(I-649) Novel Use of CT/MRI Fusion to Design Trajectories for Percutaneous Lumbar Interbody Fusion reveals Important Anatomical and Surgical Aspects of Kambin’s Triangle

Introduction: With an increasing demand for minimally invasive fusions, Kambin’s triangle has become an ever more important anatomic corridor. Recent studies have begun implementing three-dimensional imaging to visualize the area of the triangle; however, the operative relevance of these modalities is still undetermined. Using commercially-available image merging software (Brainlab, Munich, Germany), our goal was to better understand the anatomical changes in Kambin’s triangle and how pathologies can alter the safe zone thereby affecting surgical planning when determining laterality of approach.

Methods: Preoperatively, the lumbosacral nerve roots on a high-resolution T2 MRI were ‘drawn out’ manually using Brainlab’s Smartbrush feature. Next, Kambin’s triangle was ‘drawn out’ using a similar procedure, ensuring there was no overlap between the area and the nerve above. Intraoperatively, the segmented MRI was then fused with intraoperative CT images using Brainlab Curvature Correction, which auto-corrected for patient movement.

Results: 10 patients (67.2 ± 9.6 years, 40% female, BMI 28.2) were retrospectively reviewed. 100 Kambin’s triangles were individually measured. The average areas at L1-L2, L2-L3, L3-L4, and L5-S1 were 51.2 ± 8.81 mm2, 72.1 ± 12.8 mm2, 87.0 ± 10.2 mm2, 89.5 ± 19.2 mm2, and 116 ± 31.4 mm2, respectively. The trend in area followed a linear regression model (p-value = 0.005, R2 = 0.95) revealing a significant increase in size going down the lumbar spine. The most commonly operated on level was L4-L5 (80%). When pathology was present, the area of Kambin’s triangle significantly decreased at L4-L5 (p-value = 0.030) and L5-S1 (p-value = 0.003). None of the patients suffered postoperative motor or sensory deficits.

Conclusion : These results illustrate the practicality of pre-operatively segmenting lumbosacral nerves and measuring Kambin’s triangle in order to help guide surgical planning for percutaneous lumbar interbody fusions. Although there is a linear increase in the triangle’s area going down the lumbar spine, the presence of pathology can significantly reduce the safe zone.

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