Radiological and Clinical Outcomes of Monoaxial versus Polyaxial Screw Constructs in C1 Jefferson Fracture Osteosynthesis: A Retrospective Study.

Abstract

To compare radiological and clinical outcomes of monoaxial versus polyaxial screw constructs in C1 posterior osteosynthesis for Jefferson fractures. A retrospective review of 19 patients treated with direct C1 ring osteosynthesis between 2010 and 2023 was performed. Patients were grouped by screw type: monoaxial (n = 7) and polyaxial (n = 12). Radiological parameters, including atlantodental interval, lateral mass distance (LMD), fracture gap, and lateral mass overhang, were assessed. Postoperative neck range of motion was evaluated at 1 year. Clinical outcomes were measured using the visual analog scale and Neck Disability Index. Statistical comparisons were performed using nonparametric tests, with results expressed as the median (interquartile range). The monoaxial group demonstrated significantly greater anterior arch fracture gap reduction (65.8% [47.3-85.6] vs. 7.6% [6.7-21.1], P < 0.001) and anterior LMD change (1.63 [0.82-2.65] mm vs. -0.53 [-1.28 to 0.50] mm, P = 0.008). Operative time was shorter in the monoaxial group (110 [102.5-115.0] minutes vs. 130 [121.3-152.5] minutes, P = 0.019). No significant differences were found in posterior arch gap/LMD reduction, postoperative range of motion, or improvements in visual analog scale and Neck Disability Index. One polyaxial case required revision for postoperative C1-C2 subluxation. Monoaxial screws provided superior anterior arch reduction, lateral mass realignment, and shorter operative time without compromising motion or clinical outcomes. Both constructs yielded similar improvements in pain and function. Screw selection has significant implications for radiological correction in motion-preserving surgery for unstable C1 fractures; however, larger prospective studies are warranted to determine the long-term outcome.