Outcomes of Underlay Versus Over-Underlay Technique myringoplasty

Objective: In this study, the two methods of myringoplasty (underlay and over-underlay technique) were compared. Methods: Total 100 patients of COM (inactive mucosal variety) were studied for 06 months duration from 1st Oct 2015 to 31st March 2016 in the Dept of ENT & Head Neck Surgery, CMH Dhaka. The diagnosed cases of COM patients were selected according to the eligibility criteria’s by purposive sampling. 100 patients were equally divided into two groups. Patients in group1 underwent underlay method and patients in group 2 underwent over-underlay technique of myringoplasty. Patients were followed up for 6 months. Results: Graft uptake and hearing improvement was compared in both groups. In group 1 (underlay myringoplasty) graft taken rate was 92% and graft failure rate was 8%. In group 2 (Over-underlay myringoplasty) graft taken rate was 94% and failure rate was 6%. Graft uptake was 2% lower in the group1 than group 2 .The gain in hearing threshold (gain in A-B gap) in the group 1 (underlay myringoplasty) was (23.74 dB ± 3.97) and in group 2 )over-underlay myringoplasty) was (23.64 dB ± 4.03) Conclusion: The present study emphasizes the fact that there is no significant difference in short term results between the two techniques (underlay and over-underlay).


Background:
Myringoplasty is the term used for repair of perforated tympanic membrane and to improve hearing level1. Perforation of the tympanic membrane primarily results from middle ear infections, or trauma. Up to 80% of these perforations heal spontaneously 2. For the remainingMyringoplasty is usually performed. Benefits to myringoplasty include prevention of ear infections, aural discharge, improvement in hearingand protection against long-term middle ear damage by preventing the ossicularpathology, the migration of squamous epithelium around the margins of perforation 3 .
The over-underlay technique has several advantages as it is Ideal for perforations of all sizes in all quadrants, has good exposure to the anterior middle ear, no blunting, it prevents adhesions between drum and middle ear. Again total elevation of the drum remnant of the malleus provides additional advantageslike, increased overlap of the graft and drum remnant, better preparation of the graft bed, excellent medial support by the malleus handle. On the other hand the underlay technique is generally more recommended for posterior perforations. It has less risk for lateralization and less chance of squamous epithelial migration 4 .
This cross sectional prospective study conducted for a period of 06 months. It included 100 patients of COM (inactive mucosal variety) who reported to the Otolaryngology department and they were allocated into two groups. In group 1, the temporalis fascial graft was placed medial to the handle of malleus (underlay technique), in group 2 the graft was placed lateral to the handle of malleus but medial to the remnants of the tympanic membrane or fibrous annulus (over-underlay technique). The two groups were followed up for 06 months post operatively. Pre-operative and post operative conventional audiometric evaluation (PTA) were done.

Methods:
This is a Prospective cross sectional study.Total 100 patients of COM (inactive mucosal variety) were studied for 06 months duration from 1 st Oct 2015 to 31 st March 2016 in the Dept of ENT & Head Neck Surgery, CMH Dhaka. The diagnosed cases of COM patients were selected according to the eligibility criteria's by purposive sampling. 100 patients were equally divided into two groups. Patients in group1 underwent underlay method and patients in group 2 underwent overunderlay technique of myringoplasty. Patients were followed up for 6 months.
Inclusion Criteria were age 15-50 years and COM with dry central tympanic membrane perforation. Exclusion were cases of chronic suppurative otitis media of atticoantral type, cases of chronic suppurative otitis media with ossicular discontinuity, patient with Sensorineural hearing loss and mixed hearing loss, patients below 15 years and above 50 years, discharging ear and previous history of ear surgery.

Procedures of data collection, data analysis and interpretation:
At first, detailed history, physical examination and clinical investigations for GA fitness were done along with pre-operative pure tone audiometry & tympanometry in those patients who were admitted and who met the inclusion criteria. Informed written consent was obtained from the patient or guardians after full explanation of the details of the disease process and the purpose of the study. All operations were done by experienced senior ENT surgeon of CMH Dhaka with operating microscope Carl Zeiss, model: Vario S-8. The patients were followed up for a period of 06 months. Follow up schedules were at 2 nd week, 4 th week,3 rd months and 6 th month. At each visit the ear was examined with otoscope and tuning fork test performed. Post operative pure tone audiometry & tympanometry were performed at 6 th month.The patient or the attendant was interviewed by the investigator using the case record form.All data was processed manually and analyzed with the help of SPSS (Statistical package for social sciences) Version 21.0.Quantitative data was expressed as mean and standard deviation and comparison was done by [Z] test.Qualitative data was expressed as frequency and percentage and comparison was done by chisquare (F 2 ) test.  The most common presenting symptoms of these patients were otorrhoea (100%) and hearing loss (80-90%).

Results
Majority (65%) of the patients belongs to low socioeconomic group.

Discussion:
Myringoplasty is a surgical technique used to restore the integrity of tympanic membrane and to improve hearing level 5 . Repair of eardrum by doing Myringoplasty may confer considerable benefits to patients with tympanic membrane perforation that include prevention of ear infections, aural dischargeand improvement in hearing.
In underlay technique the graft is placed medial to the tympanic membrane remnant and handle of malleus 6 .On the other hand in over-underlay technique the graft is placed lateral to the malleus but medial to the remnants of the tympanic membrane or fibrous annulus 6 .The over-underlay technique has several advantages as it is ideal for perforations of all sizes in all quadrants. Itgives good exposure to the anterior middle ear, no blunting, and prevents adhesions between drum and middle ear. Again total elevation of the drum remnant of the malleus provides additional advantages like increased overlap of the graft and drum remnant, better preparation of the graft bed, excellent medial support by the malleus handle 4,7 . On the other hand the underlay technique is generally more recommended for posterior perforations. It has less risk for lateralization 4 .
Masoud et al stated that the success of the graft integration in children is slightly lower than in adults and that is due to the fact that children have persistent dysfunction of the Eustachian tube, recurrent infections of the respiratory tract with otorrhoea and lack of development of the immune system. The mean age of that study was of 34.07±7.3 and the tympanic membrane closure rate and hearing improvement was similar to other studies; therefore, indicating age is not a prognostic factors 8 . In our study, mean age of patients were 30±5 years, showed no significant difference in graft uptake, which is consistent with above study. .In our study we also found the same result (Table -2). Gerard Kelly mentioned higher prevalence of COM in lower socioeconomic group 9 . Our study (Fig -2) also revealed the same result.
Ian et al mentioned the main clinical presentations of inactive mucosal COM are hearing impairment and intermittent otorrhoea 1 . Vineet et al also mentioned the above two symptoms as most common in case of inactive mucosal COM 4 . Our study is also consistent with above studies (Fig -1).
The study of Jung mentioned that Underlay tympanoplasty is suitable for posterior TM perforation, and Over-underlay graft method is an excellent for the reconstruction of large anterior or subtotal TM perforation 10 . Our study showed the similar result (Table -5).
Different studies showed, the average gain in A-B gap was 14.5dB-16.55 dB in case of underlay technique and in case of overunderlay technique it was 16.96dB-18.75dB 4,11 .Postoperative hearing gain was little bit better in over-underlay technique. In our study we also got almost similar result (Table -7).