Fellow Indiana University Indianapolis, Indiana, United States
Introduction: After 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 has been associated with 15% infection incidence.
Methods: At Indiana University prior to 8/10/2020, wet cryopreservation of autologous bone flaps was used including storage in a sterile plastic container filled with lactated ringers solution including 80mg gentamicin and 2g nafcillin secured in an unsterile bag. Dry cryopreservation used after 8/10/2020 included storage in a commercially available 3-layer sterile bag system after wrapping the bone flap in antibiotic soaked gauze (80mg gentamicin and 2g nafcillin). All bone flaps were stored locally at -80° Celsius. We conducted a prospective comparison of infection outcomes after wet and dry cryopreservation between 8/1/2019 and 6/30/2022.
Results: 93 autologous bone flaps were included with median follow-up 8.4 months. Overall, 11.8% became infected requiring subsequent surgery. 26.3% of 19 bone flaps stored using wet cryopreservation became infected whereas 8.10% of 74 dry cryopreservation bone flaps became infected (Relative Risk 30.7%, Absolute Risk Reduction 18.2%; p0.03). Ischemic stroke requiring craniectomy (RR3.7; p0.02), tobacco use (RR6.5; p0.04), and elevated total drain output (RR4.2; p0.05) were associated with increased infection risk. Infection incidence was similar for traumatic and nontraumatic craniectomy indications (8.5% trauma versus 15.2% nontraumatic; p0.4). Average time to cranioplasty was similar in infected and uninfected patients (17.4 versus 15.7 weeks, respectively; p0.7). Infected and uninfected cranioplasties had similar subgaleal drainage duration after cranioplasty (2.6 days versus 2.1 days, respectively; p0.3). On average, infected patients spent 27.9 more days hospitalized than noninfected patients and had increased risk of additional complications relative to noninfected patients (RR10).
Conclusion : Dry cryopreservation decreases infection after cranioplasty significantly when compared with wet cryopreservation. Reduced infection incidence mitigates additional morbidity and costs attributable to cranioplasty infection.
