Skull Base Surgery: Free Fatty Autograft Evolution

Yu.A. Shulev, O.R. Akobyan

(Medical Academy of Postgraduate Education, Municipal Multi-Field Hospital N 2, Saint Petersburg)

Introduction. A fatty autograft is widely used in skull base surgery. However, we lack data on its integration into liquor spaces, temporal dynamics of hydrostatic reliability of a reconstruction zone and evolution of a transplant size in a remote postoperative period.

Methods. An initial stage of our research included experiments, carried out on chinchilla rabbits. We performed plasty of liquor spaces with a fatty autograft. It was followed by estimation of hydrostatic reliability of a reconstruction zone in 1,7 and 14 days. Histomorphologic examinations of specimens with applying histochemical methods of staining (according to Van Gizon, Weigert, Gordon-Sweet) were carried out.

The clinical study included 304 cases with different tumors of the skull base, operated in 2000-2006. Their mean age was 42.85±2.2 years. A fatty autograft was used for occlusion of the sphenoid sinus, ethmoidal labyrinth, posterior cranial fossa bottom and mastoid process cells. A mean volume of a fatty autograft was 29.6 cm3.

MR-examination was carried out in all the cases during the first 7 days after operation; in 1, 3 and 6 months; 1 and 3 years. Taking sagittal, frontal and axial T1- and T2-weighted images was mandatory. They were used for estimation of a transplant size and MR-signal intensity. We distinguished between 5 degrees of signal intensity.

Results. Hydrostatic reliability of plasty was as follows: a day after operation 98±7.3 mm Hg, in 7 days - 143±5.4 mm Hg, in 14 days - 285±15.1 mm Hg. A histological examination of specimens was indicative of firm attachment of a fatty autograft to defect edges, which ensured good sealing (physical integration). Transplant vascularization started in 7 days. Signs of complete biological integration of an autograft were observed in 14 days. Serial MR-examination demonstrated evolution of a transplant size after operation. On the average, it decreased up to 72.9±3.2% in a month, 54.8±6% in 3 months, 39.6±4.1% in a year and 38.9±4.8% in 3 years. Complete connective degeneration and lysis of a fatty autograft were revealed in 4.8% and 1.5% of cases respectively. Transplant contamination was watched in 2 cases (0.7%); 7 patients had liquorrhea (2.3%), which developed during the first 5 postoperative days before the beginning of biological integration of a transplant.

Conclusion. Thanks to its plastic and hydrostatic properties, a fatty transplant ensures effective sealing of liquor spaces, which prevents liquorrhea. According to the results of our study, there are natural and complicated forms of fatty transplant evolution. Natural evolution of an autograft can be typical and atypical. Typical evolution consists in complete biological integration of a transplant. Atypical evolution is characterized by its connective degeneration and lysis. Complicated evolution, i.e. transplant contamination, was observed in 0.7% of cases.