He regularly attends special congresses and continuing education courses that are exclusively concerned with reconstructive surgery and the conservative treatment of facial paralysis. As a specialist in plastic and aesthetic surgery, he sees his task in defect reconstruction not only in the restoration of surface continuity, but also in a holistic approach to the reconstruction of form and function. His passion are challenging microsurgical reconstructions that achieve limb preservation and thus avoid amputations after accidents, tumors or infections with the help of so-called chimeric perforator flap plastics (free tissue transplants with different tissue elements), functional muscle transplants and transfers, facial resuscitation in facial paralysis and head and neck surgery. Dr. Kehrer is able to look back on well over a thousand microsurgical, sometimes very complex procedures as well as several hundred free microsurgical tissue transplants. This wealth of experience enables him, for example, to transplant small free functional muscles into the face with the necessary routine and with great confidence. Clinically, Dr. Kehrer is a microsurgeon with a great deal of interest in high-resolution duplex ultrasound diagnostics, which is of great importance to him both in the structured planning of tissue transplants and in the monitoring (aftercare) of these after the operation. His scientific field of research for years has been facial nerve surgery on the micro- and macroanatomical level. His primary goal is to further improve surgical methods and to gain a better understanding of variable anatomy. Together with his research team, he has dissected over 100 facial halves from body donors and taken nerve samples for further analysis. He was able to describe new important aspects of the number of nerve fibers from clinically important facial nerve branches as well as from nerve branches of the chewing muscle nerve, which is also important. Furthermore, through research, a new anatomical definition of the clinically important branch systems of the facial nerve was able to be determined. Dr. Kehrer is a frequent speaker at international and national congresses, a sought-after legal expert in court proceedings and a regular reviewer of scientific articles in renowned journals in his field of expertise.