Waterjet drilling in porcine femur bone: The effect of nozzle diameter on hole geometry

Using waterjet technology in orthopedic surgery can be beneficial as it allows flexible instruments to be developed that allow easy maneuvering in the tight spaces of a joint. Controlling the drilling depth is of utmost importance to ensure clinical safety. A method for controlling the depth is by adjusting the waterjet diameter. In this study, 120 holes were drilled in porcine femora with waterjet diameters of 0.3, 0.4, 0.5 and 0.6 mm at a pressure of 700 bar and a 5 second jet time. Hole depths, diameters and bone volume fraction (BV/TV) were determined using microCT scans. A significant linear correlation was found between the nozzle diameter and the hole depth (R²=0.84, p<0.001), which results in the predictive model: hole depth (mm) = 38 × nozzle diameter (mm) - 5.5. The correlation found between the nozzle diameter and the hole diameter was significant, but less apparent (R²=0.56, p<0.001). The average BV/TV was 0.37 with a low standard deviation of 0.07. The results can be used as a first step in depth control for waterjet drilling in bone. However, additional research is required to determine the effects of variations in BV/TV of bone.