Candidate: Zhechen Du
Title: Pedicle Screw Insertion Surgical Simulator
Date: January 15, 2018
Supervisor(s): Wang, David W.
Scoliosis is a sideway spinal deformity. If the curvature is measured to be more than 50 degrees, the patient can feel significant discomfort. In such cases, surgery is required to straighten the spine. Pedicle screw insertion is a common procedure for scoliosis surgery. The technique requires the placement of screws from the pedicle into the spine. A rod is used to connect all the pedicle screws. The spine is straightened during the connection process. One of the most common techniques used for pedicle screw insertion is called the free hand technique. During free hand surgery, the surgeon creates a screw channel by manually probe into the spine. The lack of visual aid requires the surgeon to rely strongly on haptics feedback. Due to the spine sensitivity and the limited operating range, small changes in force or direction can cause the probe to breach out of the spine. If the breach reaches the spine medial, the spinal cord could be damaged. Even experienced surgeons can not prevent breach. Studies have found that surgeons with 5 or more years of surgical experience has a breach rate of 10.8 %.
In this thesis, pedicle screw insertion simulator is developed and examined in detail. The simulator combines visual and haptics sensation to recreate the channel creation process of the surgery. A 2DOF mechanical device is used for the haptics sensation. The device includes a linear actuator and a rotary motor. In addition, the system incorporates projection mapping technology to provide virtual simulation. The simulator was tuned to four different surgical scenarios by 2 expert surgeons. The scenarios are soft probing, hard probing, lateral breach, and in-out-in breach. 10 additional surgeons were asked to participant in a clinical study. Measurements were collected for analysis. The focus of the study is to find if the surgeon can recognize the simulated breach scenarios. Four research questions were examined, and they are: 1. Can the participants recognize breach during simulation? 2. Can the participants identify wrong events during simulation? 3. Is there any performance difference between expert surgeons, fellows, and residences? 4. Does simulation trials process provide a learning tool for the simulation tasks? Each question has its own null hypothesis and statistical analysis is used to determine if the null hypothesis is rejected. The main conclusion is that there is no statically significant relationship between the wrong breach or total wrong recognition rate and surgical experience. Furthermore, there is statically significant in hard probing scenario between surgical experience and vertical force variance