357 Novel Osteoconductive, Bioresorbable Bone Adhesive Provides Superior Cranial Flap Fixation Strength and Reduced CSF Leak Potential in a Cadaver Model

Abstract

INTRODUCTION: Plates and screws are the gold standard for cranial flap fixation. Unfortunately, hardware may be associated with loosening and migration. Osseous union of the fixated flap to the surrounding skull is typically incomplete. Furthermore, titanium plates and screws do not provide a watertight closure of the bone and cannot mitigate CSF leakage. METHODS: 64 craniotomies were performed in 16 cadavers by a single neurosurgeon. Frontal, pterional, parietal, and parieto-occipito-temporal flaps were created in each skull. The 64 bone flaps were fixated by 16 different neurosurgeons (4 flaps/surgeon). Each flap was secured with standard cranial plates and screws, then biomechanically tested using either quasi-static compression (1mm/min) or staircase impact (up to 60J impact energy at increments of 6J) to analyze mechanical strength. Next, the plates and screws were removed and the same bone flap was secured by the same neurosurgeon using a novel bone adhesive, Tetranite®(TN). The TN-secured flaps were then biomechanically tested in similar fashion. A subset of the TN-fixated flaps was subjected to hydrostatic fluid pressure (up to 40mm Hg at steps of 5mm Hg) to determine resistance to simulated CSF leakage prior to mechanical testing. RESULTS: TN fixation was approximately 41 times stiffer and 48 times stronger than metal fixation under quasi-static loading (stiffness 4216±1544N/mm and peak force 5456±1920N for TN vs. 103 ±81N/mm and 113±89N for metal hardware: n=32). At an impact energy of 6J, cranial flaps fixated using metal hardware migrated to a peak deflection 13 times greater than TN-fixated specimens; the residual plastic deformation was 30 times greater (peak elastic deflection 2.94± 0.81mm and plastic deflection of 1.69±0.93mm for metal hardware vs. 0.24±0.07mm and 0.06±0.04mm for TN; n=31). Of 16 TN-fixated specimens tested hydrostatically, none leaked under pressures up to 35mmHg held for 5 secs, and only 2 specimens leaked at 40mmHg. CONCLUSION: TN was biomechanically superior to standard cranial hardware for flap fixation. Additionally, TN acted to prevent fluid leakage. TN holds promise for improving cranial bone flap fixation biomechanically, cosmetically, and hydrostatically.