An Integrated System Using Ultrasound-Based Registration for Surgical Navigation of Iliosacral Screw Insertions.

Abstract

Pelvic fractures often require fixation through iliosacral joint, typically guided by fluoroscopy using an untracked C-arm device. However, this involves ionizing radiation exposure and potentially inaccurate screw placement. We introduce the Navigated Orthopaedic Fixations using Ultrasound System (NOFUSS), a radiation-free ultrasound (US)-based end-to-end system for providing real-time navigation for iliosacral screw (ISS) insertions. We performed surgeries on 8 human cadaver specimens, inserting four ISSs per specimen to directly compare NOFUSS against conventional fluoroscopy. Six specimens yielded usable (marginal or adequate quality) US images. The median screw entry error, midpoint error, and angulations errors for NOFUSS were 8.4 mm, 7.0 mm, and 1.4◦, compared to 7.5 mm (p = 0.52), 5.7 mm (p = 0.30), and 4.4◦ (p = 0.001) for fluoroscopy respectively. NOFUSS resulted in 6 (50%) breaches, compared to 2 (16.7%) in fluoroscopy (p = 0.19). The median insertion time was 7m 37s and 12m 36s per screw for NOFUSS and fluoroscopy respectively (p = 0.002). The median radiation exposure during the fluoroscopic procedure was 2m 44s, (range: 1m 44s - 3m 18s), with no radiation required for NOFUSS. When considering the three cadavers that yielded only adequate-quality US images (12 screws), the measured entry errors were 3.6 mm and 8.1 mm respectively for NOFUSS and fluoroscopy (p = 0.06). NOFUSS achieved insertion accuracies on par with the conventionalfluoroscopicmethod,andreducedinsertiontimesandradiation exposure significantly. This study demonstrated the feasibility of an automated, radiation-free, US-based surgical navigation system for ISS insertions.