Bone Flap Necrosis Due to Low-Grade Infection with Propionibacterium acnes

Background Osteonecrosis of bone flaps after cranioplasty with autologous cryoconserved bone flaps is a common phenomenon. The exact reason for it remains unknown. Case Description 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 microbiologic samples from the bone flap as the 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. Conclusions We conclude that low-grade infections play an underestimated role in bone flap necrosis after cranioplasty as well and encourage routine microbiologic sampling (extended culture and polymerase chain reaction) to rule out infection in all similar cases and suggest a routine antibiotic therapy until final microbiologic results.