In most orthopedic surgeries, knowing how far to insert surgical tools is crucial. The objective of this study was to provide guidance information on depth without tracking surgical tools. A previously developed laser guidance system for linear surgical tool insertion uses two laser beams that display the insertion point and orientation on the skin surface. However, the system only provides 4 degrees of freedom guidance (an entry point on the planned pathway line and the orientation) but do not inform surgeons on the ideal insertion depth.

This paper provides a novel method for intuitive and CT-less surgical navigation based on fluoroscopic-based navigation and laser guidance technology for minimal invasive orthopaedic surgery. This method does not require intra-operative registration of three-dimensional surface model derived from pre-operative CT/MRI volumes and is able to project surgical path planed intra-operatively onto the patient's skin directly. In this paper, implementation of this method and basic in vitro guidance accuracy validation were performed. Tool insertion path planning was performed on three 2D images from a pinhole imaging source taken at different incident angles. A 3D insertion pathway was generated and projected using two laser beams. Our Fluorolaser system has a planning accuracy of 1.07 +/- 0.60 mm, 0.73 +/- 0.38 degrees and an overall guidance accuracy of 1.11 +/- 0.62 mm, 0.80 +/- 0.68 degrees. These results demonstrate that the proposed method has great potentials to ensure accurate and intuitive surgical procedures.

PURPOSE:Conventional navigation systems for minimally invasive orthopedic surgery require a secondary monitor to display guidance information generated with CT or MRI images. Newer systems use augmented reality to project surgical plans into binocular glasses. These surgical procedures are often mentally challenging and cumbersome to perform.METHOD:A comprehensive surgical navigation system for direct guidance while minimizing radiation exposure was designed and built. System accuracy was evaluated using in vitro needle insertion experiments. The fluoroscopic-based navigation technique is combined with an existing laser guidance technique. As a result, the combined system is capable of surgical planning using two or more X-ray images rather than CT or MRI scans. Guidance information is directly projected onto the patient using two laser beams and not via a secondary monitor.RESULTS:We performed 15 in vitro needle insertion experiments as well as 6 phantom pedicle screw insertion experiments to validate navigation system accuracy. The planning accuracy of the system was found to be 2.32 mm and 2.28°, while its overall guidance accuracy was found to be 2.40 mm and 2.39°. System feasibility was demonstrated by successfully performing percutaneous pin insertion on phantoms.CONCLUSION:Quantitative and qualitative evaluations of the fluorolaser navigation system show that it can support accurate guidance and intuitive surgical tool insertion procedures without preoperative 3D image volumes and registration processes.

Most ultrasound imaging systems assume a pre-determined sound propagation speed for imaging. However, a mismatch between assumed and real sound speeds can lead to spatial shift and defocus of ultrasound image, which may limit the applicability of ultrasound imaging. The estimation of real sound speed is important for improving positioning accuracy and focus quality of ultrasound image.