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

Abstract

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.

Keywords: anatomy; decompression; lateral recess; subarticular zone; surgical anatomy.

Figure 1. Superficial anatomy and deep anatomy are superimposed. On the right side, a medial facetectomy and laminotomy are simulated, exposing the SAT and its two zones

SAT: subarticular trigone Image Credit: Spyridon Komaitis

Figure 2. Ventral view of a CT 3D reconstruction of the roof of the spinal canal. The anatomy of the SAT as well as the various anatomical landmarks, including the SSP, MESP, and LSP, are illustrated. The zones of the lateral recess with related compressive structures are also presented

CT: computed tomography, 3D: three-dimensional, SAT: subarticular trigone, SSP: superior subarticular point, MESP: medial subarticular point, LSP: lateral subarticular point Image Credit: Spyridon Komaitis

Figure 3. Superimposition of the anatomy of the SAT on the superficial level. Mean values for various measurements are illustrated for each level

SAT: subarticular trigone Image credit: Spyridon Komaitis

Figure 4. Ventral view of the roof of the spinal canal. The anatomy of the SLR is illustrated. The mean values of the distances of the SSP to SPL and the MESP to MPL are presented for each level. The relevant position of the thecal sac and nerve roots is also illustrated

SSP: superior subarticular point, SPL: superior pedicular line, SLR: sublaminar ridge, MPL: medial pedicular line, MESP: medial subarticular point Image Credit: Spyridon Komaitis

Figure 5. Axial cross-section of the lateral recess and related structures at the level of L5

AF: ascending facet Image Credit: Spyridon Komaitis

Figure 6. Midsagittal cross-section of the central canal, allowing visualization of the SAT. The anatomy of the traversing nerve root is superimposed. The flavum attachment area is also highlighted in yellow

SAT: subarticular trigone Image Credit: Spyridon Komaitis