Unilateral biportal endoscopy combined with collagen membrane for adjacent segment pathology-lumbar spinal stenosis with floating cauda equina: A case report

Unilateral biportal endoscopy (UBE) has emerged as an effective alternative to open surgery for the treatment of adjacent segment pathology (ASP) -induced lumbar spinal stenosis (LSS), offering advantages such as minimal invasiveness and accelerated recovery. An 84-year-old female patient who underwent lumbar 4–5 (L4–L5) vertebral fusion 13 years ago presented with intermittent claudication over the past year; visual analog scale (VAS) score was 9. She was diagnosed with ASP and LSS. The patient was treated with UBE surgery at our institution. During spinal endoscopic surgery, when dural tears or partial dural defects are encountered, intact but dissociated cauda equina nerve roots can be observed floating loosely within the spinal canal intraoperatively—a phenomenon we termed the cauda equina floating sign (CEFS). After adequate decompression of the spinal canal, a medical absorbable collagen membrane was applied to cover and protect the cauda equina. The procedure was successfully completed with an estimated blood loss of 50 mL and an operative time of 2.5 h. Postoperatively, the patient’s lower limb symptoms were significantly relieved. She was able to ambulate on postoperative day 5 and was discharged on day 8. Her VAS score was 3. At the 6-month follow-up, her symptoms had substantially improved, and she had resumed normal daily activities. Magnetic resonance imaging at the 1-year postoperative follow-up demonstrated adequate spinal canal decompression. The patient’s low back and lower limb pain were also significantly relieved, with a VAS score of 1. The combination of UBE and a medical absorbable collagen membrane may represent an effective therapeutic strategy for CEFS and could potentially reduce the risk of cerebrospinal fluid leakage.