INTRODUCTION DISCUSSION

RESULTS

ABSTRACT

METHODS AND MATERIALS

CONCLUSION

BIBLIOGRAFIA

Objectives: To compare a bioplastic and an autologous graft to close a tympanic membrane perforation in guinea pigs. Study design: A randomized, prospective pilot study. Year study conducted: March 2013 to March 2014. Condition studied: Tympanic membrane perforation. Subject studied: Animal model (guinea pig). Setting: The study was held in the Center of Laboratory Animals of the Universidad Panamericana, as they have guidelines for proper maintenance of experimental subjects according to the Mexican Official Standard. Intervention: Myringoplasty was performed in 26 guinea pigs. Subjects acted as their own control. In the left side, the bioplastic (alpha, omega telequelic poli [ε-Caprolactone] diol hexamethylene diisocyanate) was put in place in an underlay manner: in the right side, abdominal fascia was put in place in an underlay manner. The procedure was performed under endoscopic 0° vision. Outcome measurement: Perforation closure. Results: Nonparametric statistics were performed with Fisher exact test and the Mann-Whitney U test. We considered P < .05 statistically significant. The analysis was performed using the statistical program SPSS version 20.0 for the Mac OSX 10.6 operating system. We obtained similar closure rates between the 2 materials, and histological examination showed di f ference between the 2 grafts.Conclusions: The bioplastic is a biomaterial that can be used as graft in myringoplasty. We require more studies to assess the effectiveness and efficiency as well as to corroborate an adequate safety profile for clinical use. Disclosure: We want to thank Dr Martinez Richa and his team, who donated the bioplastic.

Descriptive analysis was performed using measures of central tendency, normally was determined by Kolmogorov Smirnov test, so nonparametric statistics was performed with Fisher exact and Mann Whitney U. We consider p <0.05 statistically significant. The analysis was performed using SPSS version 20.0 for Mac OS X 10.6 operating system. RESULTS Of the 26 study subjects 4 subjects were removed, one died of unknown causes, one subject presented Chondritis, and 2 presented stenosis of both external ear. Therefore a 100% patency of the tympanic membrane perforation was obtained in 22 experimental subjects, who presented adequate evolution after tympanoplasty. The statistical analysis results are shown in figures.

One of the main limitations of this study was the sample size, however we demonstrated reproducibility of the model and the possible use of bioplastic as tympanic graft. At present there is no animal model of chronic eardrum perforations, anecdotally, in the conception of this work we planned to use rabbit (Oryctagulus cuniculus) as an animal model but the asymmetric external ear anatomy and tortuosity of the ear makes it a bad model.

We used a previously described animal model of chronic tympanic perforation, published in Otolaryngol Head Neck Surg September 2013 vol. 149 no. 2 suppl P232. Group 1. Under endoscopic vision 0 °, perforation was confirmed, we scratched the edges of the perforation with 90 ° angled pick, then proceed to fill the eardrum with gelfoam soaked in saline, placed the sheet of alpha, omega-telechelic poly (epsilon-caprolactone) diol and hexamethylene diisocyanate [PCLDEGHDI] previously irrigated with PBS 1X solution, in an underlay manner. The follow up was performed with 0º 2,7 mm endoscope at day 30 and day 60. At day 60 subjects were sacrificed by CO2 gas chamber. Then we approach the tympanic rim and removed the whole flap, sample was fix in 10% formalin. For group 2 we proceed in the same manner the difference was the graft used, the graft consisted in muscle fascia obtainedin the abdominal region.. For histological analysis the pieces were included in paraffin blocks, cuts was performed with a Leica RM2125 microtome each 10 microns, then were included in hematoxylin and eosin for histological analysis.

In this paper we demonstrated that the alpha, omega-telechelic poly (epsilon caprolactone) d io l and hexamethy lene d i i socyana te [PCLDEGHDI] is a bioplastic that can be used as tympanic graft, we obtained a percentage similar to the gold standard (fascia) closure and did not show complications at short-term follow up; likewise with the use of this plastic, it does not require an extra approach to obtain the graft and its possible application with the endoscope, could reduce hospital costs and the possibility to use this procedure under local anesthesia in office.

The concept of repairing a perforated eardrum was described by Berthold in 1878. In 1952 Zöllner and Wullstein describe the basic concepts to reconstruct the tympanic membrane and the sound conduction mechanisms of the tympanic cavity. The aetiology of these perforations may be due to trauma, acute or chronic middle ear infections, grommet´s placement or iatrogenic. We hypothetized that alpha, omega-telechelic p o l y ( e p s i l o n - c a p r o l a c t o n e ) d i o l a n d hexamethylene diisocyanate [PCLDEGHDI] can act as graft and promote the generation of a functional neotympanum in an animal model of tympanic perforation. Alpha, omega-telechel ic poly (epsi lon-caprolactone) diol and hexamethylene was used in this study because diisocyanat is a biodegradable segmented of polyurethane, is a flexible element polycaprolactone with a molecular weight of 2,000 g / mol, and diisocyanates of aliphatic origin are nontoxic compared to their aromatic counterparts.

1.  Schmitt H. Importance of sound pressure and umbral protection in transformation of sound and hearing. Acta Otolaryngol (Stockh) 1957;49:71. 2. Møller, Aage R. Hearing : anatomy, physiology, and disorders of the auditory system/A.R. Cap. 9 Pag 210. 2da edicion. 3. Vermette P, Marois Y, Guidoin R et al. Biocompatibility of Polyurethanes. Biomedical applications of polyurethanes. p. 77-96; 2001. Eurekah 4. L. Feenstra, F. E. Kohn, and J. Feijen, ”The concept of an artificial tympanic membrane,” CIin. Otolaryngol., 9, 215-220 (1984). 5. Gibb AG, Chang SK. Myringoplasty. J Laryngol Otol 1982; 96:915-30. 6. Wever EG, Lawrence M. Physiological Acoustics. Princeton: Princeton University Press, 1954. 7. Lim DJ. Human tympanic membrane. An ultrastruc tural observation. Acta Otolaryngol (Stockh) 1970; 70:176. 8. Portmann G. Portmann M. The surgery of the deafness. Arch otlaryngol 1964;72: 230-6. 9. Berthold E. [About myringoplasty]. Wien Med Blätter 1878;26:627–39. 10. Wullstein HL. [Functional middle ear surgery with the aid of free graft]. Arch Ohr- Nas- Kehlkopfheilk 1952;161:422–35.

<Dr. Enrique Girón Archundia>

<Hospital Angeles Puebla; Universidad Panamericana>

Email: drgironarchundia@gmail.com