The effect of radiofrequency thermal ablation on histology and ultrastructure of the rabbit inferior turbinate

In ENT practice hypertrophy of the inferior turbinate is a common finding in patients with the complaint of nasal obstruction. When medical treatment fails then surgical treatment is applied. Among the applied treatments are injection of various materials into the turbinate, linear cauterization, out fracture, cryosurgery, partial and total turbinectomy, submucosal turbinate resection, laser application, and argon plasma coagulation. Since 1998 Radiofrequency Thermal Ablation (RFTA) of turbinate has been one of the preferred methods. After the application of radiofrequency to the turbinate, the protection of ciliated epithelium of the turbinate is of major importance. If this epithelium is injured, then one of the main functions of nasal cavity namely the mucociliary transport is damaged. Despite its common usage unlike other surgical approaches this surgical treatment?s effect on ciliagenesis and tissue ultrastructure has not been investigated.The aim of this study is to find out the histological effects of radiofrequency thermal ablation on the inferior turbinate through examination under light and electron microscope.The study has been performed on 14 rabbits (21 turbinates). Subjects were divided into 2 groups. In each group 7 rabbits were unilaterally operated. After application to the anteromedial portion of rabbit inferior turbinate 500J 75ºC energy via Gyrus ENT (Barlett, USA) radiofrequency thermal ablation probe, in the 1st week from the first group of rabbits, and in the 8th week from the second group of rabbits biopsies were obtained from the operated area for further evaluation. Unoperated 7 turbinates of the opposite site were selected as control group.For transmission electron microscopic examination, the tissue samples were fixed in 2.5% gluteraldehyde for 2 h, washed in phosphate buffer (pH 7.4), post-fíxed in 1% osmium tetroxide in phosphate buffer (pH 7.4) for 1 h and dehydrated in increasing concentrations of alcohol. Then, the tissues were washed with propylene oxide and embedded in epoxy-resin embedding media. Semi-thin sections about 0.5-1 ?m in thickness were cut with a glass knife on a LKB (Bromma, Sweden) ultramicrotome. The semi-thin sections were stained with toluidine blue and examined by a computerised photo-light Leica DM 4000 B microscope equipped with a Leica DC 300 FX digital camera (Stuttgart, Germany). Following this examination, the tissue blocks were trimmed, their ultra thin sections about 20 nm in thickness were taken by the same ultrotome and placed on a formvar coated copper grids. For contrast vision they were stained with uranyl acetate and lead citrate. Following staining, all the ultra thin sections were examined by a Carl Zeiss Libra 120 (Oberkochen, Germany) transmission electron microscope.Five parameters were examined: degeneration of epithelium, irregularity of basal membrane, subepithelial fibrosis, cilial length with density and degeneration. First three parameters were examined under light microscope, and the other two were examined under electron microscope. After the results were classified into 3 categories as no change, moderate change or advanced change, statistical analysis was performed by Mann-Whitney U test on SPSS 16 program.In one of the specimens of the first group respiratory epithelium was not encountered. As a result, this group?s number was adopted as six. In the first week, epithelial degeneration was observed in some specimens, however they lacked statistical significance. Basal membrane had a significant irregularity (p=0.035) and in all specimens very important development of subepithelial fibrosis was observed (p=0.008). In the first group severe loss of cilia was noted. In all specimens the cilia were dispersed and very short (p=0.035). In the same way cilia had significantly degenerated (p=0.035). Biopsies obtained in the eighth week along with the degeneration also revealed statistically significant regeneration (p>0.05).Our study revealed severe subepithelial fibrosis from the first week usage of RFTA method. Basal membrane irregularity was also noteworthy.This study demonstrated the effect of application of RFTA to inferior turbinate on cilia length and density in all specimens (p<0.05). Cilial morphology was also affected in the similar way. All ultrastructural changes are subject to regeneration with time.As a conclusion, radiofrequency thermal ablation of inferior turbinate in a long term is a reliable method, however in short term period the effect on ultrastructure of turbinate by RFTA may be considered.Key Words: inferior turbinate, radiofrequency, turbinate histology, cilial ultrastructure