Depth-adapted portal design for unilateral biportal endoscopic discectomy in a morbidly obese patient (BMI 41): technical considerations.

Morbid obesity increases operative depth and soft-tissue thickness in lumbar spine surgery, potentially complicating portal placement and working-corridor stability in unilateral biportal endoscopic (UBE) procedures. Although previous studies have reported acceptable clinical outcomes of UBE in obese patients, technical considerations for depth-adapted portal design and working corridor management at extreme operative depths have not been sufficiently described. A male patient in his late 20s, with a height of 183 cm and body weight of 137 kg (body mass index 41 kg/m2), presented with a large left L5/S1 lumbar disc herniation. Preoperative imaging suggested a deep operative corridor, with the relevant working depth ranging approximately from 80 to 100 mm depending on the laminar working area and the oblique trajectory toward the L5/S1 disc space. Because the skin contours were incompletely visualized on preoperative computed tomography (CT) due to the patient's body habitus, intraoperative O-arm navigation was used as an adjunctive tool to confirm and refine the planned portal trajectories. Two 10-mm longitudinal skin incisions were created approximately 23 mm lateral to the midline, with an interportal distance of 35 mm. Adequate fascial release wider than the skin incisions was performed to reduce soft-tissue constraint at the fascial level. UBE discectomy was completed without dural injury or technical restriction, using standard UBE instruments. Postoperatively, radicular symptoms improved promptly without neurological deficits. This case illustrates depth-dependent amplification of soft-tissue constraints in UBE. As operative depth increases, small restrictions at the fascial level may proportionally narrow the functional working corridor. Adequate fascial release and thoughtful portal spacing may help preserve triangulation and facilitate irrigation outflow in deep operative fields. Rather than proposing a fixed portal template or requiring navigation, this report emphasizes individualized, depth-aware portal planning. Navigation may be useful in selected extreme cases when surface anatomy is difficult to evaluate reliably, but the same planning principles may also be applied using fluoroscopy and careful preoperative CT/MRI assessment. In morbidly obese patients with substantial operative depth, depth-aware portal planning combined with tailored fascial management may improve the reproducibility and technical stability of UBE discectomy. These findings should be interpreted as technical observations from a single case.