Abstract:[Objective] To investigate the relationship between the nerve roots and the intervertebral space of the upper lumbar spine under unilateral biportal endoscopic(UBE) by digital anatomical method, and to provide theoretical basis for the treatment of upper lumbar spinal stenosis (LSS) with UBE. [Methods] Lumbar CTM was performed on 21 patients with LSS. The images were imported into Mimics software to establish a 3D model, and related parameters of upper lumbar spine were measured: Points of intersection between lower edge of upper lumbar lamina and medial edge of lower articular process (A) and intersection of upper edge of lower lumbar lamina and medial edge of superior articular process (B) to lateral edge of dural membrane (a1, b1), lower edge of nerve root origin (a2, b2), lower endplate of upper lumbar spine (a3, b3), and upper endplate of lower lumbar spine (a4, b4), respectively. The horizontal distance (a5, b5) between the lateral edge of the inferior articular process of lumbar spine and the intersection of the isthmus bone crest (X); Vertical distance from point B to the lower edge of the same ordinal lumbar pedicle (b6); The lower edge of the nerve root origin was located at the upper lumbar endplate (n1) and the distance to the lower lumbar endplate (n2). [Results] In L1/2-L3/4 segment, the lower edge of the nerve root origin originated from far below the intervertebral space level. The lower the segment, the closer the lower edge of the nerve root origin was to the intervertebral space level (P<0.05). Both A and B were located below the intervertebral space, above the lower edge of the starting nerve root, and the projection was within the lateral edge of the dural membrane. The lower the segment, the larger a5, b5, b6 (P<0.05). [Conclusion] There are obvious anatomical characteristics of the upper lumbar spine. The upper and lower LSS decompression range is large.Simultaneous decompression of adjacent segments on the same side and slightly larger window opening can cause one side of the lamina defect. External decompression must result in partial defects of the inferior articular process and lumbar isthmus. It is recommended that UBE decompress ipsilateral and contralateral when necessary to ensure spinal stability.