Pedicle Screw Insertion Surgical Simulator

Abstract

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 have 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. 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 experience help the surgeon improve correct breach recognition rate? 2. Can experience help the surgeon improve overall correct recognition rate? 3. Is there any performance difference between surgeons with different experience level? 4. Can the simulation trials become 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 statistically significant relationship between the wrong breach or total wrong recognition rate and surgical experience. Furthermore, there is statistically significant in hard probing scenario between surgical experience and vertical force variance. Lastly, ANOVA analysis showed that the breach force and velocity in three trials are close to statistically significant, more data may prove that the simulator can be a training tool for the tasks.