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.