Virtual surgery simulation versus traditional approaches in training of residents in cervical pedicle screw placement


Virtual surgery simulation versus traditional approaches in training of residents in cervical pedicle screw placement, by Hou et al. Arch Orthop Trauma Surg (2018).


The cervical screw placement is one of the most difficult procedures in spine surgery, which often needs a long period of repeated practices and could cause screw placement-related complications. We performed this cadaver study to investigate the effectiveness of virtual surgical training system (VSTS) on cervical pedicle screw instrumentation for residents.

Materials and methods
A total of ten novice residents were randomly assigned to two groups: the simulation training (ST) group (n = 5) and control group (n = 5). The ST group received a surgical training of cervical pedicle screw placement on VSTS and the control group was given an introductory teaching session before cadaver test. Ten fresh adult spine specimens including 6 males and 4 females were collected, and were randomly allocated to the two groups. The bilateral C3–C6 pedicle screw instrumentation was performed in the specimens of the two groups, respectively. After instrumentation, screw positions of the two groups were evaluated by image examinations.

There was significantly statistical difference in screw penetration rates between the ST (10%) and control group (62.5%, P < 0.05). The acceptable rates of screws were 100 and 50% in the ST and control groups with significant difference between each other (P < 0.05). In addition, the average screw penetration distance in the ST group (1.12 ± 0.47 mm) was significantly lower than the control group (2.08 ± 0.39 mm, P < 0.05). Conclusions This study demonstrated that the VSTS as an advanced training tool exhibited promising effects on improving performance of novice residents in cervical pedicle screw placement compared with the traditional teaching methods.

Use of 3D navigation in subaxial cervical spine lateral mass screw insertion


Open access Use of 3D Navigation in Subaxial Cervical Spine Lateral Mass Screw Insertion, by Arab et al. J Neurol Surg Rep 2018; 79(01): e1-e8

Objective Cervical spine can be stabilized by different techniques. One of the common techniques used is the lateral mass screws (LMSs), which can be inserted either by freehand techniques or three-dimensional (3D) navigation system. The purpose of this study is to evaluate the difference between the 3D navigation system and the freehand technique for cervical spine LMS placement in terms of complications. Including intraoperative complications (vertebral artery injury [VAI], nerve root injury [NRI], spinal cord injury [SCI], lateral mass fracture [LMF]) and postoperative complications (screw malposition, screw complications).

Methods Patients who had LMS fixation for their subaxial cervical spine from January 2014 to April 2015 at the Ottawa Hospital were included. A total of 284 subaxial cervical LMS were inserted in 40 consecutive patients. Surgical indications were cervical myelopathy and fractures. The screws’ size was 3.5 mm in diameter and 8 to 16 mm in length. During the insertion of the subaxial cervical LMS, the 3D navigation system was used for 20 patients, and the freehand technique was used for the remaining 20 patients. We reviewed the charts, X-rays, computed tomography (CT) scans, and follow-up notes for all the patients pre- and postoperatively.

Results Postoperative assessment showed that the incidence of VAI, SCI, and NRI were the same between the two groups. The CT scan analysis showed that the screw breakage, screw pull-outs, and screw loosening were the same between the two groups. LMF was less in the 3D navigation group but statistically insignificant. Screw malposition was less in the 3D navigation group compared with the freehand group and was statistically significant. The hospital stay, operative time, and blood loss were statistically insignificant between the two groups.

Conclusions The use of CT-based navigation in LMS insertion decreased the rate of screw malpositions as compared with the freehand technique. Further investigations and trials will determine the effect of malpositions on the c-spine biomechanics. The use of navigation in LMS insertion did not show a significant difference in VAI, LMF, SCI, or NRI as compared with the freehand technique.

Robotic drill guide positioning in spine surgery using known-component 3D–2D image registration

Robotic drill guide positioning using known-component 3D–2D image registration, by Yi, Ramchandran, Siewerdsen, and Uneri, J. of Medical Imaging (2018), 5(2):021212.


A method for x-ray image-guided robotic instrument positioning is reported and evaluated in preclinical studies of spinal pedicle screw placement with the aim of improving delivery of transpedicle K-wires and screws. The known-component (KC) registration algorithm was used to register the three-dimensional patient CT and drill guide surface model to intraoperative two-dimensional radiographs. Resulting transformations, combined with offline hand–eye calibration, drive the robotically held drill guide to target trajectories defined in the preoperative CT. The method was assessed in comparison with a more conventional tracker-based approach, and robustness to clinically realistic errors was tested in phantom and cadaver. Deviations from planned trajectories were analyzed in terms of target registration error (TRE) at the tooltip (mm) and approach angle (deg). In phantom studies, the KC approach resulted in TRE = 1.51 ± 0.51 mm and 1.01 deg ± 0.92 deg, comparable with accuracy in tracker-based approach. In cadaver studies with realistic anatomical deformation, the KC approach yielded TRE = 2.31 ± 1.05 mm and 0.66 deg ± 0.62 deg, with statistically significant improvement versus tracker (TRE = 6.09 ± 1.22 mm and 1.06 deg ± 0.90 deg). Robustness to deformation is attributed to relatively local rigidity of anatomy in radiographic views. X-ray guidance offered accurate robotic positioning and could fit naturally within clinical workflow of fluoroscopically guided procedures.