Mechanical and thermal efficiency of a single drill system for bone-anchored hearing implants

This study aimed to evaluate the mechanical performance, heat generation, bone distortion, and characteristics of bone chips generated during drilling using a novel one-step guided drill system (MONO) for installing the bone-anchored hearing system (BAHS). A comparison was made with an existing three-stage drill system (MIPS).

Drill force and torque were measured during drilling in cow tibia at different feed rates. Compact artificial bone was utilized to determine temperature increases using thermocouples placed at specific positions around the osteotomy site during drilling with the two systems at different feed rates and levels of irrigation. The effects of drilling on osteotomy characteristics and the formation of bone fragments were evaluated through micro-CT, Raman spectroscopy, and histology.

Force and torque increased with the feed rate in both systems, whereas the total work required to perform the osteotomy significantly decreased as the feed rate increased. Compared to the three-stage MIPS system, the MONO system required less work for one-step osteotomy creation, generated equal or less heat, and exhibited greater tolerance for procedural deviations in irrigation and drilling sequence. Additionally, heat generation for both systems decreased when drilling at higher feed rates. Compositional changes within the osteotomy were primarily observed under reduced irrigation protocols, while no differences were identified in bone chips across drilling protocols.

Compared with a multistep conventional drilling procedure, MONO drilling is less affected by variations in the drilling protocol, particularly in flapless and blind procedures, resulting in safer and more efficient osteotomy creation. The MONO system demonstrated superior performance in terms of energy efficiency and temperature control.