DISCUSSION

AGS has been used as a MEMP during otologic surgery for the past 60 years with the introduction of Gelfoam by Zollner and Wullstein4. This absorbable material serves to support TM grafts and ossicular chain prosthetic devices during the postoperative healing period. It has been known that AGS plays a role in enhancing epithelialization of the graft material and probably functions as an adherence promoter of the graft to the remnant of the TM2. However, there are exists some controversies regarding its use. AGS has been reported to induce an inflammatory reaction, causing fibrosis and adhesions within the middle ear, which leads to conductive hearing impairment due tothe adherence of the grafted TM to the promontory or fixation of the ossicular-chains5. Since postoperative inflammation and fibrosis in the middle ear cavity have been known as one of the reasons forthe unsuccessful hearing results after tympanoplasty, several materials have been explored to replace AGS2,6-10.
Polyurethane foam(PUF) was marketed as a MEPMand synthetic biodegradable foam. A histologic study by Dogru et al.11compared short-term and long-term appearances of middle ears packed with either AGS or PUF in a traumatic model of the rat with middle ear packing. In the reported study, the PUF induced mild inflammation and fibrosis in the middle ear in contrast to the severe inflammatory process and fibrosis associated with AGS packing. However, another study with an animal model of middle ear trauma and PUF or AGS packing showed a similar degree of inflammation and neo-osteogenesis in the middle ear with both the packingmaterials12. A recent experimental study comparingthe effects of AGS and another packing material, OtoporeTM(Stryker, USA; Otopore group) in the middle ear cavity demonstrated less inflammation, adhesion, and new bone formation in OtoporeTM packing group, despite the absence of substantiation about its long-term safety13. In a review article investigating 12 middle ear absorbable packing agents including gelfoam, Shen et al.14reported that there exists no perfect agent for middle ear packinguntil date. In addition, theysuggestedthatnone of thepacking materialswould be associated with advantages related toan immediate improvementin hearing, shorteningthe operating time, reduction in thecost and patients’ comfort, although there is a lack of clinical evidence.
There exist only a few clinical studies regarding middle ear packing materials. Most of the studies have dealt with animal models5,7,8,10,11,13,15, and only one comparative study has reported the effects ofMEMP on the outcomes of middle ear surgery in human14. Smith et al.16reported better hearingresults of the hydroxylapatite/titanium bell partial ossicularreplacement prosthesis (PORP) without gelfoam compared with the conventionalPORP with gelfoam. However, the reportedstudy had a limitation in its rationale on theeffect of MEPM as the conditions were not controlled. Previous clinical studies without gelfoam during overlay tympanoplasty or ossiculoplasty demonstrated excellentsurgical results, which guided us to perform a more scientific and clinical study to demonstrate the effect of MEPM3,17. Our study is the first prospective randomized case-control study to investigatethe effects of middle ear packing using AGS in terms of surgical results and healing processes in humans. While the overall graft success rate was not affected by middle ear packing using AGS, the delayed epithelization of TM and more severe fascia edema were observed in GPG, thereby suggesting that AGS may interrupt the healing process of TM. In addition, larger postoperative ABG was observed in GPG for up to two months,although no significant difference was shown in the third month visit. This result suggests that AGS may remain in the middle ear for more than two months, similar to previous animal studies7,18,19.Therefore,based on our study results, surgical techniqueswithout middle ear packing can be recommended to reduce patient’s discomfort caused by delayedhearing improvement and achieve a faster healing process.
Middle ear packing is essential for conventional underlay tympanoplasty to support the graft20. Therefore, even in underlay tympanoplasty, other surgical techniques without MEPM have been suggested. Yuasa et al.21 introduced simple underlay myringoplasty with fibrin glue in 1989. They inserted a connective tissue through perforation using the underlay technique and fixed it with fibrin glue without middle ear packing. However, this method exhibited limited visibility into the middle ear and a relatively low overall initial success rate of 77.7%22. Another technique, inlay butterfly cartilage tympanoplastywithout middle ear packingwas introduced by Eavey et al. in 199823. Theperforation closure rate was observed between 71 to 100%, but this method has limitationsfor patients with large perforationbecause of the small remaining part of the TM which cannot support the cartilage on its own24,25.Previously, we have introduced the technique and surgical outcomes of a modified method for overlay tympanoplasty; swing-door overlay tympanoplasty. No MEPM was required for this technique and a high success rate of graftuptake(98.4%) with satisfactory hearing results (postoperative ABG was closed to ≤20 dB in 86.9%) was observed in the study. The advantage of this surgical method is that the swing door technique provides a better surgical view and makes it easier to perform surgery than conventional overlay tympanoplasty, and can be applied to all types of chronic otitis media regardless of the size of TM perforation3.
Given that the previous animal studies demonstratedfibrosis or inflammatory reactionin the middle ear cavity by AGS, our clinical study demonstratedthe negative effects of AGS in terms of healing processes of neodrum. Also, delayed hearing improvement appeared to be comprehensible.