Full-endoscopic spine surgery represents the latest developments in minimally invasive surgery (MIS) techniques with the benefits of greater soft-tissue preservation, reduced postoperative pain and length of hospitalization while maintaining good surgical outcomes [1].

Conventional high-speed drills remain the workhorse for endoscopic bone work but carry risks of thermal injury and mechanical trauma to neurological structures [2], and reduces autologous bone chip harvest yield for interbody fusion. To overcome such issues, ultrasonic bone-cutting instruments have been introduced to spine surgery. These devices have lower tip-bone contact force, self-irrigation systems and high frequency linear oscillation that are able to selectively cut dense mineralized tissue like bone while sparing soft tissues like dura and nerve roots [3-6]. Such devices also allow for local bone to be harvested as bone chips during laminectomies and facetectomies which would otherwise be washed away as particulate matter in the continuously irrigated environment of endoscopic spine surgery if high-speed drills are used.

Studies in the past have reported the safe use of an ultrasonic bone scalpel in various forms of spine surgery including open, tubular MIS and most recently in biportal endoscopic spine surgery [7-10]. To our knowledge, the integration of ultrasonic equipment into uniportal full-endoscopic lumbar procedures has not yet been documented.

This article introduces a novel ultrasonic osteotome device (Ultrasonic Osteotomy Surgical System [UOSS]; SMTP, China) that is compatible with uniportal full-endoscopic lumbar spine surgical systems. The device consists of a handpiece, a 210-mm or 300-mm slim profile shaft and a blunt ultrasonic scalpel tip (Figures 1-3) that oscillates at a frequency of 39 kHz and an excursion of <120 µm. The long shaft allows for compatibility with uniportal endoscope systems (Figure 4). The high frequency beyond auditory range allows for a quiet yet precise cutting of noncompliant crystalline structures of mineralized tissue like bone, while more compliant surrounding soft tissue is theoretically not affected by the low excursion ultrasonic oscillation.

The safe and effective adoption of the UOSS within uniportal endoscopic lumbar interbody fusion depends on thoughtful integration of the device into the existing endoscopic workflow. This begins from the ergonomics of the operating table set up. The device consists of a long slim shaft attached to a handpiece. The operating table should be lowered to a comfortable level to align the handpiece of UOSS and scope system to minimize instrument damage and surgeon fatigue.

There are fundamental differences in mechanism of osteotomy with the UOSS compared to traditional osteotomes. Effective osteotomy with the UOSS is achieved through gentle sweeping movements rather than sustained pressure. Osteotomy cuts should be made in layers through cortical bone, then cancellous bone, then cortical bone to prevent bone fragmentation. Surgeons must develop an appreciation for the tactile feedback associated with ultrasonic cutting, particularly the subtle reduction in resistance encountered when mineralized bone is penetrated. Excessive force diminishes cutting precision and may result in unintended bony fragmentation. Continuous saline irrigation should be maintained during osteotomy to preserve visualization, limit thermal accumulation and maintain the selective cutting characteristics of UOSS. Radiofrequency ablation for hemostasis has to be coordinated with osteotomy to maintain visualization.

A notable advantage of ultrasonic osteotomy in the fusion setting is the preservation of cancellous bone chips generated during laminotomy and facetectomy. Piecemeal osteotomy cuts typically less than 1 cm by 1-cm blocks allows for efficient removal of bone within the limits of the uniportal endoscopic system. Bone chips larger than the scope cannula width cannot be removed through the scope cannula and requires further osteotomy of a free-floating piece which adds technical demand and avoidable operative time.

Despite its tissue-selective properties, the use of UOSS does not obviate the risk of neural injury. Direct contact between the ultrasonic tip and neural structures should be avoided as mechanical or thermal irritation may still occur. The UOSS should only be activated when the working tip is fully in view. This reduces the risk of unintended damage to neural structures and to the uniportal system as well.

