Anterior Column Realignment Using an Anterior-To-Psoas Approach: A Radiographic-Anatomic Feasibility Study at L1-L5

Abstract

Study Design Cross-sectional radioanatomic study. Objective To determine the feasibility of performing an anterior column realignment (ACR) using an anterior-to-psoas (ATP) approach at L1-L5. Methods Axial magnetic resonance images (MRI) of the L1-L5 disc levels obtained at a single institution were obtained and analyzed. The feasibility of performing an ACR was assessed using a combination of the size of the left oblique corridor (OC), the psoas morphology using the modified Moro classification, and the anterior disc edge to great vessel distance. Results Three hundred MRI studies obtained from 300 patients were included. All patients had a measurable left OC at the L1-L4 levels. Twenty patients (6.7%) had no measurable OC at the L4-L5 level. According to the modified Moro’s classification, a high-rising psoas was seen in 4 patients (1.3%) at the L3-L4 level and 57 patients (19.0%) at the L4-L5 level. An ALL release was considered high risk due to no measurable space between the anterior disc edge and the great vessels in 54 patients (18.0%) at the L1-L2 level, 39 patients (13.0%) at the L2-L3 level, 119 patients (39.7%) at the L3-L4 level, and 226 patients (75.3%) at the L4-L5 level. Conclusion ACR using an ATP approach is the most radioanatomically feasible at L2-L3. The L4-L5 level has the highest risk with regards to both the ATP approach and the ALL release for an ACR due to high rates of unmeasurable left OC and space between the anterior disc edge and the great vessels.

Anterior column realignment (ACR) for focal kyphotic spinal deformity using an anterior to psoas approach and anterior longitudinal ligament release

“…Therefore, in comparison with the original ACR technique using a transpsoas approach, the authors believe that performing an ACR using the ATP approach may be a safer technique when radioanatomically feasible. A prior study by Hirase et al described the radioanatomic feasibility of performing an ACR using an ATP approach at L1–L5 and found that performing this technique was considered high risk (high-rising psoas or no measurable space between the ALL and the great vessels) in 13.0% of patients at the L2–L3 level, 40.7% at the L3–L4 level, and 89.0% at the L4–L5 level ( 8 ). The majority of the patients within our cohort underwent an ACR using an ATP approach were at the L2–L3 or L3–L4 level, largely due to the location of the focal kyphotic deformity and radioanatomic feasibility as presented by Hirase et al ( 8 ).…”

“…Although a recent study demonstrated the radioanatomic feasibility of performing a complete ALL release and ACR using the ATP approach at the L1–L5 levels, to our knowledge, there are no prior studies that evaluates the clinical application of this technique ( 8 ). Thus, the objective of this study was to describe and evaluate the safety of ACR using an ATP approach with complete release of ALL and annulus for correction of focal kyphotic lumbar deformity.…”