In vitro comparison of endplate preparation in biportal endoscopic and microscopic tubular transforaminal lumbar interbody fusion procedures.

Background: Successful spinal fusion heavily depends on the condition of endplate preparation in transforaminal lumbar interbody fusion (TLIF). The microscopic tubular (MT) approach offers a fixed surgical field outside the body and primarily relies on tactile feedback for endplate preparation. In contrast, the biportal endoscopic (BE) approach offers a flexible surgical field of view inside the body, allowing for direct visualization of the entire process of endplate preparation. These differences may affect the adequacy and completeness of endplate preparation.

Purpose: To evaluate the adequacy and completeness of endplate preparation in BE- and MT-TLIF.

Study Design/setting: Anatomical study of human cadavers.

Outcome Measures: A quantitative assessment was performed using digital imaging software to calculate the percentage of the prepared endplate area (Prep %), which evaluated the adequacy of endplate preparation by comparing the prepared endplate cross-sectional area to the total endplate area. The entire endplate was divided into a grid of 6 × 8 pixels to evaluate the completeness of endplate preparation. Each pixel was qualitatively scored on a 4-point scale (0-3 points) based on the extent of bony endplate exposure and was counted based on its score. The percentage relative to the total number of pixels (Pixel%) was calculated.

Methods: Four cadaveric torsos were procured for the study. Three lumbar segments were prepared using BE- and MT-TLIF techniques in each cadaver, totaling twelve intervertebral discs and twenty-four endplates. After completing endplate preparations using each approach, the lumbar spines were excised from the cadaveric torsos. Each disc space of the lumbar spine was dissected and split open in the axial plane at the center to expose the cranial and caudal endplates. These endplates were digitally photographed, followed by a quantitative and qualitative assessment of endplate preparation. The difference between the 2 approaches was then evaluated.

Results: In terms of adequacy of endplate preparation, the Prep% was significantly larger with the BE than with the MT approach (55.10%; 44.94%; p=.001). Notably, when the entire endplate was divided into quadrants for analysis, the BE approach had significantly larger Prep% in the contralateral anterior and contralateral posterior quadrants (p<.001). In evaluating the completeness of endplate preparation, the Pixel% with complete endplate exposure (3 points) was significantly higher with the BE approach than with the MT approach (15.60%; 5.93%; p<.001). There was no significant difference in the Pixel% scored as 0, 1, or 2 points (p>.05).

Conclusion: The results of this study indicate that the BE approach provides significantly better adequacy and completeness of endplate preparation than the MT approach in TLIF surgery.

Clinical Significance: The improved adequacy and completeness of endplate preparation using the BE approach could translate into better fusion outcomes in TLIF surgery. The BE technique may allow for a more thorough preparation of the endplate, reducing the risk of fusion failure and cage subsidence.