Brent Emigh, B.Sc.

Pedicle screw spinal fixation is used specifically to achieve solid bone fusion in patients with scoliosis, fracture, spondylolisthesis, degenerative arthritis, or tumours in the spine. The pedicle screw provides a means of gripping a spinal segment and act as a firm anchor point that can be connected with an external rod. Pedicle screw insertion is challenging as the pedicle itself consists of only a narrow passage of bone into which screws need to be inserted. A previous study of screw insertion using the conventional bur-drilling and screw threading technique revealed an incidence of 13.4% for ill-placed screws.

This project will investigate the efficiency and quality of pedicle screw pilot-holes drilled using ultra-short pulsed laser ablation. Laser ablation has several potential advantages over mechanical drills used in orthopaedics such as: no mechanical vibration, non-contact intervention, and hemostatic and asceptic effects. Thermal damage to the collateral tissue is the main drawback of laser ablation; though it can be minimized through the appropriate selection of laser parameters (e.g. pulse duration, fluence, wavelength, surface cooling).

Along with finding the appropriate settings that will limit thermal damage will maintaining sufficient ablation efficiency, this project will also focus on: obtaining the desired pilot-hole diameter (~2-3mm), the effect of bone-inhomogeneity on material removal, and the impact of generated bone debris on ablation efficiency. To examine the effect of different beam parameters, a stationary femto-second Ti:Sapphire micro-machining laser system operating at a wavelength of 800nm, as well a mobile pico-second Nd:YAG laser system (Passat Canada, Toronto) operating at 1064nm, will be used to drill food-grade porcine vertebral bone. Drilled holes will be examined by light microscopy, while ablation craters and bone fractures will be analyzed using a scanning electron microscope (Philips 515, CCEM).