Bone flap infections after craniotomy: a review of 63 cases and the implications for definitions, classification and surveillance methodologies

Background: Bone flap infections (BFIs) occur following neurosurgical procedures such as craniotomies. However, they are poorly defined and often not clearly differentiated from other surgical site infection in neurosurgery.

Aim: To review data from a national adult neurosurgical centre to explore some clinical aspects to better inform definitions, classification and surveillance methodologies.

Methods: We retrospectively reviewed data on clinical samples sent for culture from patients with suspected BFI. We also accessed information recorded prospectively from national and local databases for evidence of BFI or related conditions based on terms used in surgical operative notes or discharge summaries and documented monomicrobial and polymicrobial infections related to craniotomy sites.

Findings: Between January 2016 and December 2020, we documented 63 patients with a mean age of 45 years (16-80). Craniectomy for infection of the skull was the most common terminology used to describe BFI in the coding used in a national database, 40/63 (63%), but other terms were used. A malignant neoplasm was the most common underlying condition necessitating craniectomy in 28/63 (44%) cases. Specimens submitted for microbiological investigation included 48/63 (76%) bone flaps, 38/63 (60%) fluid/pus, and 29/63 (46%) tissue. Fifty-eight (92%) patients had at least one culture-positive specimen; 32 (55%) were monomicrobial and 26 (45%) were polymicrobial. Gram-positive bacteria predominated and Staphylococcus aureus was the most common.

Conclusion: Greater clarity on how to define BFI is required to enable better classification and the carrying out of appropriate surveillance. This will inform preventative strategies and more effective patient management.