Exoscope and digital hybrid visualization in minimally invasive spine surgery

Introduction:
lntraoperative visualization and illumination is one of the key factors for successful spinal surgery. Loupes, microscopes, exoscopes and endoscopes have been used for intraoperative visualization and illumination. The KINEVO 900 integrates all that into a single unit and allows surgeons to have freedom of choice regarding choice of visualization during each step of surgery as each mode of visualization has its own pros and cons. The loupe is the entry level to the microsurgical world and best for its mobility, but it's limited in magnifications and detailed microvisualization. The microscopes have long been regarded as the best tool for microsurgical visualization, but working and positioning the microscope at an extreme angle makes the surgeon compromise his or her own neutral posture, which is detrimental on long term. An exoscope allows excellent visualization at extreme angles, as the surgeon no longer depends on the eyepieces but operates using the monitors during surgery. The main drawback was limited depth perception. This has been overcome by using newer monitors like 3D or 3D-4K monitors. Finally, the endoscope is best when looking at angles where the microscope or exoscope failed to visualize, as the camera is positioned at an angle allowing great visualization for example during lateral recess decompression. With the KINEVO 900 you can choose the best modality for visualization during each crucial step of surgery, allowing uncompromised visualization and illumination at each stage of your microsurgical work to ensure patient safety, successful surgery and finally a great outcome for your patient.

Purpose:
To evaluate the learning curve with exoscope and 3D4K hybrid visualization in terms of operating time, its advantages, disadvantages and surgical complications in tubular access Minimally Invasive Spine Surgery (MISS). To assess surgeon satisfaction with image quality, their ergonomics and their ability to do target site treatment.

Overview of Literature:
Working through tubular retractors posed a challenge. The extreme angulations during microsurgical decompression, especially contralateral decompression, cause surgeons to work unergonomically. An exoscope allowed surgeons to work ergonomically and independent of the microscope oculars, as the visualizations is provided by the large 3D4K monitors. However, the value of solely depending on exoscope and 3D4K monitors during microsurgical work remains to be proven.

Methods:
Seventy-four patients (99 levels) underwent trans tubular MISS between March 2018 to January 2019. 5 were excluded (pyogenic discitis, 2 revisions, 2 trans-tubular transoral). 69 patients were analyzed for operating time, blood loss and complications. The learning curve graph was plotted using the surgical time for each procedure. The surgeons were asked regarding their satisfaction with image quality, ability to maintain ergonomic posture and efficient target site treatment.

Results:
The operating time plateaued after 6 cases for tubular microdiscectomy and 9 for tubular decompression and MIS TLIF. The mean operating time was statistically significantly reduced after the plateau. Complications included 4 cases of dural tear. All patients improved symptomatically. No neurological deficit post-operatively.

Conclusions:
Exoscope usage is associated with a short learning curve. The surgeons benefit from ergonomic posture during surgery. The resident´s teaching is good. The main drawback is the need to rearrange the OR setup. The complications occurred are comparable to using the surgical microscope. Exoscopes with hybrid digital visualization provide excellent visualization, depth perception, clarity, and precision target site treatment.