Breakthrough in medical engineering: A bone saw with a novel integrated cooling mechanism developed at the Institute of Production Engineering and Machine Tools (IFW) at Leibniz University Hannover (LUH) is expected to prevent infections and tissue injuries during surgery. Numerous surgical interventions such as implanting knee or hip joints require the use of oscillating bone saws. Post-surgery complications often occur due to tissue injuries caused by heat dissipation during the sawing process. Currently, medical staff uses sequential procedures as well as externally applied sodium chloride solutions to prevent this. However, this increases the risk of infection.
The project "Damage-Free Sawing" at IFW - another pioneering project in biomedical research and technology, a key research area at LUH - aims to reduce the risk of infection and tissue damage. "We intend to develop a tool with integrated and closed cooling channels by means of additive manufacturing", explains Sarah Busemann, a member of project staff.
In Germany alone, more than 400,000 hip and knee endoprostheses are implanted every year - a number that is likely to increase. Like every operation, implanting an endoprosthesis poses certain risks. In addition to general complications such as bleeding or thrombosis, post-surgery instability of the implant may occur caused by infection or osteonecrosis, the death of bone tissue. Such complications may occur in the context of the sawing process, which is necessary to remove infected or disruptive bone material.
For this, hand-operated oscillating bone saws are used. Friction between bones and the saw blade generates heat that exceeds the non-critical range (> 42 degrees Celsius) therefore causing tissue damage. Conventional methods for reducing the thermal impact including sequential procedures and external cooling via a sodium chloride solution increase the risk of infection. Furthermore, these approaches are not suitable for eliminating the risk of osteonecrosis.
To date, it was not possible to fit cooling channels into conventional saw blades with very thin diameters (0.9-1.5 millimetres). However, a wide variety of shapes can be produced through metal laser melting. Within the scope of the project "Sägen ohne Schäden" (damage-free sawing), conducted in collaboration with the industry partners Bionic Production GmbH and Gebr. Brasseler GmbH, additive manufacturing technologies are used to develop and realise saw blades with integrated and closed cooling channels.
Tests on artificial bone with conventional saw blades demonstrated that temperatures exceeding 100 degrees Celsius may occur in some areas. "The results of our fluid simulations as well as analogue tests on printed saw blades with integrated cooling channels were quite promising. We were able to reduce the temperature to a biocompatible range", says Sarah Busemann. In further simulations and practical tests, the project team will now develop saw blades with the required mechanical stability and the necessary cooling capacity.
Note to editors:
For further information, please contact Sarah Busemann, Institute of Production Engineering and Machine Tools (Tel. +49 511 762 18279, Email busemann@ifw.uni-hannover.de).
