Bone Flap Necrosis due to Low Grade Infection with Propionibacterium Acnes

Osteonecrosis of bone flaps after cranioplasty with autologeous cryo-conserved bone flaps is a common phenomenon. The exact reason for it remains unknown. We present a case of a 67-year old patient who had a bone flap necrosis after elective craniotomy and underwent secondary cranioplasty. A low-grade infection with Propionibacterium acnes was detected in microbiological samples from the bone flap as cause of the lysis. We discuss similarities with aseptic implant loosening and present recent evidence that low-grade infections might be the underlying reason in several cases. We conclude that low-grade infections play an underestimated role in bone flap necrosis after cranioplasty as well and encourage routine microbiological sampling (extended culture and PCR) to rule out infection in all similar cases and suggest a routine antibiotic therapy until final microbiological results.