Analysis was performed of two patient cohorts who underwent fixation without fusion for unstable thoracolumbar and lumbar fractures: (I) minimally invasive surgery (MIS) group using combined monoaxial-polyaxial pedicle screws inserted percutaneously; (II) open surgery (OS) group using Schanz screw constructs. Our aim was to compare radiographic and clinical indices of the 'gold standard' of open Schanz screw to MIS monoaxial-polyaxial screw constructs.
There were 13 patients in the MIS group and 19 in the OS group. Primary outcomes were the correction of fracture angulation and percentage loss of reduction until fracture union. Patient demographics, fracture classification, perioperative data and complications were also collected.
There was no significant difference in cohorts when comparing demographics and fracture classification. Operative time was 50 minutes less and haemoglobin drop was 9 g/L less in the MIS group. Radiation exposure was significantly higher in the MIS group. Pre-operatively, the mean kyphotic angle was 22° in the MIS and 16° in the OS group. Both groups achieved similar on-table correction. On immediate postoperative erect radiographs, the MIS group lost 15% of correction vs. 55% in the OS group. At final follow-up, both groups had a further loss of position, but significantly higher in the OS group (28% vs. 96%).
Combined polyaxial-monoaxial screw MIS constructs demonstrate favorable radiological and clinical outcomes for treatment of unstable thoracolumbar and lumbar fractures. Our study also demonstrates higher rates of radiological collapse in the OS cohort.