Abstract
Objective:
The aim of this study was to define a method to identify the location of the great vessel bifurcation (GVB) in relation to the L5/S1 disc and measure the lumbo-sacral angle (LSA) at L5/S1 using routine lumbar spine MRI images on standard PACS software. The information can be used for surgical planning of anterior lumbar interbody fusion (ALIF) at L5/S1 with a plate and cage.
Method:
Axial and sagittal T2 sections of 192 lumbar spine MRI scans were viewed simultaneously to classify the position of the GVB and the LSA. A further 75 scans were assessed independently by 2 examiners (E1/E2) utilizing the same classification to record the GVB position (High (H), Middle (M), Low (L)) and size of the LSA using standard radiology software. Twenty five images were randomly selected for repeat measurements one month later.
Results:
Inter and Intra-observer agreements were excellent for LSA (0.92, R1=0.92, R2=0.94) and moderate for GVB (0.76, R1=0.85, R2=0.75). Reduced GVB correlation was primarily observed in the high (E1=64% vs E2=50.7%, =57.3%) and Middle (E1=25.3% vs E2=40%, =32.7%) categories. LSA was most prevalent between 121–130° in both assessors (E1= 57.3% vs E20=61.3%, =59.5%).
Conclusion:
MRI assessment of GVB height and LSA is feasible and can aid surgical planning of L5/S1 ALIF and permit selection of the implants that best suit the patient's specific anatomy. The results indicate that anterior plate placement, without impingement on the great vessels, would be possible in 90% of cases with a majority having an LSA of between 125° and 130°.
