The Importance of Planning Ahead: A Three-Dimensional Analysis of the Novel Trans-Facet Corridor for Posterior Lumbar Interbody Fusion Using Segmentation Technology.

Background: The rise of minimally invasive lumbar fusions and advanced imaging technologies has facilitated the introduction of novel surgical techniques with the trans-facet approach being one of the newest additions. We aimed to quantify any pathology-driven anatomic changes to the trans-facet corridor, which could thereby alter the ideal laterality of approach to the disc space.

Methods: In this retrospective cohort study, we measured the areas and maximum permissible cannula diameters of the trans-facet corridor using commercially available software (BrainLab, Munich, Germany). Exiting and traversing nerve roots, thecal sacs, and lumbar vertebrae were manually segmented on T2-SPACE magnetic resonance imaging. Spondylolisthesis, disc protrusions, and disc space heights were recorded.

Results: A total of 118 trans-facet corridors were segmented bilaterally in 16 patients (65.6 ± 12.1 years, 43.8% female, body mass index 29.2 ± 5.1 kg/m). The mean areas at L1-L2, L2-L3, L3-L4, and L4-L5 were 89.4 ± 24.9 mm, 124 ± 39.4 mm, 123 ± 26.6 mm, and 159 ± 42.7 mm, respectively. The mean permissible cannula diameter at the same levels were 7.85 ± 1.43 mm, 8.98 ± 1.72 mm, 8.93 ± 1.26 mm, and 10.2 ± 1.94 mm, respectively. Both parameters increased caudally. Higher degrees for spondylolisthesis were associated with larger areas and maximum cannula diameters on regression analysis (P < 0.001).

Conclusions: Our results illustrate that pathology, like spondylolisthesis, can increase the area of the trans-facet corridor. By understanding this effect, surgeons can better decide on the optimal approach to the disc while taking into consideration a patient's unique anatomy.