Waterjet drilling in porcine bone: the effect of the nozzle diameter and bone architecture on the hole dimensions.

Abstract Using waterjets instead of rigid drill bits for bone drilling can be beneficial due to the absence of thermal damage and a consequent sharp cut. Additionally, waterjet technology allows the development of flexible instruments that facilitate maneuvering through complex joint spaces. Controlling the drilling depth is of utmost importance to ensure clinical safety, but is challenging given the local variations in structural properties of the bone. The goal of this study was to deduce a descriptive mathematical equation able to predict the hole depth and diameter based on the local structural properties of the bone at given waterjet diameters. 210 holes were drilled in porcine femora and tali with waterjet diameters ( D nozzle ) of 0.3, 0.4, 0.5 and 0.6 mm at a pressure of 700 bar and a 5 s jet time. Hole depths ( L hole ) , diameters ( D hole ) and bone architectural properties were determined using microCT scans. The most important bone architectural property is the bone volume fraction ( BV/TV ), resulting in the significant predictive equations: L hole =34.3 ⁎ D nozzle 2 −17.6 ⁎ BV/TV+10.7 ( R 2 =0.90, p hole =3.1 ⁎ D nozzle −0.45 ⁎ BV/TV+0.54 ( R 2 =0.58, p =0.02), with L hole , D hole and D nozzle in mm. Drilling to a specific depth in bone tissue with a known BV/TV is possible, thereby contributing to the safe application of waterjet technology in orthopedic surgery.