Risk factors for supplementary posterior instrumentation after anterolateral decompression and instrumentation in thoracolumbar burst fractures

Background: In spite of the established benefits of anterolateral decompression and instrumentation (ALDI) for thoracolumbar burst fractures (TLBF), the indications for supplementary posterior instrumentation remain unclear. Methods: A retrospective review of clinical and radiographic data of a prospective cohort of 73 patients who underwent ALDI for TLBF from T12 to L4. Results: The mean age of the cohort was 42 ± 15 years, with 49 males and 24 females. Forty-six patients had neurological deficit, and 27 were intact. Owing to symptomatic settling, supplemental posterior instrumentation was performed in 7 out of 73 patients. The age of patients requiring supplemental posterior instrumentation (59 ± 14 years) exceeded that of patients who did not (41 ± 16, p = 0.004). Otherwise, the patients who required posterior instrumentation were comparable to those treated with ALDI in terms of body mass index (BMI), American Spinal Injury Association (ASIA) scores on admission and follow-up, residual spinal canal, and local kyphosis on admission and follow-up. The posterior ligamentous complex (PLC) integrity was assessed in 38 patients in whom the MRI scans were retrievable, 31 successfully treated with ALDI, and all 7 undergoing supplementary posterior instrumentation. Subgroup analysis demonstrated that there was no difference in the incidence of PLC disruption between the 2 groups (p = 0.257). Conclusions: Secondary supplemental posterior instrumentation was deemed necessary in 10% of cases following ALDI. Age was the only significant risk factor predicating supplemental posterior instrumentation.