Comparison of clinical outcomes of different screw types in posterior short-segment internal fixation for thoracolumbar compression fractures

English Keywords:Thoracolumbar compression fracture  Surgery  Monoaxial screw  Polyaxial screw  Efficacy

English Abstract:

  【Abstract】 Objectives: To compare the clinical efficacy of monoaxial versus polyaxial screws in posterior short-segment transpedicular internal fixation at the injured vertebra for thoracolumbar compression fractures.Methods: A retrospective analysis was conducted on 103 patients treated with posterior reduction and short-segment internal fixation for thoracolumbar compression fractures in our hospital between June 2015 and October 2023. There were 59 males and 44 females, with an average age of 45.2±12.2 years(21-67 years). The upper or lower vertebrae adjacent to the injured level were fixed with monoaxial screws, while the injured vertebrae were fixed with either monoaxial screws or polyaxial screws. All the patients were followed up for 15.5±7.5 months(12-33 months). Operative time and intraoperative blood loss were recorded, and radiographic parameters including anterior vertebral height of injured vertebrae and, adjacent upper and lower vertebrae, local kyphotic Cobb angle, wedge angle were measured preoperatively, immediately postoperatively, and at final follow-up on X-ray images. The patients were divided into a monoaxial screw group and a polyaxial screw group. There were no statistically significant differences in gender, age, AO classification and compression degree of the injured vertebrae between the two groups(P＞0.05). Each group was further stratified into 3 subgroups by compression degree: group A(<30%), group B(30%-50%), group C(>50%). The ratio of the collapsed height of the injured vertebrae, local kyphotic Cobb angle and vertebral wedge angle were recorded for each patient subgroup. The fracture reduction efficacy and differences in postoperative follow-up outcomes were compared between the monoaxial screw group and polyaxial screw group. Results: There were 55 cases in the monoaxial screw group and 48 cases in the polyaxial screw group. Hospital stay, operative time, and VAS scores of low back pain were comparable between the two groups(P>0.05), but polyaxial screw group had significantly less blood loss(P<0.05). For subgroup analysis, in group A, 23 cases were fixed with monoaxial screws, and 20 cases were fixed with polyaxial screws; In group B, 17 cases with monoaxial screws, 14 cases with polyaxial screws; In group C, 15 cases with monoaxial screws, 14 cases with polyaxial screws. In group A, the immediate postoperative anterior vertebral height of injured vertebrae, local kyphotic Cobb angle and vertebral wedge angle were not statistically different between monoaxial and polyaxial screw fixations(P>0.05). In group B, monoaxial screws showed significantly better immediate postoperative height correction(P<0.001), but no difference at final follow-up(P=0.664). In group C, monoaxial screws achieved significantly better height correction at immediate postoperation and final follow-up(P<0.05). No internal fixation loosening or breakage occurred in either group during follow-up. Conclusions: For thoracolumbar compression fractures with over 50% vertebral compression, monoaxial pedicle screws fixed at the fractured vertebra have significantly better immediate postoperative vertebral reduction effect and long-term efficacy than polyaxial screws.