Haptic Training Simulator for Pedicle Screw Insertion in Scoliosis Surgery

Abstract

This thesis develops a haptic training simulator that imitates the sensations experienced by a surgeon in pedicle screw insertions in a scoliosis surgery.

Pedicle screw insertion is a common treatment for fixing spinal deformities in idiopathic scoliosis. Surgeons using the free hand technique are guided primarily by haptic feedback. A vital step in this free hand technique is the use of a probe to make a channel through the vertebrae pedicle. This is a sensitive process which carries risk of serious mechanical, neurological and vascular complications. Surgeons are currently trained using cadavers or live patients. Cadavers often have vertebrae that are softer than the real surgeons would typically encounter, while training on live patients carries the obvious issue of increased risk of complications to the patient. In this thesis, a haptic virtual reality simulator is designed and studied as a training tool for surgeons in this procedure.

Creating a pathway through the pedicle by the free-hand technique is composed of two main degrees of freedom: rotation and linear progression. The rotary stage of the device which was developed by a previous student, is enhanced in this research by adding hardware, improving the haptic model and proposing techniques to couple the rotary and linear degree of freedom. Haptic model parameters for a spine surgery with normal bone density are then clinically tuned within a user study. Over ten surgeons of varying experience levels used the simulator and were able to change various parameters in order to tune the simulator to what felt most realistic. The surgeons also evaluated the simulator for its feasibility and usefulness. Four research questions were investigated. First, can a reference set of values be found that replicate the surgeon's interpretation of the surgical scenario? Second, how are the rotary stage parameters influenced in the presence of linear effects? Third, do the results differ across different expertise levels? Finally, can the simulator serve as a useful tool in the education of surgical trainees for teaching channel creation in pedicle screw insertion? Statistical analysis are carried out to examine the research questions. The results indicates the feasibility of the simulator for surgical education.