Technical considerations for time-efficient four-level biportal endoscopic lumbar interbody fusion in a frail elderly patient with severe lumbar deformity: a case report.

Background: Biportal endoscopic lumbar interbody fusion (BE-LIF) has recently emerged as a minimally invasive alternative to conventional open lumbar fusion surgery. However, long-segment endoscopic fusion for multilevel degenerative lumbar stenosis with associated degenerative scoliosis remains technically challenging because prolonged operative time and perioperative morbidity may substantially increase in frail elderly patients. Case Description: An 86-year-old man presented with severe back pain, bilateral radiating leg pain, progressive bilateral lower-extremity weakness, and left foot drop, progressing from one-cane ambulation to wheelchair dependence. Radiologic evaluation demonstrated severe multilevel lumbar spinal stenosis with degenerative scoliosis from L2 to S1, accompanied by severe foraminal stenosis, asymmetric disc collapse, and rotational deformity. Because the patient's symptoms and neurologic deficits could not be attributed to a single level, the deterioration was considered multifactorial, resulting from combined multilevel central, lateral recess, and foraminal neural compression. Given the patient's advanced age, frailty, cardiovascular comorbidity, continued aspirin therapy, and the high risk associated with conventional open deformity correction, four-level BE-LIF from L2 to S1 was performed using a workflow-oriented strategy to minimize operative burden. Osteotome-assisted facetectomy facilitated rapid exposure of the ligamentum flavum and disc space. Rather than extensive bilateral posterior decompression, restoration of disc and foraminal height through cage insertion was prioritized to achieve neural decompression while minimizing operative burden. Total skin-to-skin operative time was 265 minutes. No intraoperative dural tear, neurologic deterioration, cage migration, or conversion to open surgery occurred. At 1-month follow-up, visual analog scale scores for back and leg pain improved from 7 to 2 and from 8 to 2, respectively. Conclusions: Four-level BE-LIF may represent a feasible minimally invasive alternative for carefully selected elderly patients with multilevel lumbar degenerative deformity who are poor candidates for conventional open deformity correction. A workflow-oriented strategy incorporating unilateral posterior decompression, early cage insertion, and individualized pedicle screw fixation may improve operative efficiency while preserving the posterior ligamentous complex.