Biomechanical assessment of endoscopic cross-over top decompression in cervical spinal stenosis: a finite element...

In patients with severe central canal stenosis or posterior vertebral body osteophytes, endoscopic techniques often face challenges such as limited decompression range, endoscopic visual blind spots, and inadequate decompression. To address these limitations, our team innovatively developed a modified posterior cervical endoscopic decompression technique termed "Cross-over top Decompression (COTD)", drawing on clinical experience in lumbar endoscopic decompression and biomechanical principles. This study aims to compare its biomechanical performance with endoscopic unilateral laminotomy for bilateral decompression (Endo-ULBD), to verify its feasibility for comprehensive spinal canal decompression.

Three finite element models were established: normal cervical C5-6 (M0), Endo-ULBD (M1), and Cross-over top decompression (M2). Segmental range of motion (ROM) and maximum Von Mises stress of the intervertebral disc at C5-6 were analyzed to evaluate biomechanical stability.

Regarding the range of ROM, both M1 and M2 exhibited a consistent pattern of changes when compared to M0. Specifically, the ROM in both models increased markedly by 90.4% during flexion and by 2.95% during extension. In contrast, the increases observed during left lateral bending, right lateral bending, left rotation, and right rotation were all below 14%, with no obvious differences between M1 and M2. Regarding the maximum Von Mises stress on intervertebral discs, the patterns of change observed in models M1 and M2 were notably consistent. Compared to model M0, both models exhibited a marked increase in stress under flexion conditions, with an increase of 91.46% in M1 and 92.49% in M2. In contrast, stress variations during extension, lateral bending, and rotational movements were minimal, with no obvious differences in stress values between M1 and M2.

Compared with the normal cervical spine (M0), both Cross-over top and Endo-ULBD (M1) result in increased segmental ROM and elevated intervertebral disc stress, but these parameters show no obvious difference between the two techniques. By preserving facet joint stability, Cross-over top achieves adequate central spinal canal decompression while maintaining comparable biomechanical stability to Endo-ULBD, providing a reliable biomechanical basis for its clinical application.