Feasibility of Intraoperative Intraspinal Endosonography Using a Miniaturized Ultrasound Probe Through an Extended Interlaminar Lumbar Approach: A Pilot Study

Background/Objectives: Intraoperative ultrasound was explored in the 1980s to assess lumbar spinal decompression; however, conventional probes require large bony windows and are poorly suited for minimally invasive surgery. This technical note evaluates the feasibility of intraoperative intraspinal endosonography (IOISES) using a miniaturized linear ultrasound probe introduced directly into the spinal canal through a microsurgical access corridor. Methods: This observational feasibility study included two patients undergoing lumbar spine surgery (microdiscectomy for disc herniation and decompression for spinal stenosis). After decompression and hemostasis, a miniaturized linear probe (Fujifilm L51K) connected to an Arietta A65 system was inserted into the spinal canal via an extended interlaminar approach. Imaging was performed prior to wound closure. The primary outcome was the technical feasibility of probe insertion and image acquisition. The secondary outcomes included intraoperative usability, visualization of neural structures, and integration into the surgical workflow. Results: Probe insertion and imaging were successful in both cases (100%). IOISES enabled high-resolution visualization of the dural sac and nerve roots, allowing intraoperative visualization of the extent of decompression. Probe handling and rotation were feasible without forced manipulation. No adverse events occurred, and the technique was integrated into the surgical workflow without prolonging operative time. Conclusions: IOISES is technically feasible and enables real-time intraspinal visualization during minimally invasive spinal surgery. This approach represents a shift from extraspinal to intraspinal ultrasound imaging. Further studies are required to evaluate reproducibility and clinical impact.