Liquid nitrogen: Cryo-sterilization Method for Free Bone Flap

Objective: Several oncological sterilization methods involving autoclaving, irradiation, merging in antibiotic impregnated saline, or pasteurization have been developed for skull bone after an infiltrating tumor excision or compound skull fracture. Liquid nitrogen is nitrogen in a liquid state at a very low temperature, at atmospheric pressure; liquid nitrogen boils at −196 °C (−321 °F). Nitrogen was first liquefied at the Jagiellonian University on 15 April 1883 by Polish physicists, ZygmuntWróblewski and Karol Olszewski. Several cranioplasty methods involving titanium mesh and acrylic used as bone substitute to achieve total removal of bone infiltrating meningioma aiming to introduce Liquid nitrogen (LN) as an efficient way of sterilization and eradication tool for the free craniotomy flap. Methods: This is a prospective study carried on 29 cases of convexity lesion. We merge the free flap craniotomy over the convexity meningioma in liquid nitrogen (LN2), bone specimens were obtained before and after merging in liquid nitrogen and sent to neuropathologists to document the presence of tumor cells before merging in liquid nitrogen (LN2). Follow up CT scan is done after 3 months to ensure bone viability and to exclude necrosis. Results: 22 cases established as meningioma WHO grade I with variable histological pattern. Three cases of meningioma grade II and one case grade III. One case of hemangiopericytoma grade III. 2 cases of Rosia-Dorfman disease. Neuropathology for the bone specimens of meningioma cases results revealed 22 positive specimens (84.6%) and negative for tumor cells in 4 cases (15.4%). Tumor cells was detected in the one case of hemangiopericytoma. Conclusion: LN2 is an efficient method of sterilization for free bone flaps in convexity tumors, providing a new concept of autologous bone flap.Larger series and longer follow up is recommended to compare the rate of tumor recurrence for LNS sterilized bone flaps with other modality.