Cranial facet joint violations by percutaneously placed pedicle screws adjacent to a minimally invasive lumbar spinal fusion.

Department of Orthopedic Surgery, Yonsei University College of Medicine, National Health Insurance Medical Center, 1232, Baekseok St, Ilsan district, Goyang City, Gyeonggi province, 410-719, Republic of Korea.
The spine journal: official journal of the North American Spine Society (Impact Factor: 2.9). 04/2011; 11(4):295-302. DOI: 10.1016/j.spinee.2011.02.007
Source: PubMed

ABSTRACT Protecting cranial facet joint is a modifiable risk factor that may decrease the incidence of adjacent segment disease after lumbar spinal fusion. Percutaneously instrumented screws may more frequently violate cranial facet joints because of the potential limitation of screw entry site selection. To our knowledge, however, there is no study that has evaluated the cranial facet joint violations adjacent to minimally invasive lumbar fusion related to percutaneously placed pedicle screws.
We investigated the incidence and relating factors of cranial facet joint violations by percutaneous pedicle screws.
A retrospective study of prospectively collecting data.
The sample comprises 184 pedicle screws percutaneously placed at the cranial fusion segments in 92 patients who underwent minimally invasive lumbar spinal fusion.
The facet joint violations adjacent to a cranial fusion segment were examined on the postoperative computed tomography (CT) scans.
Two independent observers retrospectively examined all the postoperative CT images. A facet joint was considered violated if any of the following situations were encountered: pedicle screw clearly within the facet joint; pedicle screw head clearly within the facet joint; and pedicle screw and/or screw head within 1 mm from or abutting the facet joint, without clear joint involvement.
The incidence of the violations was 50% (46/92) of all patients and 31.5% (58/184) of all screws, which were significantly higher than the previously reported rates with the traditional open procedure (50% vs. 23.5% of all patients, p<.001; 31.5% vs. 15.2% of all screws, p<.001). The violations occurred approximately 3.3 times more frequently at the most cranial pedicle screws of L5 pedicle than at the other pedicles (70.8% vs. 42.6%, odds ratio [OR]=3.3, p=.021). Logistic regression analysis revealed a significant trend toward reducing the incidence of the violations as increasing the year of surgery (OR=0.7, p=.008). The incidence showed no significant relationships with patients' age, gender, body mass index, preoperative diagnosis, the number of fused segments, or the side of screw placement.
Our data raise a concern about the higher incidence of cranial facet joint violations by percutaneously placed pedicle screws than that previously reported rates by traditionally instrumented screws. Furthermore, more care should be taken to avoid cranial facet joint violations when the surgeon is a novice to percutaneous pedicle screw placement and/or minimally invasive fusion surgery is considered at the L5-S1 segment.

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    ABSTRACT: Object A reported risk factor for adjacent-segment disease is injury to the superior facet joint from pedicle screw placement. Given that the facet joint is not typically visualized during percutaneous pedicle screw insertion, there is a concern for increased facet violation (FV) in minimally invasive fusion procedures. The purpose of this study was to analyze and compare the incidence of FV among patients undergoing minimally invasive transforaminal lumbar interbody fusion (MITLIF) and open transforaminal lumbar interbody fusion (TLIF). The impact of O-arm navigation compared with traditional fluoroscopy on FV in MITLIF is also assessed, as are risk factors for FV. Methods The authors identified a consecutive population of patients who underwent MITLIF with percutaneous pedicle screw placement, as well as a matched cohort of patients who underwent open TLIF. Postoperative CT imaging was assessed to determine intraarticular FV due to pedicle screw placement. Patients were stratified into minimally invasive and open TLIF groups. Within the MITLIF group, the authors performed a subanalysis of image guidance methods used in cases of FV. Two-tailed Student t-test, ANOVA, chi-square testing, and logistic regression were used for statistical analysis. Results A total of 282 patients were identified, with a total of 564 superior pedicle screw placements. The MITLIF group consisted of 142 patients with 284 screw insertions. The open TLIF group consisted of 140 patients with 280 screw insertions. Overall, 21 (7.4%) of 282 patients experienced FV. A total of 21 screws violated a facet joint for a screw-based FV rate of 3.7% (21 of 564 screws). There were no significant differences between the MITLIF and open TLIF groups in the percentage of patients with FV (6.3% vs 8.6%) and or the percentage of screws with FV (3.2% vs 4.3%) (p = 0.475 and p = 0.484, respectively). Further stratifying the MI group into O-arm navigation and fluoroscopic guidance subgroups, the patient-based rates of FV were 10.8% (4 of 37 patients) and 4.8% (5 of 105 patients), respectively, and the screw-based rates of FV were 5.4% (4 of 74 screws) and 2.4% (5 of 210 screws), respectively. There was no significant difference between the subgroups with respect to patient-based or screw-based FV rates (p = 0.375 and p = 0.442, respectively). The O-arm group had a significantly higher body mass index (BMI) (p = 0.021). BMI greater than 29.9 was independently associated with higher FV (OR 2.36, 95% CI 1.65-8.53, p = 0.039). Conclusions The findings suggest that minimally invasive pedicle screw placement is not associated with higher rates of FV. Overall violation rates were similar in MITLIF and open TLIF. Higher BMI, however, was a risk factor for increased FV. The use of O-arm fluoroscopy with computer-assisted guidance did not significantly decrease the rate of FV.
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