Background
Endoscopic surgery has demonstrated its effectiveness against disc herniations. However, there are limitations in its use in removing a highly up-migrated lumbar disc in hidden zone. This study aimed to introduce the biportal endoscopic approach for the treatment of a highly up-migrated lumbar disc and to report the preliminary surgical outcomes.
Methods
This study included 28 patients with a highly up-migrated lumbar disc who underwent biportal endoscopic surgery through one-level above contralateral corridor for disc removal. Patients were re-evaluated by postoperative MRI to confirm the successful removal of ruptured fragments. Simple X-ray was obtained for assessing the development of spinal instability. Back and leg pain were evaluated using Visual Analog Scale (VAS) scores. The satisfaction rate of clinical outcomes was assessed using the modified MacNab criteria.
Results
The mean age of patients was 62.3 years, and the mean follow-up period was 21.4 months. Compared to preoperative scores, VAS scores of back and leg pain significantly improved. At the final follow-up, two patients had unfavorable outcome due to the presence of residual leg pain. There was no new development of segmental instability or spondylolisthesis.
Conclusions
Biportal endoscopic approach with one-level above contralateral corridor may be an alternative treatment method for a highly up-migrated lumbar disc, with advantages including direct visualization of the hidden zone from the tail of ruptured fragment to the ruptured site, preservation of the facet joint and pars interarticularis.

Objective
This study aimed to describe the surgical technique in patients with cervical herniated disc treated with unilateral biportal endoscopic spinal surgery.
Materials and Methods
Working and viewing portals were created in each unilateral paravertebral area at the target disc level. Under exploring by endoscopic view, effective decompression was possible via safe access to the medial foramen with minimal laminectomy and facetectomy. We evaluated 27 patients, and clinical outcome was analyzed using the visual analogue scale (VAS), Neck disability index (NDI), Macnab criteria, and motor function of involved upper extremity, all assessed before and 3, 6 months post procedure.
Results
The VASs for axial neck pain and upper extremity pain decreased from 6.8 to 1.9 and 7.7 to 1.5, respectively, at 6 months post procedure. The NDIs were improved from 45.5 to 13.0 at 6 months post procedure. According to the Macnab criteria, an ‘Excellent’ , ‘Good’ , and ‘Fair’ result was obtained in 55.6%, 29.6%, and 14.8% subjects, respectively. The motor power of involved upper extremity improved as an approximately one grade on average at 6 months post procedure; 3.9±0.8 to 4.8±0.4.
Conclusions
Unilateral biportal endoscopic spinal cervical surgery can be an efficient and safe intervention in patients with cervical herniated disc.