Recognition of these technical considerations and adherence to a structured learning curve are critical to optimizing safety and outcomes during early clinical adoption.

All patients provided written informed consent for the publication of clinical details and images. We conducted this study in compliance with the principles of our institutional review board.

Seven patients underwent U-ELIF for 10 segments with the aid of UOSS from 1 May 2025 to 15 August 2025. Three patients underwent 2-level U-ELIF while 4 patients underwent single level U-ELIF. Three patients had lumbar spondylolisthesis while the other 4 patients had lumbar spinal stenosis. The group included 2 men and 5 women. The average age of the patients was 61.7 (range, 49.0–71.0) years. Total average operating time was 252 minutes (209 minutes for single level U-ELIF; 312 minutes for double level U-ELIF). There were no complications directly associated with decompression laminotomy or ipsilateral total facetectomy using the ultrasonic osteotome. Specifically, there was no incidence of dura tear or neural structure injury in all 7 cases. There was no incidence of endoscopic breakage or lens damage from the use of UOSS in all 7 cases. All patients experienced improvements in their lower limb radicular symptoms and were ambulating by postoperative day (POD) one. The average length of stay (LOS) was 4.5 (range, 2–5) days. One patient was cleared for home by institution physiotherapist on POD1 while 4 patients were cleared on POD2, but they opted to stay in the hospital for 1 to 3 extra days while awaiting home care arrangements. All patients reported early postoperative improvement in radicular symptoms.

In the presented technical note, we demonstrated the safe usage of UOSS in U-ELIF. The use of UOSS provides bone selectivity with reduced mechanical and thermal insult to adjacent neural structures, an attribute that is particularly valuable in the constrained uniportal corridor. Large open and MIS series have demonstrated a favorable safety profile and comparable or improved outcomes with ultrasonic devices versus high-speed drills [3-4,6,8-9]. Comparative studies have also reported lower blood loss and trends towards reduced durotomies with ultrasonic devices [8-9]. Endoscopic applications in the thoracic and cervical spine have shown feasibility and safety when working near the cord and exiting roots [11,12].

The presented report focuses on fusion rather than decompression alone. A practical advantage of ultrasonic bone work in U-ELIF is the preservation of cancellous bone chips from laminectomy and total facetectomy which would otherwise be sacrificed if high-speed drills were used. These bone chips can be recycled as local autograft for interbody grafting, reducing reliance on allograft or bone extenders. The controlled cutting mechanics also facilitate precise facetectomy and endplate exposure under continuous irrigation.

From a workflow perspective, the long-shaft ultrasonic instrument integrates smoothly into uniportal ergonomics when activation discipline is maintained and tip selection matches the sheath dimension. This new device allows the uniportal endoscopic surgeons to reap the benefits provided by ultrasonic devices that were previously limited due to the design nature of such products being not compatible with uniportal interfaces.

Our early series across 10 segments demonstrated no UOSS related neurological or dural complications, aligning with prior safety reports in open, MIS and biportal endoscopic cohorts [7-10]. While the use of the UOSS in U-ELIF has several advantages, it is important to acknowledge its limitations as well. One limitation of this study is that the findings are based on the experience of a single surgeon in a single large medical center limited to 6 weeks of follow-up. Therefore, these results may not be generalizable to other patient populations and are too small for direct comparison against a population of patients undergoing U-ELIF with conventional high-speed drill. The 6-week follow-up data is also too short to draw conclusions if the use of UOSS in U-ELIF provides benefits to fusion results. Future studies with larger sample sizes across multiple centers and multiple surgeons with longer follow ups are required to confirm the safety and efficacy of UOSS in U-ELIF.

Ultrasonic osteotome assisted U-ELIF is feasible and safe in our early experience. The device enables controlled bone removal, excellent visualization under irrigation and preservation of local autograft for interbody fusion. Larger comparative studies with longer follow-up are needed to confirm the benefits in clinical outcomes and fusion success.