Autogenous skull flaps stored frozen for more than 6 months: do they remain viable?

Autogenous cranioplasties with cryopreserved skull flaps are associated with disproportionately high infection and bone resorption rates. Bone flap non-viability may be a contributing factor. Viable osteoblasts have been cultured recently from cryopreserved long bones. Cryopreserved skull bone may also remain viable based on histological observations. However, cell culture studies have not been performed on skull bone to assess viability. Bone explant cell cultures were performed on 27 skull flaps stored at -30 °C for more than 6 months. Biopsies were taken from the flaps, washed in phosphate buffer saline and cultured in Dulbecco's Modified Eagle's medium at 37 °C in 5% carbon dioxide for 3 weeks. Fresh skull bone samples served as controls. While control samples showed growth of osteoblasts, no osteoblasts were cultured from the study specimens at 3 weeks. In conclusion, skull flaps cryopreserved at -30 °C for more than 6 months are non-viable. Further research characterizing impact of different storage conditions on skull flap viability is warranted.