J Minim Invasive Spine Surg Tech.  2025 Apr;10(1):45-51. 10.21182/jmisst.2025.02040.

A Novel Paraspinal Approach With Unilateral Biportal Endoscopy for Hidden Zone Lumbar Disc Herniations: A Technical Note and Outcomes

• Pestonji MD
• Gunjotikar S

• KMID: 2567495
• DOI: http://doi.org/10.21182/jmisst.2025.02040

Abstract

Objective
The management of hidden zone lumbar disc herniation has been considered technically challenging due to its difficult surgical exposure. Paraspinal unilateral biportal endoscopy (UBE) is a minimally invasive surgical procedure that has recently gained popularity and has several advantages. Therefore, the authors describe their novel technique of paraspinal UBE for the treatment of upmigrated lumbar disc herniations in the hidden zone of MacNab and present clinical outcomes.
Methods
Twelve patients underwent paraspinal UBE to retrieve the upmigrated disc herniation from under the axilla of the exiting nerve root. The operation duration, blood loss, complications, and recurrences were recorded. Clinical outcomes were assessed using the Oswestry Disability Index (ODI) and visual analogue scale (VAS) scores. Patient satisfaction was evaluated using the modified MacNab criteria.
Results
After a mean follow-up period of 12.9 months, all patients experienced complete relief from neurological symptoms. VAS and ODI scores significantly improved at the final follow-up. According to the modified MacNab criteria, 11 patients achieved an excellent outcome, while one patient had a good outcome due to transient exiting nerve root irritation that resolved with medication after 8 weeks. No major complications were noted.
Conclusion
The paraspinal UBE procedure ensures adequate visualization and removal of the herniated disc with minimal bony resection. In conclusion, paraspinal UBE is a safe and effective surgical procedure for managing disc herniations in the hidden zone of MacNab, particularly at higher lumbar levels.

Keyword

Paraspinal unilateral biportal endoscopy; Upmigrated disc herniation; Hidden zone of MacNab; Kambin triangle; Foraminal approach