | |