Bone flap storage following craniectomy: a survey of practices in major Australian neurosurgical centres

The resurgence of decompressive craniectomy surgeries for management of intracranial hypertension has led to a parallel increase in cranioplasty procedures for subsequent reconstruction of the resultant extensive skull defects. Most commonly, cranioplasties are performed using the patients' own cryopreserved skull flaps. Currently, there are no standardized guidelines for freeze-storage of bone flaps either nationally or internationally. In this initial study, the authors surveyed major neurosurgical centres throughout Australia to document current clinical practices.

Twenty-five neurosurgical centres affiliated with major public, teaching hospitals in all Australian states were included in the current survey study. A standardized survey guide incorporating standardized questions was used for data collection either by phone interviews and/or electronic (email) communication. Details regarding bone flap preparation following craniectomy, temperature and duration of freeze-storage, infection control/micro-contamination detection protocols, pre-implantation procedures were specifically recorded.

Cranioplasty using cyropreserved autogenous bone flaps remains the most common (96%) mode of skull defect reconstruction in major neurosurgical centres throughout Australia. Following the initial craniotomy, the harvested skull flaps were most frequently (88%) double- or triple-bagged under dry, sterile conditions. In 16% of hospitals, skull flaps were irrigated either with antibiotic mixed-saline or Betadine prior to cryopreservation. Skull biopsies or swabs were obtained from the skull flaps for micro-contamination studies in accordance with departmental protocol in 68% of hospitals surveyed. Subsequently, the bone flaps were cryopreserved at wide ranging temperatures between -18°C to -83°C, for variable time intervals (6 months to 'until patient deceased'). Twelve neurosurgical centres (48%) elected for bone flap storage to be undertaken at the local bone bank. In the remainder (52%) of the hospitals, bone flaps were cryopreserved in locally maintained freezers. Prior to re-implantation of the skull flaps at subsequent cranioplasty surgeries, six (24%) of the neurosurgical centres had specific thawing procedures involving immersion of the frozen bone flaps in Ringer's solution and/or Betadine. Further pre-implantation bacteriological cultures from bone biopsies or swabs were obtained only in three (12%) hospitals.

This study has documented highly varied skull flap cryopreservation and storage practices in neurosurgical centres throughout Australia. These differences may contribute to relatively high complication rates of infection and bone resorption reported in the literature. The results of the current study argue for the further need of high quality clinical and basic science research, which aims to characterize the effect of current skull flap management practices and freeze-storage conditions on the biological and biomechanical properties of skull bone.