Towards improved orthopaedic drilling at hard to reach bone sites

Abstract

Bone drilling is a crucial part of orthopaedic surgery. Internal fixation is a ommon orthopaedic procedure that requires drilling to improve healing of bone fractures. Tight spaces around hard to reach bone fractures impede the surgeon during the procedure. As a result there is an increased risk of complications such as thermonecrosis, overshoot into soft tissue, micro-crack formation and drill bit breakage. Therefore, a novel procedure is proposed, where drilling is done using a compact Self-Feeding Angled Drill Attachment (SFADA). The SFADA is a crucial part of the new procedure, because it can generate a controlled feed in a onfined space. Four concepts were developed that met these functionalities. Based on the design specifications a final concept was selected. The concept based on a differential thread and a lead/lag bevel gear was deemed the most feasible. Materials and dimensions were assigned to the mechanism based on an analysis of the critical components. A compact demonstrator of 80x40x36 mm was built. Measurements were performed and the results showed the SFADA’s ability to perform controlled drilling in a confined space. Furthermore, the SFADA can generate a speed of 1500 rpm and feed of 1.5 mm/s, with load forces and torques up to respectively 20 N and 0.2 Nm. The design of the SFADA is an important step in the improvement of bone drilling at hard to reach bone sites.