How to Prevent Nerve Root Injury in Uniportal Full Endoscopic Lumbar Fusion Surgery? Insights From a Cadaveric Anatomic Study With Simulation Surgery

Abstract

Study Design. The study included two fresh-frozen cadavers. Objective. To elucidate the positional relationship between surgical instruments and nerve roots during full endoscopic facet-sparing (FE fs-TLIF) and facet-resecting (FE fr-TLIF) lumbar interbody fusion and propose safe instrumentation insertion procedures and recommend cage glider designs aimed at protecting nerve roots. Summary of Background Data. Endoscopic surgical techniques are increasingly used for minimally invasive lumbar fusion surgery with FE fr-TLIF and FE fs-TLIF being common approaches. However, the risk of nerve root injury remains a significant concern during these procedures. Methods. Eight experienced endoscopic spine surgeons performed uniportal FE fr-TLIF and FE fs-TLIF on cadaveric lumbar spines, totaling 16 surgeries. Post-operation, soft tissues were removed to assess the positional relationship between the cage entry point and nerve roots. Distances between the cage entry point, traversing nerve root, and exiting nerve root were measured. Safe instrumentation design and insertion procedures were determined. Results. In FE fr-TLIF, the mean distance between the cage entry point and traversing nerve root was significantly shorter compared to FE fs-TLIF (3.30±1.35 mm vs. 8.58±2.47 mm, respectively; P<0.0001). Conversely, the mean distance between the cage entry point and the exiting nerve root was significantly shorter in FE fs-TLIF compared to FE fr-TLIF (3.73±1.97 mm vs. 6.90±1.36 mm, respectively; P<0.0001). For FE fr-TLIF, prioritizing the protection of the traversing root using a two-bevel tip cage glider was crucial. In contrast, for FE fs-TLIF, a single-bevel tip cage glider placed in the caudal location was recommended. Conclusion. This study elucidates the anatomical relationship between cage entry points and nerve roots in uniportal endoscopic lumbar fusion surgery. Protection strategies should prioritize the traversing root in FE fr-TLIF and the exiting root in FE fs-TLIF, with corresponding variations in surgical techniques. Level of Evidence. V