Introduction
Various absorbable and non-absorbable materials have been placed in the middle ear during surgery in order to: promote the growth of new, healthy middle-ear mucosa; maintain a middle ear free of adhesions; and support the neotympanic membrane. WullsteinReference Wullstein1 advocated the use of absorbable gelatin sponge, marketed today as Gelfoam® or Gelfilm®. Non-absorbable plastic sheeting composed of polyethyleneReference House2 or paraffin waxReference Rambo3, Reference Tabb4 has been used. Teflon® and Silastic®Reference Shea5 have also been used in ear surgery.
During Tympanoplasty, the first stage of disease treatment involves removal of most of the middle-ear mucoperiosteum, with subsequent insertion of non-absorbable synthetic materials in some cases. Three to six months post-operatively, when the middle-ear cavity is healthy and well ventilated and the tympanic membrane well healed, the second stage of surgery involves removal of the inserted material and reconstruction of the sound-conducting mechanism.Reference Tabb4, Reference Farrior6–Reference Sheeny and Crabtree8
Silastic (silicone plastic) sheets are commonly used surgically to form a physical barrier against adhesion. The ideal barrier to adhesion formation would be a non-reactive, flexible, absorbable substance with no long-term toxicity. Liening et al. Reference Liening, McGath and Mckinney9 have compared polydioxanone sheets with silicone plastic sheets, placed within the middle ear of Mongolian gerbils. They found polydioxanone sheets to be as effective and well tolerated as silicone plastic sheets in this animal model.
After surgical procedures involving resection of middle-ear mucosa, Silastic sheeting has been used to restore the mucosal lining of the middle-ear space and to prevent mucosal adhesions between the medial surface of the tympanic membrane and the promontory. Ng and LinthicumReference Ng and Linthicum10 examined six temporal bones from patients with permanent Silastic sheeting placed in the middle-ear cavity during single-stage tympanoplasty. In all six bones, no histological evidence of foreign body reaction or chronic inflammation was observed in the surrounding middle ear. Furthermore, the middle-ear space was lined by apparently normal, continuous middle-ear mucosa. In four temporal bones, there was no evidence of significant submucosal fibrosis. In two bones, significant submucosal fibrosis was found, and was attributed to concurrent middle-ear disease rather than to the presence of Silastic sheeting. The authors concluded that insertion of Silastic sheeting into the middle ear during single-stage procedures may prevent adhesions between mucosal surfaces.
The aims of the current study were: (Reference Wullstein1) to evaluate the role of Silastic sheeting inserted into the tympanic cavity during single-stage tympanoplasty for chronic otitis media, as regards the prevention of adhesion formation and/or recurrence, and (Reference House2) to evaluate the effect of such Silastic sheeting on post-operative hearing.
Patients and methods
This retrospective study was approved by the research ethics committee of the Mansoura University Faculty of Medicine.
One hundred and six patients suffering from chronic otitis media were included in the study. All patients had been admitted to the otorhinolaryngology department of the Mansoura University Faculty of Medicine between 2003 and 2009, and were selected for inclusion based on intra-operative findings. The inclusion criteria comprised the concomitant presence of intact ossicles and middle-ear adhesions. Exclusion criteria comprised the presence of ossicular necrosis, cholesteatoma, granulation tissue tympanosclerosis and poor eustachian tube function.
All patients underwent routine ENT examination, radiological assessment and audiological evaluation (i.e. pure tone and speech audiometry). Audiometry was undertaken pre-operatively and one and 12 months post-operatively.
Patients were divided into two groups.
The first group comprised 74 patients (46 men and 28 women), aged between 19 and 46 years. Seventy-one patients had chronic suppurative otitis media, while three had chronic adhesive non-suppurative otitis media with an intact tympanic membrane. These patients underwent single-stage tympanoplasty via an endaural approach; surgery included eradication of disease and permanent insertion of 0.127 mm Silastic sheets in the medial wall of the tympanic cavity, between the malleus and incus, and lateral to the long process of the incus.
The second group comprised the remaining 32 patients (21 men and 11 women), aged between 18 and 42 years. All had chronic suppurative otitis media. Single-stage tympanoplasty was performed in the same manner as in the first group, but without insertion of Silastic sheeting.
Statistical analysis
Data were expressed as the arithmetic mean ± standard deviation (SD). Student's t-test was used to test for significant change in air conduction, bone conduction and air–bone gap, comparing the two patient groups pre-operatively and at one and 12 months post-operatively. Statistical significance was realised at the probability level p < 0.05. Statistical analysis was performed using the MedCalc software for medical statistics.Reference Schoonjans, Zalata, Depuydt and Comhaire11
Results
Pre-operatively, there were no statistically significant differences between the Silastic and non-Silastic groups as regards air conduction and air–bone gap (Table I).
Hearing parameters in the two groups: pre-operative
Data represent means ± standard deviations. *Statistically significant (p < 0.05, Student's t-test). AC = air conduction; BC = bone conduction; ABG = air–bone gap
One month post-operatively, there was a statistically significant difference between the air conduction as well as bone conduction results of the two groups (Table II).
