Abstract
Introduction
Cervical pedicle screws (CPS) are an alternative technique to lateral mass fixation. We present our experience of 67 patients who underwent image-guided CPS instrumentation, either exclusively or as part of a construct. Implant precision, as measured by the orthogonal view evaluation method (OVEM), and complications are reported in all patients.
Materials and Methods
Retrospective chart review of a single institution experience of 67 consecutive patients, with 356 screws placed (Table 1), including 232 subaxial pedicle screws. Implant precision was measured using OVEM (unpublished data). This allows multiple orthogonal views along the long axis of the screw through the bone target on CT multiplanar images. Grade I: no bone breach, GrIa: screw thread breach, GrII: internal screw diameter breach, and GrIII: neurovascular injury. Complications including those related to implant placement are presented in Table 2.
Results
There were two implant-related complications. One, when a lateral mass screw was pulled out and replaced with a CPS. The other was because of a post CPS placement radiculopathy, which resolved on screw revision. There were three postoperative wound infections (4.5%) and five patients with postoperative pneumonia (7.5%).
Screw precision
|
|
||||||
|---|---|---|---|---|---|---|
|
|
|
|
|
|
|
|
|
Total |
356 |
177 (50%) |
95 (27%) |
84 (23%) |
0 (0%) |
|
|
Location |
||||||
|
Pedicle |
293 |
127 (43%) |
88 (30%) |
78 (27%) |
0 (0%) |
< 0.001 |
|
Lateral mass |
53 |
41 (77%) |
7 (13%) |
5 (9%) |
0 (0%) |
|
|
Pars |
10 |
9 (90%) |
0 (0%) |
1 (10%) |
0 (0%) |
|
|
Vertebra |
||||||
|
C1 |
10 |
8 (80%) |
0 (0%) |
2 (20%) |
0 (0%) |
0.001 |
|
C2 |
37 |
29 (78%) |
6 (16%) |
2 (5%) |
0 (0%) |
|
|
C3 |
47 |
17 (36%) |
18 (38%) |
12 (26%) |
0 (0%) |
|
|
C4 |
46 |
19 (41%) |
15 (33%) |
12 (26%) |
0 (0%) |
|
|
C5 |
43 |
17 (40%) |
12 (28%) |
14 (33%) |
0 (0%) |
|
|
C6 |
53 |
17 (32%) |
19 (36%) |
17 (32%) |
0 (0%) |
|
|
C7 |
43 |
21 (49%) |
5 (12%) |
17 (40%) |
0 (0%) |
|
|
D1 |
51 |
31 (61%) |
15 (29%) |
5 (10%) |
0 (0%) |
|
|
D2 |
13 |
8 (62%) |
3 (23%) |
2 (15%) |
0 (0%) |
|
|
D3 |
5 |
4 (80%) |
0 (0%) |
1 (20%) |
0 (0%) |
|
|
D4 |
2 |
1 (50%) |
1 (50%) |
0 (0%) |
0 (0%) |
|
|
D5 |
0 |
0 (0%) |
0 (0%) |
0 (0%) |
0 (0%) |
|
|
D6 |
2 |
2 (100%) |
0 (0%) |
0 (0%) |
0 (0%) |
|
|
D7 |
2 |
1 (50%) |
1 (50%) |
0 (0%) |
0 (0%) |
|
|
D8 |
2 |
2 (100%) |
0 (0%) |
0 (0%) |
0 (0%) |
|
Complications of subaxial pedicle screw placement (N = 67 patients)
|
|
|
|
|---|---|---|
|
Abbreviations: CSF, cerebrospinal fluid. |
||
|
VA injury |
0 |
0.0 |
|
CSF leak |
0 |
0.0 |
|
Infection |
3 |
4.5 |
|
Pneumonia |
5 |
7.5 |
|
Misplacement/revision |
2 |
3.0 |
|
Screw loosening (asympt) |
3 |
4.5 |
|
Screw pullout |
0 |
0.0 |
|
Screw breakage |
0 |
0.0 |
Conclusion
CPS is an alternative screw implantation technique which appears to be safe and effective with two screw revisions necessary (3% patients), with no neurovascular injury. There was a 23% navigational “failure” using OVEM criteria (GrII), which may be attributed to strict precision criteria. CPS may be useful when high biomechanical loads are anticipated, where there is poor bone quality or a pedicle fracture.