The effect of fusion levels on clinical outcomes in traumatic lower lumbar vertebral fractures.

BACKGROUND: Fractures of the lower lumbar spine (LLS) are uncommon and present unique biomechanical challenges. This study aimed to assess and compare the clinical and radiological outcomes of short-segment posterior instrumentation (SSPI) versus long-segment posterior instrumentation (LSPI). METHODS: A retrospective cohort of patients aged 18-63 years who underwent posterior instrumentation for thoracolumbar (TL, T10-L2) or LLS (L3-L5) fractures between 2005 and 2022 was analyzed. SSPI was applied for AO type A2-A4 injuries, while LSPI was reserved for type B2, B3, and C injuries. Functional outcomes were assessed using the Oswestry Disability Index (ODI) and visual analog scale (VAS), while radiological alignment was evaluated with the sagittal Cobb angle (SCA). Forty-nine patients were included: 33 with thoracolumbar (TL) fractures and 16 with LLS fractures. RESULTS: Eight LLS patients underwent SSPI, eight received LSPI, and all TL fractures were treated with SSPI. SCA improved significantly in all groups (p<0.001). In LLS fractures, LSPI resulted in worse function (ODI 40.6+-15.4 vs. 25.4+-7.2, p=0.040; VAS 3.0+-1.7 vs. 2.2+-2.4, p=0.038) compared with SSPI. Functional outcomes for LL-SSPI and TL-SSPI were comparable. SSPI achieved similar radiological correction with 19% shorter operative time and reduced blood loss. CONCLUSION: In this study, the SSPI method was found to be a safe option for the management of LLS fractures from both clinical and radiological perspectives. In contrast, the LSPI method should be reserved for highly unstable injuries, as it may have a detrimental effect on lumbar function.