Incomplete (A3) versus complete (A4) thoracolumbar burst fractures: results from a prospective international multicenter cohort study.

Objective The objective was to compare incomplete (A3) versus complete (A4) thoracolumbar burst fractures managed nonoperatively or operatively with respect to reaching minimal clinically important difference (MCID) in Oswestry Disability Index (ODI) score.Methods A prospective observational international multicenter cohort study was conducted. After stratification using the AO Spine Thoracolumbar Injury Classification System, A3 and A4 outcomes were analyzed separately within nonoperative and operative management groups. Outcomes included absolute and relative improvement in ODI scores between discharge and 12-month follow-up. Kaplan-Meier curves were generated and compared with the log-rank test. Multivariable Cox regression models were constructed. The Cox regression models were adjusted using the key covariates of age, sex, thoracolumbar injury classification and severity (TLICS) score, and the interaction between fracture type and treatment type. Additional adjustment was performed for discharge ODI scores to compare relative improvement.Results In total, 198 neurologically intact patients were identified, with incomplete fractures (58.6%) being more common than complete burst fractures (41.4%). The rate of nonoperative management was significantly higher among A3 than A4 fractures (48.3% vs 24.4%, p < 0.01). A4 fractures demonstrated a higher mean TLICS score than A3 fractures (2.8 vs 2.4, p = 0.04). There were no significant functional differences in MCID in ODI scores, defined as an improvement in 12.8 points within 1 year after treatment (HR 1.21, 95% CI 0.86-1.70, p = 0.28). Examination of only the surgically treated cohort of patients also revealed no significant difference in achieving relative ODI score improvement within 1 year after treatment between those with A4 and those with A3 fractures (HR 1.19, 95% CI 0.78-1.82, p = 0.43). A similar finding was demonstrated for the nonoperative cohort, with no difference between the incomplete or complete burst fracture morphologies (HR 1.24, 95% CI 0.68-2.27, p = 0.48). Odds of achieving an absolute ODI score of 20 or less were also similar between patients with A4 and A3 fractures, regardless of whether operative (HR 0.81, 95% CI 0.52-1.25, p = 0.34) or nonoperative (HR 0.72, 95% CI 0.38-1.35, p = 0.30) management was pursued.Conclusions Patients with A3 and A4 fractures had similar odds to reach MCID in ODI score at 1 year. Even when exclusively considering the nonoperative cohort of patients who sustained A4 fractures with perceived increased biomechanical stability, there was no difference in functional improvement compared to patients with A3 fractures. Further large prospective multicenter studies are required to specifically assess radiographic outcomes and compare surgical approaches in the management of A3 and A4 fractures.