Posterior Approach for Structural Thoracolumbar/lumbar Curves In Adolescent Idiopathic Scoliosis Lowest Instrumented Vertebra Selection And Complications Risk: A Systematic Review And Meta Analysis

Introduction: Definitive guidelines informing where to stop instrumentations in thoracolumbar and lumbar idiopathic scoliosis deformity correction do not exist.
The present study systematically analyzes the different surgical criteria to determine the LIV in thoracolumbar and lumbar structural curves.

Methods: A literature review was performed via PubMed and Embase, from inception to 04/01/2024. The following search strategies containing the terms: Lenke 5, Lenke 5 and posterior surgery, Lower instrumented vertebra and Lenke 5, Lower instrumented vertebra and Lenke 3, lower instrumented vertebra and Lenke 6, lower end vertebra and scoliosis were done.

Results: The search yielded a total of 1693 articles. After scanning for title and abstract and eliminating the duplicates, 22 studies were selected. L2 was the LIV for five patients. Pooled instrumentation rates for L3, L4, and L5 were 70.8% (95% CI 64.3-77.3, I²=98.4%, p< 0.001), 22.3% (95% CI 17.5-27.1, I²=96.81%, p< 0.001), and 2.1% (95% CI 0.9-3.3, I²=80.53, p< 0.001), respectively. The pooled rate of complications for L3=LIV was 11.1% (95% CI 7.4-14.8, I²=88.95%, p< 0.001), for L4=LIV was 7.4% (95% CI 3.6-11.3, I²=22.87%, p=0.226), and for L5=LIV was 43.8% (95% CI 17.8-69.7, I²=77.69%, p=0.004). When the L3 and L4 LIV complications were compared across eight studies, no significant difference was found between groups (p=0.26). Four studies compared the complications between the L4 LIV and L5 LIV groups, favoring the L4 group (OR 0.17, 95% CI 0.08-0.36, p< 0.00001). Six studies compared the complication rates between LIV=LEV-1 and LIV=LEV, with the LEV group having significantly fewer associated alignment complications than the LEV-1 group (OR 8.43, 95% CI 3.62-19.66, p< 0.00001). Four studies compared the complications between LIV=LEV and LIV=LEV+1, again favoring the LEV group (OR 0.23, 95% CI 0.08-0.63, p=0.004).

Conclusion : The ideal fixation for thoracolumbar/lumbar curves (Lenke 3/5/6) can be L3 or L4. Fixation to L5 should be avoided due to the increased risk of coronal imbalance and severe decompensation.