Microsurgical and Descriptive Three-Dimensional Analysis of the Subarticular Trigone: A Guidemap for Standardizing Lateral Recess Decompression

Background Lateral recess decompression has remained a cornerstone spinal procedure for decades. Despite its popularity, a significant lack of evidence in the literature exists concerning microsurgical anatomy and pertinent surgical landmarks, resulting in non-standardized nomenclature, descriptions, and surgical approaches. Objective This study provides an in-depth microsurgical and descriptive analysis of the subarticular trigone (SAT), serving as an anatomical guide and a tool to foster consistency in nomenclature and standardization of surgical approaches. Methods We analyzed 35 high-resolution lumbar spine CT scans, employing three-dimensional (3D) processing techniques. The SAT is introduced to delineate the bony prominence enveloping the superiomedial quadrant of the pedicle. The SAT encompasses two zones: (1) a superior zone above the superior pedicular line, corresponding to the medial part of the body of the ascending facet (AF), and (2) an inferior zone between the superior and middle pedicular lines, corresponding to the root of the AF and the medial pars/superior lamina. The superior subarticular point (SSP) and medial subarticular point (MESP) serve as key reference landmarks. The SAT forms the roof of the lateral recess and the region requiring resection during decompression of the traversing root in this anatomical corridor. Various measurements, including SSP and MESP to lateral pars, tip of the facet and spino-laminar junction distance, mean width of the sublaminar ridge (SLR), and percentage of the facet that requires resection for adequate SAT decompression, were carried out. Results The mean distance of the SSP to the lateral pars ranges from 7 to 9.2 mm, to the tip of the descending from 9.3 to 10.1 mm, and to the spino-laminar junction from 6.7 to 8.1 mm. The MESP is located at a mean distance of 5.4-6.9 mm from the medial pedicular line. The mean width of the SLR varies from 18.6 to 29.4 mm. Finally, the percentage of total facet width that needs to be removed to adequately decompress the SAT extends from 32% at L4 to 36% at L1. Conclusions This study presents comprehensive insights into the surgical, descriptive, and correlative anatomy of the lateral recess, emphasizing the SAT. The extrapolated data offer a framework for achieving uniformity in surgical planning and advocate for standardized nomenclature.