Lowering Cranioplasty Infection Incidence with Novel Bone Flap Storage Protocol: A Retrospective Cohort Study

Abstract

IntroductionAfter craniectomy, autologous bone flaps may be stored using wet or dry cryopreservation. After brain edema subsides, they are replaced during an operation termed “cranioplasty.” Cranioplasty is associated with 15% infection incidence. MethodsWe conducted a retrospective comparison of infection outcomes between “wet” and “dry” cryopreservation of cranioplasty bone flaps. Historically, bone flaps were stored utilizing “wet” cryopreservation – bone flap storage in 1 L of Lactated Ringer’s solution containing 80mg gentamicin and 2g nafcillin in a sterile plastic container secured in an unsterile plastic bag. Our newer dry cryopreservation protocol involved storage in gauze soaked in 80mg gentamicin and 2g nafcillin within a 3-layer sterile bag system. Results119 autologous bone flaps were included with median follow-up of 3.9 months from cranioplasty. Overall, 10.9% became infected requiring subsequent surgery. 18.4% of 49 bone flaps stored using wet cryopreservation became infected compared to only 5.7% of 70 dry cryopreservation bone flaps (p 0.038; Relative risk 0.311; Absolute risk reduction 12.7%). Tobacco use (p 0.076; RR 3.17) was not associated with increased infection risk. Infection incidence was similar for traumatic craniectomy indications compared to the other indications (12.0% trauma versus 10.1% other; p 0.750). On average, infected cranioplasty patients spent 8.5 more days hospitalized and faced increased risk of additional complications. ConclusionDry cryopreservation significantly decreases infection after cranioplasty when compared with wet cryopreservation, which mitigates additional morbidity, mortality, and costs attributable to cranioplasty infection. Other nonmodifiable risk factors for cranioplasty infection were identified.