The Effect Lateral Mass Screw Facet Joint Violation on Radiographic and Clinical Outcomes After Posterior Cervical Fusion

Introduction: In posterior cervical fusion (PCF), the potentially devasting effect of vertebral artery injury from lateral mass screw over-medialization is well understood. However, the impact of a cranial screw trajectory leading to facet joint violation is yet to be characterized. Placement of trans-articular lateral mass screws may increase cortical purchase area and construct strength but could risk persistent axial neck pain, screw loosening, and pseudoarthrosis. This study determined if lateral mass screw facet joint violation relative to standard lateral mass screw placement predicted adverse clinical or radiographic outcomes after PCF.

Methods: All adult patients who underwent C2-T2 PCF for myelopathy or myeloradiculopathy at an academic center between 2013-2020 were retrospectively identified. Patients were grouped based on the presence or absence of lateral mass screw facet joint violation assessed on postoperative CT scan with subgroups including laterality and number of facet joint violations. Preoperative and short- and long-term postoperative radiographic outcomes (fusion status, local cervical alignment, global alignment) and patient reported outcomes measures (PROMs) were collected. Univariate analysis compared patient demographics, surgical factors, and change in alignment and PROMs across facet joint violation groups.

Results: A total of 79 patients met the inclusion criteria (51 facet joint violation, 20 bilateral facet joint violation). There were no significant differences in patient and surgical factors and preoperative bone quality between facet joint violation groups (p>0.05). Preoperative and postoperative alignment parameters (DJK, T1-T4 kyphosis, C2 SVA, C2-7 lordosis, T1 slope) or PROMs (VAS Neck, NDI, SF-12) at all short- and long-term follow-up intervals did not differ significantly by the presence or absence of unilateral and bilateral facet joint violation (p>0.05). There were no significant variations in rates of fusion, screw loosening, and revision surgery across facet joint violation groups (p>0.05). The number of facet joint violations was not found to correlate with radiographic or clinical outcomes (rho < 0.3).

Conclusion : There were no significant differences in PROMs, fusion status, and screw loosening based on the presence or extent of lateral mass facet joint violation in PCF. Surgeons may place trans-articular lateral mass screws to maximize cortical purchase area and construct rigidity without apparent compromise to postoperative outcomes.