A Curved-Drilling Approach in Core Decompression of the Femoral Head Osteonecrosis Using a Continuum Manipulator

In conventional core decompression of osteonecrosis, surgeons cannot successfully reach the whole area of the femoral head due to rigidity of the instruments currently used. To address this issue, we present design and fabrication of a novel steerable drill using a continuum dexterous manipulator (CDM) and two different flexible cutting tools passing through the lumen of the CDM. A set of experiments investigated functionality and efficiency of the curved-drilling approach and the flexible tools on simulated cancellous bone. Geometry of the cutter head, rotational and feed velocity of the tool, and pulling tension of the CDM cables have been identified as the effective curved-drilling parameters. Considering these parameters, we investigated drilling trajectory, contact force, and mass removal for various combinations of feed-velocities (0.05, 0.10, and 0.15 mm/s) and cable tensions (6, 10, 15, and 25 N) with constant rotational speed of 2250 r/min. Results show that: first, pulling tension of the cable is the most dominant parameter affecting the curved-drilling trajectory; and second, the proposed steerable drill is able to achieve 40° bend without buckling. Based on these results we developed a method for planning drill trajectories and successfully verified abilities for S-shape and multiple-branch drilling. The verification experiments were performed on both simulated and human cadaveric bones.