INTRODUCTION

According to RONIS et al. the cyanoacrylates manufactured in 1949 by ARDIS only had their adhesive properties noticed in 1959 by COOVER and, as such, began to be considered for use in medicine (1,2). Their efficacy has been proved in many specialties, specially in general surgery and dermatology, used to replace sutures in the binding of skin incisions. Many papers have proven their efficacy as adhesives in other body structures, from rigid, such as bones and cartilages, to soft tissue such as vascular and neurological tissues (3-6). Besides, all acrylates have anti-bacterial properties and, as such, do not need to be sterilized. Some papers show that they can even be used to seal up contaminated wounds (7).

In the beginning, the many acrylates developed presented some varied degrees of tissue toxicity, however, new formulations of longer molecular chains were created in order to mitigate this drawback. The so called initial acrylates, of short chain are the ethyl-2-cyanoacrylate (Super-Bonder®) and the methyl-2-cyanoacrylate (Eastman 910 Monomer®). The long chain ones, newer and less toxic are the isobutylcyanoacrylate (Bucrylate®) and the 2-cyanobutylacrylate (Histoacril®). Still, among the long chain ones we have: Octylcyanoacrilate (Octiyl®), and 4 metacryloiloxietyl trimelytato anidro with metylmetacrylate (4 Meta/MMA-TBB®), and later on, the fluoroalkilcya¬noacrylate was developed.
Many studies with animals try to compare the degrees of toxicity among the cyanoacrylates (2,8-15). The so called short chain ones (ethyl-2-cyanoacrilate) are always more toxic than their long chain counterparts and were replaced by the latter in medical practice. In all these comparative experimental studies, the quantities of cyanoacrylates used within cavities such as the nasal sinuses, the mastoid bone and the tympanic cavity were always larger than what was usually used in the surgical practice.

In general otolaryngology, the cyanoacrylates have been mainly used in the closure of surgical incisions related to head and neck procedures (16). According to SAMUEL et al. (16), they started to be used in otology back in 1969, in tympanoplasties and ossiculoplasties. Later works demonstrated their efficacy in facial nerve surgery and to fix ossicular chain interpositions (1,8-10,13,15-17). As we saw, many authors use cyanoacrylates routinely in their surgeries with very good results, notwithstanding, some believe that the fibrin glue or the bone cement are more adequate for medical purposes as tissue adherent materials (18-21). We did not find any paper about the use of any adherent substance in order to bind the Teflon prosthesis to an ossicle during stapedotomy, either the incus, or the malleus.

Our goal with this work is to report on two cases of patients who underwent stapedotomy and had their prosthesis glued to an ossicle with cyanoacrylate.

CASE REPORT

Case 1: V.A., 44 year old female, previously operated because of right side otosclerosis, with good results (Figure 1), had her hearing loss recur in the same side (Figure 2). She had normal otoscopy. We then proceeded to review the stapedotomy procedure we saw total erosion of the longer incus limb and the Teflon prosthesis loose within the middle ear. Since it was no longer possible to fit the prosthesis to the incus, this prosthesis was removed, cut and glued to the incus body with cyanoacrylate (Figure 3). The hearing gap was merged (Figure 4) and the patient remains with good hearing (it's been four years now). We have not observed any clinical sign of local toxicity.
Case 2: M.M.J., 32 year old female, with past history of ear infections and bilateral conductive hearing loss (Figure 5). She had previously undergone tympanoplasty with ossicular chain repositioning, in which the incus body was placed between the stapes and the malleus. The functional result was poor (Figure 6), however the tympanic hole was patched. During review surgery we saw a fixation of the stapes footplate and stapedotomy was indicated, even without the incus. The middle ear mucosa was normal. The stapes footplate was perforated, the 6mm Teflon prosthesis was placed in the footplate orifice and directly glued to the malleus with cyanoacrylate (Figure 7). The malleus was initially detached from the ear drum and released from the mucosa. The patient had excellent auditory gain, and such result still lasts after 1 year (Figure 8).

DISCUSSION

In some instances, during a stapedotomy, when there is erosion of the incus long limb or even the lack of the whole structure the surgeon may have a serious technical difficulty. In these cases we are able to reconstruct the ossicular chain continuity by placing the prosthesis directly from the malleus all the way to the stapes footplate. Although there are proper prosthesis for this, they are expensive and may not be available, specially when their need is only seen during the surgery itself. We may use a steel wire to make a long prosthesis linking the malleus to the oval window, removing all the footplate (stapedectomy). Notwithstanding, this procedure is not easy and we don't always have a steel wire available.

This paper shows the possibility of using a conventional 6 mm x 0,6 mm Teflon prosthesis directly glued to the incus body or the malleus limb. In both cases, the glue was very carefully placed in order to avoid spilling it over noble structures, specially the footplate. One drop of cyanoacrylate was placed on a metal surface, and with the tip of a delicate otologic surgery instrument, was taken in a minimum quantity to bind the prosthesis to the ossicle. We have to bear in mind that long chain cyanoacrylates (specially Histoacril - the one most studied) are considered less toxic and therefore more appropriate for surgical use. This procedure should be carried out by experienced surgeons in order to avoid gluing the ossicular chain to other structures.

Many similar surgeries have been carried out in our service, with excellent results. The cases presented here were so chosen because they have a long post operative follow up, showing that when properly used, cyanoacrylate does not cause side effects to the patient.

FINAL COMMENTS

Often times the ear surgeon is faced with difficult situations when placing the prosthesis during a stapedotomy procedure, specially when incus parts are missing. In such situations, cyanoacrylates may be of great help in fixing these prosthesis.

REFERENCES

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Figure 1. Case 1. Right ear stapedotomy post operative.
Figure 2. Case 1. Sudden hearing worsening in the right ear.

Figure 3. Case 1. Image of a cut Teflon prosthesis, introduced in the stapes footplate perforation and bound with cyanoacrylate to the incus body. The malleus process on the top.
Figure 4. Case 1. Surgical review post operative, lasting for 4 years.
Figure 5. Case 2. Bilateral hearing loss with past history of repetition otitis during childhood.
Figure 6. Case 2. Post operative of incus placement between the stapes and the malleus.
Figure 7. 6mm prosthesis stapedotomy, placed in the footplate perforation and glued directly to the malleus limb with cyanoacrylate.
Figure 8. Interposition review post operative. Stapedotomy was carried out and the Teflon prosthesis was glued to the malleus with cyanoacrylate.