[O-arm Versus C-arm: Comparison of the Learning Curves and Accuracy in Transpedicular Screw Fixation of Lumbar Spondylolisthesis].

Purpose of the study: The annual number of spinal fusion procedures has been increasing and is well documented worldwide. The O-arm is slowly becoming the standard for transpedicular screw insertion. The accuracy and safety of this method have been confirmed by many studies. Therefore, the learning curve of this method and its use by younger surgeons is the focus of our investigation. Longer operative time and radiation exposure to the patient are its only disadvantages. Our aim was to evaluate the learning curve of neurosurgical residents receiving specialist training and to demonstrate the safety and accuracy compared to the conventional C-arm-guided screw insertion used in the surgical management of spondylolisthesis.

Material and methods: Two groups of patients were evaluated - a retrospective cohort composed of patients with degenerative lumbar spinal instability indicated for C-arm-guided posterior transpedicular screw fixation and a prospective group of patients with the same diagnosis and surgical indication for O-arm-navigated screw insertion. In the retrospective group, the surgeons were largely experienced certified spine surgeons and neurosurgeons, whereas in the prospective group there were mainly neurosurgical residents receiving specialist training under the supervision of a certified physician. Both groups underwent a postoperative CT scan to evaluate the pedicle screw malposition using the Grade system and the anatomical plane of malposition. The operative times for both groups were recorded and for the O-arm navigated group a learning curve from the introduction of the method was generated. The values obtained were statistically analysed.

Results: A relatively favourable learning curve of the O-arm-navigation was obtained, with operative times approximating the Carm-guided group at two years after the introduction of the method. Safety of the O-arm navigation applied by less experienced surgeons was confirmed through statistically significantly higher accuracy achieved in the O-arm group at the expense of longer operative times. Also, a significantly lower number of significant Grade 2 and 3 malposition was reported in the O-arm group.

Discussion: The higher accuracy of transpedicular screw insertion in the navigation method has been confirmed multiple times. In our study, even in the group of less experienced surgeons. The favourable learning curve of neurological residents receiving specialist training is less documented. Time efficiency of the method and its safety when applied by younger surgeons could help make O-arm navigation the new gold standard in spine surgery. The longer operative time, the purchase price of the device, and a relatively higher radiation exposure to the patient continue to be its disadvantages.

Conclusions: Based on the data obtained, a conclusion can be drawn that the O-arm navigation in spine surgery represents a safer and more accurate method for transpedicular fixation compared to the conventional C-arm technique, even when used by less experienced surgeons. In future, we should focus on increasing its time-efficiency. We are convinced that the navigationassisted spinal instrumentation will soon become a necessity for spine surgery centres.

Key words: O-arm, transpedicular fixation, spondylolisthesis, fusion, navigation, learning curve.