How accurate is fluoroscopy-guided percutaneous pedicle screw placement in minimally invasive TLIF?

Introduction: The accuracy of pedicle screws placement has been the subject of many studies and varied rates of screw malposition have been reported. This study evaluates the placement of pedicle screw inserted percutaneously, guided by intraoperative 2D fluoroscopy, in minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). Methods: Retrospective study of patients who underwent MIS-TLIF from 2007 to 2016 in a single center, for degenerative pathology. All patients had a follow-up lumbar CT scan one year after surgery to evaluate pedicle violation, location and degree. Gertzbein classification was used for description of the degree of violation. Results: This study included 241 patients, with a mean age of 57 years (SD 11.69). A total of 1045 screws were evaluated. Most patients were fused at L4-L5 or L5-S1 levels. The total rate of pedicle walls’ violation was 13.97%, however only 4.31% of the screws presented violations exceeding 2 mm. Only 5 patients were reoperated because of complaints related to screw malposition (0.48% of all screws). There was a trend for an increased rate of pedicle violation for upper lumbar pedicles (p < 0.001). For S1 screws, violations were more common on left pedicle screws (17.89% vs 7.53%, p = 0.03), with an Odds Ratio of 2.68 (95% CI: 1.07–6.80). Conclusion: Percutaneous pedicle screw insertion guided by intraoperative 2 D fluoroscopy in MIS-TLIF is safe and most of pedicle violations seem to be minor and without clinical consequences. In S1 screws, the surgeon's side was more prone to violation.