A comparison of monoaxial and polyaxial pedicle screws in thoracolumbar fracture

Purpose: To evaluate the use of short-segment posterior fixation with monoaxial and polyaxial pedicle screws in thoracolumbar fractures Methods: All patients who underwent short-segment posterior fixation with monoaxial pedicle screws or polyaxial pedicle screws in the injured vertebra of a thoracolumbar fracture (T12-L2) in our hospital between June 2012 and December 2018 were categorised into two groups: monoaxial pedicle screws group (group A) and polyaxial pedicle screws group (group B). We compared the Thoracolumbar Injury Severity Score (TLISS), American Spinal Injury Association (ASIA) score, the fracture level, Arbeitsgemeinschaft für Osteosynthesefragen (AO) classification, hospital stay, injury-to-operation interval, and associated injuries between the two groups. In addition, the prevertebral height ratio, the injured vertebra Cobb angle, and the injured vertebral endplate centre ratio were measured preoperatively, postoperatively, and at the final follow-up. Results: There were 63 patients (21 males and 42 females) with an average age of 44.7 years. Compared with group B, the injury vertebral endplate centre ratio significantly increased postoperatively and at the final follow-up (P<0.05) in group A. Conclusion: Short-segment posterior fixation with monoaxial or polyaxial pedicle screws via the fracture level for thoracolumbar fracture can achieve kyphosis correction, reduce sagittal alignment correction failure, and maintain anterior vertebral height. The insertion of monoaxial pedicle screws at the fracture level after thoracolumbar vertebral fracture has a flick up effect on the central vertebral body of the injured vertebrae, which is beneficial to the recovery of the vertebral endplate.