Navigation Improve Pedicle Screw Placement Accuracy? Comparison Between Navigated and Non-navigated Percutaneous and Open Fixations

Level

Group ON

Group O

Group PN

Group P

D10

D11

D12

Total

218

220

230

236

ON open computed tomography (CT)-based navigation, O open free-hand, PN percutaneous CT-based navigation, P percutaneous fluoroscopy-guided

All patients were operated in the prone position on a carbon-top radiolucent table.

For patients in in the ON and PN groups a preoperative CT scan (CT scan 24-multislice GE Healthcare, Little Chalfont, UK) was performed in the prone position and transferred to the computer navigation platform which reconstructed data to provide real-time intraoperative three-dimensional images of the vertebra.

In the O and P groups, screws were implanted according to the Roy-Camille technique [28]. The procedure in the P group was assessed using the C-arm in a step-by-step fashion, while in the O group, we performed just a final check at the end of the procedure with the C-arm.

Postoperative CT scans with sagittal and coronal reconstruction were performed in each patient. The position of each screw was reviewed by a neurosurgeon and a radiologist uninvolved in the procedure and classified according to a four-point grading scale: grade 0 (screws fully contained in the pedicle); grade 1 (perforating screws, up to 2 mm misplacement); grade 2 (perforating screws, between 2 and 4 mm misplacement); and grade 3 (perforating screws, greater than 4 mm misplacement) [25] (Fig. 1).

Fig. 1

Examples of grade 1 screw misplacement (a caudal, b cranial, c anterior, d lateral, e medial); grade 2 misplacement (f medial, g lateral); and grade 3 misplacement (h medial, anterior)

Statistical relationships between various groups were assessed by two-way analysis of variance (ANOVA) t-test, while the Fisher least significant difference (LSD) method was employed for determining statistical significance. Significance was defined as P < O = 0.05.

Results

Thoracic pedicle screws were not included in the analysis, because the low number did not allow any statistical analysis.

Screw distribution, according to the Neo classification [24], is shown in Table 2.

Table 2

Direction of breaches in lumbar vertebrae

Screw placement	Group ON	Group O	Group PN	Group P
Lateral axial/coronal Grade 1 Grade 2 Grade 3	4 (1.9 %) 1 (0.5 %)	2 (0.9 %) 2 (0.9 %)	6 (2.8 %) 1 (0.5 %) 2 (0.9 %)	10 (4.7 %) 3 (1.4 %) 1 (0.5 %)
Medial axial/coronal Grade 1 Grade 2 Grade 3	1 (0.5 %)		8 (3.7 %) 5 (2.3 %) 2 (0.9 %)	7 (3.3 %) 3 (1.4 %) 8 (3.7 %)
Anterior axial Grade 1 Grade 2 Grade 3	4 (1.9 %)	11 (5.1 %) 1 (0.5 %) 2 (0.9 %)	8 (3.7 %)	10 (4.7 %) 4 (1.9 %) 6 (2.8 %)
Caudal sagittal/coronal Grade 1 Grade 2 Grade 3	5 (2.3 %)			2 (0.9 %) 1 (0.5 %)
Cranial sagittal/coronal Grade 1 Grade 2 Grade 3	1 (0.5 %)			1 (0.5 %)

ON open CT-based navigation, O open free-hand, PN percutaneous CT-based navigation, P percutaneous fluoroscopy-guided

Statistical analysis of collected data showed a significant difference in accuracy between the ON and PN groups (P: 0.0263) and between the ON and P groups (P: 0.0258): a particular difference was observed in anterior misplacement between the ON and P groups (P: 0.0153) (Table 3).

We also considered each single vertebra, but we found no significant differences (Table 4).

Table 3

Statistical analysis of differences in lumbosacral screw misplacement according to placement method

	Total misplaced screws (p value)	Anterior misplacement (p value)	Lateral misplacement (p value)	Medial displacement (p value)	Caudal misplacement (p value)	Cranial misplacement (p value)
Group ON vs Group O	0.580	0.214	0.742	0.423	0.423	0.423
Group ON vs Group PN	0.0263	0.423	0.184	0.0848	0.423	0.423
Group ON vs Group P	0.0258	0.0153	0.188	0.0599	0.635	1
Group O vs Group PN	0.204	0.0742	0.370	0.102	—	—
Group O vs Group P	0.0641	0.321	0.289	0.0591	0.225	0.423
Group PN vs Group P	0.0742	0.0742	0.370	0.729	0.225	0.423

ON open CT-based navigation, O open free-hand, PN percutaneous CT-based navigation, P percutaneous fluoroscopy-guided, statistical significative P values in bold type

Table 4

Statistical analysis for each vertebra

	L2	L3	L4	L5	S1
Group ON vs Group O	0.182	0.229	1	0.769	0.291
Group ON vs Group PN	1	0.664	0.0917	0.839	0.340
Group ON vs Group P	0.127	0.508	0.252	0.948	0.426
Group O vs Group PN	0.182	0.0917	0.138	0.391	0.323
Group O vs Group P	0.124	0.860	0.201	1	0.373
Group PN vs Group P	0.206	0.495	0.435	0.866	0.0577