Long-Term Analysis of the Results of Free Fat Graft Used for Reconstruction in Skull Base Surgery

Introduction: Fat grafts are widely used in skull base surgery for reinforcement of dural closure and obliteration of dead space. As graft integration into CSF spaces, watertight durability, and evolution of graft size in postoperative period has not been sufficiently studied, this study aims at analyzing the results of free fat graft usage.

Methods: At the beginning of our research, we investigated the principles of early graft integration and evaluated watertight durability closure. Fat and fascial grafts at dural reconstruction were compared. Then, a histomorphological study was conducted. The clinical part included 450 patients with different skull base tumors. The mean age was 43.4 years (range, 29-80 years). Fat grafts were used to occlude the following defects: sphenoid sinus, ethmoid sinus, and mastoid air cells. MRIs were performed both 7 days after operation and in the long term after surgery. Graft size and MRI signal intensity were measured. The mean follow-up was 74 months (range, 12-120 months).

Results: Experimentally, a fat graft provides the most watertight durability closure compared with a fascial graft. Histological study showed complete physical graft integration in 1 day after surgery, beginning of vascularization in 7 days, and complete biological graft integration n 14 days. Serial MRI study showed the mean graft size reduction to 71.6% after 1 month, to 38.3% after 3 years, and 35.9% after 10 years. In 7.8% of patients, fibrous graft transformation occurred, 1.1% had graft lysis, and 0.4% had graft infection. No cases of lipoid meningitis were detected. The rate of CSF leak was 2%. All cases of CSF leak were noticed in the first 5 days after surgery.

Conclusion: Fat graft serves as an effective dural watertight closure and helps to decrease CSF leak rate. By analyzing the type of fat graft, we can speak of natural and complicated evolutions. Natural evolution can be typical and atypical. Typical evolution provides complete biological graft integration. Atypical evolution is fibrous graft transformation or graft lysis.