Hearing parameters in the two groups: 1 mth post-operative
Data represent means ± standard deviations. *Statistically significant (p < 0.05, Student's t-test). Mth = month; AC = air conduction; BC = bone conduction; ABG = air–bone gap
One year post-operatively, there were statistically significant differences between the two groups as regards air conduction, bone conduction and air–bone gap (Table III).
Hearing parameters in the two groups: 1 yr post-operative
Data represent means ± standard deviations. *Statistically significant (p < 0.05, Student's t-test). Mth = month; AC = air conduction; BC = bone conduction; ABG = air–bone gap
Over the one-year follow-up period, no extrusion or reaction to the Silastic sheeting was noted. Graft failure occurred in three patients in the Silastic group; however, these patients had better post-operative hearing, and no adhesions were found at revision surgery. Graft failure also occurred in three patients in the non-Silastic group, whose hearing deteriorated post-operatively; at revision surgery, marked adhesions were observed.
Discussion
Chronic otitis media is very common in Egypt. To the best of our knowledge, the current study represents the first published evaluation of the effect of middle-ear Silastic sheeting on hearing outcome, one year after insertion.
Silastic is an important material in numerous medical and pharmaceutical devices. In middle-ear surgery, it has been used within the middle ear after tympanoplasty to prevent adhesions between the graft and the promontory,Reference Fayad and House12 as a graft to close tympanic membrane perforations,Reference Courteney-Harris, Ford, Ganiwalla and Mangat13 and as a form of dressing.Reference McDonald, Facer and Clark14, Reference Zeitoun, Sandhu, Kuo and Macnamara15
A novel method for cutting Silastic sheeting has recently been described by Randhawa and Choa:Reference Randhawa and Choa16 the sheeting is cut with scissors while still in its packaging, where it is immobilised by static and adherent to the packaging window, thus avoiding the production of irregularly shaped strips.
In patients with chronic otitis media, the most common adhesions sites are the posterior part of the mesotympanum and the attic. In addition, the tympanic membrane may become thickened and bound to the inner tympanic wall in the region of the promontory, a condition usually known as atelectasis. Moreover, the ossicles and window areas are often involved, and adhesions may pass from one ossicle to another or bind the ossicles to the tympanic membrane or to the bony walls of the tympanic cavity.Reference Gibb17 In our study, deterioration of hearing was detected a few months after tympanoplasty in some cases. Re-exploration of these cases revealed adhesions around the stapes, between the incus and the handle of the malleus, and between the posterior tympanic membrane and the medial wall. Some patients also had adhesion of the anterior tympanic membrane to the medial wall.
Our study assessed the effect of Silastic sheeting inserted into the middle ear to prevent adhesions following tympanoplasty for chronic otitis media. Where such adhesions did form post-operatively, they were excised and Silastic sheeting inserted in the tympanic cavity, as described above, to prevent re-adhesions. Evaluation at one month post-operatively showed improved hearing in all patients; however, this improvement was statistically significant for both air conduction and bone conduction.
At the end of the one-year follow-up period, a significant difference was found for all hearing parameters (i.e. air conduction, bone conduction and air–bone gap), comparing patients treated with Silastic sheet insertion versus those treated with tympanoplasty alone. In the non-Silastic group, post-operative hearing deterioration affected both air and bone conduction. In this group, the deterioration in air conduction hearing can be explained by the occurrence of adhesions causing stiffness in middle-ear structures. The deterioration of bone conduction in this group can be attributed to the mass of the fibrous adhesions causing a mass tilt effect. This theory is supported by the fact that deterioration of bone conduction thresholds was significantly greater at high frequencies compared with low ones (data not shown).
Two patients in the Silastic group developed post-operative infection, which was controlled by antibiotics.
Failure of graft ‘take’ was observed in three cases in each group. In the three patients from the Silastic group, surgical re-exploration found no adhesions or reactions to the Silastic sheeting, whereas marked adhesions were noted in the three patients from the non-Silastic group.
These study findings are in agreement with those of Ng and Linthicum.Reference Ng and Linthicum10 Both studies found no reaction to the inserted Silastic sheeting. In addition, the stable hearing improvement observed in patients treated with Silastic sheeting supports the absence of re-adhesions. Moreover, no adhesions were detected in the three Silastic group patients who required surgical re-exploration.
• Following tympanoplasty, the formation of middle-ear adhesions can adversely affect hearing outcomes
• This study investigated the effect of Silastic sheeting inserted into the middle ear during tympanoplasty
• Silastic sheeting is inert and can prevent the formation or recurrence of middle-ear adhesions, resulting in sustainably improved post-operative hearing
Fish and MayReference Fish and May18 have recommended the use of thick Silastic sheeting or Gelfilm in the tympanic cavity and eustachian tube where the middle-ear mucosa is defective, and also to prevent the recurrence of retraction pockets.
Placement of Silastic sheeting helps middle-ear mucosa to regrow in areas where it had previously been absent due to disease or surgery, and also helps prevent adhesion formation between the graft and the promontory. As a result, it facilitates the healing of the middle-ear space, ultimately leading to a better functional hearing outcome.
Conclusion
Silastic sheeting can help prevent the formation or recurrence of middle-ear adhesions, resulting in sustainably improved hearing. We recommend the insertion of Silastic sheeting into the middle ear during tympanoplasty.
