AUSS Assisted ACAF Technique in the Treatment of Ossification of the Posterior Longitudinal Ligament Extending to the C2 Segment.

Objective: This study aims to propose and evaluate the clinical efficacy of a novel non-coaxial endoscopic-assisted technique for establishing the "Shelter Space" in Anterior Controllable Antedisplacement and Fusion (ACAF) for treating high-level (C2-involved) cervical ossification of the posterior longitudinal ligament (COPLL).

Methods: Sixteen patients diagnosed with high-level OPLL (involving C2) who underwent AUSS (Arthroscopic-Assisted Uni-Portal Spinal Surgery) assisted ACAF treatment were enrolled, and their outcomes were analyzed. The OPLL below C2 was managed via ACAF, including discectomy at involved levels, appropriately removing the anterior part of the affected vertebrae below C2, placement of intervertebral cages, fixation with anterior cervical plates, and isolation of the vertebrae-OPLL complex (VOC). For C2-level OPLL, after achieving hemostasis, the posteroinferior portion of the C2 vertebral body was ground under non-coaxial endoscopic assistance based on the thickness of C2-OPLL to create a "shelter" facilitating anterior displacement of the ossified mass posterior to C2. Finally, the C2 OPLL and the VOC from lower segments were elevated. Preoperative and postoperative clinical and radiological parameters, along with surgical complications, were documented.

Results: Postoperative CT and MRI confirmed adequate spinal cord decompression using the AUSS assisted ACAF technique. Significant improvements were observed in the Reserve Space for the Cord at the Edge (RSCE) and the occupying rate (OR) of the spinal canal. No specific complications were observed postoperatively. At the final follow-up of 12 months, all patients exhibited marked neurological recovery.

Conclusion: The AUSS assisted ACAF technique effectively circumvents the technical challenges and complications associated with traditional open Shelter techniques, enhancing surgical precision and feasibility. This method is a viable, user-friendly, and effective approach for managing high-level COPLL with myelopathy. However, large-scale studies with control groups are warranted to further validate the universality and safety of this technique.