Exoscopic Extraforaminal Lumbar Interbody Fusion for Lumbar Degenerative Disease: Technical Considerations and...

Background/Objectives: Extraforaminal lumbar interbody fusion provides indirect decompression without entering the spinal canal, but its uptake has been limited by poor visualization and risk of exiting nerve root injury. We describe a minimally invasive exoscopic extraforaminal lumbar interbody fusion (exELIF) technique and evaluate its clinical and radiological outcomes. This study aims to describe the exELIF technique and report its early clinical and radiological outcomes. Methods: Twenty-six patients with lumbar degenerative diseases underwent exELIF using a 3D exoscope (ORBEYE). The procedure was performed through bilateral 30-40 mm posterior incisions. Clinical outcomes were assessed using the Japanese Orthopedic Association score preoperatively and at 1-year follow-up. Postoperative computed tomography evaluated interbody fusion. Operative time, blood loss, and complications were recorded. Results: Mean operative time was 131 ± 51 min, and mean estimated blood loss was 82 ± 99 mL. The mean JOA score improved from 15.2 ± 2.2 to 24.3 ± 2.6, with a mean recovery rate of 66% at 1 year. Interbody fusion was achieved in 96%. In an exploratory CUSUM analysis of 18 single-level fluoroscopy-guided cases, a transition in operative time was observed at approximately the 10th case; operative time and estimated blood loss decreased from 141.5 ± 39.2 min and 89.0 ± 77.8 mL in cases 1-10 to 80.1 ± 6.7 min and 21.2 ± 18.1 mL in cases 11-18 (p < 0.001 and p = 0.035, respectively), indicating a reduction of operative time with accumulated experience rather than a formally established learning curve. Three patients developed transient exiting nerve root symptoms that resolved spontaneously during follow-up. One patient at the L5/S level required revision surgery due to left L5 nerve root palsy caused by posterior migration of the bone graft; this complication led to a modification of the technique, with posterior bone grafting no longer performed at L5/S. Partial screw loosening was observed in 5 patients (19%), all of which were asymptomatic and required no additional intervention. Conclusions: ExELIF provides excellent visualization in deep surgical fields, allowing the use of conventional surgical instruments through minimally invasive incisions. This is an early feasibility report of a single-institution retrospective case series with a heterogeneous cohort and no control group; the present data therefore do not establish superiority over conventional or endoscopic ELIF. Within these limits, exELIF was associated with acceptable early clinical improvement and a high interbody fusion rate, and progressive reduction in operative time with experience suggests that it may be a technically feasible minimally invasive option for selected patients with lumbar degenerative disease and for revision surgery after lumbar decompression.