Neurological Safety of Endoscopic Transforaminal Lumbar Interbody Fusion: A Magnetic Resonance Neurography Study

Objective. A magnetic resonance neurography (MRN) study was conducted to assess the neurological safety of endoscopic transforaminal lumbar intervertebral fusion (endo-TLIF). Materials and Methods. A total of 56 healthy volunteers (29 men, 27 women; average age, 44 yr; age range, 21–60 yr) were included in the study. Coronal MRN images were collected from L2/L3 to L5/S1. The working triangle, modified working zone, and safest working zone areas, as well as the vertical and horizontal safe operation diameters, were measured. Linear regression analyses were conducted to explore the correlations between general characteristics (sex, age, height, body mass index) and the measured radiographic indicators. Results. MRN can effectively evaluate the operation zone of endo-TLIF. The safest working zone, modified working zone, and working triangle areas were largest at L4/L5 (92.4±23.4, 136±35.6, and 197±41.7 mm2, respectively) and smallest at L2/L3 (45.5±12.9, 68.1±19.5, and 92.6±24.4 mm2, respectively). The vertical safe operation diameter was large at L4/L5 and L2/L3 (5.34±0.8 and 5.42±0.9 mm, respectively) and smallest at L5/S1 (2.94±0.9 mm). The horizontal safe operation diameter was large at L4/L5 (7.28±1.2 mm) and smaller at L5/S1 and L2/L3 (4.28±1.0 and 4.77±0.8 mm, respectively). Conclusions. L4/L5 has the lowest risk of nerve injury, and may be the safest level for beginners initiating endo-TLIF in their practice. We recommend that coronal MRN is routinely performed before endo-TLIF to minimize the risk of neurological injury.