COMPARISON OF MONO AND POLY-AXIAL PEDICLE SCREW FIXATION IN THORACOLUMBAR A3/A4 FRACTURES

ABSTRACT Objective: This study aims to compare the use of mono-axial and poly-axial screws in AOSpine type A3 and A4 thoracolumbar fractures. Methods: Prospective case-control study involving patients treated surgically with short fixation using mono-axial or poly-axial screws. The type of treatment was chosen according to the surgeons’ preference and implant availability. The qualitative variables used were the type of implant (mono-axial or poly-axial), type of fracture (A3 or A4), neurological deficit, use of an additional screw in the fractured vertebra, and need for reoperation. The quantitative variables were preoperative Cobb (CobbPre); immediate postoperative Cobb (CobbPOI); late postoperative Cobb (CobbPOL); Delta (∆) kyphosis; preoperative anterior vertebral body collapse (AVBC%); postoperative AVBC%; ∆ AVBC%. For quantitative variables, the Student’s T Test was used. Results: 35 patients were included, 22 in the mono-axial group (eight patients A3 and 14 A4) and 13 in the poly-axial group (two patients A3 and 11 A4). The postoperative AVBC% was statistically superior for the mono-axial group (mean of 0.60±0.09 in the pre-operative AVBC% to 0.77±0.11 in the post-operative), compared to the poly-axial group (0.60±0.12 to 0.69± 0.13), p=0.04. ∆ AVBC% was also statistically different (0.17±0.10 in the mono-axial group and 0.08±0.12 in the poly-axial group), p=0.01. The other quantitative variables had no significant differences. Conclusion: Surgical treatment using mono-axial screws was statistically superior in recovering anterior vertebral body height. Level of Evidence III; Prospective Case-Control Study.