Journal of Surgical Simulation 2020; 7: 8 - 15

Published: 02 November 2020


Original article

Comparison of verbal, graphical and kinaesthetic cues for instructing pedicle screw cannulation angles within a virtual environment

Stewart McLachlin, Antony H. Bateman, Albert J. Yee and Cari Whyne
Corresponding author: Stewart McLachlin, Mechanical and Mechatronics Engineering, Room E5 3001, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada. Email:


Background: Instrumented spinal fusion surgery requires accurate angulation of surgical instruments relative to the anatomic planes for safe screw insertion into the vertebral anatomy. The visuospatial skills necessary for this surgery are developed through training and experience; however, there is a lack of available technologies to simulate this training environment. This study investigated a virtual environment to compare tool angulation performance of training and trained spine surgeons using different information delivery modalities.

Methods: Nineteen surgeons were presented with tool angulation information using three different modalities within a custom virtual simulator (3D Slicer). In random order, angles were presented in 5° increments up to 50°, using three different methods: verbal, graphical or kinaesthetic. Participants were asked to reproduce the angles using a 25 cm probe tracked using a Leap Motion controller. The tool angle was recorded in a single plane and the absolute error was calculated from the desired angle.

Results: Overall, there was a significant improvement in participant tool orientation accuracy with the kinaesthetic delivery method (angle error, 2.9° ± 2.2°) compared with the verbal (4.8° ± 3.9°) and graphical delivery methods (4.7° ± 4.0°). Distribution of absolute error values ranged from 0° to 21°; the largest errors were most common in the verbal delivery modality (P < 0.05). Angles were overestimated in 62% of tests. Participants with more surgical experience (fellowship trained) were more accurate than resident-level trainees (P < 0.05).

Conclusions: Small tool orientation errors (mean, <5°) occur when surgeons reproduce specific two-dimensional tool angles; accuracy was improved with kinaesthetic training. These findings support the value of virtual simulation for technical skills development outside the operating room.


surgical training; visuospatial skills; motion tracking; virtual simulation; tool orientation